We are searching data for your request:
Upon completion, a link will appear to access the found materials.
The first humans emerged in Africa around two million years ago, long before the modern humans known as Homo sapiens appeared on the same continent.
There’s a lot anthropologists still don’t know about how different groups of humans interacted and mated with each other over this long stretch of prehistory. Thanks to new archaeological and genealogical research, they’re starting to fill in some of the blanks.
The First Humans
First things first: A “human” is anyone who belongs to the genus Homo (Latin for “man”). Scientists still don’t know exactly when or how the first humans evolved, but they’ve identified a few of the oldest ones.
One of the earliest known humans is Homo habilis, or “handy man,” who lived about 2.4 million to 1.4 million years ago in Eastern and Southern Africa. Others include Homo rudolfensis, who lived in Eastern Africa about 1.9 million to 1.8 million years ago (its name comes from its discovery in East Rudolph, Kenya); and Homo erectus, the “upright man” who ranged from Southern Africa all the way to modern-day China and Indonesia from about 1.89 million to 110,000 years ago.
In addition to these early humans, researchers have found evidence of an unknown “superarchaic” group that separated from other humans in Africa around two million years ago. These superarchaic humans mated with the ancestors of Neanderthals and Denisovans, according to a paper published in Science Advances in February 2020. This marks the earliest known instance of human groups mating with each other—something we know happened a lot more later on.
Early Humans, Neanderthals, Denisovans Mixed It Up
After the superarchaic humans came the archaic ones: Neanderthals, Denisovans and other human groups that no longer exist.
Archaeologists have known about Neanderthals, or Homo neanderthalensis, since the 19th century, but only discovered Denisovans in 2008 (the group is so new it doesn’t have a scientific name yet). Since then, researchers have discovered Neanderthals and Denisovans not only mated with each other, they also mated with modern humans.
“When the Max Plank Institute [for Evolutionary Anthropology] began getting nuclear DNA sequenced data from Neanderthals, then it became very clear very quickly that modern humans carried some Neanderthal DNA,” says Alan R. Rogers, a professor of anthropology and biology at the University of Utah and lead author of the Science Advances paper. “That was a real turning point… It became widely accepted very quickly after that.”
As a more recently-discovered group, we have far less information on Denisovans than Neanderthals. But archaeologists have found evidence that they lived and mated with Neanderthals in Siberia for around 100,000 years. The most direct evidence of this is the recent discovery of a 13-year-old girl who lived in that cave about 90,000 years ago. DNA analysis revealed that her mother was a Neanderthal and her father was a Denisovan.
Human Evolution Was Messy
Scientists are still figuring out when all this inter-group mating took place. Modern humans may have mated with Neanderthals after migrating out of Africa and into Europe and Asia around 70,000 years ago. Apparently, this was no one-night stand—research suggests there were multiple encounters between Neanderthals and modern humans.
Less is known about the Denisovans and their movements, but research suggests modern humans mated with them in Asia and Australia between 50,000 and 15,000 years ago.
Until recently, some researchers assumed people of African descent didn’t have Neanderthal ancestry because their predecessors didn’t leave Africa to meet the Neanderthals in Europe and Asia. But in January 2020, a paper in Cell upended that narrative by reporting that modern populations across Africa also carry a significant amount of Neanderthal DNA. Researchers suggest this could be the result of modern humans migrating back into Africa over the past 20,000 years after mating with Neanderthals in Europe and Asia.
Given these types of discoveries, it may be better to think about human evolution as a “braided stream,” rather than a “classical tree of evolution,” says Andrew C. Sorensen, a postdoctoral researcher in archaeology at Leiden University in the Netherlands. Although the majority of modern humans’ DNA still comes from a group that developed in Africa (Neanderthal and Deniosovan DNA accounts for only a small percentage of our genes), new discoveries about inter-group mating have complicated our view of human evolution.
“It seems like the more DNA evidence that we get—every question that gets answered, five more pop up,” he says. “So it’s a bit of an evolutionary wack-a-mole.”
Early Human Ancestors Shared Skills
Human groups that encountered each other probably swapped more than just genes, too. Neanderthals living in modern-day France roughly 50,000 years ago knew how to start a fire, according to a 2018 Nature paper on which Sorensen was the lead author. Fire-starting is a key skill that different human groups could have passed along to each other—possibly even one that Neanderthals taught to some modern humans.
“These early human groups, they really got around,” Sorensen says. “These people just move around so much that it’s very difficult to tease out these relationships.”
How did humans really evolve?
Almost two million years ago, a band of brave explorers left their families behind in their warm, tropical home and sought refuge in northern lands. Armed with sharp stone tools and their wits, they followed the coast as far north as they could, then began to veer east, settling on the sunny, fertile shores of an inland sea that today we call the Mediterranean. Their children spread further north and east, and a million years later they had established settlements along the coasts of today's Europe, England, and China.
A few hundred thousand years passed, when suddenly a new wave of immigrants emerged from Africa - the children of all the people our first adventurers left behind. They swarmed off the continent, following the route of their brethren. But what happened next? Did the new immigrants eradicate their strange cousins and colonize their lands? Settle down with them and have families? Or were they not strangers at all, but just far-flung satellites in the same family, who had kept in distant touch via trade routes for a million years?
Most of us are familiar with the basic outlines of the human evolutionary story. Our distant ancestors were a group of ape-like creatures who started walking upright millions of years ago in Africa, eventually developing bigger brains and scattering throughout the world to become modern humans of today. Now, advances in genetics have given us a sharper understanding of what happened in between the "scattering" and the "buying the latest iPad" chapters of the tale. The question is, which version of the story do you believe? It's one of the biggest questions in human evolution today. Here's what you need to know about it.
Who are the heroes of our story?
Human evolution wasn't a simple linear progression from ape-like hominid, to the humans of today. Early humans moved through several stages of evolution over time, but they were also wanderers who moved through many spaces. As they spread out across the land from their origins in southern Africa, they separated into different bands but continued to evolve. Our story here is about what happened to us as we scattered across the globe, and there are four major players in this evolutionary drama.
About two million years ago there was an archaic human called Homo ergaster who lived in Africa. She used fairly sophisticated methods to create stone tools, and taught those methods to her children. At some point, probably about 1.8 million years ago, H. ergaster split into many different bands. Some wound up crossing out of Africa and into the Middle East, Asia and Europe. Others stayed behind.
This is where things begin to get interesting. (See map above.) The H. ergaster groups who headed out into Asia eventually developed their own culture and distinct skull structure. They were evolving in a very different environment from their cousins back in Africa, so their bodies changed and so did their toolsets. Most of what remains from this era is fragmentary at best - a few bits of human skeletons, and a lot of stone tools. So we can track how the tools change more easily than how our ancestors' bodies did. Based on a combination of these new tools and a few telltale skull shape differences, scientists have dubbed these people Homo erectus. Their culture and communities lasted for hundreds of thousands of years, and spread throughout China and down into Java.
At the same time, another group of H. ergaster was drifting into Europe, creating homes in what are now Italy, Spain, France, Germany, and England, among others. They evolved a thicker brow and more barrel-chested body. These are the early humans popularly called Neandertals. Anthroplogists call them Homo neanderthalensis.
Back in Africa, H. ergaster was busy too. She was establishing homebases all over the coasts of the continent, reaching from South Africa all the way up to Algeria and Morocco. And about 200 thousand years ago, H. ergaster's skeletal shape had become indistinguishable from those of modern humans. Homo sapiens had emerged. And now things get complicated.
What happened when H. ergaster's children met?
A few years ago, anthropologist John Relethford summed up the complicated debate over what happened next by offering a somewhat simplified way to understand the three dominant theories.
The "African replacement" theory, sometimes called the "recent African origins" theory, holds that H. sapiens charged out Africa and crushed H. neanderthalensis and H. erectus under her feet. Basically H. sapiens replaced her distant cousins. This theory is simple, and the "mitochondrial Eve" discoveries of biochemist Rebecca Cann and colleagues support it with genetic evidence that shows all humans on Earth can trace their genetic ancestry to a H. sapiens woman from Africa.
But if you step back for a second and look at this theory from a historical perspective it starts to seem more unlikely. First of all, it assumes that H. sapiens treated her brethren as enemies, or as some anthropologists seem to suggest, she saw them as animals rather than members of her family. The question is: How likely is it that a group of tired H. sapiens wanderers, coming upon a community of H. erectus with tools and recognizably human faces, would attack them or ignore them as "animals"? Most likely they would trade with the locals, and possibly spend a while hanging out with them as they rested on their long journey.
And that's the kind of thinking that got the multi-regional theory started. Popularized by anthropologist Milford Wolpoff (see one of his papers on it here [PDF]), this theory fits with the same evidence that supports the African replacement theory - it's just a very different interpretation of the evidence. Wolpoff suggested that H. sapiens didn't sweep H. erectus and H. neanderthalensis away, but instead never really lost track of them in the first place.
Wolpoff's idea hinges on the very sensible notion that H. ergaster didn't leave Africa, but instead forged a pathway that many other archaic humans followed - in both directions. Just as humans had trade routes that linked far-flung lands in recorded history, our earliest ancestors probably had something similar. There is plenty of evidence that humans left many outposts along the route from Africa to Asia and Europe. Who is to say H. sapiens wasn't always intermingling and interbreeding with H. erectus and H. neanderthalensis? If Wolpoff and his colleagues are right - and evolutionary biologist John Hawks has presented compelling genetic evidence for this [ PDF ] - then H. sapiens probably didn't arise in Africa and colonize the rest of the world. Instead, she arose at roughly the same time throughout the world through this extended network.
The multi-regional theory does not suggest that two or three separate human lineages evolved in parallel, by the way. That's a common misinterpretation. It just suggests that there weren't two distinct waves of immigration like that map above suggests. Instead, immigration (and evolution of H. sapiens) started 1.8 million years ago and never stopped.
There is a kind of middle-of-the-road theory, too, which many dub the assimilation theory. Vinayak Eswaran and colleagues outline a theory like this in a recent paper , where they argue that genetic evidence suggests that there were two distinct waves of immigration out of Africa - the archaic human one, and the H. sapiens one. But as H. sapiens moved out into the world, she assimilated the local H. erectus and H. neanderthalensis peoples.
So basically, in the assimilation theory model H. sapiens didn't destroy her kindred, nor was she deeply interrelated with them as in the multi-regional theory. She met them as strangers, but forged alliances and formed families with them. Gradually, though, H. sapiens became the dominant culture.
Why do we know so little about this?
Anthropologists agree on most basic facts about where people migrated and when. How can we have three such divergent theories? The simple answer is that the evidence is scarce: Some stages in human evolution only appear in one or two bones.
Paleoanthropology is the scientific study of human evolution. Paleoanthropology is a subfield of anthropology, the study of human culture, society, and biology. The field involves an understanding of the similarities and differences between humans and other species in their genes, body form, physiology, and behavior. Paleoanthropologists search for the roots of human physical traits and behavior. They seek to discover how evolution has shaped the potentials, tendencies, and limitations of all people. For many people, paleoanthropology is an exciting scientific field because it investigates the origin, over millions of years, of the universal and defining traits of our species. However, some people find the concept of human evolution troubling because it can seem not to fit with religious and other traditional beliefs about how people, other living things, and the world came to be. Nevertheless, many people have come to reconcile their beliefs with the scientific evidence.
Early human fossils and archeological remains offer the most important clues about this ancient past. These remains include bones, tools and any other evidence (such as footprints, evidence of hearths, or butchery marks on animal bones) left by earlier people. Usually, the remains were buried and preserved naturally. They are then found either on the surface (exposed by rain, rivers, and wind erosion) or by digging in the ground. By studying fossilized bones, scientists learn about the physical appearance of earlier humans and how it changed. Bone size, shape, and markings left by muscles tell us how those predecessors moved around, held tools, and how the size of their brains changed over a long time. Archeological evidence refers to the things earlier people made and the places where scientists find them. By studying this type of evidence, archeologists can understand how early humans made and used tools and lived in their environments.
Understanding the Evolution of Human Thought
How did they think? Were they self-aware? How did they interact with others? Did they have the capacity to be creative? Could they argue? Did they dream? Could they imagine? How did we get from there to modern times?
They say dead men tell no tales.
“It’s hard enough to tell what the cognitive abilities are of somebody who’s standing in front of you,” says Alison Brooks , an archaeologist at George Washington University. “So it’s really hard to tell for someone who’s been dead for half a million years or a quarter million years.”
Evolution is the product of a slow, ever-changing process precipitated by a host of environmental factors. So we can almost certainly agree that the way we imagine, problem-solve, think, and create must be vastly different today than it was in the times of our paleolithic relatives.
For centuries, our neanderthal cousins and homo sapiens remained two separate family lines shrouded in mystery — one based on limited technology (in the years before Darwin’s eponymous The Order of Species, scientists licked fossils to determine their origins) and archaic, wide-sweeping, sometimes pejorative judgments based on fossil findings and human remains. In other words, much of science then was based on assumptions and beliefs.
Only recently has new research indicated that we share a lot more in common with these Neanderthals than we imagined. And, it’s precisely this research that puts a flashpoint in the discussion of what it is that truly makes us human. That’s coupled with a lot of research that extends beyond the world of anthropology, including a host of research areas including evolutionary biology, philosophy, and neuroscience.
To understand the foundation of early man’s thinking, we need to start at one of the most confounding principles of human thought: the origins of human consciousness. That’s to say, when did we start being aware, creative and mindful?
Timeline of Human Evolution
The first of modern humans — the Homo Sapiens, arrived about 200,000 years ago. The genetic shift in the Homo Sapien brain is relatively recent in the pantheon of evolutionary history. But, there wasn’t a lightning bolt moment when humans emerged and started thinking consciously and rationally.
Here are a few clues that helped scientists piece together the riddle of how, when, and why human beings began to think differently, and how it impacted our evolution:
- 150,000 years: Shells, some with complex geometric shapes and iconography, shows that humans thought about items around them for decoration or ornamentation.
- 140,000 years: The first evidence of long-distance trade — ochre and bead ornaments are passed relay style , from group to group.
- 110,000 years: Beads comprised of sea snail shells showed that early humans had started to create things that were designed to be seen. Scientists speculate that these shell beads, some of which may have been brought from very far, were the first time humans thought symbolically. The beads may also have been used to differentiate and identify where groups belonged.
- 50,000 years: Scientists believe this period is when humans take a leap forward. More rapidly than ever before, people start to show hallmarks that differentiate from their primate relatives—humans start to bury their dead in ritualistic ceremonies, and hunting shifts to complex and well-imagined techniques, including traps.
- 30,000 years: The oldest cave art has been connected to this period, and murals in France have been connected to the Stone Age artists.
- 18,000 years: Advances in stone tools have been directly tied to a species of early humans referred to as “hobbit people” in Indonesia. Research linked tools to the Homo Floresiensis by dating layers of ash and calcite on fossil findings. This group, one of the last of early humans before Homo Sapiens, may have used tools between 50,000 and 190,00 years ago.
- 10,000 years: Agricultural villages sprout up, and people begin domesticating animals, including dogs.
- 5,500 years: Humans start to advance metallurgy — smelting copper and tin and incorporating them in stone implements.
- 5,000 years: Earliest signs of writing emerge .
According to Genevieve Von Petzinger , these clues have helped scientists identify and classify early humans’ modern thinking as it relates to the artifacts or processes they used:
“Since we are looking for evidence of mental changes that took place within the soft tissue of the brain, we can’t identify them directly, but luckily there are other ways to gauge how our ancestors’ minds may have been developing. To this end, researchers have compiled a list of practices and artifact types that strongly hint that symbolic thought processes are at work. Evidence includes the selection and preparation of particular shades of ochre, burials with grave goods, personal ornamentation, and the creation of geometric or iconographic representations. If most or all of these elements are present, the chances are good that you’re dealing with fully modern humans.”
When archaeologists discovered an abalone shell in a 2008 cave excavation in South Africa, it contained traces of a rust-colored paint. Early humans used paint, but this discovery showed something much more exciting. It revealed that more than 100,000 years ago, creators of the piece had to procure the ingredients and make the paint. The shell was a merely a vessel for storage. The discovery provided a depth of knowledge about human thinking far beyond the simple fact that they painted. It proved they were capable of advanced thinking and planning. In fact, it may be one of the earliest moments that showcase innovation.
Despite the difficulty in scientists coming to an agreement about what makes human thought special, these discoveries are the foundation for the evolution of modern cognition.
The remarkable fact is that all of us living today are the end product of an incredible story of success against all odds: Each of us carries DNA that stretches back in an unbroken line to the beginnings of humanity and beyond. — Genevieve Von Petzinger
Writing Changed Everything
The one thing that separates us from other mammals is our ability to construct and use language.
Much of our understanding of early man and evolution is buried in the earth, scrawled on cave walls, and carved into rock tools. Yet, this riddle remains the source of intense, drawn-out scientific debates. Some scientists believe that early humans communicated verbally as early as 50,000 years ago and others think earlier human ancestors spoke two million years ago. In the absence of audio recorders and iPhones, the language of earlier versions of mankind became one of the bigger mysteries in the evolutionary tale.
Some of the earliest known writing found in what is present-day Iran, a still undecipherable language printed on clay tablets, stretches back 5,000 years —a recent blip on the geologic radar. Everything before that can only be interpreted in the context of the absence of language and writing.
What makes human thinking unique?
Memory is one of the things that distinguishes creatures in the animal kingdom. Without memory, it would be difficult for species to evolve.
There are three components to memory:
Procedural – recalling connections to response and stimuli
Semantic – remembering things that are not inherently present, and providing a creature to construct a visual, mental model of something.
Episodic – Recalling individual events in the order which they happened.
Humans are one of a few creatures on the planet to have an episodic memory, and it’s likely the reason why we as a species have been able to advance, learn from the past, and evolve at a rapid rate. While animals clearly have memory, it appears to be semantic—the ability to understand bits and pieces of the “who,” “what,” and “where.”
But, what about our ability to move through memories like a movie—to go back and forth in time and call up events, people, and places?
This form of memory—mental time travel—may be the just one critical component to human intelligence that is unsurpassed in the wild. The concept of our mind’s ability to move through time was hypothesized by Dr. Endel Tulving , who called it chronesthesia, an ability by humans, acquired through evolution, to be cognizant of the past as well as the future. For now, it seems to be unique to humans, but there has been recent research indicating that some birds share this unique mental trait.
Dr. Tulving noted that this form of memory is necessary for evolution. While you can call up equations or facts with semantic thinking, or acquire experiences and memories with “episodic” thought, there’s no way to survive as a species without the ability to remember specific points from our past or to predict what might happen in the future based on experience.
According to Tulving , recalling and replaying events in the past has helped us to evolve by allowing us to update critical information while continuing to deal with rapid changes and chaos in the world around us.
Michael Tomasello , head of a research group at the Max Planck Institute for Evolutionary Anthropology in Leipzig, deals with analyzing how human thinking compares to that of our primate relatives. His findings have led to advances in our understanding of human evolution.
His lab proved that of the three major components of consciousness (collective, individual, and joint), only individual intentionality—the ability to imagine an outcome as a reward, such as climbing a tree to grab food—is shared with apes.
Putting the pieces together
After thousands of years, we all share similar needs to eat and to procreate, but only modern humans have the innate ability to network.
“We have a fundamental urge to link our minds together,” notes Thomas Suddendorf, an evolutionary psychologist at the University of Queensland in Australia.
The ability to network in turn creates a unique competitive advantage that places humans at the top of the chain. “This allows us to take advantage of the strengths of others,” he says.
By doing so, we’ve been able to move from hunter-gatherers to a species that is predicated on its accumulation of knowledge and its ability to collaborate and build joint experiences, creations, and imaginations. Plenty of animals work together in packs, and birds and bees have highly sophisticated minds. Bees have highly organized hive hierarchy, but there’s no proof they are calling on their personal memory.
We’re the only species that is simultaneously on a quest to understand why we have arrived where we’re at today, how we got here, and yet, at the same time, be in the position to create an outcome of our choosing. It’s why we are able to envision a world that goes beyond our wildest imagination — one with driverless cars, flying machines, robots, and space travel.
There is evidence that we are not finished evolving. Several predictions for our future are terrifying, but some point to technology and culture-shaping the way our grandchildren and great-grandchildren will look. With medical advances, and more people living into adulthood, Darwin’s theory of the survival of the fittest flies out the window. Instead, humans may select mates based on intellectual abilities for greater earning power, and technological advances may create humans who are better nourished, and therefore taller than their ancestors. One thing’s for sure, with modern advances in technology, the next iteration of people will have no shortage of places to learn about life and how we got here.
How our sense of smell evolved, including in early humans
A group of scientists led by Dr Kara Hoover of the University of Alaska Fairbanks and including Professor Matthew Cobb of The University of Manchester, has studied how our sense of smell has evolved, and has even reconstructed how a long-extinct human relative would have been able to smell.
The sense of smell plays a decisive role in human societies, as it is linked to our taste for food, as well as our identification of pleasant and unpleasant substances.
We have about 4 million smell cells in our noses, divided into about 400 different types. There is tremendous genetic variability within and between populations for our ability to detect odours. Each smell cell carries just one type of receptor or 'lock' on it -- the smell floats through the air, fits into the 'lock' and then activates the cell.
Most receptors can detect more than one smell, but one, called OR7D4, enables us to detect a very specific smell called androstenone, which is produced by pigs and is found in boar meat. People with different DNA sequences in the gene producing the OR7D4 receptor respond differently to this smell -- some people find it foul, some sweet, and others cannot smell it at all. People's responses to androstenone can be predicted by their OR7D4 DNA sequence, and vice versa.
Professor Cobb from The University of Manchester's Faculty of Life Sciences and the other researchers studied the DNA that codes for OR7D4 from over 2,200 people from 43 populations around the world, many of them from indigenous groups. They found that different populations tend to have different gene sequences and therefore differ in their ability to smell this compound.
For example, they found that populations from Africa -- where humans come from -- tend to be able to smell it, while those from the northern hemisphere tend not to. This shows that when humans first evolved in Africa, they would have been able to detect this odour.
Statistical analysis of the frequencies of the different forms of the OR7D4 gene from around the world suggested that the different forms of this gene might have been subject to natural selection.
One possible explanation of this selection is that the inability to smell androstenone was involved in the domestication of pigs by our ancestors -- andostroneone makes pork from uncastrated boars taste unpleasant to people who can smell it. Pigs were initially domesticated in Asia, where genes leading to a reduced sensitivity to androstenone have a high frequency.
The group also studied the OR7D4 gene in the ancient DNA from two extinct human populations, Neanderthals and the Denisovans, whose remains were found at the same site in Siberia, but who lived tens of thousands of years apart.
The group found that Neanderthal OR7D4 DNA was like our own -- they would have been able to smell androstenone. The Denisovans are a mysterious group of our extinct relatives -- we do not know what they looked like, and they are known from only one tooth and a finger bone, from different individuals.
Their DNA showed a unique mutation, not seen in humans or Neanderthals, that changed the structure of the OR7D4 receptor.
Team-member Hiroaki Matsunami at Duke University in the USA reconstructed the Denisovan OR7D4 and studied how this tiny part of a long-extinct nose responded to androstenone. It turned out that despite the mutation, the Denisovan nose functioned like our own. Both of our close relatives, like our early human ancestors, would have been able to detect this strange smell.
This research shows how global studies of our genes can give insight into how our taste for different foods may have been influenced by variation in our ability to smell, and, excitingly, show that it is possible to see back into deep evolutionary time and reconstruct the sensory world of our distant ancestors.
The research was carried out by scientists from the University of Alaska Fairbanks, State University of New York, Duke University and The University of Manchester, and is published in the journal Chemical Senses.
The untold story of evolution
H uman evolution must be the greatest story never told. It begins in an unknowable past and continues mysteriously for the next five or six million years. Is it a thriller, an epic or a comedy of errors? There is no dust jacket, no title page, no dedication, no acknowledgements. Almost all the text is missing, apart from the occasional phrase, sentence or paragraph, seemingly torn at random from the great six-million-year narrative. If the story of humanity is a single volume, then only the last page survives.
Every so often, scholars find yet another fossilised scrap of the missing narrative, a new character enters, and the plot takes a new twist. Some things are clear: the story began in Africa, between 5m and 7m years ago, with the last common ancestor of two kinds of chimpanzee and of Homo sapiens sapiens. Charles Darwin calculated as much when he began telling the story in The Descent of Man (1871). "We thus learn that man is descended from a hairy, tailed quadruped, probably arboreal in its habits, and an inhabitant of the Old World," he wrote.
Anthropologists agree on the human-ape connection. The consent is there in the titles of books published in the past 40 years: The Aquatic Ape, The Naked Ape, The Third Chimpanzee, The Talking Ape, Our Inner Ape, The Thinking Ape, The Monkey in the Mirror, The Hunting Apes, The Ape that Spoke and The Artificial Ape.
These books are all attempts to work backwards, from what we are now to what we might have been. The fact that zoologists, anthropologists and palæontologists can write so many books with the word "ape" in the title tells us two things. One is that the evidence is so sparse that people are free to frame a favourite hypothesis about what it was that made humans different. The other is that the human-chimpanzee connection is so clear that there is nowhere else to begin.
First, the family likeness: chimpanzees struggle for status, vocalise, communicate, play politics, use subterfuge, show aggression, reject outsiders, groom and support each other, betray each other and resort to violence or sexual bribery to get their way. Chimpanzees display awareness of self, ability to reason, and a grasp of numbers. Chimpanzees are opportunistic omnivores that also make and use tools for gain, and groups of chimpanzees in the wild have separate traditions, practices and ways of doing things that they pass down the generations. That is, chimpanzees have culture. Chimpanzees and humans have a genetic kinship so close that they share almost 99% of their DNA.
The Victorians called them "man-like apes". Twentieth-century scientists and observers started referring to humans as naked apes. Early in the 21st century, some taxonomists and conservationists began a campaign to change the chimpanzee genus from Pan to Homo, so close are the parallels between the species.
But the African chimpanzee is an endangered species, down to perhaps 150,000, while the human population is about to tip seven billion. The implication is that, long ago, the earliest human ancestors also lived in small social groups, and co-operated and competed for the resources of the woodland and the savannah. Why did humans become so different: bipedal, upright, hairless, with limited strength, feeble jaws, bad backs, embarrassingly large heads and brains with a cerebral cortex four times the size of a chimp's?
For decades, the conventional evolutionary lineage was a simple one: shambling simian stands upright, evolves into bipedal hairy brute, then slouching hairy brute with hand axe and finally into hairless human with BlackBerry. This is the ladder theory of human evolution. It was kicked away long ago. Discoveries in Africa – a femur here, a fragment of skull there, a pelvis, now and again a partial skeleton, a set of footprints fossilised in ancient volcanic mud – reveal a picture more of confusion than direction: a flowering of creatures more or less apelike or manlike, some of them possibly direct ancestors, some of them probably cousins along a parallel lineage, all of them trying to make a subsistence living in a very different Africa, millions of years ago. The fossils turn up in South Africa, East Africa, Ethiopia and even the Sahel. They have generic names such as Sahelanthropus, Ardipithecus, Orrorin, Australopithecus, Paranthropus, and Kenyanthropus, and their remains were unearthed from the dust, stone and mud sediments laid down 3m, 4m and 5m years ago.
Two million years ago, creatures that bear the generic name Homo begin to appear in the fossil record: Homo habilis, Homo ergaster, Homo erectus, and with them appear worked stone tools, hand axes, things for chipping and cutting. Hardly any of these early human relics is complete. Palaeoanthropologists were once fond of saying that the entire human fossil record could be laid out on one table, or packed in a matching set of Gucci luggage, but this is no longer true. What is true is that even 2m years ago, the human lineage begins to look like a bush, with species sprouting in all directions.
And then the story starts to get really complicated. At some point, early humans get up and start moving. They spread. They pack their hand axes, leave Africa and start to colonise the Middle East, Europe, and South Asia. And there is more than one migration out of Africa: first Homo erectus or something even more primitive, and then, much later, Homo sapiens. And they continue to differentiate into new species. At one point in human history, around 40,000 years ago, modern humans must have shared the planet with at least four other human cousins: Homo erectus, the Neanderthals, a strange, small-brained human found only on the island of Flores in Indonesia, affectionately known as the Hobbit and most recent of all, species X: a separate human genetic lineage identified in 2010 only by DNA extracted from a finger bone found in a Siberian cave.
What gave early humans their get-up-and-go? Why did humans develop large brains and long legs? Should the first mobile humans be classed as asylum seekers, driven from their native land by climate change? Or were they economic migrants, on the lookout for better opportunities in wide-open Europe and Asia?
Brains are what biologists call expensive items: the human brain at rest consumes 20% of the daily calorific intake. In other words, brains have to be fed. So a large, greedy brain becomes valuable only if it helps to deliver even more food and greater security. So was the larger brain a genetic mutation that increasingly delivered a selective advantage in the struggle for survival? And how did humans get from thinking about food-gathering strategies to thinking about taxonomy, tax-avoidance and Twitter?
The big brain story may have begun in the trees. Arboreal primates that search over wide areas for food in the canopy seem to know what is good for them: they often ignore easy supplies and go looking for special foods. They seem to have a notion of a balanced diet – protein-rich leaves and high-calorie fruits and not too much fibre – and they have been watched deliberately selecting plants with medicinal properties. All this requires a working memory, a mental map of where to go and what to look for. According to at least one study, the primates that hunt high and low for the quality fare tend to have larger brains than those that do not.
Then the human story begins at some point with climate change: in a cooler and more arid continent, once-arboreal creatures had to start exploiting the woodland and savannah. It would clearly be an advantage to stand up and walk on two feet, to see further, to have a hand free to carry an infant. Pair bonding – love and marriage to non-biologists – is already an evolutionary feature, and a bipedal male could go further to find food for his family, and carry it back.
"Darwin argued that bipedalism freed the hands," says Chris Stringer, head of human origins at the Natural History Museum. "He was arguing that 150 years ago and it is still there. But there is another view worth considering: it could have begun in the trees. Orangutans, for instance, walk bipedally." To get to the tastiest forage, orangutans walk along branches, holding on to yet higher branches. So there could have been a long period when early members of the not-yet-human family walked on the ground, and lived in trees.
And by this time, brain size had begun to increase. There are new challenges, new opportunities, new foods to try and new difficulties to overcome. In the past three decades, researchers have floated a number of ideas about how the human story might have developed. Did hominids start to develop bigger brains because they lost most of their body hair? A hairless human with a talent for exuding sweat would be at less risk of overheating longer legs would enhance the surface-to-volume ratio and keep the brain cool and as a bonus, ticks, lice and other parasites would have nowhere to hide.
Or did hominids become free to develop bigger brains because their jaw muscles began to shrink, allowing the cranium to expand? Did early humans start to develop even bigger brains because they became increasingly efficient endurance runners that could get to a carcass before the hyenas and vultures, and strip away a nourishing meal of meat, fat and marrow? Did humans begin to stand upright by taking to the water – and to nourish bigger brains with high-protein deliveries of fish and shellfish?
Did humans discover the use of fire millions of years ago, long before the colonisation of Europe? Cooking would make plants both more nourishing and easier to digest it would dispose of infections and pathogens in meat, and it would deliver greater supplies of energy per mouthful. Teeth, jaws and digestive tracts could shrink, and so brains could get bigger. Did humans grow bigger brains because the extra neural circuitry was needed to make sense of the demands of social and co-operative life?
"I think a lot of our brain is actually mapping relationships, and mind-reading our friends and enemies: what are they doing? You need a lot of processing power to do that well," says Stringer. "If you are starting to hunt animals, you have to out-think them, and that is driving the growth of more processing power and bigger memory. So I think the social brain and meat-eating was the key to that."
Somehow, out of this million-year-mix of food, fear and hunter-gatherer companionship in Africa, complex language emerged. The human who could frame the sentence "You wait behind that rock at the end of the ravine and I'll drive the deer towards you" has demonstrated awareness of cause and effect, of geography, of zoology, of strategy, of co-operation for future mutual advantage. Somewhere in such a sentence there is also the germ of the first play for two actors, the first computer game and the first adventure story.
But there are no neat stories to be told of the first departure from the African homeland. Once again, the evidence is fragmentary, sometimes teasingly ambiguous, and capriciously rare. But there is enough to confirm the presence of early human species in Georgia, in Spain, Portugal, Germany and Britain as early as 800,000 years ago, and also in the Middle East and South Asia. The first migrants could have been pushed out of the country by climate change, or competition for resources, or the desire for somewhere new. They could possibly have made a direct crossing by water from the Horn of Africa to what is now Yemen, or they could have travelled up the Nile Valley and across what is now Gaza into Europe and the Middle East. This fabulous odyssey may not have been intended, it may have just happened. Hunter-gatherers follow game, and when the game disappears, they move on. All these first migrants needed to do was to hug the coast: first up the western shore of the Red Sea, and then down the coast of Arabia.
"They just extended in that ribbon of the coast, out of Africa, around Arabia, around the southern Asian coast: at low sea level, they could have got all the way to Java just on the coast. Then they just need to invent boats along the way and they can get to Australia," says Stringer. "One mile a year and you have gone all the way to Java in 10,000 years."
And in the course of this great adventure, the migrants change. New species appear, and with them, new behaviour. The Neanderthals become the first to formally bury their dead.
And long afterwards, modern humans turn up. Once again, the story begins somewhere in Africa, nobody knows for sure where, and once again, at least 60,000 years ago – and maybe, on recent enigmatic evidence of stone tools in Arabia, as long as 125,000 years ago – a new human species begins to leave Africa and spread around the planet, across all of Europe and Asia, and then finally across the arid freezing plains that will in time become the Bering Straits, to Alaska and then the whole of the Americas. Modern humans are still hunter-gatherers, but around 30,000 years ago there is evidence of sophisticated technologies based on stone and bone and shell. They use needles, decorate with ochre, create works of astonishing art, put on ornaments, and exhibit a sense of religion – the evidence for all these things lies alongside the human fossils. In Europe, these newcomers live alongside the Neanderthals, hunt the same animals, gather the same seeds and fruits. There is recent evidence that – somewhere in the European chapter of this story – modern humans and Neanderthals must have interbred, but in all other respects, the Neanderthals seem to be a different species.
Long before the end of the last ice age, the Neanderthals and all the other human species that have travelled the same road vanish altogether, leaving the newcomers alone of their kind, and in undisputed possession of the planet.
How Did Humans Evolve? - HISTORY
The Biology of Skin Color: Black and White
The evolution of race was as simple as the politics of race is complex
By Gina Kirchweger
Ten years ago, while at the university of Western Australia, anthropologist Nina Jablonski was asked to give a lecture on human skin. As an expert in primate evolution, she decided to discuss the evolution of skin color, but when she went through the literature on the subject she was dismayed. Some theories advanced before the 1970s tended to be racist, and others were less than convincing. White skin, for example, was reported to be more resistant to cold weather, although groups like the Inuit are both dark and particularly resistant to cold. After the 1970s, when researchers were presumably more aware of the controversy such studies could kick up, there was very little work at all. "It's one of these things everybody notices," Jablonski says, "but nobody wants to talk about."
No longer. Jablonski and her husband, George Chaplin, a geographic information systems specialist, have formulated the first comprehensive theory of skin color. Their findings, published in a recent issue of the Journal of Human Evolution, show a strong, somewhat predictable correlation between skin color and the strength of sunlight across the globe. But they also show a deeper, more surprising process at work: Skin color, they say, is largely a matter of vitamins.
Jablonski, now chairman of the anthropology department at the California Academy of Sciences, begins by assuming that our earliest ancestors had fair skin just like chimpanzees, our closest biological relatives. Between 4.5 million and 2 million years ago, early humans moved from the rain forest and onto the East African savanna. Once on the savanna, they not only had to cope with more exposure to the sun, but they also had to work harder to gather food. Mammalian brains are particularly vulnerable to overheating: A change of only five or six degrees can cause a heatstroke. So our ancestors had to develop a better cooling system.
The answer was sweat, which dissipates heat through evaporation. Early humans probably had few sweat glands, like chimpanzees, and those were mainly located on the palms of their hands and the bottoms of their feet. Occasionally, however, individuals were born with more glands than usual. The more they could sweat, the longer they could forage before the heat forced them back into the shade. The more they could forage, the better their chances of having healthy offspring and of passing on their sweat glands to future generations.
A million years of natural selection later, each human has about 2 million sweat glands spread across his or her body. Human skin, being less hairy than chimpanzee skin, "dries much quicker," says Adrienne Zihlman, an anthropologist at the University of California at Santa Cruz. "Just think how after a bath it takes much longer for wet hair to dry."
Hairless skin, however, is particularly vulnerable to damage from sunlight. Scientists long assumed that humans evolved melanin, the main determinant of skin color, to absorb or disperse ultraviolet light. But what is it about ultraviolet light that melanin protects against? Some researchers pointed to the threat of skin cancer. But cancer usually develops late in life, after a person has already reproduced. Others suggested that sunburned nipples would have hampered breast-feeding. But a slight tan is enough to protect mothers against that problem.
During her preparation for the lecture in Australia, Jablonski found a 1978 study that examined the effects of ultraviolet light on folate, a member of the vitamin B complex. An hour of intense sunlight, the study showed, is enough to cut folate levels in half if your skin is light. Jablonski made the next, crucial connection only a few weeks later. At a seminar on embryonic development, she heard that low folate levels are correlated with neural-tube defects such as spina bifida and anencephaly, in which infants are born without a full brain or spinal cord.
Jablonski and Chaplin predicted the skin colors of indigenous people across the globe based on how much ultraviolet light different areas receive. Graphic by Matt Zang, adapted from the data of N. Jablonski and G. Chaplin
Jablonski later came across three documented cases in which children's neural-tube defects were linked to their mothers' visits to tanning studios during early pregnancy. Moreover, she found that folate is crucial to sperm development -- so much so that a folate inhibitor was developed as a male contraceptive. ("It never got anywhere," Jablonski says. "It was so effective that it knocked out all folate in the body.") She now had some intriguing evidence that folate might be the driving force behind the evolution of darker skin. But why do some people have light skin?
As far back as the 1960s, the biochemist W. Farnsworth Loomis had suggested that skin color is determined by the body's need for vitamin D. The vitamin helps the body absorb calcium and deposit it in bones, an essential function, particularly in fast-growing embryos. (The need for vitamin D during pregnancy may explain why women around the globe tend to have lighter skin than men.) Unlike folate, vitamin D depends on ultraviolet light for its production in the body. Loomis believed that people who live in the north, where daylight is weakest, evolved fair skin to help absorb more ultraviolet light and that people in the tropics evolved dark skin to block the light, keeping the body from overdosing on vitamin D, which can be toxic at high concentrations.
By the time Jablonski did her research, Loomis's hypothesis had been partially disproved. "You can never overdose on natural amounts of vitamin D," Jablonski says. "There are only rare cases where people take too many cod-liver supplements." But Loomis's insight about fair skin held up, and it made a perfect complement for Jablonski's insight about folate and dark skin. The next step was to find some hard data correlating skin color to light levels.
Until the 1980s, researchers could only estimate how much ultraviolet radiation reaches Earth's surface. But in 1978, NASA launched the Total Ozone Mapping Spectrometer. Three years ago, Jablonski and Chaplin took the spectrometer's global ultraviolet measurements and compared them with published data on skin color in indigenous populations from more than 50 countries. To their delight, there was an unmistakable correlation: The weaker the ultraviolet light, the fairer the skin. Jablonski went on to show that people living above 50 degrees latitude have the highest risk of vitamin D deficiency. "This was one of the last barriers in the history of human settlement," Jablonski says. "Only after humans learned fishing, and therefore had access to food rich in vitamin D, could they settle these regions."
Humans have spent most of their history moving around. To do that, they've had to adapt their tools, clothes, housing, and eating habits to each new climate and landscape. But Jablonski's work indicates that our adaptations go much further. People in the tropics have developed dark skin to block out the sun and protect their body's folate reserves. People far from the equator have developed fair skin to drink in the sun and produce adequate amounts of vitamin D during the long winter months.
Jablonski hopes that her research will alert people to the importance of vitamin D and folate in their diet. It's already known, for example, that dark-skinned people who move to cloudy climes can develop conditions such as rickets from vitamin D deficiencies. More important, Jablonski hopes her work will begin to change the way people think about skin color. "We can take a topic that has caused so much disagreement, so much suffering, and so much misunderstanding," she says, "and completely disarm it."
(From Discover, Vol. 22, No. 2, February, 2001. Gina Kirchweger © 2001. Reprinted with permission of Discover. )
Although related to the more general problem of the origin of language, the evolution of distinctively human speech capacities has become a distinct and in many ways separate area of scientific research.      The topic is a separate one because language is not necessarily spoken: it can equally be written or signed. Speech is in this sense optional, although it is the default modality for language.
Uncontroversially, monkeys, apes and humans, like many other animals, have evolved specialised mechanisms for producing sound for purposes of social communication.  On the other hand, no monkey or ape uses its tongue for such purposes.   Our species' unprecedented use of the tongue, lips and other moveable parts seems to place speech in a quite separate category, making its evolutionary emergence an intriguing theoretical challenge in the eyes of many scholars. 
Nevertheless, recent insights in human evolution - more specifically our Pleistocene littoral evolution  - help understand how human speech evolved: different biological preadaptations to spoken language find their origin in our waterside past, such as our larger brain (thanks to DHA and other brain-specific nutrients in seafoods), voluntary breathing (breath-hold diving for shellfish etc.) and suction feeding of soft-slippery seafoods. Suction feeding explains why humans, as opposed to other hominoids, evolved hyoidal descent (tongue-bone descended in the throat), closed tooth-rows (with incisiform canine teeth) and a globular tongue perfectly fitting in our vaulted and smooth palate (without transverse ridges as in apes): all this allowed the pronunciation of consonants. Other, probably older, preadaptations to human speech are territorial songs and gibbon-like duetting and vocal learning. Vocal learning, the ability to imitate sounds - as in many birds and bats and a number of Cetacea and Pinnipedia - is arguably required for locating or finding back (amid the foliage or in the sea) the offspring or parents. Indeed, independent lines of evidence (comparative, fossil, archeological, paleo-environmental, isotopic, nutritional, and physiological) show that early-Pleistocene "archaic" Homo spread intercontinentally along the Indian Ocean shores (they even reached overseas islands such as Flores) where they regularly dived for littoral foods such as shell- and crayfish  which are extremely rich in brain-specific nutrients, explaining Homo's brain enlargement.  Shallow-diving for seafoods requires voluntary airway control, a prerequisite for spoken language. Seafood such as shellfish generally does not require biting and chewing, but stone tool use and suction feeding. This finer control of the oral apparatus was arguably another biological preadaptation to human speech, especially for the production of consonants. 
The term modality means the chosen representational format for encoding and transmitting information. A striking feature of language is that it is modality-independent. Should an impaired child be prevented from hearing or producing sound, its innate capacity to master a language may equally find expression in signing. Sign languages of the deaf are independently invented and have all the major properties of spoken language except for the modality of transmission.     From this it appears that the language centres of the human brain must have evolved to function optimally irrespective of the selected modality.
"The detachment from modality-specific inputs may represent a substantial change in neural organization, one that affects not only imitation but also communication only humans can lose one modality (e.g. hearing) and make up for this deficit by communicating with complete competence in a different modality (i.e. signing)."
This feature is extraordinary. Animal communication systems routinely combine visible with audible properties and effects, but no one is modality-independent. No vocally impaired whale, dolphin or songbird, for example, could express its song repertoire equally in visual display. Indeed, in the case of animal communication, message and modality are not capable of being disentangled. Whatever message is being conveyed stems from the intrinsic properties of the signal.
Modality independence should not be confused with the ordinary phenomenon of multimodality. Monkeys and apes rely on a repertoire of species-specific "gesture-calls" — emotionally expressive vocalisations inseparable from the visual displays which accompany them.   Humans also have species-specific gesture-calls — laughs, cries, sobs and so forth — together with involuntary gestures accompanying speech.    Many animal displays are polymodal in that each appears designed to exploit multiple channels simultaneously.
The human linguistic property of "modality independence" is conceptually distinct from this. It allows the speaker to encode the informational content of a message in a single channel while switching between channels as necessary. Modern city-dwellers switch effortlessly between the spoken word and writing in its various forms — handwriting, typing, e-mail and so forth. Whichever modality is chosen, it can reliably transmit the full message content without external assistance of any kind. When talking on the telephone, for example, any accompanying facial or manual gestures, however natural to the speaker, are not strictly necessary. When typing or manually signing, conversely, there's no need to add sounds. In many Australian Aboriginal cultures, a section of the population — perhaps women observing a ritual taboo — traditionally restrict themselves for extended periods to a silent (manually signed) version of their language.  Then, when released from the taboo, these same individuals resume narrating stories by the fireside or in the dark, switching to pure sound without sacrifice of informational content.
Speaking is the default modality for language in all cultures. Humans' first recourse is to encode our thoughts in sound — a method which depends on sophisticated capacities for controlling the lips, tongue and other components of the vocal apparatus.
The speech organs, everyone agrees, evolved in the first instance not for speech but for more basic bodily functions such as feeding and breathing. Nonhuman primates have broadly similar organs, but with different neural controls.  Apes use their highly flexible, maneuverable tongues for eating but not for vocalizing. When an ape is not eating, fine motor control over its tongue is deactivated.   Either it is performing gymnastics with its tongue or it is vocalising it cannot perform both activities simultaneously. Since this applies to mammals in general, Homo sapiens is exceptional in harnessing mechanisms designed for respiration and ingestion to the radically different requirements of articulate speech. 
The word "language" derives from the Latin lingua, "tongue". Phoneticians agree that the tongue is the most important speech articulator, followed by the lips. A natural language can be viewed as a particular way of using the tongue to express thought.
The human tongue has an unusual shape. In most mammals, it is a long, flat structure contained largely within the mouth. It is attached at the rear to the hyoid bone, situated below the oral level in the pharynx. In humans, the tongue has an almost circular sagittal (midline) contour, much of it lying vertically down an extended pharynx, where it is attached to a hyoid bone in a lowered position. Partly as a result of this, the horizontal (inside-the-mouth) and vertical (down-the-throat) tubes forming the supralaryngeal vocal tract (SVT) are almost equal in length (whereas in other species, the vertical section is shorter). As we move our jaws up and down, the tongue can vary the cross-sectional area of each tube independently by about 10:1, altering formant frequencies accordingly. That the tubes are joined at a right angle permits pronunciation of the vowels [i], [u] and [a], which nonhuman primates cannot do.  Even when not performed particularly accurately, in humans the articulatory gymnastics needed to distinguish these vowels yield consistent, distinctive acoustic results, illustrating the quantal nature of human speech sounds.  It may not be coincidental that [i], [u] and [a] are the most common vowels in the world's languages.  Human tongues are a lot shorter and thinner than other mammals and are composed of a large number of muscles, which helps shape a variety of sounds within the oral cavity. The diversity of sound production is also increased with the human’s ability to open and close the airway, allowing varying amounts of air to exit through the nose. The fine motor movements associated with the tongue and the airway, make humans more capable of producing a wide range of intricate shapes in order to produce sounds at different rates and intensities. 
In humans, the lips are important for the production of stops and fricatives, in addition to vowels. Nothing, however, suggests that the lips evolved for those reasons. During primate evolution, a shift from nocturnal to diurnal activity in tarsiers, monkeys and apes (the haplorhines) brought with it an increased reliance on vision at the expense of olfaction. As a result, the snout became reduced and the rhinarium or "wet nose" was lost. The muscles of the face and lips consequently became less constrained, enabling their co-option to serve purposes of facial expression. The lips also became thicker, and the oral cavity hidden behind became smaller.  "Hence", according to one major authority, "the evolution of mobile, muscular lips, so important to human speech, was the exaptive result of the evolution of diurnality and visual communication in the common ancestor of haplorhines".  It is unclear whether our lips have undergone a more recent adaptation to the specific requirements of speech.
Respiratory control Edit
Compared with nonhuman primates, humans have significantly enhanced control of breathing, enabling exhalations to be extended and inhalations shortened as we speak. While we are speaking, intercostal and interior abdominal muscles are recruited to expand the thorax and draw air into the lungs, and subsequently to control the release of air as the lungs deflate. The muscles concerned are markedly more innervated in humans than in nonhuman primates.  Evidence from fossil hominins suggests that the necessary enlargement of the vertebral canal, and therefore spinal cord dimensions, may not have occurred in Australopithecus or Homo erectus but was present in the Neanderthals and early modern humans.  
The larynx or voice box is an organ in the neck housing the vocal folds, which are responsible for phonation. In humans, the larynx is descended, it is positioned lower than in other primates.This is because the evolution of humans to an upright position shifted the head directly above the spinal cord, forcing everything else downward. The repositioning of the larynx resulted in a longer cavity called the pharynx, which is responsible for increasing the range and clarity of the sound being produced. Other primates have almost no pharynx therefore, their vocal power is significantly lower.  Our species is not unique in this respect: goats, dogs, pigs and tamarins lower the larynx temporarily, to emit loud calls.  Several deer species have a permanently lowered larynx, which may be lowered still further by males during their roaring displays.  Lions, jaguars, cheetahs and domestic cats also do this.  However, laryngeal descent in nonhumans (according to Philip Lieberman) is not accompanied by descent of the hyoid hence the tongue remains horizontal in the oral cavity, preventing it from acting as a pharyngeal articulator. 
Despite all this, scholars remain divided as to how "special" the human vocal tract really is. It has been shown that the larynx does descend to some extent during development in chimpanzees, followed by hyoidal descent.  As against this, Philip Lieberman points out that only humans have evolved permanent and substantial laryngeal descent in association with hyoidal descent, resulting in a curved tongue and two-tube vocal tract with 1:1 proportions. Uniquely in the human case, simple contact between the epiglottis and velum is no longer possible, disrupting the normal mammalian separation of the respiratory and digestive tracts during swallowing. Since this entails substantial costs — increasing the risk of choking while swallowing food — we are forced to ask what benefits might have outweighed those costs. The obvious benefit — so it is claimed — must have been speech. But this idea has been vigorously contested. One objection is that humans are in fact not seriously at risk of choking on food: medical statistics indicate that accidents of this kind are extremely rare.  Another objection is that in the view of most scholars, speech as we know it emerged relatively late in human evolution, roughly contemporaneously with the emergence of Homo sapiens.  A development as complex as the reconfiguration of the human vocal tract would have required much more time, implying an early date of origin. This discrepancy in timescales undermines the idea that human vocal flexibility was initially driven by selection pressures for speech.
At least one orangutan has demonstrated the ability to control the voice box. 
The size exaggeration hypothesis Edit
To lower the larynx is to increase the length of the vocal tract, in turn lowering formant frequencies so that the voice sounds "deeper" — giving an impression of greater size. John Ohala argues that the function of the lowered larynx in humans, especially males, is probably to enhance threat displays rather than speech itself.  Ohala points out that if the lowered larynx were an adaptation for speech, we would expect adult human males to be better adapted in this respect than adult females, whose larynx is considerably less low. In fact, females invariably outperform males in verbal tests, falsifying this whole line of reasoning. W. Tecumseh Fitch likewise argues that this was the original selective advantage of laryngeal lowering in our species. Although (according to Fitch) the initial lowering of the larynx in humans had nothing to do with speech, the increased range of possible formant patterns was subsequently co-opted for speech. Size exaggeration remains the sole function of the extreme laryngeal descent observed in male deer. Consistent with the size exaggeration hypothesis, a second descent of the larynx occurs at puberty in humans, although only in males. In response to the objection that the larynx is descended in human females, Fitch suggests that mothers vocalizing to protect their infants would also have benefited from this ability. 
Neanderthal Speech Edit
Most specialists credit the Neanderthals with speech abilities not radically different from those of modern Homo sapiens. An indirect line of argument is that their tool-making and hunting tactics would have been difficult to learn or execute without some kind of speech.  A recent extraction of DNA from Neanderthal bones indicates that Neanderthals had the same version of the FOXP2 gene as modern humans. This gene, once mistakenly described as the "grammar gene", plays a role in controlling the orofacial movements which (in modern humans) are involved in speech. 
During the 1970s, it was widely believed that the Neanderthals lacked modern speech capacities.  It was claimed that they possessed a hyoid bone so high up in the vocal tract as to preclude the possibility of producing certain vowel sounds.
The hyoid bone is present in many mammals. It allows a wide range of tongue, pharyngeal and laryngeal movements by bracing these structures alongside each other in order to produce variation.  It is now realised that its lowered position is not unique to Homo sapiens, while its relevance to vocal flexibility may have been overstated: although men have a lower larynx, they do not produce a wider range of sounds than women or two-year-old babies. There is no evidence that the larynx position of the Neanderthals impeded the range of vowel sounds they could produce.  The discovery of a modern-looking hyoid bone of a Neanderthal man in the Kebara Cave in Israel led its discoverers to argue that the Neanderthals had a descended larynx, and thus human-like speech capabilities.   However, other researchers have claimed that the morphology of the hyoid is not indicative of the larynx's position.  It is necessary to take into consideration the skull base, the mandible and the cervical vertebrae and a cranial reference plane.  
The morphology of the outer and middle ear of Middle Pleistocene hominins from Atapuerca SH in Spain, believed to be proto-Neanderthal, suggests they had an auditory sensitivity similar to modern humans and very different from chimpanzees. They were probably able to differentiate between many different speech sounds. 
Hypoglossal canal Edit
The hypoglossal nerve plays an important role in controlling movements of the tongue. In 1998, one research team used the size of the hypoglossal canal in the base of fossil skulls in an attempt to estimate the relative number of nerve fibres, claiming on this basis that Middle Pleistocene hominins and Neanderthals had more fine-tuned tongue control than either australopithecines or apes.  Subsequently, however, it was demonstrated that hypoglossal canal size and nerve sizes are not correlated,  and it is now accepted that such evidence is uninformative about the timing of human speech evolution. 
Distinctive features theory Edit
According to one influential school,   the human vocal apparatus is intrinsically digital on the model of a keyboard or digital computer. If so, this is remarkable: nothing about a chimpanzee's vocal apparatus suggests a digital keyboard, notwithstanding the anatomical and physiological similarities. This poses the question as to when and how, during the course of human evolution, the transition from analog to digital structure and function occurred.
The human supralaryngeal tract is said to be digital in the sense that it is an arrangement of moveable toggles or switches, each of which, at any one time, must be in one state or another. The vocal cords, for example, are either vibrating (producing a sound) or not vibrating (in silent mode). By virtue of simple physics, the corresponding distinctive feature — in this case, "voicing" — cannot be somewhere in between. The options are limited to "off" and "on". Equally digital is the feature known as "nasalisation". At any given moment the soft palate or velum either allows or doesn't allow sound to resonate in the nasal chamber. In the case of lip and tongue positions, more than two digital states may be allowed.
The theory that speech sounds are composite entities constituted by complexes of binary phonetic features was first advanced in 1938 by the Russian linguist Roman Jakobson.  A prominent early supporter of this approach was Noam Chomsky, who went on to extend it from phonology to language more generally, in particular to the study of syntax and semantics.    In his 1965 book, Aspects of the Theory of Syntax,  Chomsky treated semantic concepts as combinations of binary-digital atomic elements explicitly on the model of distinctive features theory. The lexical item "bachelor", on this basis, would be expressed as [+ Human], [+ Male], [- Married].
Supporters of this approach view the vowels and consonants recognized by speakers of a particular language or dialect at a particular time as cultural entities of little scientific interest. From a natural science standpoint, the units which matter are those common to Homo sapiens by virtue of our biological nature. By combining the atomic elements or "features" with which all humans are innately equipped, anyone may in principle generate the entire range of vowels and consonants to be found in any of the world's languages, whether past, present or future. The distinctive features are in this sense atomic components of a universal language.
|Pronounced with the lower lip against the teeth:||[f] (fan)||[v] (van)|
|Pronounced with the tongue against the teeth:||[θ] (thin, thigh)||[ð] (then, thy)|
|Pronounced with the tongue near the gums:||[s] (sip)||[z] (zip)|
|Pronounced with the tongue bunched up:||[ʃ] (pressure)||[ʒ] (pleasure)|
In recent years, the notion of an innate "universal grammar" underlying phonological variation has been called into question. The most comprehensive monograph ever written about speech sounds, Sounds of the World's Languages, by Peter Ladefoged and Ian Maddieson,  found virtually no basis for the postulation of some small number of fixed, discrete, universal phonetic features. Examining 305 languages, for example, they encountered vowels that were positioned basically everywhere along the articulatory and acoustic continuum. Ladefoged concludes that phonological features are not determined by human nature: "Phonological features are best regarded as artifacts that linguists have devised in order to describe linguistic systems."  The controversy remains unresolved.
Self-organization theory Edit
Self-organization characterizes systems where macroscopic structures are spontaneously formed out of local interactions between the many components of the system.  In self-organized systems, global organizational properties are not to be found at the local level. In colloquial terms, self-organization is roughly captured by the idea of "bottom-up" (as opposed to "top-down") organization. Examples of self-organized systems range from ice crystals to galaxy spirals in the inorganic world, and from spots on the leopard skins to the architecture of termite nests or shape of a flock of starlings.
According to many phoneticians, the sounds of language arrange and re-arrange themselves through self-organization    Speech sounds have both perceptual ("how you hear them") and articulatory ("how you produce them") properties, all with continuous values. Speakers tend to minimize effort, favoring ease of articulation over clarity. Listeners do the opposite, favoring sounds that are easy to distinguish even if difficult to pronounce. Since speakers and listeners are constantly switching roles, the syllable systems actually found in the world's languages turn out to be a compromise between acoustic distinctiveness on the one hand, and articulatory ease on the other.
How, precisely, do systems of vowels, consonants and syllables arise? Agent-based computer models take the perspective of self-organisation at the level of the speech community or population. The two main paradigms here are (1) the iterated learning model and (2) the language game model. Iterated learning focuses on transmission from generation to generation, typically with just one agent in each generation.  In the language game model, a whole population of agents simultaneously produce, perceive and learn language, inventing novel forms when the need arises.  
Several models have shown how relatively simple peer-to-peer vocal interactions, such as imitation, can spontaneously self-organize a system of sounds shared by the whole population, and different in different populations. For example, models elaborated by Berrah et al.,  as well as de Boer,  and recently reformulated using Bayesian theory,  showed how a group of individuals playing imitation games can self-organize repertoires of vowel sounds which share substantial properties with human vowel systems. For example, in de Boer's model, initially vowels are generated randomly, but agents learn from each other as they interact repeatedly over time. Agent A chooses a vowel from her repertoire and produces it, inevitably with some noise. Agent B hears this vowel and chooses the closest equivalent from her own repertoire. To check whether this truly matches the original, B produces the vowel she thinks she has heard, whereupon A refers once again to her own repertoire to find the closest equivalent. If this matches the one she initially selected, the game is successful, otherwise, it has failed. "Through repeated interactions," according to de Boer, "vowel systems emerge that are very much like the ones found in human languages." 
In a different model, the phonetician Björn Lindblom  was able to predict, on self-organizational grounds, the favored choices of vowel systems ranging from three to nine vowels on the basis of a principle of optimal perceptual differentiation.
Further models studied the role of self-organization in the origins of phonemic coding and combinatoriality, which is the existence of phonemes and their systematic reuse to build structured syllables. Pierre-Yves Oudeyer developed models which showed that basic neural equipment for adaptive holistic vocal imitation, coupling directly motor and perceptual representations in the brain, can generate spontaneously shared combinatorial systems of vocalizations, including phonotactic patterns, in a society of babbling individuals.   These models also characterized how morphological and physiological innate constraints can interact with these self-organized mechanisms to account for both the formation of statistical regularities and diversity in vocalization systems.
Gestural theory Edit
The gestural theory states that speech was a relatively late development, evolving by degrees from a system that was originally gestural. Our ancestors were unable to control their vocalization at the time when gestures were used to communicate however, as they slowly began to control their vocalizations, spoken language began to evolve.
Three types of evidence support this theory:
- Gestural language and vocal language depend on similar neural systems. The regions on the cortex that are responsible for mouth and hand movements border each other.
- Nonhuman primates minimize vocal signals in favor of manual, facial and other visible gestures in order to express simple concepts and communicative intentions in the wild. Some of these gestures resemble those of humans, such as the "begging posture", with the hands stretched out, which humans share with chimpanzees. 
Research has found strong support for the idea that spoken language and signing depend on similar neural structures. Patients who used sign language, and who suffered from a left-hemisphere lesion, showed the same disorders with their sign language as vocal patients did with their oral language.  Other researchers found that the same left-hemisphere brain regions were active during sign language as during the use of vocal or written language. 
Humans spontaneously use hand and facial gestures when formulating ideas to be conveyed in speech.   There are also, of course, many sign languages in existence, commonly associated with deaf communities as noted above, these are equal in complexity, sophistication, and expressive power, to any oral language. The main difference is that the "phonemes" are produced on the outside of the body, articulated with hands, body, and facial expression, rather than inside the body articulated with tongue, teeth, lips, and breathing.
Many psychologists and scientists have looked into the mirror system in the brain to answer this theory as well as other behavioral theories. Evidence to support mirror neurons as a factor in the evolution of speech includes mirror neurons in primates, the success of teaching apes to communicate gesturally, and pointing/gesturing to teach young children language. Fogassi and Ferrari (2014) monitored motor cortex activity in monkeys, specifically area F5 in the Broca’s area, where mirror neurons are located. They observed changes in electrical activity in this area when the monkey executed or observed different hand actions performed by someone else. Broca’s area is a region in the frontal lobe responsible for language production and processing. The discovery of mirror neurons in this region, which fire when an action is done or observed specifically with the hand, strongly supports the belief that communication was once accomplished with gestures. The same is true when teaching young children language. When one points at a specific object or location, mirror neurons in the child fire as though they were doing the action, which results in long term learning 
Critics note that for mammals in general, sound turns out to be the best medium in which to encode information for transmission over distances at speed. Given the probability that this applied also to early humans, it's hard to see why they should have abandoned this efficient method in favor of more costly and cumbersome systems of visual gesturing — only to return to sound at a later stage. 
By way of explanation, it has been proposed that at a relatively late stage in human evolution, our ancestors' hands became so much in demand for making and using tools that the competing demands of manual gesturing became a hindrance. The transition to spoken language is said to have occurred only at that point.  Since humans throughout evolution have been making and using tools, however, most scholars remain unconvinced by this argument. (For a different approach to this puzzle — one setting out from considerations of signal reliability and trust — see "from pantomime to speech" below).
Little is known about the timing of language's emergence in the human species. Unlike writing, speech leaves no material trace, making it archaeologically invisible. Lacking direct linguistic evidence, specialists in human origins have resorted to the study of anatomical features and genes arguably associated with speech production. While such studies may provide information as to whether pre-modern Homo species had speech capacities, it is still unknown whether they actually spoke. While they may have communicated vocally, the anatomical and genetic data lack the resolution necessary to differentiate proto-language from speech.
Using statistical methods to estimate the time required to achieve the current spread and diversity in modern languages today, Johanna Nichols — a linguist at the University of California, Berkeley — argued in 1998 that vocal languages must have begun diversifying in our species at least 100,000 years ago. 
More recently — in 2012 — anthropologists Charles Perreault and Sarah Mathew used phonemic diversity to suggest a date consistent with this.  "Phonemic diversity" denotes the number of perceptually distinct units of sound — consonants, vowels and tones — in a language. The current worldwide pattern of phonemic diversity potentially contains the statistical signal of the expansion of modern Homo sapiens out of Africa, beginning around 60-70 thousand years ago. Some scholars argue that phonemic diversity evolves slowly and can be used as a clock to calculate how long the oldest African languages would have to have been around in order to accumulate the number of phonemes they possess today. As human populations left Africa and expanded into the rest of the world, they underwent a series of bottlenecks — points at which only a very small population survived to colonise a new continent or region. Allegedly such a population crash led to a corresponding reduction in genetic, phenotypic and phonemic diversity. African languages today have some of the largest phonemic inventories in the world, while the smallest inventories are found in South America and Oceania, some of the last regions of the globe to be colonized. For example, Rotokas, a language of New Guinea, and Pirahã, spoken in South America, both have just 11 phonemes,   while !Xun, a language spoken in Southern Africa has 141 phonemes. The authors use a natural experiment — the colonization of mainland Southeast Asia on the one hand, the long-isolated Andaman Islands on the other — to estimate the rate at which phonemic diversity increases through time. Using this rate, they estimate that the world's languages date back to the Middle Stone Age in Africa, sometime between 350 thousand and 150 thousand years ago. This corresponds to the speciation event which gave rise to Homo sapiens.
These and similar studies have however been criticized by linguists who argue that they are based on a flawed analogy between genes and phonemes, since phonemes are frequently transferred laterally between languages unlike genes, and on a flawed sampling of the world's languages, since both Oceania and the Americas also contain languages with very high numbers of phonemes, and Africa contains languages with very few. They argue that the actual distribution of phonemic diversity in the world reflects recent language contact and not deep language history - since it is well demonstrated that languages can lose or gain many phonemes over very short periods. In other words, there is no valid linguistic reason to expect genetic founder effects to influence phonemic diversity.  
Early speculations Edit
"I cannot doubt that language owes its origin to the imitation and modification, aided by signs and gestures, of various natural sounds, the voices of other animals, and man's own instinctive cries."
In 1861, historical linguist Max Müller published a list of speculative theories concerning the origins of spoken language:  These theories have been grouped under the category named invention hypotheses. These hypotheses were all meant to understand how the first language could have developed and postulate that human mimicry of natural sounds were how the first words with meaning were derived.
- Bow-wow. The bow-wow or cuckoo theory, which Müller attributed to the German philosopher Johann Gottfried Herder, saw early words as imitations of the cries of beasts and birds. This theory, believed to be derived from onomatopoeia, relates the meaning of the sound to the actual sound formulated by the speaker.
- Pooh-pooh. The Pooh-Pooh theory saw the first words as emotional interjections and exclamations triggered by pain, pleasure, surprise and so on. These sounds were all produced on sudden intakes of breath, which is unlike any other language. Unlike emotional reactions, spoken language is produced on the exhale, so the sounds contained in this form of communication are unlike those used in normal speech production, which makes this theory a less plausible one for language acquisition. 
- Ding-dong. Müller suggested what he called the Ding-Dong theory, which states that all things have a vibrating natural resonance, echoed somehow by man in his earliest words. Words are derived from the sound associated with their meaning for example, “crash became a word for thunder, boom for explosion.” This theory also heavily relies on the concept of onomatopoeia.
- Yo-he-ho. The yo-he-ho theory saw language emerging out of collective rhythmic labor, the attempt to synchronize muscular effort resulting in sounds such as heave alternating with sounds such as ho. Believed to be derived from the basis of human collaborative efforts, this theory states that humans needed words, which might have started off as chanting, to communicate. This need could have been to ward off predators, or served as a unifying battle cry.
- Ta-ta. This did not feature in Max Müller's list, having been proposed in 1930 by Sir Richard Paget.  According to the ta-ta theory, humans made the earliest words by tongue movements that mimicked manual gestures, rendering them audible.
A common concept of onomatopoeia as the first source of words is present however, there is a glaring problem with this theory. Onomatopoeia can explain the first couple of words all derived from natural phenomenon, but there is no explanation as to how more complex words without a natural counterpart came to be.  Most scholars today consider all such theories not so much wrong — they occasionally offer peripheral insights — as comically naïve and irrelevant.   The problem with these theories is that they are so narrowly mechanistic. They assume that once our ancestors had stumbled upon the appropriate ingenious mechanism for linking sounds with meanings, language automatically evolved and changed.
Problems of reliability and deception Edit
From the perspective of modern science, the main obstacle to the evolution of speech-like communication in nature is not a mechanistic one. Rather, it is that symbols — arbitrary associations of sounds with corresponding meanings — are unreliable and may well be false.  As the saying goes, "words are cheap".  The problem of reliability was not recognised at all by Darwin, Müller or the other early evolutionist theorists.
Animal vocal signals are for the most part intrinsically reliable. When a cat purrs, the signal constitutes direct evidence of the animal's contented state. One can "trust" the signal not because the cat is inclined to be honest, but because it just can't fake that sound. Primate vocal calls may be slightly more manipulable,  but they remain reliable for the same reason — because they are hard to fake.  Primate social intelligence is Machiavellian — self-serving and unconstrained by moral scruples. Monkeys and apes often attempt to deceive one another, while at the same time remaining constantly on guard against falling victim to deception themselves.  Paradoxically, it is precisely primates' resistance to deception that blocks the evolution of their vocal communication systems along language-like lines. Language is ruled out because the best way to guard against being deceived is to ignore all signals except those that are instantly verifiable. Words automatically fail this test. 
Words are easy to fake. Should they turn out to be lies, listeners will adapt by ignoring them in favor of hard-to-fake indices or cues. For language to work, then, listeners must be confident that those with whom they are on speaking terms are generally likely to be honest.  A peculiar feature of language is "displaced reference", which means reference to topics outside the currently perceptible situation. This property prevents utterances from being corroborated in the immediate "here" and "now". For this reason, language presupposes relatively high levels of mutual trust in order to become established over time as an evolutionarily stable strategy. A theory of the origins of language must, therefore, explain why humans could begin trusting cheap signals in ways that other animals apparently cannot (see signalling theory).
"Kin selection" Edit
The "mother tongues" hypothesis was proposed in 2004 as a possible solution to this problem.  W. Tecumseh Fitch suggested that the Darwinian principle of "kin selection"   — the convergence of genetic interests between relatives — might be part of the answer. Fitch suggests that spoken languages were originally "mother tongues". If speech evolved initially for communication between mothers and their own biological offspring, extending later to include adult relatives as well, the interests of speakers and listeners would have tended to coincide. Fitch argues that shared genetic interests would have led to sufficient trust and cooperation for intrinsically unreliable vocal signals — spoken words — to become accepted as trustworthy and so begin evolving for the first time.
Critics of this theory point out that kin selection is not unique to humans. Ape mothers also share genes with their offspring, as do all animals, so why is it only humans who speak? Furthermore, it is difficult to believe that early humans restricted linguistic communication to genetic kin: the incest taboo must have forced men and women to interact and communicate with non-kin. So even if we accept Fitch's initial premises, the extension of the posited "mother tongue" networks from relatives to non-relatives remains unexplained. 
"Reciprocal altruism" Edit
Ib Ulbæk  invokes another standard Darwinian principle — "reciprocal altruism"  — to explain the unusually high levels of intentional honesty necessary for language to evolve. 'Reciprocal altruism' can be expressed as the principle that if you scratch my back, I'll scratch yours. In linguistic terms, it would mean that if you speak truthfully to me, I'll speak truthfully to you. Ordinary Darwinian reciprocal altruism, Ulbæk points out, is a relationship established between frequently interacting individuals. For language to prevail across an entire community, however, the necessary reciprocity would have needed to be enforced universally instead of being left to individual choice. Ulbæk concludes that for language to evolve, early society as a whole must have been subject to moral regulation.
Critics point out that this theory fails to explain when, how, why or by whom "obligatory reciprocal altruism" could possibly have been enforced. Various proposals have been offered to remedy this defect.  A further criticism is that language doesn't work on the basis of reciprocal altruism anyway. Humans in conversational groups don't withhold information to all except listeners likely to offer valuable information in return. On the contrary, they seem to want to advertise to the world their access to socially relevant information, broadcasting it to anyone who will listen without thought of return. 
"Gossip and grooming" Edit
Gossip, according to Robin Dunbar, does for group-living humans what manual grooming does for other primates — it allows individuals to service their relationships and so maintain their alliances. As humans began living in larger and larger social groups, the task of manually grooming all one's friends and acquaintances became so time-consuming as to be unaffordable. In response to this problem, humans invented "a cheap and ultra-efficient form of grooming" — vocal grooming. To keep your allies happy, you now needed only to "groom" them with low-cost vocal sounds, servicing multiple allies simultaneously while keeping both hands free for other tasks. Vocal grooming (the production of pleasing sounds lacking syntax or combinatorial semantics) then evolved somehow into syntactical speech. 
Critics of this theory point out that the very efficiency of "vocal grooming" — that words are so cheap — would have undermined its capacity to signal commitment of the kind conveyed by time-consuming and costly manual grooming.  A further criticism is that the theory does nothing to explain the crucial transition from vocal grooming — the production of pleasing but meaningless sounds — to the cognitive complexities of syntactical speech.
From pantomime to speech Edit
According to another school of thought, language evolved from mimesis — the "acting out" of scenarios using vocal and gestural pantomime.    Charles Darwin, who himself was skeptical, hypothesized that human speech and language is derived from gestures and mouth pantomime.  This theory, further elaborated on by various authors, postulates that the genus Homo, different from our ape ancestors, evolved a new type of cognition. Apes are capable of associational learning. They can tie a sensory cue to a motor response often trained through classical conditioning.  However, in apes, the conditioned sensory cue is necessary for a conditioned response to be observed again. The motor response will not occur without an external cue from an outside agent. A remarkable ability that humans possess is the ability to voluntarily retrieve memories without the need for a cue (e.g. conditioned stimulus). This is not an ability that has been observed in animals except language-trained apes. There is still much controversy on whether pantomime is a capability for apes, both wild and captured.  For as long as utterances needed to be emotionally expressive and convincing, it was not possible to complete the transition to purely conventional signs.    On this assumption, pre-linguistic gestures and vocalisations would have been required not just to disambiguate intended meanings, but also to inspire confidence in their intrinsic reliability.  If contractual commitments   were necessary in order to inspire community-wide trust in communicative intentions, it would follow that these had to be in place before humans could shift at last to an ultra-efficient, high-speed — digital as opposed to analog — signalling format. Vocal distinctive features (sound contrasts) are ideal for this purpose. It is therefore suggested that the establishment of contractual understandings enabled the decisive transition from mimetic gesture to fully conventionalised, digitally encoded speech.   
"Ritual/speech coevolution" Edit
The ritual/speech coevolution theory was originally proposed by the distinguished social anthropologist Roy Rappaport  before being elaborated by anthropologists such as Chris Knight,  Jerome Lewis,  Nick Enfield,  Camilla Power  and Ian Watts.  Cognitive scientist and robotics engineer Luc Steels  is another prominent supporter of this general approach, as is biological anthropologist/neuroscientist Terrence Deacon. 
These scholars argue that there can be no such thing as a "theory of the origins of language". This is because language is not a separate adaptation but an internal aspect of something much wider — namely, human symbolic culture as a whole.  Attempts to explain language independently of this wider context have spectacularly failed, say these scientists, because they are addressing a problem with no solution. Can we imagine a historian attempting to explain the emergence of credit cards independently of the wider system of which they are a part? Using a credit card makes sense only if you have a bank account institutionally recognized within a certain kind of advanced capitalist society — one where communications technology has already been invented and fraud can be detected and prevented. In much the same way, language would not work outside a specific array of social mechanisms and institutions. For example, it would not work for an ape communicating with other apes in the wild. Not even the cleverest ape could make language work under such conditions.
"Lie and alternative, inherent in language, . pose problems to any society whose structure is founded on language, which is to say all human societies. I have therefore argued that if there are to be words at all it is necessary to establish The Word, and that The Word is established by the invariance of liturgy." 
Advocates of this school of thought point out that words are cheap. As digital hallucinations, they are intrinsically unreliable. Should an especially clever ape, or even a group of articulate apes, try to use words in the wild, they would carry no conviction. The primate vocalizations that do carry conviction — those they actually use — are unlike words, in that they are emotionally expressive, intrinsically meaningful and reliable because they are relatively costly and hard to fake.
Speech consists of digital contrasts whose cost is essentially zero. As pure social conventions, signals of this kind cannot evolve in a Darwinian social world — they are a theoretical impossibility.  Being intrinsically unreliable, language works only if you can build up a reputation for trustworthiness within a certain kind of society — namely, one where symbolic cultural facts (sometimes called "institutional facts") can be established and maintained through collective social endorsement.  In any hunter-gatherer society, the basic mechanism for establishing trust in symbolic cultural facts is collective ritual.  Therefore, the task facing researchers into the origins of language is more multidisciplinary than is usually supposed. It involves addressing the evolutionary emergence of human symbolic culture as a whole, with language an important but subsidiary component. 
Critics of the theory include Noam Chomsky, who terms it the "non-existence" hypothesis — a denial of the very existence of language as an object of study for natural science.  Chomsky's own theory is that language emerged in an instant and in perfect form,  prompting his critics in turn to retort that only something that doesn't exist — a theoretical construct or convenient scientific fiction — could possibly emerge in such a miraculous way.  The controversy remains unresolved.
Twentieth century speculations Edit
Festal origins Edit
The essay "The festal origin of human speech", though published in the late nineteenth century,  made little impact until the American philosopher Susanne Langer re-discovered and publicised it in 1941. 
"In the early history of articulate sounds they could make no meaning themselves, but they preserved and got intimately associated with the peculiar feelings and perceptions that came most prominently into the minds of the festal players during their excitement."
The theory sets out from the observation that primate vocal sounds are above all emotionally expressive. The emotions aroused are socially contagious. Because of this, an extended bout of screams, hoots or barks will tend to express not just the feelings of this or that individual but the mutually contagious ups and downs of everyone within earshot.
Turning to the ancestors of Homo sapiens, the "festal origin" theory suggests that in the "play-excitement" preceding or following a communal hunt or other group activity, everyone might have combined their voices in a comparable way, emphasizing their mood of togetherness with such noises as rhythmic drumming and hand-clapping. Variably pitched voices would have formed conventional patterns, such that choral singing became an integral part of communal celebration.
Although this was not yet speech, according to Langer, it developed the vocal capacities from which speech would later derive. There would be conventional modes of ululating, clapping or dancing appropriate to different festive occasions, each so intimately associated with that kind of occasion that it would tend to collectively uphold and embody the concept of it. Anyone hearing a snatch of sound from such a song would recall the associated occasion and mood. A melodic, rhythmic sequence of syllables conventionally associated with a certain type of celebration would become, in effect, its vocal mark. On that basis, certain familiar sound sequences would become "symbolic".
In support of all this, Langer cites ethnographic reports of tribal songs consisting entirely of "rhythmic nonsense syllables". She concedes that an English equivalent such as "hey-nonny-nonny", although perhaps suggestive of certain feelings or ideas, is neither noun, verb, adjective, nor any other syntactical part of speech. So long as articulate sound served only in the capacity of "hey nonny-nonny", "hallelujah" or "alack-a-day", it cannot yet have been speech. For that to arise, according to Langer, it was necessary for such sequences to be emitted increasingly out of context — outside the total situation that gave rise to them. Extending a set of associations from one cognitive context to another, completely different one, is the secret of metaphor. Langer invokes an early version of what is nowadays termed "grammaticalization" theory to show how, from, such a point of departure, syntactically complex speech might progressively have arisen.
Langer acknowledges Emile Durkheim as having proposed a strikingly similar theory back in 1912.  For recent thinking along broadly similar lines, see Steven Brown on "musilanguage",  Chris Knight on "ritual"  and "play",   Jerome Lewis on "mimicry",   Steven Mithen on "Hmmmmm"  Bruce Richman on "nonsense syllables"  and Alison Wray on "holistic protolanguage". 
Mirror neuron hypothesis (MSH) and the Motor Theory of Speech Perception
The mirror neuron hypothesis, based on a phenomenon discovered in 2008 by Rizzolatti and Fabbri, supports the motor theory of speech perception. The motor theory of speech perception was proposed in 1967 by Liberman, who believed that the motor system and language systems were closely interlinked.  This would result in a more streamlined process of generating speech both the cognition and speech formulation could occur simultaneously. Essentially, it is wasteful to have a speech decoding and speech encoding process independent of each other. This hypothesis was further supported by the discovery of motor neurons. Rizzolatti and Fabbri found that there were specific neurons in the motor cortex of macaque monkeys which were activated when seeing an action.  The neurons which are activated are the same neurons in which would be required to perform the same action themselves. Mirror neurons fire when observing an action and performing an action, indicating that these neurons found in the motor cortex are necessary for understanding a visual process.  The presence of mirror neurons may indicate that non-verbal, gestural communication is far more ancient than previously thought to be. Motor theory of speech perception relies on the understanding of motor representations that underlie speech gestures, such as lip movement. There is no clear understanding of speech perception currently, but it is generally accepted that the motor cortex is activated in speech perception to some capacity.
The term "musilanguage" (or "hmmmmm") refers to a pre-linguistic system of vocal communication from which (according to some scholars) both music and language later derived. The idea is that rhythmic, melodic, emotionally expressive vocal ritual helped bond coalitions and, over time, set up selection pressures for enhanced volitional control over the speech articulators. Patterns of synchronized choral chanting are imagined to have varied according to the occasion. For example, "we're setting off to find honey" might sound qualitatively different from "we're setting off to hunt" or "we're grieving over our relative's death". If social standing depended on maintaining a regular beat and harmonizing one's own voice with that of everyone else, group members would have come under pressure to demonstrate their choral skills.
Archaeologist Steven Mithen speculates that the Neanderthals possessed some such system, expressing themselves in a "language" known as "Hmmmmm", standing for Holistic, manipulative, multi-modal, musical and mimetic.  p. 169-175 In Bruce Richman's earlier version of essentially the same idea,  frequent repetition of the same few songs by many voices made it easy for people to remember those sequences as whole units. Activities that a group of people were doing while they were vocalizing together — activities that were important or striking or richly emotional — came to be associated with particular sound sequences, so that each time a fragment was heard, it evoked highly specific memories. The idea is that the earliest lexical items (words) started out as abbreviated fragments of what were originally communal songs.
"Whenever people sang or chanted a particular sound sequence they would remember the concrete particulars of the situation most strongly associated with it: ah, yes! we sing this during this particular ritual admitting new members to the group or, we chant this during a long journey in the forest or, when a clearing is finished for a new camp, this is what we chant or these are the keenings we sing during ceremonies over dead members of our group."
As group members accumulated an expanding repertoire of songs for different occasions, interpersonal call-and-response patterns evolved along one trajectory to assume linguistic form. Meanwhile, along a divergent trajectory, polyphonic singing and other kinds of music became increasingly specialized and sophisticated.
To explain the establishment of syntactical speech, Richman cites English "I wanna go home". He imagines this to have been learned in the first instance not as a combinatorial sequence of free-standing words, but as a single stuck-together combination — the melodic sound people make to express "feeling homesick". Someone might sing "I wanna go home", prompting other voices to chime in with "I need to go home", "I'd love to go home", "Let's go home" and so forth. Note that one part of the song remains constant, while another is permitted to vary. If this theory is accepted, syntactically complex speech began evolving as each chanted mantra allowed for variation at a certain point, allowing for the insertion of an element from some other song. For example, while mourning during a funeral rite, someone might want to recall a memory of collecting honey with the deceased, signaling this at an appropriate moment with a fragment of the "we're collecting honey" song. Imagine that such practices became common. Meaning-laden utterances would now have become subject to a distinctively linguistic creative principle — that of recursive embedding.
Hunter-gatherer egalitarianism Edit
Many scholars associate the evolutionary emergence of speech with profound social, sexual, political and cultural developments. One view is that primate-style dominance needed to give way to a more cooperative and egalitarian lifestyle of the kind characteristic of modern hunter-gatherers.   
According to Michael Tomasello, the key cognitive capacity distinguishing Homo sapiens from our ape cousins is "intersubjectivity". This entails turn-taking and role-reversal: your partner strives to read your mind, you simultaneously strive to read theirs, and each of you makes a conscious effort to assist the other in the process. The outcome is that each partner forms a representation of the other's mind in which their own can be discerned by reflection.
Tomasello argues that this kind of bi-directional cognition is central to the very possibility of linguistic communication. Drawing on his research with both children and chimpanzees, he reports that human infants, from one year old onwards, begin viewing their own mind as if from the standpoint of others. He describes this as a cognitive revolution. Chimpanzees, as they grow up, never undergo such a revolution. The explanation, according to Tomasello, is that their evolved psychology is adapted to a deeply competitive way of life. Wild-living chimpanzees from despotic social hierarchies, most interactions involving calculations of dominance and submission. An adult chimp will strive to outwit its rivals by guessing at their intentions while blocking them from reciprocating. Since bi-directional intersubjective communication is impossible under such conditions, the cognitive capacities necessary for language don't evolve.   
In the scenario favoured by David Erdal and Andrew Whiten,   primate-style dominance provoked equal and opposite coalitionary resistance — counter-dominance. During the course of human evolution, increasingly effective strategies of rebellion against dominant individuals led to a compromise. While abandoning any attempt to dominate others, group members vigorously asserted their personal autonomy, maintaining their alliances to make potentially dominant individuals think twice. Within increasingly stable coalitions, according to this perspective, status began to be earned in novel ways, social rewards accruing to those perceived by their peers as especially cooperative and self-aware. 
Reverse dominance Edit
While counter-dominance, according to this evolutionary narrative, culminates in a stalemate, anthropologist Christopher Boehm   extends the logic a step further. Counter-dominance tips over at last into full-scale "reverse dominance". The rebellious coalition decisively overthrows the figure of the primate alpha-male. No dominance is allowed except that of the self-organized community as a whole.
As a result of this social and political change, hunter-gatherer egalitarianism is established. As children grow up, they are motivated by those around them to reverse perspective, engaging with other minds on the model of their own. Selection pressures favor such psychological innovations as imaginative empathy, joint attention, moral judgment, project-oriented collaboration and the ability to evaluate one's own behavior from the standpoint of others. Underpinning enhanced probabilities of cultural transmission and cumulative cultural evolution, these developments culminated in the establishment of hunter-gatherer-style egalitarianism in association with intersubjective communication and cognition. It is in this social and political context that language evolves. 
Scenarios involving mother-infant interactions Edit
"Putting the baby down" Edit
According to Dean Falk's "putting the baby down" theory, vocal interactions between early hominin mothers and infants sparked a sequence of events that led, eventually, to our ancestors' earliest words.  The basic idea is that evolving human mothers, unlike their monkey and ape counterparts, couldn't move around and forage with their infants clinging onto their backs. Loss of fur in the human case left infants with no means of clinging on. Frequently, therefore, mothers had to put their babies down. As a result, these babies needed reassurance that they were not being abandoned. Mothers responded by developing "motherese" — an infant-directed communicative system embracing facial expressions, body language, touching, patting, caressing, laughter, tickling and emotionally expressive contact calls. The argument is that language somehow developed out of all this.
While this theory may explain a certain kind of infant-directed "protolanguage" — known today as "motherese" — it does little to solve the really difficult problem, which is the emergence among adults of syntactical speech. [ citation needed ]
Co-operative breeding Edit
Evolutionary anthropologist Sarah Hrdy  observes that only human mothers among great apes are willing to let another individual take hold of their own babies further, we are routinely willing to let others babysit. She identifies lack of trust as the major factor preventing chimp, bonobo or gorilla mothers from doing the same: "If ape mothers insist on carrying their babies everywhere . it is because the available alternatives are not safe enough." The fundamental problem is that ape mothers (unlike monkey mothers who may often babysit) do not have female relatives nearby. The strong implication is that, in the course of Homo evolution, allocare could develop because Homo mothers did have female kin close by — in the first place, most reliably, their own mothers. Extending the Grandmother hypothesis,  Hrdy argues that evolving Homo erectus females necessarily relied on female kin initially this novel situation in ape evolution of mother, infant and mother's mother as allocarer provided the evolutionary ground for the emergence of intersubjectivity. She relates this onset of "cooperative breeding in an ape" to shifts in life history and slower child development, linked to the change in brain and body size from the 2 million year mark.
Primatologist Klaus Zuberbühler  uses these ideas to help explain the emergence of vocal flexibility in the human species. Co-operative breeding would have compelled infants to struggle actively to gain the attention of caregivers, not all of whom would have been directly related. A basic primate repertoire of vocal signals may have been insufficient for this social challenge. Natural selection, according to this view, would have favored babies with advanced vocal skills, beginning with babbling (which triggers positive responses in care-givers) and paving the way for the elaborate and unique speech abilities of modern humans.
Was "mama" the first word? Edit
These ideas might be linked to those of the renowned structural linguist Roman Jakobson, who claimed that "the sucking activities of the child are accompanied by a slight nasal murmur, the only phonation to be produced when the lips are pressed to the mother's breast . and the mouth is full".  He proposed that later in the infant's development, "this phonatory reaction to nursing is reproduced as an anticipatory signal at the mere sight of food and finally as a manifestation of a desire to eat, or more generally, as an expression of discontent and impatient longing for missing food or absent nurser, and any ungranted wish." So, the action of opening and shutting the mouth, combined with the production of a nasal sound when the lips are closed, yielded the sound sequence "Mama", which may, therefore, count as the very first word. Peter MacNeilage sympathetically discusses this theory in his major book, The Origin of Speech, linking it with Dean Falk's "putting the baby down" theory (see above).  Needless to say, other scholars have suggested completely different candidates for Homo sapiens' very first word. 
Niche construction theory Edit
While the biological language faculty is genetically inherited, actual languages or dialects are culturally transmitted, as are social norms, technological traditions and so forth. Biologists expect a robust co-evolutionary trajectory linking human genetic evolution with the evolution of culture.  Individuals capable of rudimentary forms of protolanguage would have enjoyed enhanced access to cultural understandings, while these, conveyed in ways that young brains could readily learn, would, in turn, have become transmitted with increasing efficiency.
In some ways like beavers, as they construct their dams, humans have always engaged in niche construction, creating novel environments to which they subsequently become adapted. Selection pressures associated with prior niches tend to become relaxed as humans depend increasingly on novel environments created continuously by their own productive activities.   According to Steven Pinker,  language is an adaptation to "the cognitive niche". Variations on the theme of ritual/speech co-evolution — according to which speech evolved for purposes of internal communication within a ritually constructed domain — have attempted to specify more precisely when, why and how this special niche was created by human collaborative activity.   
"Consider a knight in chess. Is the piece by itself an element of the game? Certainly not. For as a material object, separated from its square on the board and the other conditions of play, it is of no significance for the player. It becomes a real, concrete element only when it takes on or becomes identified with its value in the game. Suppose that during a game this piece gets destroyed or lost. Can it be replaced? Of course, it can. Not only by some other knight but even by an object of quite a different shape, which can be counted as a knight, provided it is assigned the same value as the missing piece."
The Swiss scholar Ferdinand de Saussure founded linguistics as a twentieth-century professional discipline. Saussure regarded a language as a rule-governed system, much like a board game such as chess. In order to understand chess, he insisted, we must ignore such external factors as the weather prevailing during a particular session or the material composition of this or that piece. The game is autonomous with respect to its material embodiments. In the same way, when studying language, it's essential to focus on its internal structure as a social institution. External matters (e.g., the shape of the human tongue) are irrelevant from this standpoint. Saussure regarded 'speaking' (parole) as individual, ancillary and more or less accidental by comparison with "language" (langue), which he viewed as collective, systematic and essential.
Saussure showed little interest in Darwin's theory of evolution by natural selection. Nor did he consider it worthwhile to speculate about how language might originally have evolved. Saussure's assumptions in fact cast doubt on the validity of narrowly conceived origins scenarios. His structuralist paradigm, when accepted in its original form, turns scholarly attention to a wider problem: how our species acquired the capacity to establish social institutions in general.
"The basic processes and relations which give verbal behavior its special characteristics are now fairly well understood. Much of the experimental work responsible for this advance has been carried out on other species, but the results have proved to be surprisingly free of species restrictions. Recent work has shown that the methods can be extended to human behavior without serious modification."
In the United States, prior to and immediately following World War II, the dominant psychological paradigm was behaviourism. Within this conceptual framework, language was seen as a certain kind of behaviour — namely, verbal behavior,  to be studied much like any other kind of behavior in the animal world. Rather as a laboratory rat learns how to find its way through an artificial maze, so a human child learns the verbal behavior of the society into which it is born. The phonological, grammatical and other complexities of speech are in this sense "external" phenomena, inscribed into an initially unstructured brain. Language's emergence in Homo sapiens, from this perspective, presents no special theoretical challenge. Human behavior, whether verbal or otherwise, illustrates the malleable nature of the mammalian — and especially the human — brain.
Chomskyan Nativism Edit
Nativism is the theory that humans are born with certain specialized cognitive modules enabling us to acquire highly complex bodies of knowledge such as the grammar of a language.
"There is a long history of study of the origin of language, asking how it arose from calls of apes and so forth. That investigation in my view is a complete waste of time because language is based on an entirely different principle than any animal communication system."
From the mid-1950s onwards, Noam Chomsky,   Jerry Fodor  and others mounted what they conceptualized as a 'revolution' against behaviorism. Retrospectively, this became labelled 'the cognitive revolution'.   Whereas behaviorism had denied the scientific validity of the concept of "mind", Chomsky replied that, in fact, the concept of "body" is more problematic.  Behaviourists tended to view the child's brain as a tabula rasa, initially lacking structure or cognitive content. According to B. F. Skinner, for example, richness of behavioral detail (whether verbal or non-verbal) emanated from the environment. Chomsky turned this idea on its head. The linguistic environment encountered by a young child, according to Chomsky's version of psychological nativism, is in fact hopelessly inadequate. No child could possibly acquire the complexities of grammar from such an impoverished source.  Far from viewing language as wholly external, Chomsky re-conceptualized it as wholly internal. To explain how a child so rapidly and effortlessly acquires its natal language, he insisted, we must conclude that it comes into the world with the essentials of grammar already pre-installed.  No other species, according to Chomsky, is genetically equipped with a language faculty — or indeed with anything remotely like one.  The emergence of such a faculty in Homo sapiens, from this standpoint, presents biological science with a major theoretical challenge.
Speech act theory Edit
One way to explain biological complexity is by reference to its inferred function. According to the influential philosopher John Austin,  speech's primary function is active in the social world.
Speech acts, according to this body of theory, can be analyzed on three different levels: elocutionary, illocutionary and perlocutionary. An act is locutionary when viewed as the production of certain linguistic sounds — for example, practicing correct pronunciation in a foreign language. An act is illocutionary insofar as it constitutes an intervention in the world as jointly perceived or understood. Promising, marrying, divorcing, declaring, stating, authorizing, announcing and so forth are all speech acts in this illocutionary sense. An act is perlocutionary when viewed in terms of its direct psychological effect on an audience. Frightening a baby by saying 'Boo!' would be an example of a "perlocutionary" act.
For Austin, "doing things" with words means, first and foremost, deploying illocutionary force. The secret of this is community participation or collusion. There must be a 'correct' (conventionally agreed) procedure, and all those concerned must accept that it has been properly followed.
"One of our examples was, for instance, the utterance 'I do' (take this woman to be my lawful wedded wife), as uttered in the course of a marriage ceremony. Here we should say that in saying these words we are doing something — namely, marrying, rather than reporting something, namely that we are marrying."
In the case of a priest declaring a couple to be man and wife, his words will have illocutionary force only if he is properly authorized and only if the ceremony is properly conducted, using words deemed appropriate to the occasion. Austin points out that should anyone attempt to baptize a penguin, the act would be null and void. For reasons which have nothing to do with physics, chemistry or biology, baptism is inappropriate to be applied to penguins, irrespective of the verbal formulation used. 
This body of theory may have implications for speculative scenarios concerning the origins of speech. "Doing things with words" presupposes shared understandings and agreements pertaining not just to language but to social conduct more generally. Apes might produce sequences of structured sound, influencing one another in that way. To deploy illocutionary force, however, they would need to have entered a non-physical and non-biological realm — one of shared contractual and other intangibles. This novel cognitive domain consists of what philosophers term "institutional facts" — objective facts whose existence, paradoxically, depends on communal faith or belief.   Few primatologists, evolutionary psychologists or anthropologists consider that nonhuman primates are capable of the necessary levels of joint attention, sustained commitment or collaboration in pursuit of future goals.   
"the deciphering of the genetic code has revealed our possession of a language much older than hieroglyphics, a language as old as life itself, a language that is the most living language of all — even if its letters are invisible and its words are buried in the cells of our bodies."
Biosemiotics is a relatively new discipline, inspired in large part by the discovery of the genetic code in the early 1960s. Its basic assumption is that Homo sapiens is not alone in its reliance on codes and signs. Language and symbolic culture must have biological roots, hence semiotic principles must apply also in the animal world.
The discovery of the molecular structure of DNA apparently contradicted the idea that life could be explained, ultimately, in terms of the fundamental laws of physics. The letters of the genetic alphabet seemed to have "meaning", yet meaning is not a concept that has any place in physics. The natural science community initially solved this difficulty by invoking the concept of "information", treating information as independent of meaning. But a different solution to the puzzle was to recall that the laws of physics in themselves are never sufficient to explain natural phenomena. To explain, say, the unique physical and chemical characteristics of the planets in our solar system, scientists must work out how the laws of physics became constrained by particular sequences of events following the formation of the Sun.
According to Howard Pattee, the same principle applies to the evolution of life on earth, a process in which certain "frozen accidents" or "natural constraints" have from time to time drastically reduced the number of possible evolutionary outcomes. Codes, when they prove to be stable over evolutionary time, are constraints of this kind. The most fundamental such "frozen accident" was the emergence of DNA as a self-replicating molecule, but the history of life on earth has been characterized by a succession of comparably dramatic events, each of which can be conceptualized as the emergence of a new code.  From this perspective, the evolutionary emergence of spoken language was one more event of essentially the same kind.   
The Handicap principle Edit
In 1975, the Israeli theoretical biologist Amotz Zahavi    proposed a novel theory which, although controversial, has come to dominate Darwinian thinking on how signals evolve. Zahavi's "handicap principle" states that to be effective, signals must be reliable to be reliable, the bodily investment in them must be so high as to make cheating unprofitable.
Paradoxically, if this logic is accepted, signals in nature evolve not to be efficient but, on the contrary, to be elaborate and wasteful of time and energy. A peacock's tail is the classic illustration. Zahavi's theory is that since peahens are on the look-out for male braggarts and cheats, they insist on a display of quality so costly that only a genuinely fit peacock could afford to pay. Needless to say, not all signals in the animal world are quite as elaborate as a peacock's tail. But if Zahavi is correct, all require some bodily investment — an expenditure of time and energy which "handicaps" the signaller in some way.
Animal vocalizations (according to Zahavi) are reliable because they are faithful reflections of the state of the signaller's body. To switch from an honest to a deceitful call, the animal would have to adopt a different bodily posture. Since every bodily action has its own optimal starting position, changing that position to produce a false message would interfere with the task of carrying out the action really intended. The gains made by cheating would not make up for the losses incurred by assuming an improper posture — and so the phony message turns out to be not worth its price.  p. 69 This may explain, in particular, why ape and monkey vocal signals have evolved to be so strikingly inflexible when compared with the varied speech sounds produced by the human tongue. The apparent inflexibility of chimpanzee vocalizations may strike the human observer as surprising until we realize that being inflexible is necessarily bound up with being perceptibly honest in the sense of "hard-to-fake".
If we accept this theory, the emergence of speech becomes theoretically impossible. Communication of this kind just cannot evolve.  The problem is that words are cheap. Nothing about their acoustic features can reassure listeners that they are genuine and not fakes. Any strategy of reliance on someone else's tongue — perhaps the most flexible organ in the body — presupposes unprecedented levels of honesty and trust. To date, Darwinian thinkers have found it difficult to explain the requisite levels of community-wide cooperation and trust.
An influential standard textbook is Animal Signals, by John Maynard Smith and David Harper.  These authors divide the costs of communication into two components, (1) the investment necessary to ensure transmission of a discernible signal (2) the investment necessary to guarantee that each signal is reliable and not a fake. The authors point out that although costs in the second category may be relatively low, they are not zero. Even in relatively relaxed, cooperative social contexts — for example, when communication is occurring between genetic kin — some investment must be made to guarantee reliability. In short, the notion of super-efficient communication — eliminating all costs except those necessary for successful transmission — is biologically unrealistic. Yet speech comes precisely into this category.
The graph shows the different signal intensities as a result of costs and benefits. If two individuals face different costs but have the same benefits, or have different benefits but the same cost, they will signal at different levels. The higher signal represents a more reliable quality. The high-quality individual will maximize costs relative to benefits at a high signal intensities, while the low-quality individual maximizes their benefits relative to cost at low signal intensity. The high-quality individual is shown to take more risks (greater cost), which can be understood in terms of honest signals, which are expensive. The stronger you are, the more easily you can bear the cost of the signal, making you a more appealing mating partner. The low-quality individuals are less likely to be able to afford a specific signal, and will consequently be less likely to attract a female. 
Cognitive linguistics Edit
Cognitive linguistics views linguistic structure as arising continuously out of usage. Speakers are forever discovering new ways to convey meanings by producing sounds, and in some cases, these novel strategies become conventionalized. Between the phonological structure and semantic structure, there is no causal relationship. Instead, each novel pairing of sound and meaning involves an imaginative leap.
In their book, Metaphors We Live By, George Lakoff and Mark Johnson helped pioneer this approach, claiming that metaphor is what makes human thought special. All language, they argued, is permeated with metaphor, whose use in fact constitutes distinctively human — that is, distinctively abstract — thought. To conceptualize things which cannot be directly perceived — intangibles such as time, life, reason, mind, society or justice — we have no choice but to set out from more concrete and directly perceptible phenomena such as motion, location, distance, size and so forth. In all cultures across the world, according to Lakoff and Johnson, people resort to such familiar metaphors as ideas are locations, thinking is moving and mind is body. For example, we might express the idea of "arriving at a crucial point in our argument" by proceeding as if literally traveling from one physical location to the next.
Metaphors, by definition, are not literally true. Strictly speaking, they are fictions — from a pedantic standpoint, even falsehoods. But if we couldn't resort to metaphorical fictions, it's doubtful whether we could even form conceptual representations of such nebulous phenomena as "ideas", thoughts", "minds", and so forth.
The bearing of these ideas on current thinking on speech origins remains unclear. One suggestion is that ape communication tends to resist the metaphor for social reasons. Since they inhabit a Darwinian (as opposed to morally regulated) social world, these animals are under strong competitive pressure not to accept patent fictions as valid communicative currency. Ape vocal communication tends to be inflexible, marginalizing the ultra-flexible tongue, precisely because listeners treat with suspicion any signal which might prove to be a fake. Such insistence on perceptible veracity is clearly incompatible with metaphoric usage. An implication is that neither articulate speech nor distinctively human abstract thought could have begun evolving until our ancestors had become more cooperative and trusting of one another's communicative intentions. 
Natural science vs social science interpretations Edit
Social reality Edit
When people converse with one another, according to the American philosopher John Searle, they're making moves, not in the real world which other species inhabit, but in a shared virtual realm peculiar to ourselves. Unlike the deployment of muscular effort to move a physical object, the deployment of illocutionary force requires no physical effort (except the movement of the tongue/mouth to produce speech) and produces no effect which any measuring device could detect. Instead, our action takes place on a quite different level — that of social reality. This kind of reality is in one sense hallucinatory, being a product of collective intentionality. It consists, not of "brute facts" — facts which exist anyway, irrespective of anyone's belief — but of "institutional facts", which "exist" only if you believe in them. Government, marriage, citizenship and money are examples of "institutional facts". One can distinguish between "brute" facts and "institutional" ones by applying a simple test. Suppose no one believed in the fact — would it still be true? If the answer is "yes", it's "brute". If the answer is "no", it's "institutional". 
"Imagine a group of primitive creatures, more or less like ourselves . Now imagine that acting as a group, they build a barrier, a wall around the place where they live . The wall is designed to keep intruders out and keep members of the group in . Let us suppose that the wall gradually decays. It slowly deteriorates until all that is left is a line of stones. But let us suppose that the inhabitants continue to treat the line of stones as if it could perform the function of the wall. Let us suppose that, as a matter of fact, they treat the line of stones just as if they understood that it was not to be crossed . This shift is the decisive move in the creation of institutional reality. It is nothing less than the decisive move in the creation of what we think of as distinctive in humans, as opposed to animals, societies."
The facts of language in general and of speech, in particular, are, from this perspective, "institutional" rather than "brute". The semantic meaning of a word, for example, is whatever its users imagine it to be. To "do things with words" is to operate in a virtual world which seems real because we share it in common. In this incorporeal world, the laws of physics, chemistry, and biology do not apply. That explains why illocutionary force can be deployed without exerting muscular effort. Apes and monkeys inhabit the "brute" world. To make an impact, they must scream, bark, threaten, seduce or in other ways invest bodily effort. If they were invited to play chess, they would be unable to resist throwing their pieces at one another. Speech is not like that. A few movements of the tongue, under appropriate conditions, can be sufficient to open parliament, annul a marriage, confer a knighthood or declare war.  To explain, on a Darwinian basis, how such apparent magic first began to work, we must ask how, when and why Homo sapiens succeeded in establishing the wider domain of institutional facts.
Nature or society? Edit
"Brute facts", in the terminology of speech act philosopher John Searle,  are facts which are true anyway, regardless of human belief. Suppose you don't believe in gravity: jump over a cliff and you'll still fall. Natural science is the study of facts of this kind. "Institutional facts" are fictions accorded factual status within human social institutions. Monetary and commercial facts are fictions of this kind. The complexities of today's global currency system are facts only while we believe in them: suspend the belief and the facts correspondingly dissolve. Yet although institutional facts rest on human belief, that doesn't make them mere distortions or hallucinations. Take my confidence that these two five-pound banknotes in my pocket are worth ten pounds. That's not merely my subjective belief: it's an objective, indisputable fact. But now imagine a collapse of public confidence in the currency system. Suddenly, the realities in my pocket dissolve.
Scholars who doubt the scientific validity of the notion of "institutional facts" include Noam Chomsky, for whom language is not social. In Chomsky's view, language is a natural object (a component of the individual brain) and its study, therefore, a branch of natural science. In explaining the origin of language, scholars in this intellectual camp invoke non-social developments — in Chomsky's case, a random genetic mutation.  Chomsky argues that language might exist inside the brain of a single mutant gorilla even if no one else believed in it, even if no one else existed apart from the mutant — and even if the gorilla in question remained unaware of its existence, never actually speaking.  In the opposite philosophical camp are those who, in the tradition of Ferdinand de Saussure, argue that if no one believed in words or rules, they simply would not exist. These scholars, correspondingly, regard language as essentially institutional, concluding that linguistics should be considered a topic within social science. In explaining the evolutionary emergence of language, scholars in this intellectual camp tend to invoke profound changes in social relationships.   
Criticism. Darwinian scientists today see little value in the traditional distinction between "natural" and "social" science. Darwinism in its modern form is the study of cooperation and competition in nature — a topic which is intrinsically social.  Against this background, there is an increasing awareness among evolutionary linguists and Darwinian anthropologists that traditional inter-disciplinary barriers can have damaging consequences for investigations into the origins of speech.   
Lucy, an Australopithecus afarensis, is one of the first known relatives of mankind and her species body’s structure was designed for walking upright. Previous research of how early hominins gave birth usually emphasized the baby's head and the mother's pelvis and ignored the newborn's shoulders.
In this study, however, DeSilva and his colleagues noticed that humans and apes have broad, inflexible shoulders, while early hominins appear that they did as well. Personal experience helped DeSilva to examine the role that infants' shoulders played in early hominin birth. As he stated, "With the birth of my own children, I started to get very interested in how Australopithecus gave birth and parented their children millions of years ago.”
He also told Live Science this is the first time a study focuses on the newborn’s shoulders and not its head, “This is the first time the width of the shoulders has been considered in an attempt to reconstruct childbirth in early hominins. I'm excited anytime we can take these old fossils and bring them back to life and reconstruct what our ancestors and extinct relatives were doing."
How Humans Became Moral Beings
Why do people show kindness to others, even those outside their families, when they do not stand to benefit from it? Being generous without that generosity being reciprocated does not advance the basic evolutionary drive to survive and reproduce.
Christopher Boehm, an evolutionary anthropologist, is the director of the Jane Goodall Research Center at the University of Southern California. For 40 years, he has observed primates and studied different human cultures to understand social and moral behavior. In his new book, Moral Origins, Boehm speculates that human morality emerged along with big game hunting. When hunter-gatherers formed groups, he explains, survival essentially boiled down to one key tenet—cooperate, or die.
First of all, how do you define altruism?
Basically, altruism involves generosity outside of the family, meaning generosity toward non-kinsmen.
Why is altruism so difficult to explain in evolutionary terms?
A typical hunter-gatherer band of the type that was universal in the world 15,000 years ago has a few brothers or sisters, but almost everyone else is unrelated. The fact that they do so much sharing is a paradox genetically. Here are all these unrelated people who are sharing without being bean counters. You would expect those who are best at cheating, and taking but not giving, to be coming out ahead. Their genes should be on the rise while altruistic genes would be going away. But, in fact, we are evolved to share quite widely in bands.
What did Charles Darwin say about this “altruism paradox?”
Charles Darwin was profoundly perplexed by the fact that young men voluntarily go off to war and die for their groups. This obviously didn’t fit with his general idea of natural selection as being individuals pursuing their self-interests.
He came up with group selection as an answer to this paradox. The way it worked, if one group has more altruists than another, it is going to outcompete the other group and outreproduce it. The groups with fewer altruists would have fewer survivors. Therefore, altruism would spread at the expense of selfishness.
The problem with group selection has been that it is very hard to see how it could become strong enough to trump selection between individuals. You need an awful lot of warfare and genocide to really make group selection work.
And what did Darwin have to say about the origins of the human conscience?
What he did really was to take the conscience, set it aside as something very special and then basically say, “I throw up my hands. I can’t tell you how this could have evolved. What I can tell you is that any creature that became as intelligent and as sympathetic as humans would naturally have a conscience.”
Fast-forward a century and half—where are we now in understanding the origins of human morality and conscience?
Well, there are quite a few books on the subject. But they are almost all arguments out of evolutionary design that is, they simply look at morality and see how it functions and how it could have been genetically useful to individuals. My book is the first to actually try to look at the natural history of moral evolution. At what time and how did developments take place which led us to become moral? In a way, this is a new field of study.
Can you tell us about the database you have created to help you draw your conclusions?
It has been argued that all of the human hunter-gatherers that live today have been so politically marginalized that they really can’t be compared with prehistoric human beings who were hunting and gathering. I think that is flat-out wrong.
Since the 1970s, we have learned that the rate of climate change was just incredible in the late Pleistocene. Therefore, there was plenty of marginalization taking place 50,000 years ago, just as there has been today. Like today, some of it surely was political, in the sense that when there would be a climate downswing, everything would be scarce and hunting bands would be fighting with each other over resources.
What I have done is to look at all of the possible hunter-gatherer societies that have been studied. I simply got rid of all of those that could have never existed in the Pleistocene—mounted hunters who have domesticated horses that they got from the Spaniards, fur trade Indians who started buying rifles and killing fur-bearing animals and some very hierarchical people who developed along the northwest coast of North America. So far, I’ve very carefully gone through about 50 of the remaining societies, looking for things that they mostly share. Then, I project the patterns of shared behavior back into the period when humans were culturally modern. Now, that only gets us back to 45,000, maybe 100,000 years ago. If you go back beyond that, then there are problems, because you are not dealing with the same brains and the same cultural capacity.
About when did humans acquire a conscience?
Getting pinned down on a date is very dangerous because every scholar is going to have something to say about that. But let me just give you some probabilities. First of all, there could be little doubt that humans had a conscience 45,000 years ago, which is the conservative date that all archaeologists agree on for our having become culturally modern. Having a conscience and morality go with being culturally modern. Now, if you want to guess at how much before that, the landmark that I see as being the most persuasive is the advent of large game hunting, which came about a quarter of a million years ago.
According to your theory, how did the human conscience evolve?
People started hunting large ungulates, or hoofed mammals. They were very dedicated to hunting, and it was an important part of their subsistence. But my theory is that you cannot have alpha males if you are going to have a hunting team that shares the meat fairly evenhandedly, so that the entire team stays nourished. In order to get meat divided within a band of people who are by nature pretty hierarchical, you have to basically stomp on hierarchy and get it out of the way. I think that is the process.
My hypothesis is that when they started large game hunting, they had to start really punishing alpha males and holding them down. That set up a selection pressure in the sense that, if you couldn’t control your alpha tendencies, you were going to get killed or run out of the group, which was about the same as getting killed. Therefore, self-control became an important feature for individuals who were reproductively successful. And self-control translates into conscience.
Over how long of a period did it take to evolve?
Well, Edward O. Wilson says that it takes a thousand generations for a new evolutionary feature to evolve. In humans, that would come to 25,000 years. Something as complicated as a conscience probably took longer than that. It has some bells and whistles that are total mysteries, such as blushing with shame. No one has the slightest idea how that evolved. But I would say a few thousand generations, and perhaps between 25,000 and 75,000 years.
In what ways is morality continuing to evolve?
It is very hard to make a statement about that. I’ll make a few guesses. Prehistorically, psychopaths were probably easy to identify and were dealt with, as they had to be dealt with, by killing them. And, today, it would appear that in a large anonymous society many psychopaths really have free rein and are free to reproduce. We may need to take further moral steps at the level of culture to deal with an increase of psychopathy in our populations. But this would be over thousands of years.
Morality certainly evolves at the cultural level. For example, the American media in the last year have suddenly become very, very interested in bullies—so have school officials. Our social control is now focused much more than it ever was on bullying. It has been a major topic with hunter-gatherers. So, in a sense, you could say our moral evolution at the cultural level has rather suddenly moved back to an ancient topic.