Baboon Sounds May Hold the Key to Understanding the Formation of Human Language

Baboon Sounds May Hold the Key to Understanding the Formation of Human Language

A new study proposes that baboon grunts and barks might have more in common with human speech than most people believe. Their findings may help in the struggle to discover just how human speech developed.

Acoustical Analysis Surprises the Scientific World

According to a study published January 11, 2017 in the open-access journal PLOS ONE, an acoustical analysis of the grunts, barks, wahoos, copulation calls, and yaks from baboons showed that - just like human beings who use several vowels during speech - these animals seem to make five distinct vowel-like sounds.

The researchers, led by Dr. Louis-Jean Boë of Grenoble Alpes University, studied the acoustics of 1,335 baboon sounds, as well as the non-human primates’ tongue anatomy. Their research suggests that the human vocal system developed from abilities that already existed in ancestors such as the Guinea baboon.

  • The Origins of Human Language: One of the Hardest Problems in Science
  • Neanderthal study reveals origin of language is far older than once thought

Guinea Baboon Portrait. (Hamish Irvine/ CC BY NC 2.0 )

“Similarities between humans and baboons suggest that the vowels of human speech probably evolved from ancient articulatory precursors that were passed on and refined all along the hominid line,” co-author of the study, Joel Fagot, told Neuroscience News .

Additionally, they found similar muscles in baboon tongues as human tongues, which could be the key to our ability to make vowel sounds. As CTV News reports , the scientists wrote:

"Language is a key difference between humans and the rest of the natural world, but the origin of our speech remains one of the greatest mysteries of science. The evidence developed in this study does not support the hypothesis of the recent, sudden, and simultaneous appearance of language and speech in modern Homo sapiens. It suggests that spoken languages evolved from ancient articulatory skills already present in our last common ancestor ... about 25 million years ago."

Anatomical structure of the baboon tongue and muscle recruitment during ‘vowel-like segments’ (VLS) production. VLS refers to any continuous section within a vocalization containing a consistent and detectable formant structure. ( Boë et al )

The Origins of Human Language: One of the Hardest Problems in Science

As reported before on Ancient Origins , the beginning of human language has been a mystery pestering scientists for centuries. One of the biggest issues with this topic is that empirical evidence is still lacking despite our great advances in technology. This lack of concrete evidence even led to a past prohibition of any future debates regarding the origins of communication by the Linguistic Society of Paris. Despite the obstacles, a number of researchers including psychologists, anthropologists, archaeologists, and linguists continue studying the topic.

  • Help Save Elfdalian, the Ancient Viking Forest Language of Sweden
  • Three-Thousand-Year-Old Living Language Loses Last Monolingual Speaker

An important Neanderthal study from 2014, however, pushed the origins of language back further than most of the scientific world believed until recent years. An international team of scientists led by Associate Professor Stephen Wroe, a zoologist and paleontologist from the University of New England, made a revolutionary discovery which challenges the notion that Homo sapiens are unique in their capacity for speech and language. The current study also supports this idea – and pushes the beginnings of language even further back in the hominid line.

The research team in the 2014 Neanderthal study utilized 3D x-ray imaging technology to examine a 60,000-year-old Neanderthal hyoid bone that had been discovered in the Kebara Cave in Israel in 1989. The hyoid bone, otherwise called the lingual bone, is a small, u-shaped bone situated centrally in the upper part of the neck, beneath the mandible but above the larynx. The function of the hyoid is to provide an anchor point for the muscles of the tongue and for those in the upper part of the front of the neck.

Image depicting the location of the hyoid bone and larynx in a modern human. ( Lasaludfamiliar)

The hyoid bone, which is the only bone in the body not connected to any other, is generally thought to be the foundation of speech - and it has only been found in the right place in humans and Neanderthals. Other animals have versions of the hyoid, but only the human variety is said to be in the right position to work in unison with the larynx and tongue and make us the chatterboxes of the animal world. Without it, scientists say we'd be making noises much like chimpanzees.

A Loose Parallel Between Human Vowels and Baboon Vocalizations

However, the “noises” chimpanzees make might not be as primitive as you’d think - as recent studies on monkeys have identified five vowels, implying a link to the origins of human language.

Linear predictive coding (LPC) and spectrograms and formants (audio and speech processing and analysis) for different Guinea baboon “noises” by VLS class. ( Boë et al )

Furthermore, the authors of the current study wrote that the larynx’s position may not be as key to speech as generally believed – at least regarding vowel sounds:

“Several recent discoveries have begun to challenge this dominant view that a low larynx is required for vowel systems. First, descended and dynamically descending larynges have been discovered in animal species with no documented ability to produce systems of vowel-like sounds. Second, human infants, with their larynx still high, produce the same range of vowel qualities as adults. Third, modeling suggests that the production of vocalic sounds does not depend on the position of the larynx, but rather on the control of tongue muscles and lips to properly constrict the vocal tract. Fourth, simulations also suggest that Neanderthal vocal anatomies supported phonetic capacities equivalent to modern Homo sapiens . All these findings reopen the possibility that vocalic systems might very well be present in nonhuman primates, in spite of their high larynx.”

  • A Unique Form of Ancient Communication: The Whistling Island of La Gomera
  • Europeans share more language and genes with Asia than previously thought

Professor Scott Moisik of the Max Planck Institute for Psycholinguistics in the Netherlands, who didn’t take part in the new study, believes that its findings fit with his own experiences listening to primates in zoos and online animal videos, in an email to The Associated Press he said:

"When I hear a cat on YouTube produce a vocalization that very much sounds like 'oh long Johnson,' or the 'no' cat, or a dog that gets pretty-darned close in imitating 'I love you' ... I am led to believe that, to use the words of Boë and company, 'speech precursors' (however rudimentary or limited) go back further than 25 million years ago.”

He and colleague Dan Dediu also pointed out that vowels are just part of the equation and further research on consonant production is needed too before concrete conclusions can be made.


The cultural evolution of language

Key design features of language can be explained as the result of cultural evolution.

Experiments have found that structure emerges through transmission and communication.

Cultural transmission leads to compressible representations.

Communicative use leads to expressive languages.

Human language has unusual structural properties that enable open-ended communication. In recent years, researchers have begun to appeal to cultural evolution to explain the emergence of these structural properties. A particularly fruitful approach to this kind of explanation has been the use of laboratory experiments. These typically involve participants learning and interacting using artificially constructed communication systems. By observing the evolution of these systems in the lab, researchers have been able to build a bridge between individual cognition and population-wide emergent structure. We review these advances, and show how cultural evolution has been used to explain the origins of structure in linguistic signals, and in the mapping between signals and meanings.


Florence Nightingale: Early Life

Florence Nightingale was born on May 12, 1820, in Florence, Italy to Frances Nightingale and William Shore Nightingale. She was the younger of two children. Nightingale’s affluent British family belonged to elite social circles. Her mother, Frances, hailed from a family of merchants and took pride in socializing with people of prominent social standing. Despite her mother’s interest in social climbing, Florence herself was reportedly awkward in social situations. She preferred to avoid being the center of attention whenever possible. Strong-willed, Florence often butted heads with her mother, whom she viewed as overly controlling. Still, like many daughters, she was eager to please her mother. “I think I am got something more good-natured and complying,” Florence wrote in her own defense, concerning the mother-daughter relationship.

Florence’s father was William Shore Nightingale, a wealthy landowner who had inherited two estates—one at Lea Hurst, Derbyshire, and the other in Hampshire, Embley Park—when Florence was five years old. Florence was raised on the family estate at Lea Hurst, where her father provided her with a classical education, including studies in German, French and Italian.

From a very young age, Florence Nightingale was active in philanthropy, ministering to the ill and poor people in the village neighboring her family’s estate. By the time she was 16 years old, it was clear to her that nursing was her calling. She believed it to be her divine purpose.

When Nightingale approached her parents and told them about her ambitions to become a nurse, they were not pleased. In fact, her parents forbade her to pursue nursing. During the Victorian Era, a young lady of Nightingale’s social stature was expected to marry a man of means—not take up a job that was viewed as lowly menial labor by the upper social classes. When Nightingale was 17 years old, she refused a marriage proposal from a “suitable” gentleman, Richard Monckton Milnes. Nightingale explained her reason for turning him down, saying that while he stimulated her intellectually and romantically, her “moral�tive nature…requires satisfaction, and that would not find it in this life.” Determined to pursue her true calling despite her parents’ objections, in 1844, Nightingale enrolled as a nursing student at the Lutheran Hospital of Pastor Fliedner in Kaiserwerth, Germany.


Was "nom, nom" the sound for eating?

Credit: Aleksandra Ćwiek, et al. / Scientific Reports

Making a list — and making noises — is one thing finding out if anyone understands them is another. The researchers tested out their iconic sounds in two different experiments.

In an online experiment, speakers of 25 different languages were asked to match the meaning of iconic sounds to six written labels. They listened to three performances for each of the 30 candidates, 90 recordings in all.

Participants correctly identified the sounds' meaning roughly 65 percent of the time.

Some meanings were more readily understood than others. "Sleep" was correctly identified by almost 99 percent, as opposed to "that," understood by only 35 percent. The most often understood sounds were "eat," "child," "sleep," "tiger," and "water." The least? "That," "gather," "sharp," "dull," and "knife."

The researchers next conducted field experiments to capture the meaningfulness of the sounds in oral cultures with inconsistent literacy levels. For these people, researchers played twelve iconic sounds for animals and inanimate objects as listeners identified each from a grid of pictures. The volunteers correctly identified the sounds' meanings about 56 percent of the time, again above the level of chance.


Early Voices: The Leap to Language

Bower birds are artists, leaf-cutting ants practice agriculture, crows use tools, chimpanzees form coalitions against rivals. The only major talent unique to humans is language, the ability to transmit encoded thoughts from the mind of one individual to another.

Because of language's central role in human nature and sociality, its evolutionary origins have long been of interest to almost everyone, with the curious exception of linguists.

As far back as 1866, the Linguistic Society of Paris famously declared that it wanted no more speculative articles about the origin of language.

More recently, many linguists have avoided the subject because of the influence of Noam Chomsky, a founder of modern linguistics and still its best-known practitioner, who has been largely silent on the question.

Dr. Chomsky's position has ''only served to discourage interest in the topic among theoretical linguists,'' writes Dr. Frederick J. Newmeyer, last year's president of the Linguistic Society of America, in ''Language Evolution,'' a book of essays being published this month by Oxford University Press in England.

In defense of the linguists' tepid interest, there have until recently been few firm facts to go on. Experts offered conflicting views on whether Neanderthals could speak. Sustained attempts to teach apes language generated more controversy than illumination.

But new research is eroding the idea that the origins of language are hopelessly lost in the mists of time. New clues have started to emerge from archaeology, genetics and human behavioral ecology, and even linguists have grudgingly begun to join in the discussion before other specialists eat their lunch.

''It is important for linguists to participate in the conversation, if only to maintain a position in this intellectual niche that is of such commanding interest to the larger scientific public,'' writes Dr. Ray Jackendoff, Dr. Newmeyer's successor at the linguistic society, in his book 'ɿoundations of Language.''

Geneticists reported in March that the earliest known split between any two human populations occurred between the !Kung of southern Africa and the Hadza of Tanzania. Since both of these very ancient populations speak click languages, clicks may have been used in the language of the ancestral human population. The clicks, made by sucking the tongue down from the roof of the mouth (and denoted by an exclamation point), serve the same role as consonants.

That possible hint of the first human tongue may be echoed in the archaeological record. Humans whose skeletons look just like those of today were widespread in Africa by 100,000 years ago. But they still used the same set of crude stone tools as their forebears and their archaic human contemporaries, the Neanderthals of Europe.

Then, some 50,000 years ago, some profound change took place. Settlements in Africa sprang to life with sophisticated tools made from stone and bone, art objects and signs of long distance trade.

Though some archaeologists dispute the suddenness of the transition, Dr. Richard Klein of Stanford argues that the suite of innovations reflects some specific neural change that occurred around that time and, because of the advantage it conferred, spread rapidly through the population.

That genetic change, he suggests, was of such a magnitude that most likely it had to do with language, and was perhaps the final step in its evolution. If some neural change explains the appearance of fully modern human behavior some 50,000 years ago, ''it is surely reasonable to suppose that the change promoted the fully modern capacity for rapidly spoken phonemic speech,'' Dr. Klein has written.

Apes' Signals Fall Short of Language

At first glance, language seems to have appeared from nowhere, since no other species speaks. But other animals do communicate. Vervet monkeys have specific alarm calls for their principal predators, like eagles, leopards, snakes and baboons.

Researchers have played back recordings of these calls when no predators were around and found that the vervets would scan the sky in response to the eagle call, leap into trees at the leopard call and look for snakes in the ground cover at the snake call.

Vervets can't be said to have words for these predators because the calls are used only as alarms a vervet can't use its baboon call to ask if anyone noticed a baboon around yesterday. Still, their communication system shows that they can both utter and perceive specific sounds.

Dr. Marc Hauser, a psychologist at Harvard who studies animal communication, believes that basic systems for both the perception and generation of sounds are present in other animals. ''That suggests those systems were used way before language and therefore did not evolve for language, even though they are used in language,'' he said.

Language, as linguists see it, is more than input and output, the heard word and the spoken. It's not even dependent on speech, since its output can be entirely in gestures, as in American Sign Language. The essence of language is words and syntax, each generated by a combinatorial system in the brain.

If there were a single sound for each word, vocabulary would be limited to the number of sounds, probably fewer than 1,000, that could be distinguished from one another. But by generating combinations of arbitrary sound units, a copious number of distinguishable sounds becomes available. Even the average high school student has a vocabulary of 60,000 words.

The other combinatorial system is syntax, the hierarchical ordering of words in a sentence to govern their meaning.

Chimpanzees do not seem to possess either of these systems. They can learn a certain number of symbols, up to 400 or so, and will string them together, but rarely in a way that suggests any notion of syntax. This is not because of any poverty of thought. Their conceptual world seems to overlap to some extent with that of people: they can recognize other individuals in their community and keep track of who is dominant to whom. But they lack the system for encoding these thoughts in language.

How then did the encoding system evolve in the human descendants of the common ancestor of chimps and people?

Babbling and Pidgins Hint at First Tongue

One of the first linguists to tackle this question was Dr. Derek Bickerton of the University of Hawaii. His specialty is the study of pidgins, which are simple phrase languages made up from scratch by children or adults who have no language in common, and of creoles, the successor languages that acquire inflection and syntax.

Dr. Bickerton developed the idea that a proto-language must have preceded the full-fledged syntax of today's discourse. Echoes of this proto-language can be seen, he argued, in pidgins, in the first words of infants, in the symbols used by trained chimpanzees and in the syntax-free utterances of children who do not learn to speak at the normal age.

In a series of articles, Dr. Bickerton has argued that humans may have been speaking proto-language, essentially the use of words without syntax, as long as two million years ago. Modern language developed more recently, he suggests, perhaps with appearance of anatomically modern humans some 120,000 years ago.

The impetus for the evolution of language, he believes, occurred when human ancestors left the security of the forest and started foraging on the savanna. ''The need to pass on information was the driving force,'' he said in an interview.

Foragers would have had to report back to others what they had found. Once they had developed symbols that could be used free of context -- a general word for elephant, not a vervet-style alarm call of 'ɺn elephant is attacking!'' -- early people would have taken the first step toward proto-language. ''Once you got it going, there is no way of stopping it,'' Dr. Bickerton said.

But was the first communicated symbol a word or a gesture? Though language and speech are sometimes thought of as the same thing, language is a coding system and speech just its main channel.

Dr. Michael Corballis, a psychologist at the University of Auckland in New Zealand, believes the gesture came first, in fact as soon as our ancestors started to walk on two legs and freed the hands for making signs.

Chimpanzees have at least 30 different gestures, mostly used to refer to other individuals.

Hand gestures are still an expressive part of human communication, Dr. Corballis notes, so much so that people even gesticulate while on the telephone.

He believes that spoken words did not predominate over signed ones until the last 100,000 years or so, when a genetic change may have perfected human speech and led to its becoming a separate system, not just a grunted accompaniment for gestures.

Critics of Dr. Corballis's idea say gestures are too limited they don't work in the dark, for one thing. But many concede the two systems may both have played some role in the emergence of language.

As Societies Grew The Glue Was Gossip

Dr. Bickerton's idea that language must have had an evolutionary history prompted other specialists to wonder about the selective pressure, or evolutionary driving force, behind the rapid emergence of language.

In the mere six million years since chimps and humans shared a common ancestor, this highly complex faculty has suddenly emerged in the hominid line alone, along with all the brain circuits necessary to map an extremely rapid stream of sound into meaning, meaning into words and syntax, and intended sentence into expressed utterance.

It is easy to see in a general way that each genetic innovation, whether in understanding or in expressing language, might create such an advantage for its owners as to spread rapidly through a small population.

''No one will take any notice of the guy who says 'Gu-gu-gu' the one with the quick tongue will get the mates,'' Dr. Bickerton said. But what initiated this self-sustaining process?

Besides Dr. Bickerton's suggestion of the transition to a foraging lifestyle, another idea is that of social grooming, which has been carefully worked out by Dr. Robin Dunbar, an evolutionary psychologist at the University of Liverpool in England.

Dr. Dunbar notes that social animals like monkeys spend an inordinate amount of time grooming one another. The purpose is not just to remove fleas but also to cement social relationships. But as the size of a group increases, there is not time for an individual to groom everyone.

Language evolved, Dr. Dunbar believes, as a better way of gluing a larger community together.

Some 63 percent of human conversation, according to his measurements, is indeed devoted to matters of social interaction, largely gossip, not to the exchange of technical information, Dr. Bickerton's proposed incentive for language.

Dr. Steven Pinker of the Massachusetts Institute of Technology, one of the first linguists to acknowledge that language may be subject to natural selection, disputes Dr. Dunbar's emphasis on social bonding a fixed set of greetings would suffice, in his view.

Dr. Pinker said it was just as likely that language drove sociality: it was because people could exchange information that it became more worthwhile to hang out together.

''Three key features of the distinctively human lifestyle -- know-how, sociality and language -- co-evolved, each constituting a selection pressure for the others,'' Dr. Pinker writes in ''Language Evolution,'' the new book of essays.

But sociality, from Dr. Dunbar's perspective, helps explain another feature of language: its extreme corruptibility. To convey information, a stable system might seem most efficient, and surely not beyond nature's ability to devise. But dialects change from one village to another, and languages shift each generation.

The reason, Dr. Dunbar suggests, is that language also operates as a badge to differentiate the in group from outsiders thus the Gileadites could pick out and slaughter any Ephraimite asked to say ''shibboleth'' because, so the writer of Judges reports, ''He said sibboleth: for he could not frame to pronounce it right.''

From Family Failing First Gene Emerges

A new approach to the evolution of language seems to have been opened with studies of a three-generation London family known as KE. Of its 29 members old enough to be tested, 14 have a distinctive difficulty with communication. They have trouble pronouncing words properly, speaking grammatically and making certain fine movements of the lips and tongue.

Asked to repeat a nonsense phrase like ''pataca pataca pataca,'' they trip over each component as if there were three different words.

Some linguists have argued that the KE family's disorder has nothing specific to do with language and is some problem that affects the whole brain. But the I.Q. scores of affected and unaffected members overlap, suggesting the language systems are specifically at fault. Other linguists have said the problem is just to do with control of speech. But affected members have problems writing as well as speaking.

The pattern of inheritance suggested that a single defective gene was at work, even though it seemed strange that a single gene could have such a broad effect. Two years ago, Dr. Simon Fisher and Prof. Tony Monaco, geneticists at the University of Oxford in England, discovered the specific gene that is changed in the KE family. Called FOXP2, its role is to switch on other genes, explaining at once how it may have a range of effects. FOXP2 is active in specific regions of the brain during fetal development.

The gene's importance in human evolution was underlined by Dr. Svante Paabo and colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. In a study last year they reported that FOXP2 is highly conserved in evolution -- in other words, that the precise sequence of units in FOXP2's protein product is so important that any change is likely to lead to its owner's death.

In the 70 million years since people and mice shared a common ancestor, there have been just three changes in the FOXP2 protein's 715 units, Dr. Paabo reported. But two of those changes occurred in the last six million years, the time since humans and chimps parted company, suggesting that changes in FOXP2 have played some important role in human evolution.

Sampling the DNA of people around the world, Dr. Paabo found signs of what geneticists call a selective sweep, meaning that the changed version of FOXP2 had spread through the human population, presumably because of some enormous advantage it conferred.

That advantage may have been the perfection of speech and language, from a barely comprehensible form like that spoken by the affected KE family members to the rapid articulation of ordinary discourse. It seems to have taken place about 100,000 years ago, Dr. Paabo wrote, before modern humans spread out of Africa, and is 'ɼompatible with a model in which the expansion of modern humans was driven by the appearance of a more proficient spoken language.''

FOXP2 gives geneticists what seems to be a powerful entry point into the genetic and neural basis for language. By working out what other genes it interacts with, and the neural systems that these genes control, researchers hope to map much of the circuitry involved in language systems.

Linguists Return To Ideas of Origins

The crescendo of work by other specialists on language evolution has at last provoked linguists' attention, including that of Dr. Chomsky. Having posited in the early 1970's that the ability to learn the rules of grammar is innate, a proposition fiercely contested by other linguists, Dr. Chomsky might be expected to have shown keen interest in how that innateness evolved. But he has said very little on the subject, a silence that others have interpreted as disdain.

As Dr. Jackendoff, the president of the Linguistic Society of America, writes: ''Opponents of Universal Grammar argue that there couldn't be such a thing as Universal Grammar because there is no evolutionary route to arrive at it. Chomsky, in reply, has tended to deny the value of evolutionary argumentation.''

But Dr. Chomsky has recently taken a keen interest in the work by Dr. Hauser and his colleague Dr. W. Tecumseh Fitch on communication in animals. Last year the three wrote an article in Science putting forward a set of propositions about the way that language evolved. Based on experimental work by Dr. Hauser and Dr. Fitch, they argue that sound perception and production can be seen in other animals, though they may have been tweaked a little in hominids.

A central element in language is what linguists call recursion, the mind's ability to bud one phrase off another into the syntax of an elaborate sentence. Though recursion is not seen in animals, it could have developed, the authors say, from some other brain system, like the one animals use for navigation.

Constructing a sentence, and going from A to Z through a series of landmarks, could involve a similar series of neural computations. If by some mutation a spare navigation module developed in the brain, it would have been free to take on other functions, like the generation of syntax. ''If that piece got integrated with the rest of the cognitive machinery, you are done, you get music, morality, language,'' Dr. Hauser said.

The researchers contend that many components of the language faculty exist in other animals and evolved for other reasons, and that it was only in humans that they all were linked. This idea suggests that animals may have more to teach about language than many researchers believe, but it also sounds like a criticism of evolutionary psychologists like Dr. Pinker and Dr. Dunbar, who seek to explain language as a faculty forced into being by specifics of the human lifestyle.

Dr. Chomsky rejects the notion that he has discouraged study of the evolution of language, saying his views on the subject have been widely misinterpreted.

''I have never expressed the slightest objection to work on the evolution of language,'' he said in an e-mail message. He outlined his views briefly in lectures 25 years ago but left the subject hanging, he said, because not enough was understood. He still believes that it is easy to make up all sorts of situations to explain the evolution of language but hard to determine which ones, if any, make sense.

But because of the importance he attaches to the subject, he returned to it recently in the article with Dr. Hauser and Dr. Fitch. By combining work on speech perception and speech production with a study of the recursive procedure that links them, ''the speculations can be turned into a substantive research program,'' Dr. Chomsky said.

Others see Dr. Chomsky's long silence on evolution as more consequential than he does. ''The fact is that Chomsky has had, and continues to have, an outsize influence in linguistics,'' Dr. Pinker said in an e-mail message. Calling Dr. Chomsky both ''undeniably, a brilliant thinker'' and 'ɺ brilliant debating tactician, who can twist anything to his advantage,'' Dr. Pinker noted that Dr. Chomsky ''has rabid devotees, who hang on his every footnote, and sworn enemies, who say black whenever he says white.''

''That doesn't leave much space,'' Dr. Pinker went on, 'ɿor linguists who accept some of his ideas (language as a mental, combinatorial, complex, partly innate system) but not others, like his hostility to evolution or any other explanation of language in terms of its function.''

Biologists and linguists have long inhabited different worlds, with linguists taking little interest in evolution, the guiding theory of all biology. But the faculty for language, along with the evidence of how it evolved, is written somewhere in the now decoded human genome, waiting for biologists and linguists to identify the genetic program that generates words and syntax.


Discussion

Implications for the genesis of mutation

We set out to test whether differences in baboon and human mutation rates are readily explained by their life histories. As a starting point, we considered a simple model in which mutations are proportional to cell divisions, females have the same number of cell divisions in the 2 species, and per-cell division mutation rates over ontogenesis are the same in the 2 species. Under these assumptions, we would expect a stronger paternal age effect in baboons and a higher male mutation bias in humans. Neither of these expectations are met: The paternal age effect is not discernably stronger in baboons, and the male bias is similar—as it is in other mammals for which direct pedigree estimates of sex-specific rates exist (Fig 3B).

A likely possibility is that some of our assumptions are wrong. In particular, a recent review argued that germline mutations are replicative in origin and hence track cell divisions but that the rate of SSC divisions is much lower than previously believed [45]. Although plausible [45,46], this explanation alone would not explain our findings: If mutations were due to replication errors and if rates of SSC divisions were very low, then without making further assumptions, we would expect human and baboon paternal mutation rates per generation to be highly similar, when they are not. In turn, the approximately 2-fold lower mutation rate observed in baboon compared with human females could be explained if there are fewer rounds of DNA replication in baboons than humans (or greater replication fidelity). Thus, individual observations can be explained under a replicative model by invoking specific parameters.

Taken together with other studies, however, our findings add to a growing set of observations that do not readily fit a model in which most germline mutations track cell divisions, including that (1) in humans and in baboons, there is a maternal age effect on mutations, which contributes a substantial proportion of maternal mutations, despite the absence of cell divisions after the birth of the future mother [17,19,32 this paper] (2) the male mutation bias in humans is already approximately 3:1 by puberty, when germ cells from the 2 sexes are thought to have experienced similar numbers of cell divisions by then [32] (3) in humans, the male mutation bias barely increases with parental age, and even less so once CpG transitions are excluded, despite ongoing SSC divisions [32] and (4) the sex bias in mutation rates is roughly similar across mammals [this paper 4]. Observation 1 indicates that a non-negligible fraction of mutations in females are nonreplicative. Observations 2–4 could be explained by replication errors if we assume that a number of current beliefs about spermatogenesis are incorrect: namely, that there are more (or more mutagenic) cell divisions in males than females before puberty and that there are fewer (or less mutagenic) cell divisions in males after puberty. Even if both conditions hold, all the parameters would still need to conveniently cancel out both within humans and across mammals to generate an apparent dependence on absolute time rather than on cell divisions [16] and a relative stability of the male bias in mutation.

An alternative is that germline mutations are predominantly due to damage in both sexes. Accounting for all 4 observations would require damage to accrue at a relatively fixed rate across mammals, but at a somewhat higher rate in males than in females, and be inefficiently repaired relative to the cell cycle length [16]. In principle, this hypothesis could then explain the relative stability of the male mutation bias with parental ages in humans, the similarity of the male mutation bias across mammals, and the similarity of the mutation spectrum in the 2 sexes. It would also explain why primate mutation rates per generation appear to roughly follow typical ages of reproduction [this paper 25]. However, it too requires a number of assumptions, and these remain to be tested (e.g., [47]).

Comparing contemporary mutation rates and substitution rates

Studies of divergence in primates clearly demonstrate that neutral substitution rates vary substantially across the phylogeny [29]. Notably, the olive baboon has accrued 35% more substitutions along its lineage as compared with humans since their common ancestor (Fig 4A). If neutral, mutations are expected to fix at the rate at which they arise [48]. Thus, we would expect the mutation rate per unit time in baboons to be substantially higher than that in humans. To evaluate this hypothesis, we converted our de novo germline mutation rates to yearly rates using a sex-averaged model that accounts for sex-specific relationships of mutation rates to age and sex-specific life history traits [42]. This yielded yearly mutation rates of 5.49×10 −10 in baboons, 35% (95% CI 18%–51%) larger than the rate of 4.08×10 −10 in humans (Fig 4B). Thus, the ratio of present-day yearly mutation rates appears to be quite consistent with the observed substitution rate ratio in these 2 species.

(A) Phylogenetic relationship between humans and baboons with a marmoset (New World monkey) outgroup. Branch lengths denote the autosomal substitution rate per bp since the OWM–marmoset split as measured using data from [29] for all mutation types at putatively neutral regions of the genome. The relative branch length difference between baboon and human lineages is indicated in purple. (B) Sex-averaged mutation rates per year. Mutation rates were based on fitted values for typical generation times (i.e., assuming 32.0 and 28.2 years in human males and females, respectively, and 10.7 and 10.2 years in baboon males and females) and turned into a sex-averaged per-year mutation rate following [42]. Vertical lines indicate the span covered by the 95% CIs of the intercept and slope of the age effect regressions. (C) The ratio of yearly mutation and substitution rates in baboon relative to human, as estimated for the different possible types involving combinations of strong (S: G/C) and weak (W: A/T) bp. Each point denotes a different type, and strong-to-weak (S>W) types were separated into those that occurred at a CpG or a non-CpG site. Points are colored according to whether GC-biased gene conversion is expected to favor (light red), disfavor (dark red), or have no effect (blue) on the mutation type. Horizontal lines denote 95% CIs on the mutation rate ratio computed by resampling of 50 cM blocks. The upper CI for CpG S>W extends out of frame to 2.8. Point estimates for the substitution rates in baboons and humans were taken from [29]. The identity line is drawn in gray for reference. (D) Predicted divergence times of humans and OWMs as a function of parental ages. Divergence times were predicted using mutation and autosomal substitution rates measured in humans (teal) and baboons (orange), across a span of plausible past generation times. Each point within the shaded areas represents the divergence time calculated at a particular paternal generation time (x-axis) and paternal-to-maternal generation time ratio (ranging from 0.8 to 1.2) as indicated in purple. The dashed gray line indicates a plausible upper bound for the split time inferred from the fossil record [49,50]. Underlying data for this figure can be found in S2 Data. BGC, biased gene conversion bp, base pair cM centimorgan CpG, 5′-cytosine-phosphate-guanine-3′ OWM, Old World monkey.

Because biased gene conversion on mutation acts like selection and influences the substitution process, we further broke up substitutions by type, depending on whether the fixation probability was increased, decreased, or unaffected by biased gene conversion our findings are as expected, with mutations favored (or disfavored) by biased gene conversion showing slightly higher (or lower) substitution rates relative to mutation rates (Fig 4C). Although imprecisely estimated, mutation types not subject to biased gene conversion (Strong [G/C] > Strong and Weak [A/T] > Weak) show good agreement between mutation and substitution rates.

If mutations are neutral and accumulate at a fixed rate, we can relate divergence levels to mutation rates in order to estimate the mean time to the most recent common ancestor (MRCA), in this case of OWMs and great apes. Dividing the human neutral substitution rate by the yearly mutation rate yields a time of 64 million years (My), whereas the same calculation using rates estimated in baboons yields a divergence time of 65 My. Yet evidence from the fossil record dates the OWM–great ape population split time to at most 35 My [49,50]. Although divergence-based estimates are for the mean time to the MRCA rather than the split time, these two are expected to be very similar for species so diverged (in units of Ne generations, where Ne is the effective population size) [51]. Thus, the number of substitutions suggests a split time that is implausibly old.

A possible explanation is that yearly mutation rates in both human and baboon lineages have slowed towards the present because of changes in life history traits alone [14,28,42]. We explored this hypothesis by examining the effect of historical generation time on the inferred mean time to the common ancestor (Fig 4D). We varied paternal generation times ranging from a lower bound of 3 years (the average age of reproduction of various New World monkey species [51]) in both species to upper bounds of 32 years in humans and 15 years in baboons we further allowed the male-to-female generation time ratio to vary from 0.8 to 1.2 [42]. We used the age effect point estimates published by Gao and colleagues [32] as the age effect parameters of humans in our model, reasoning that—being drawn from a larger sample—these estimates would be more precise in humans. Given that we had too few baboon trios to estimate parameters precisely, we assumed that the strength of the parental age effects in baboons are similar to that of humans and used the estimates of Gao and colleagues to model mutation accumulation in baboons as well, despite tentative evidence that the baboon paternal age effect may be weaker (S7 Fig). Our analysis suggested that, in both species, implausibly low generation times of approximately 3–5 years would be required to yield divergence times that are more in line with fossil-based estimates and even then, barely so. Instead using our own estimates for the age effect parameters in baboon males and females leads to the same conclusion (S8 Fig). Thus, our results extend the puzzle first pointed out by Scally and Durbin [53] of an apparent disconnect between the evolutionary times suggested by phylogenetic and pedigree data in humans. Reconciling them now requires not only a slowdown of the mutation rate per generation in humans but also in baboons.

A parallel slowdown in both lineages seems highly unlikely if mutations are replicative in origin, given that changes in life history cannot plausibly explain the magnitude of the effect. In principle, one might imagine that germline mutation rates in the 2 species are shaped by the same exogenous mutagen and that a shift occurring after their split affected rates similarly in both lineages, leading to a parallel slowdown. If so, the change in damage rate could not have affected the ratio of male-to-female mutations much, because α appears to be similar in both species. To evaluate this possibility, it will be important to obtain comparable estimates from more species, in particular, an outgroup to OWM and apes, such as a New World monkey. An alternative is that the OWM fossil record has been misinterpreted to suggest a more recent split time of OWMs and apes than is truly the case.

More generally, although we have argued above that germline mutation patterns in humans and baboons are more easily explained if they are primarily due to damage, such a hypothesis does not provide an immediate explanation for why per-year mutation and substitution rates vary across mammalian species or tend to be higher in shorter-lived ones [12,14–16,54]. One possibility is that rates of damage co-vary somewhat with life history traits [55], with a tendency towards higher damage rates in shorter-lived species. In that regard, it would be interesting to characterize substitution rates in sets of species that differ in their environmental exposures and metabolic rates and examine differences in their mutation spectrum in light of known mutagens (e.g., [9]).


Language and its Importance to Society | Essay

From what has been written so far it is clear that man is possessed of natural sociality. His disposition to band together with his fellows for lower or for higher purposes is one of his fundamental characteristics. To understand his fellows and to be understood by them, men were impelled to the production of language without which they could not communicate with each other.

The desire of communication was the main cause of language making. Nowhere has the old proverb “Necessity is the mother of invention” received a better illustration than in the history of language it was to satisfy the wants of daily life that the faculty of speech was first exercised. Charles Winick has defined language as “a system of arbitrary vocal symbols, used to express communicable thoughts and feelings and enabling the members of a social group or speech community to interact and to co-operate.” It is the medium of oral expression.

The Origin of Language:

Language is an institution:

Language is a product not of one cause but of several factors. It is, in fact a social creation, a human invention an unconscious invention of a whole community. As Professor Whitney has observed, it is as much an institution as a body of unwritten laws, and like these it has been called forth by the needs of developing society.”

The linguists are not in a position to form any conjectures as to the precise point in the history of man at which the germs of speech should have appeared, and the time which they should have occupied in the successive steps of their development. That the process was a slow one, all agree.

To quote Whitney, “Language making is a mere incident of social life and of cultural growth. It is as great an error to hold that at some period men are engaged in making and laying up expressions for their own future use and that of their descendants, as that, at another period, succession shall find expression. Each period provides just what it has occasion for, nothing more. The production of language is a continuous process it varies in rate and kind with the circumstances and habits of the speaking community, but it never ceases there was never a time when it was more truly going than at present.”

Thus language is not the creation of one person or of one period but it is an institution, on which hundreds of generations and countless individual workers have worked.

Three Instrumentalities of Expression:

The traditional instrumentalities of expression are gestures, grimace and tone. Gesture means the changes of the position of the various parts of the body, especially of the most mobile parts, the arms and hands grimace means the change of expression of features of the countenance, and tone is the utterance of or the production of audible sound.”

These are also termed natural means of expression. In the first stages of communicative expression, all these three were used together, and in fact, there can never have been a period or stage in which all the three instrumentalities were not put to use together. They are used even today. It is very interesting to know what signs or what facial expressions were used for words.”

James gave a list of 104 signs employed by the North American Indians in the place of words. Darkness, for instance, was indicated by extending the hands horizontally forwards and backwards and passing one over the other so as to touch it once or twice a man by a finger held up vertically running by first doubling the arm upon itself and then throwing the elbow backwards and forwards. Out of these three instrumentalities of expression voice or tone has won to itself the chief and almost exclusive part in communication.

How long man, after he came into such being as he now is physically and intellectually, continued to communicate with signs is a question which is idle to try to answer even conjecturally. How the first scanty and formless signs have been changed into the immense variety and fullness of existing speech, it is impossible to point out because nearly the whole process is hidden in the darkness of an impenetrable past.

Probably the man had to undergo the same labour in learning the speech which a child has now to undergo in learning its mother-tongue with this difference that primitive man was a grown child who painfully elaborated a language for himself whereas the individual child has but to acquire a language already formed.

The Importance of Language:

Language is a constituent element of civilization. It raised man from a savage state to the plane which he was capable of reaching. Man could not become man except by language. An essential point in which man differs from animals is that man alone is the sole possessor of language. No doubt animals also exhibit certain degree of power of communication but that is not only inferior in degree to human language, but also radically diverse in kind from it.

Language is one of the most marked, conspicuous, as well as fundamentally characteristic of the faculties of man. The importance of language for man and society cannot be minimised. As a personal thing, language is not only a mode of communication between individuals but is also a way for the expression of their personality.

Sociologically, language moulds the individual from infancy. The child comes to know most of the things of the world through language.

It is an important attribute of his personality. Its importance to the society lies in the following:

(i) Easy Social Contact:

Firstly, it makes social contact easy. Society, as we have seen, is a web of social relationships which imply development of social contacts among the individuals with language contacts become easy to be established because men can easily exchange their ideas. According to E. H. Sturtevant, “A language is a system of arbitrary vocal symbols by which members of a social group cooperate and interact.

Secondly, language helps or hinders the spread of culture. Ideas require language. Sometimes an idea or concept is hard to translate because the language has no words with which to express it. We are facing this difficulty in our country because Hindi, our national language does not possess terms for a number of English words used in sciences.

The Hindi linguists have coined some words to replace English as a medium of instruction. These coined words are, however, more difficult to understand and remember than the English words. Language conserves our culture which it passes to posterity. Language may be called culture-carrier.

The culture that exists at a given time and place has come from the past and is the result of accumulation of things, attitudes, ideas, knowledge, error and prejudice. The animals as we have seen are incapable of speech except for a few sounds and so incapable of having any culture and civilization. It is man alone who through language has acquired a high degree of culture and civilization. As pointed out above it raised man from savage state to a noble state.

(iii) Easy Conveyance of Ideas:

Thirdly, language gives a capacity for conveying ideas about a great variety of things. In times when there was no language the ideas were transmitted by signs or cries which were not easy to interpret. Man felt great difficulty in the clear expression of states of emotion.

There was no uniformity of these signs or cries. Some of these signs were quite complicated, for instance, ‘man’ was denoted- by extending the forefinger, the rest of the hand being shut, and drawing a line with it from the pit of the stomach down as far as can be conveniently reached.

But with the invention of language now a number of ideas and states of emotion can be conveyed in an easy and simple way. A language that could transmit an idea such as “the flood came and destroyed the houses” through delicate variations in sound was an achievement far superior Lo the transmission of ideas by a variety of cries.

Thus importance of language to society is clear. It has led man from mere clumsy animal to a human being in the real sense of the word. It has simplified the conveyance of ideas, smoothed social contacts, conserved our culture and transmitted it Lo posterity. In fact, language is very valuable possession which has elevated man from the level of a savage to the plane of the ‘Lord of Creation’.

Need for a Universal Language:

The people of different parts of the world speak different languages. Not only that, people living in the same territory use different languages or speak different dialects. These differences in the language of the people of the world have served to limit inter-group communication and perpetuate social isolation.

Since language is a great medium of communication the assumption has been made that if the people of the world have the same language it may help a great deal in removing the culture barriers and bring the people of the world nearer to each other thereby serving the cause of international understanding and cooperation.

No doubt, a universal language may help in the cultural unification of the people of the world and remove misunderstanding that grow out of inability to communicate effectively, but the practical difficulty is to find out such a language.

The proponents of different languages claim that ‘their language is better than any other language and that it alone provides a more efficient means of communication that it is more explicit, more logical, more flexible and far more easier to master.

Efforts have also been made to improve the existing languages, to make them more simplified and logical. But as yet no universal single language has been agreed upon and consequently the linguistic differences continue. It is also difficult for any people to learn more readily any other language than the mother-tongue.


Erikson’s Stages of Psychosocial Development

Erikson’s psychosocial stages of development focus on the resolution of different crises to become a successful, complete person.

Learning Objectives

Summarize Erikson’s stages of psychosocial development

Key Takeaways

Key Points

  • Erik Erikson (1902–1994) was a stage theorist who took Freud’s controversial psychosexual theory and modified it into an eight-stage psychosocial theory of development.
  • During each of Erikson’s eight development stages, two conflicting ideas must be resolved successfully in order for a person to become a confident, contributing member of society. Failure to master these tasks leads to feelings of inadequacy.
  • Erikson’s eight stages of psychosocial development include trust vs. mistrust, autonomy vs. shame/doubt, initiative vs. guilt, industry vs. inferiority, identity vs. role confusion, intimacy vs. isolation, generativity vs. stagnation, and integrity vs. despair.
  • Erikson also expanded upon Freud’s stages by discussing the cultural implications of development certain cultures may need to resolve the stages in different ways based upon their cultural and survival needs.

Key Terms

  • psychosocial: Having both psychological and social aspects.
  • autonomy: Self-government freedom to act or function independently.

Erikson’s Theory

Erik Erikson (1902–1994) was a stage theorist who took Freud’s controversial theory of psychosexual development and modified it as a psychosocial theory. Erikson emphasized that the ego makes positive contributions to development by mastering attitudes, ideas, and skills at each stage of development. This mastery helps children grow into successful, contributing members of society. During each of Erikson’s eight stages, there is a psychological conflict that must be successfully overcome in order for a child to develop into a healthy, well-adjusted adult.

Erik Erikson: Erikson developed his eight stages of psychosocial development based on Freud’s psychosexual theory.

Stages of Psychosocial Development

Erikson’s stages of psychosocial development are based on (and expand upon) Freud’s psychosexual theory. Erikson proposed that we are motivated by the need to achieve competence in certain areas of our lives. According to psychosocial theory, we experience eight stages of development over our lifespan, from infancy through late adulthood. At each stage there is a crisis or task that we need to resolve. Successful completion of each developmental task results in a sense of competence and a healthy personality. Failure to master these tasks leads to feelings of inadequacy.

Erikson also added to Freud’s stages by discussing the cultural implications of development certain cultures may need to resolve the stages in different ways based upon their cultural and survival needs.

Trust vs. Mistrust

From birth to 12 months of age, infants must learn that adults can be trusted. This occurs when adults meet a child’s basic needs for survival. Infants are dependent upon their caregivers, so caregivers who are responsive and sensitive to their infant’s needs help their baby to develop a sense of trust their baby will see the world as a safe, predictable place. Unresponsive caregivers who do not meet their baby’s needs can engender feelings of anxiety, fear, and mistrust their baby may see the world as unpredictable. If infants are treated cruelly or their needs are not met appropriately, they will likely grow up with a sense of mistrust for people in the world.

Autonomy vs. Shame/Doubt

As toddlers (ages 1–3 years) begin to explore their world, they learn that they can control their actions and act on their environment to get results. They begin to show clear preferences for certain elements of the environment, such as food, toys, and clothing. A toddler’s main task is to resolve the issue of autonomy vs. shame and doubt by working to establish independence. This is the “me do it” stage. For example, we might observe a budding sense of autonomy in a 2-year-old child who wants to choose her clothes and dress herself. Although her outfits might not be appropriate for the situation, her input in such basic decisions has an effect on her sense of independence. If denied the opportunity to act on her environment, she may begin to doubt her abilities, which could lead to low self-esteem and feelings of shame.

Initiative vs. Guilt

Once children reach the preschool stage (ages 3–6 years), they are capable of initiating activities and asserting control over their world through social interactions and play. According to Erikson, preschool children must resolve the task of initiative vs. guilt. By learning to plan and achieve goals while interacting with others, preschool children can master this task. Initiative, a sense of ambition and responsibility, occurs when parents allow a child to explore within limits and then support the child’s choice. These children will develop self-confidence and feel a sense of purpose. Those who are unsuccessful at this stage—with their initiative misfiring or stifled by over-controlling parents—may develop feelings of guilt.

Industry vs. Inferiority

During the elementary school stage (ages 6–12), children face the task of industry vs. inferiority. Children begin to compare themselves with their peers to see how they measure up. They either develop a sense of pride and accomplishment in their schoolwork, sports, social activities, and family life, or they feel inferior and inadequate because they feel that they don’t measure up. If children do not learn to get along with others or have negative experiences at home or with peers, an inferiority complex might develop into adolescence and adulthood.

Identity vs. Role Confusion

In adolescence (ages 12–18), children face the task of identity vs. role confusion. According to Erikson, an adolescent’s main task is developing a sense of self. Adolescents struggle with questions such as “Who am I?” and “What do I want to do with my life?” Along the way, most adolescents try on many different selves to see which ones fit they explore various roles and ideas, set goals, and attempt to discover their “adult” selves. Adolescents who are successful at this stage have a strong sense of identity and are able to remain true to their beliefs and values in the face of problems and other people’s perspectives. When adolescents are apathetic, do not make a conscious search for identity, or are pressured to conform to their parents’ ideas for the future, they may develop a weak sense of self and experience role confusion. They will be unsure of their identity and confused about the future. Teenagers who struggle to adopt a positive role will likely struggle to “find” themselves as adults.

Intimacy vs. Isolation

People in early adulthood (20s through early 40s) are concerned with intimacy vs. isolation. After we have developed a sense of self in adolescence, we are ready to share our life with others. However, if other stages have not been successfully resolved, young adults may have trouble developing and maintaining successful relationships with others. Erikson said that we must have a strong sense of self before we can develop successful intimate relationships. Adults who do not develop a positive self-concept in adolescence may experience feelings of loneliness and emotional isolation.

Generativity vs. Stagnation

When people reach their 40s, they enter the time known as middle adulthood, which extends to the mid-60s. The social task of middle adulthood is generativity vs. stagnation. Generativity involves finding your life’s work and contributing to the development of others through activities such as volunteering, mentoring, and raising children. During this stage, middle-aged adults begin contributing to the next generation, often through childbirth and caring for others they also engage in meaningful and productive work which contributes positively to society. Those who do not master this task may experience stagnation and feel as though they are not leaving a mark on the world in a meaningful way they may have little connection with others and little interest in productivity and self-improvement.

Integrity vs. Despair

From the mid-60s to the end of life, we are in the period of development known as late adulthood. Erikson’s task at this stage is called integrity vs. despair. He said that people in late adulthood reflect on their lives and feel either a sense of satisfaction or a sense of failure. People who feel proud of their accomplishments feel a sense of integrity, and they can look back on their lives with few regrets. However, people who are not successful at this stage may feel as if their life has been wasted. They focus on what “would have,” “should have,” and “could have” been. They face the end of their lives with feelings of bitterness, depression, and despair.


The analogy with evolution via natural selection

Darwin himself, in developing the concept of evolution of species via natural selection, made an analogy to the evolution of languages. For the analogy to hold, we need a pool of individuals with variable traits, a process of replication creating new individuals whose traits depend on those of their "parents", and a set of environmental processes that result in differential success in replication for different traits.

We can cast each of the just-listed types of language change in such a framework. For example, in child language acquisition, different grammatical or different lexical patterns may be more or less easily learnable, resulting in better replication for grammatical or lexical variants that are "fitter" in this sense.

There are some key differences between grammars/lexicons and genotypes. For one thing, linguistic traits can be acquired throughout one's life from many different sources, although intitial acquisition and (to a lesser extent) adolescence seem to be crucial stages. Acquired (linguistic) traits can also be passed on to others. One consequence is that linguistic history need not have the form of a tree, with languages splitting but never rejoining, whereas genetic evolution is largely constrained to have a tree-like form (despite the possibility of transfer of genetic material across species boundaries by viral infection and so on). However, as a practical matter, the assumption that linguistic history is a sort of tree structure has been found to be a good working approximation.

In particular, the basic sound structure and morphology of languages usually seems to "descend" via a tree-structured graph of inheritance, with regular, lawful relationships between the patterns of "parent" and "child" languages.


We are because we can talk

Of course, the fact that monkeys don’t talk like humans isn’t purely due to the physical limitations of their vocal tracts. They also lack the neural networks necessary for producing and processing speech.

One key contributor to the evolution of human speech is the FOXP2 transcription factor. Humans, Neanderthals, and Denisovans share a mutation in the gene for FOXP2 that nonhuman primates lack. Early evidence of FOXP2’s role in human speech and language comes from studies of the KE family, a large extended family living in London in the second half of the 20th century. Some members had only one copy of FOXP2 and had extreme difficulty talking their speech was unintelligible, and problems extended to orofacial motor control. They also had difficulties forming and understanding English sentences.

The importance of FOXP2 has been further confirmed by knock-in mouse studies. When the human version of the gene for the FOXP2 transcription factor is inserted into mouse embryos, the animals exhibited enhanced synaptic connectivity and malleability in cortical–basal ganglia neural circuits that regulate motor control, including speech.11 The evolution of these circuits appears to have a deep evolutionary history going back to the Permian age, 300 million years ago. Avian versions of the FOXP1 and FOXP2 transcription factors act on the basal ganglia circuits involved when songbirds learn and execute songs. 12

Exactly how the brain dictates the movement of the vocal tract to produce speech remains murky. Many studies have shown that “matrisomes” of neurons in the motor cortex are instruction sets for the motor commands that orchestrate a learned act.13 Assemblies of neurons in the motor cortex are formed when a task is learned, and these assemblies guide coordinated muscle activity. To sip a cup of coffee or type at a keyboard, for example, hand, arm, wrist, and other movements are coded in matrisomes. Similar matrisomes likely govern the muscles that move the tongue, lips, jaw, and larynx and control lung pressure during speech, but researchers are just starting to explore this idea. In short, brains and anatomy were both involved in the evolution of human speech and language.

In 1971, Yale’s Edmund Crelin and I published our computer modeling study of a reconstructed Neanderthal vocal tract.14 We concluded that Neanderthals had vocal tracts that were similar to those of newborn human infants and monkeys and hence could not produce the quantal vowels [a], [i], and [u]. However, the available archaeological evidence suggested that their brains were quite advanced, and that, unlike monkeys, they could talk, albeit with reduced intelligibility. We concluded that Neanderthals possessed both speech and language. In short, current research suggests a deep evolutionary origin for human language and speech, with our ancestors possessing capabilities close to our own as long as 300,000 years ago. 14

Speech is an essential part of human culture, and thus of human evolution. In the first edition of On the Origin of Species, Darwin stressed the interplay of natural selection and ecosystems: human culture acts as an agent to create new ecosystems, which, in turn, directs the course of natural selection. Language is the mechanism by which the aggregated knowledge of human cultures is transmitted, and until very recent times, speech was the sole medium of language. Humans have retained a strange vocal tract that enhances the robustness of speech. We could say that we are because we can talk.

Philip Lieberman is the George Hazard Crooker University Professor Emeritus at Brown University.


Watch the video: ΑΝΑΛΥΣΗ ΣΥΜΜΑΧΙΚΩΝ ΕΞΕΛΙΞΕΩΝ ΑΠΟ ΕΝΑΝ ΠΟΥ ΒΛΕΠΕΙ!