Saturday, 9 May 2009

Grooming, Gossip and the Evolution of Language(1996), by Robin Dunbar

Robin Dunbar (born 1947) is a British anthropologist and evolutionary biologist specialising in primate behaviour.

His 1996 work Grooming, Gossip and the Evolution of Language pulls together his work on the social group sizes of various primates, including humans and the correlation with neocortex size relative to body mass. Although not intended as a work of popular science, the book’s style is very accessible and it may be read by non-specialists as well as academics.

The work appears to have been a considerable influence on the science-fiction novel Evolution, by Stephen Baxter.

The following is a chapter-by-chapter summary of this work:

Chapter 1. “Talking Heads”.
Describes the experience of being groomed by a monkey from the viewpoint of one of its peers: notes the similarities with the innuendoes and subtleties of everyday social experience of humans. The social life of humans, with its petty squabbles, joys and frustrations, is not unlike that of other primates. But there is one major difference – human language.

Curiously, when humans talk, most of the conversation is social tittle-tattle. Even in common-rooms of universities, etc, conversations about cultural, political, philosophical and scientific matters account for no more than a quarter of the conversation. The Sun devotes 78% of its copy to “human interest” stories and even the Times only devotes 57% to serious matters. Our much-vaunted capacity for language seems to be mainly used for exchanging information on social matters [anybody doubting Dunbar’s assertion needs look no further than Facebook]. Why should this be so?

Chapter 2. ”Into the Social Whirl”.
The answer may lie with our primate heritage. Monkeys and apes are highly sociable, their lives revolving around the small group of individuals with whom they live. They could not exist without their friends and relations.

Our ape ancestors faced disaster 10 million years ago as the climate became dryer and colder, causing their forest habitat to retreat. Monkeys became a nuisance, able to eat unripe fruit because their stomachs contain enzymes to neutralise the tannin that they contain that would give apes and humans an upset stomach. About 7 million years ago, one population of apes found itself forced out onto the savannahs bordering the forests. Mortality would have been desperately high but those that survived did so because they were able to exploit the new conditions.

All primates have had to deal with predators ranging from various felids, canids, monkey-eating eagles and even other primates. There are two main ways of dealing with primates. One is to be larger than any likely predator; the other is to live in a large group. The latter option reduces the risk in a number of ways: more eyes to detect a marauding predator; strength in numbers – a large group can drive off or even kill a predator; finally a large number of group-members fleeing in different directions will confuse a predator, often for long enough for all to get away.

But group living has disadvantages too. Social animals have to strike a balance between the dangers of predators and the problems of social tensions. The primate solution is for small groups to form coalitions within the larger overall living group. Such alliances take many forms, depending on the overall social and sexual dynamics of the species concerned. In all cases, however, grooming is the key to maintaining these alliances.

Primate alliances are built on the ability of animals to form inferences about the suitability and reliability of potential allies, but apes and monkeys can also practice deception and manipulative behaviour. They can do this because they can calculate the effect their actions are likely to have.

Chapter 3. “The Importance of Being Ernest”.
Grooming takes up a considerable amount of a monkey’s time, typically 10% though it can be as much as 20%. Grooming apparently releases endorphins, but while this encourages animals to groom it isn’t the evolutionary reason for it. One problem among social animals is “defection”, i.e. where one fails to return a favour. A solution is to make defection expensive, and grooming requires a considerable investment of time. Building alliances therefore requires commitment and it is therefore usually better to maintain existing relationships than try to build new ones.

In addition to grooming, monkeys use vocalisation to maintain their alliances. Monkeys make contact calls when moving through dense vegetation to enable the animals to keep track of one another. But subtle differences have been found in the utterances made by vervet monkeys depending on whether they are approaching a dominant animal or a subordinate one. Other calls were given when spotting another vervet group, or when moving out into open grassland. When these calls were recorded and played back, monkeys would look up when hearing calls from animals dominant over them, but ignore those from subordinates. Vervets also make a variety of predator warning calls which depend on the type of predator spotted. Other species use contact calls to keep in touch with preferred grooming partners.

But does any species, other than humans, have language? Attempts to teach apes to use language since the 1960s have produced unconvincing results, the oft-cited cases of Washoe, Kanzi etc notwithstanding. Human communications are on another level. What are they used for and why did they evolve?

Chapter 4. “Of Brains and Groups and Evolution”.
While bigger brains generally mean a smarter animal, the rule doesn’t always hold good because the size of the animal must also be taken into account. For example, whales and elephants have larger brains than humans, but they have to deal with a far greater muscle-mass than a human brain. When the relative brain-size is computed, it can be seen that the distributions for various groups of animals lie on different plains. Dinosaurs and fish lie below birds, which in turn lie below mammals. But among the mammals, there is also a hierarchy: marsupials lie at the bottom, followed by insectivores, then ungulates, then carnivores and finally at the top, primates. Here again there are levels: the prosimians at the bottom and the monkeys and apes at the top. The human brain is about nine times the size of the brain of a typical human-sized mammal and twelve times that of a human-sized insectivore [if such a species existed].

Why is this? It could not be due to chance, because of the high energy budget of a large brain, which is 20% of total in humans despite accounting for just 2% of total body mass. 1970s theories focussed on the need for greater problem-solving abilities; for example fruit eaters need bigger brains than herbivores, because supplies of fruit are harder to find.

Finding brightly-coloured fruit does require colour vision, which in turn requires more brain-power to process the input. Primates possess superior colour vision to other mammals [but so do birds and insects]. However this theory fails to explain why not all fruit eaters have large brains.

That social complexity might be linked to primate brain size was considered but not taken seriously until 1988, when British psychologists Dick Byrne and Andrew Whiten proposed what has become known as the Machiavellian Intelligence Hypothesis. This is based on the fact that monkeys and apes are able to use very sophisticated forms of social knowledge about each other. This knowledge about how others behave is used to predict how they might behave in the future and relationships are based upon these predictions.

The main problem with the theory was that many thought it was too nebulous to test. One problem for Dunbar was confounding factors: fruit eating primates require larger territories than leaf-eaters because the fruit is more widely-spaced. But many fruit-eaters such as baboons and chimpanzees are larger than leaf-eating monkeys and live in larger groups. There are four factors – body-size, brain-size, group-size and fruit-eating. The problem was to ensure that correlation between any two of these factors was not a consequence of both being correlated for quite distinct reasons with a third.

Dunbar decided to consider not the total brain size but the neocortex, which is the “thinking” part of the brain, where consciousness arises. The neocortex comprises the “grey matter” popularly associated with intelligence and it surrounds the deeper white matter in the cerebrum. In small mammals such as rodents it is smooth, but in primates and other larger mammals it has deep grooves (sulci) and wrinkles (gyri) which increase its surface area without greatly increasing its volume.

Dunbar then correlated the size of the neocortex against group size. He chose this as a measure of social complexity because of the volume of data available from field workers on many primate species and because it is a simple numerical value rather than a subjective assessment. Also group size is a measure of social complexity – the larger the group, the more relationships there are to keep track of. Dunbar found that there was a very good fit between the data and the ratio of neocortex volume to total brain volume. The findings provided support for the Machiavellian Intelligence Hypothesis – large brains were linked to the need to hold large groups together. Dunbar was also able to find the same the same correlation between neocortex ratio and group size in non-primate mammals such as vampire bats and some of the larger carnivores.

But just how does neocortex size relate to group size? There are possibilities beyond simply keeping track of social relationships. One is that the neocortex/group size correlation is more to do with quality rather than quantity of intra-group relationships. The Machiavellian hypothesis suggests that the key is the use primates make of their knowledge of others. There are two interpretations: firstly the relationship might be with the size of coalitions primates habitually remain rather than total group size, though larger coalitions are required in larger groups. The second is that primates need to be able to balance conflicting interests – playing one off against another, keeping as many happy as possible.

Research showed that primates form “grooming cliques”, with grooming occurring outside these groups being perfunctory and lacking enthusiasm; and distress calls from non-members likely to be ignored. Grooming seemed to be the glue that held coalitions together. When data about grooming clique size was combined with the data about group size and neocortex ratio, a good fit was found. As group size increases, so larger coalitions are required for mutual protection when living in these large groups.

Since humans are primates, it should be possible to predict group size for humans. The number turns out to be approximately 150 – Dunbar’s Number, as it is now known. Modern living – with millions living in cities – makes this prediction hard to test. However when considering hunter-gatherer societies – which is how we lived in pre-agricultural times, the largest grouping is a tribe, typically numbering 1500-2000 people who all speak the same language or dialect. Within tribes, smaller groupings known as clans can sometimes be discerned. Clan size - with very little variation – averages 150.

150 turns up elsewhere – early Neolithic villages typically had a population of around that number; religious communities such as the Hutterites and the Mormons lived in groups of 150; businesses can function informally with fewer than 150 employees, but require a formal management structure when the headcount exceeds this; army companies typically number around 150 men and so on.

The number of close friends and relatives people have tends to be around 11-12 with a fair degree of consistency. This corresponds to the “grooming clique” in primate societies, suggesting a neurological basis. Finally the maximum number of faces people can put a name has been found to be around 1500-2000 – suspiciously close to the size of a tribe in traditional societies.

Returning to grooming, a problem arises in that the larger primate group size is, the larger the grooming cliques need to be, and the more time needs to be devoted to grooming. Baboons and chimps have a group size of 50-55 individuals, and the amount of time they spend grooming is close to the upper limit of time that can be so spent without making inroads into the time needed to feed etc. If humans relied on grooming, then 40% of the day would have to be devoted to this activity.

The solution, Dunbar suggests, was language, which enabled several individuals to be “groomed” at once. When it comes to social networking, language has other advantages over grooming in that detailed information can be exchanged about individuals not actually present. Language is a “cheap and ultra-efficient form of grooming”. Dunbar rejects the conventional explanation of language evolving as a means to co-ordinate activities such as hunting more efficiently and suggests instead that it evolved primarily to allow humans to exchange social gossip.

Chapter 5. “The Ghost in the Machine”. Language is for communication [contra Bickerton, 1990], somebody trying to influence the mind of another individual. We also consider implications of what people are saying, their body language, etc. We assume everybody behaves with conscious purpose and try to divine their intentions, often extending this to animals and even inanimate objects. Philosophers however doubted if consciousness existed outside of the human world.

Rene Descartes assumed that while humans had minds, animals – which lack language – did not and were nothing more than automatons. However in the second half of the 19th Century Darwin and his contemporaries began to reconsider the emotional and mental lives of animals. A view eventually emerged that since it was not possible to see into the minds of animals, studies should focus on their observable behaviour. The result was the psychological school known as “Behaviourism”, which held sway right up until the 1980s.

Since then, however, attention has switched to “Theory of Mind”. This means the ability to understand what another individual is thinking, to ascribe beliefs that might differ from one’s own and to believe that that individual does experience those beliefs as mental states. Furthermore ToM enables individuals to handle “orders of intentionality” or beliefs about what another believes; for example “I believe x” is first-order intentionality, “I believe that he believes X” is second-order and so on. Humans can at most handle six orders, as in the following sentence due to Dan Dennett:

“I suspect [1] that you wonder [2] whether I realise [3] how hard it is for you to be sure that you understand [4] whether I mean [5] to be saying that you can recognise [6] that I can believe [7] you want [8] me to explain that most of us can only keep track of five or six orders.”

In the 1980s it was discovered that children are not born with a theory of mind and that this does not develop until 4 - 4 ½ years old. Up until then they will fail the so-called “false belief test” which asks if the child is aware that somebody can hold a false belief. For example, the child is shown an object such as a doll or some sweets being put in a particular place in the presence of another individual called (say) Fred. Fred then leaves and the object is moved. Fred returns and the child is asked where they think Fred thinks the object is. Very young children fail the test by saying they think Fred thinks the object is in the new location. They cannot grasp that Fred doesn’t know the object has been moved and that he would assume it was still in its original location. Only older children, with ToM, pass this test. Autism is a failure to develop ToM.

Tests have been carried out on animals to see how their ToM compares with humans and to see if they have self-awareness. An early test was the mirror test, to see if an animal could recognise that a reflection of itself in a mirror was not another individual. Chimps can readily pass such tests, other great apes appear to be competent but gibbons and monkeys invariably fail, as do non-primates such as elephants and porpoises. The validity of this approach has been questioned, as animals do not encounter mirrors in the wild [though of course they might see their reflections in water].

“Tactical deception” is where one individual tries to exploit another by manipulating its knowledge of a situation. To practice tactical deception, an individual must have at least second-order intentionality. It appears to be virtually absent from the prosimians, rare in New World monkeys, but common among the socially-advanced Old World monkeys (baboons, macaques) and chimpanzees. The frequency with which species practiced tactical deception was found to show a good fit with relative neocortex size.

Dunbar reasoned that in species with a large relative neocortex size, low-ranking males should be able to use their brains to exploit loopholes in the system and mate with females, gain access to bananas, etc. Tests showed that this was the case; for example a low-ranking male would feign disinterest in a box containing a cache of bananas in the hope that a higher-ranking male who arrived on the scene shortly after would conclude that the box was locked.

Tests aimed at showing whether apes and monkeys have ToM have involved obtaining a food reward from a baited box and two human assistants, one of whom is not present when the bait is moved. The ape or monkey then had to choose which assistant they wanted to open a box. Chimps did reasonably well at the test, though less so than six-year-old children. This and other tests led researchers to conclude that chimps had limited theory of mind, but monkeys completely lacked it.

Chimps seem to be able to go to third-order intentionality on occasions, but humans can readily surpass this. Humans can envisage people and situations that do not exist in actuality – a prerequisite for producing literature. Humans are able to detach themselves from their immediate surroundings. Dunbar argues that this is a pre-requisite for both science and religion, though some of his colleagues object to the comparison! However both require one to question the world as we find it, which in turn requires third-order intentionality at minimum.

If fourth-order intentionality and above is required for science and religion, it is no mystery why only humans have these things. But if third-order intentionality will suffice, could apes not also have science and religion? It is conceivable, but the main problem is that apes lack language and so could not transmit their ideas to their peers.

Chapter 6. “Up through the Mists of Time”.
Five million years ago, one ape lineage seems to have made more use of the woodlands that lie beyond the edges of the shrinking forests. Animals travelling between the trees here are more exposed to the sun and Peter Wheeler has calculated that an animal walking upright under these conditions receive up to a third less heat from the sun, especially around the middle of the day. They also benefit from the slightly breezier conditions at heights above three feet. Also these upright apes could have shed body hair over the parts of their bodies not exposed to direct sunlight and improved cooling properties by sweating through the skin. A naked biped ape would expend half the amount of water on sweating compared with a furry quadruped ape.

Bipedalism begun fairly early in the hominid lineage, because “Lucy”, 3.3 my old, was already bipedal as inferred from the shape of the pelvis and the articulation of the knee and hip joints. The Laetoli footprints in Tanzania, 3.5 my old, were also made by bipeds. Quite likely these early hominids were naked although they were still more apes than humans.

In their new woodland habitat, these apes had to contend with greater predation, and in response they grew larger and increased their group size. While Lucy was a diminutive 4ft tall, the Narikitome Boy had reached a height of 5ft3 at age 11 and would have topped 6ft had he survived to adulthood. But how do we know their group size increased? The link with neocortex size offers a clue, and the link with grooming time might offer a clue as to when language evolved.

Archaeologists [in 1996] favoured a recent date of 50,000 years ago – the date of the [now abandoned] Upper Palaeolithic Revolution. Anatomists [even then] favoured a date of around 250,000 years ago, co-incident with the emergence of Homo sapiens. This was based on the fact that an asymmetry between the two halves of the brain could be detected at this point. In modern humans, the left hemisphere – where the language centres are located – is larger than the right. This, they argued, was evidence for the appearance of language.

To try to resolve the issue, Dunbar and Leslie Aiello tried to solve the group size issue and find the group size threshold that precipitated language. They reasoned it must lie somewhere between the 20% maximum grooming time for any existing primate and the predicted grooming time of 40% for humans, possibly 30%. They then discovered that in primates and carnivores [but obviously not elephants and whales], neocortex ratio is directly related to total brain size [I assume that means a linear relationship]. Given that estimates for cranial capacity were available for extinct hominids, it was possible to calculate the predicted group sizes. These remained within the ranges of existing apes at first, but rose above this with the appearance of genus Homo. 150 was reached 100,000 years ago, but by 250,000 years ago group sizes would already have reached 120-130, and grooming time would have hit a prohibitive 33-35%. But even 500,000 years ago, group sizes were at 115-120 with corresponding grooming times of 30-33%. [Rather confusingly, Dunbar then cites this time as coinciding with the emergence of Homo sapiens, having dated this event to 250,000 a short while previously. In 1996, humans from this far back were generally lumped together as archaic Homo sapiens; the term Homo heidelbergenis is now generally preferred.]

Homo erectus [then described as the predecessor to our own species] had a predicted group size of 100-120, with grooming time requirements of 25-30%. Dunbar and Aiello took the view that H. erectus lacked language. They also noted no drastic jump in grooming time at any point, which they take to mean that language emerged gradually over a long period of time.

As group sizes increased, so vocalisation began to supplement grooming; probably this process began two million years ago, with the emergence of Homo erectus. As time passed, so the meanings conveyed by the vocalizations increased, though the purpose would have remained largely social. Humans were exploiting the greater efficiency of language as a bonding mechanism to allow themselves to live in larger groups without increasing the amount of time required for social networking. Interestingly, modern hunter-gatherers spend around 3.5 hours for women and 2.7 hours for men on social interaction in a 12 hour day, or about 25%, compared to the 20% maximum observed for other primates.

On this view, the Neanderthals must also have possessed language. They did not become extinct for lack of language, but lacked the technological and cultural sophistication of the incoming Cro-Magnons. Later, the Native Americans and Australian Aborigines suffered the same fate [basically Dunbar is advancing an Upper Palaeolithic version of the Guns, Germs and Steel argument advanced by Jared Diamond (Diamond, 1997)].

What drove the increase in human group size? Baboons can get by with group sizes of 50, why can’t we, especially as we are larger and can carry defensive weapons? Indeed, hunter-gatherers typically live in temporary camps of around 30-35 individuals. Dunbar puts forward three possibilities:

Firstly, our forbears may have occupied more open habitats than those of baboons and needed greater protection. Gelada monkeys live in very open habitats with high risk of predation. They live in groups of 100-250 [so why don’t geladas have bigger brains than humans?].

The second possibility is that human groups were threatened by rival human groups, and bigger group sizes were needed to fend them off.

The third possibility is that following the emergence of Homo erectus, humans became nomadic and left Africa. In unknown territory, they would have had to wonder further to find resources and they would have encountered hostile residents determined to exclude them. This does occasionally happen with hamadryas baboons. Migrants are always at a disadvantage, but one solution is to establish reciprocal alliances with neighbouring groups. This happens with the !Kung San of the Kalahari, who live in communities of 100-200 individuals, but these are dispersed into smaller family-based groups of 25-40. This is known as a fission-fusion system, because members are constantly coming and going. The same characteristic is seen with chimpanzees – the primary community is around 55, but foraging parties often only occupy 3-5 individuals. That we share this characteristic with chimpanzees suggests it emerged very early in our history.

Dunbar opts for this third theory.

The theory that language emerged to facilitate social bonding should be testable. Investigating conversations in various informal situations, Dunbar and his students discovered that conversation groups did not typically exceed four. Conversation groups start when two or three people start talking. Others join in, but once the number of participants rises above four it is difficult to hold everybody’s attention and the group tends to fissions as two distinct conversations start. At any one time, only one person will normally be speaking and the others will be listening, just as at any one time only one ape or monkey will be doing the grooming. If the speaker corresponds to the “groomer” then they are “grooming” up to three others rather than only one, meaning group size could potentially treble. The group size of 55 for chimps and baboons becomes very close to the “Dunbar Number” of 150.

The limit of four people in a conversation group arises from the distance apart people must stand if they form a circle. Once the diameter of the circle increases beyond a certain point, it is not possible for everybody to hear everybody else clearly without shouting, assuming normal background noise levels. The critical distance turns out to be two feet, and it is difficult for more than four people to all remain within this distance of each other.

The researchers also learned that as per Dunbar’s predictions, 60-70% of the conversations concerned social topics. Politics, religion, work etc took up no more than 2-3% and even sport and leisure topics accounted for barely 10%.

Taken together, this data supports Dunbar’s theory that language evolved primarily to facilitate social bonding.

The expensive tissue hypothesis is based on the enormous energy costs of running a brain, which in humans takes up 20% percent of the total energy budget. But total energy production of mammals is a function of size and humans generate no more energy than any other mammal of that size, despite having a brain nine times larger than a typical human-sized mammal. Where does the energy to run the brain come from? Clearly it must come from savings elsewhere [unlike governments, humans have to balance the books]. In addition to the brain, the biggest energy consumers are the heart, kidneys, liver and gut – indeed these use up between them 85-90% of the body’s energy budget. The heart, kidneys and liver cannot be downsized, which leaves only the gut. With a smaller, less-efficient gut, humans have to eat high energy easy to assimilate foods. Meat is one such food, and the shift from the predominantly vegetarian diet of the australopithecines to one with higher meat content seems to have corresponded to the initial increase in brain size. Initially this would have come from scavenging, but the second phase of brain expansion, 500,000 years ago seems to correspond to the beginnings of organized hunting. Aiello and Wheeler believe that big brains only became possible with a switch to meat eating.

But big brains had another cost – the problem of getting a large brained infant down the narrow birth canal. The problem was solved by what is in effect premature birth, with a huge investment required by the parents in post-natal care. Women couldn’t do it all on their own; men had to do their bit. The tendency to male-female pair bonding was the result. Sexual dimorphism, considerable in even australopithecines, reduced. Differences in canine teeth, pronounced in cases of sexual dimorphism, almost vanished. Human males are only slightly larger than females. The implications are a shift from a strongly polygamous mating system to one that is only mildly so. Harem groups became smaller, with males having to make do with two females, and many having to get by with just the one! Provisioning more than one female would also have been expensive [a trend that has continued to the present day].

Chapter 7. “The First Words”. There are three competing theories for the origins of language. The first states that the earliest languages were gesture-based; the second that it arose from monkey-like vocalizations; and the third is that it arose from music.

The gestural theory arises from the fact that fine motor control used for speech and aimed throwing is generally located in the left hemisphere of the brain. In addition to fine motor control, precise control of breathing is required and for this it was necessary for the monkey’s dog-like chest to change to the flattened chest characteristic of apes. When the body’s weight is on the arms, it restricts the chests ability to expand and contract and monkeys can only breathe once with each stride.

When apes adopted a climbing lifestyle, the monkey rib-cage was a major problem. In monkeys, the shoulder blades prevent the arms swinging in a circle, which prevents them from reaching above their heads while climbing. Eventually the scapula moved round to the back of the ribcage and arm-joints became positioned on the outer edge of the chest. The flattened rib cage of the apes was the result, which had the additional benefit of freeing the constraints on breathing.

The anatomical changed permitted aimed throwing. Chimps could out-throw Olympic athletes, but their accuracy is poor because they lack the fine motor control of humans. But our fine motor control, so the theory goes, could also be used to control speech.

The problems with this theory are language involves conceptual thinking, which is quite different to aimed throwing; the complexity possible with gestures is limited; and gestures require people to be in visual contact. Communication would be impossible after dark, when one might have expected a lot of social gossip to take place.

But why did fine motor control evolve in the left hemisphere? Dunbar suggests it is because the right hemisphere was already fully utilised processing emotional information. He speculates the speech evolved in the left hemisphere because there was room there, and fine motor control evolved there later – either for the same reason or because the left side is associated with conscious thought, which is required for aimed throwing. This is the reverse of the sequence of events required by the gesture theory. The reason the majority of us are right-handed is because sensory and motor control nerves from one side of the body cross over to the other side of the brain; the left hemisphere controls the right hand side of the body, and vice-versa.

There is a greater sensitivity to visual cues on the left hand side of the visual field. This lateralization seems to have appeared very early on and fossil trilobites tend to have more scars on the right side, suggesting pursuing predators attached more frequently from the left hand side.

Lateralization of language in the left hemisphere meant that this side became the seat of consciousness, where as emotional behaviour was seated in the right hemisphere [as Dunbar points out, this was the basis of Julian Jaynes’ theory about “bicameral minds” (Jaynes, 1976)].

It turns out that music and poetry are located in the right side. This also suggests that the theory of a musical origin for language cannot be correct.

Dunbar turns to the vocalizations of monkeys as the origins of language [a conclusion that Bickerton (1990) rejects]. He considers the predator-specific calls of vervets and also conversational patterns of gelada monkeys. The calls of these animals appear to be timed in anticipation of others rather than in simple response, just as human conversation is carried on by one individual anticipating the end of the speaker’s phrase or sentence rather than simply waiting for them to stop speaking. The vervet’s calls are an archetypal proto-language in which arbitrary sounds can be used to refer to specific objects, and overtones can be applied to increase the information content. Formalizing sound patterns to carry more information is but a small step; language is but a further small step [though Bickerton would disagree].

If it is accepted that the beginnings of language were the vocalizations of primates, there are still alternative views on the next step. One theory is that language arose out of song-and-dance rituals designed to co-ordinate the emotional states of group members [c.f. Mithen, 2006]. While Dunbar believes language arose to exchange social gossip, he considers this alternative viewpoint.

No society lacks song-and-dance, which on the face of it odd. Much has parallels with bird-song, which is used to defend territory or advertise for a mate. Maasai warriors, Maoris, All Blacks and Scots Guards use ritual song and dance (the Haka, bagpipes, etc) before going into battle. But song is also used in churches and bars in circumstances not associated with battle. Here Dunbar considers the “crowd effect” which leads to groups of people being amenable to far more extreme and intolerant views than individuals. Psychologists identified this phenomenon in the 1960s and referred to it as a “risky shift”. It led to the Crusades, Northern Ireland, Rwanda and Yugoslavia [the Nazis were of course consciously exploiting the phenomenon back in the 1930s at Nuremberg, though Dunbar does not mention this].

Dunbar believes that the explanation is that song and dance is an expensive activity. Deep bass tones are particularly difficult to produce. They are associated with a large and powerful body. Even among humans, there is a tendency to assume powerful, successful people to be tall. In every US presidential election since the war, the taller candidate has won. [The sequence was broken in 2000, when George W Bush (6ft) defeated Al Gore (6ft1) and subsequently held off the challenge of an even taller man, John Kerry (6ft4), in 2004. However in 2008 the taller candidate won when Barack Obama (6ft2) defeated John McCain (5ft9).] People often comment on how small the Queen is [she was positively dwarfed by Michelle Obama (5ft11)]. There is no doubt that smaller people have to work harder to get to the top and have to be fairly bloody-minded. But, as Napoleon and others have shown, it certainly can be done.

It does however appear to be almost universal that deep voices are needed to create a lasting impression. The peculiar deep voice associated with Margaret Thatcher is about half an octave below her natural voice. Thatcher’s advisers encouraged her to lower her voice after she became Tory leader in 1975.

Trying to hold together a group of 150 people is difficult even now and it must have been even harder 250,000 years ago in the woodlands of Africa. Song and dance would have had a role to play. The activity would have stimulated endorphin production. Chris Knight believes that the use of ritual to coordinate human groups by synchronising emotional states is a very ancient feature of human behaviour, coinciding with the rise of human culture and language. Ritual language would have been required to co-ordinate such activities, and this may have been the final stimulus for the evolution of language [I have to say I’m dubious; such organized rituals would surely have required the participants to already be behaviourally modern]. Dunbar is unconvinced and believes this use for language only came later. He believes song-and-dance may well have preceded language, but it was at first informal, unstructured and spontaneous, like chanting at football matches. [This probably explains why attempts by clubs and fan groups to orchestrate the atmosphere at football clubs with schemes such as “singing sections” invariably fail; also fans tend to devote at least as much time to chants abusing the referee or rival teams as they do to songs encouraging their own side.]

If language evolved to facilitate group cohesion, then who spoke first – men or women? In most primate species, females form the core of society. Males typically leave their birth group at puberty, often wondering from group to group in search of enhanced mating opportunities. Chimps [though not bonoboes] are an exception.

If early human societies were matriarchal [like the bonoboes] then language may have evolved first among females, and Chris Knight believes this was principally to help keep the men in line and ensure they invested in them and their children. This would explain that among modern humans women are generally better at verbal communication and have better social skills than men [says who?].

But in fact human society seems to be patriarchal. Evidence for this is that among most [but not all, e.g. the Karen people of Burma – see Wells (2002)] traditional societies, brides move to the village of their new husband, a system known as patrilocality. But most of these societies live in conditions where men control all the resources needed for successful reproduction, such land and hunting grounds. In more equitable societies, such as hunter-gatherers and modern industrial societies, female kinship and alliances are much stronger and matrilocality (where the man moves) may be the norm. [Does this explain the strongly sexually-differentiated culture in one particular work place with which I was familiar? On one occasion the women seemed to be in unusually high spirits all day but refused to share the reason for their good humour with any of the men. It eventually emerged that one of their numbers had just got engaged – to a man she’d already been living with for some years. At least the question of who had to move where after the marriage did not arise!]

Among Central African hunter-gatherers, Y-chromosomal genes are more widely distributed than X-chromosomal genes, which tend to be clustered, suggesting women remain close to their kin-groups, whereas men move across wide areas. A similar picture emerges from the impoverished east end of London in the 1950s, where women were dependent on the support of female kin in order to reproduce successfully and men tended to live closer to their in-laws than to their own parents.

Female kin-bonding may have been a more important force in human evolution than is often supposed [possibly because the people doing the supposing were mostly men]. The pressure to evolve language may have come from the need to form and service female alliances rather than male hunting activities.

Chapter 8. “Babel’s legacy”.
Languages change with surprising speed, the Romance languages for example having all arisen from Latin within two millennia (and having emerged as distinct languages well before that).

The Tower of Babel actually did exist and was a seven-stage ziggurat built some time during the 6th/7th century BC in what is now Iraq during the second flowering of Babylonian culture. Dunbar suggests that the Biblical story is a folk memory of a time when everybody in the world spoke the same language, but I am highly dubious. Even if we accept as late an emergence for human language as 50,000 years ago, it is inconceivable that a folk memory could persist for such a period of time. Dunbar cites the Norse legend of Ragnarok - the end of the world - as a possible folk memory. This legend tells of a world fire followed by the Fimbulvetr, a great winter lasting three years. This he equates to the folk memory of a period of global cooling. He cites a “little ice age” that affected northern Europe around 1000 BC. A more likely explanation is the eruption of Thera in the Mediterranean in 1600 BC, which would have produced a “volcanic winter” - a period of global cooling induced by dust and aerosols ejected into the upper atmosphere. These would also have led to spectacular sunsets around the world, possibly accounting for the “world fire”. At all events, the timescales are vastly different. The Babel legend is more likely a metaphor for poor project management of the kind that continues to bedevil large projects to the present day.

Dunbar then discusses the origins of the Indo-European languages, supporting Marija Gimbutas’ Kurgan Hypothesis. As I have already discussed this topic in this articleI will skip this section. Dunbar goes on to discuss attempts to reconstruct Nostratic, other linguistic superfamilies and the so-called “proto-World” [which might be ancestral to these superfamilies, but almost certainly wasn’t the first language ever spoken, since behaviourally-modern humans were probably living in Africa for at least 150,000 years before migrating to other parts of the world (McBrearty & Brooks, 2000)].

Why do languages change? This is followed by a section on language change that is also covered by my article about Indo-European origins, before asking the central question of just why does this happen? Dunbar notes that the vocalizations of other animals also show regional variations which he equates with linguistic dialects. He speculates on a common cause and believes there must be an evolutionary purpose for it.

Most higher organisms, including humans, tend to favour kin over non-kin. Bill Hamilton showed that there are two ways of getting one’s genes into the next generation. One is to reproduce oneself and the other is to help a relative to reproduce. This principle is known as kin selection. But how does one identify kin? One way is by accent and dialect – if these are the same as your own, then in pre-industrial times they were likely to be related to you. If a group migrates, then over a few generations the language will gradually change to a distinctive dialect. The group will thus gain a distinct identity.

There is some evidence to suppose dialects evolve faster in regions of higher population density. In pre-agricultural times, the rate of language change might have been much slower.

Chapter 9. “The Little Rituals of Life”.
This chapter is concerned with sexual section, first proposed by Charles Darwin, of which the peacock’s tail is the classic example.

Leda Cosmides was able to show that people could solve the so-called “Wason Selection” test with a far higher success rate if it was framed as a social problem rather than in terms of pure logic. She believes that humans have an inbuilt social problem-solving ability which recognises social contract situations and detects violations. Without such a mechanism, human social groups would collapse, with everybody acting in their own interest. Co-operation is essential to the survival of not only a group, but its individual members, so there is evolutionary pressure to develop such mechanisms for policing rules established for the common good. Dunbar believes that language is an important part of this system.

Language may ensure the bonding of a group in a number of ways. In addition to enabling one to keep track of friends, it can also be used to exchange information about cheats. Finally it may be used to influence what people think about us, i.e. for reputation-management. You can flatter people or be rude to them, depending on circumstances. But which function was the crucial one driven by evolutionary pressure, and which were the ones that were convenient spin-offs?

A study carried out for Dunbar showed that only 5% of conversation time is devoted to criticism and negative gossip, with a similar amount of time being spent on giving advice on how to handle social situations. Most of the time was devoted to who is doing what etc, suggesting that “policing” cheats might not have been languages primary function. While a primary function might not be one that’s needed that often, Dunbar argues it is a very expensive mechanism considering there is the far cheaper option of simply beating up the cheats! Indeed the problem of cheats is a consequence of living in large groups, which would not have happened without language in the first place.

Another study did show that while single sex groups were likely to simply exchange gossip, in mixed-sex groups there was a considerable increase in discussions about work, academic matters, politics etc with men showing the greater increase. A further study showed that of the time devoted to social gossip, men spent far more time talking about themselves than did women.

Dunbar interpreted the results as a “vocal lek”. A lek is a display area where males gather to advertise their qualities to potential mates. It is common among antelope and some birds, such as the peacock, which do not pair for life. Each peacock will defend a small territory in an area frequented by females, displaying whenever one approaches. The females wonder from one male to another before making their choice. In the “vocal lek” the men were basically trying to impress the women.

Body language and eye contact play a key part in initiating new relationships, especially for women. This [unsurprisingly] is an ancient primate habit. In species where one male controls a harem, such as the hamadryas baboon, even if a rival male is more powerful than the harem male, he will only move in if a female’s body language indicates she is not particularly interested in her current male. Normally the females follow the male closely, but sometimes they will delay and the male stops and looks back. Rival males can detect such subtle cues.

Males also need to advertise their fitness to reproduce, and in hunter-gatherer societies, one way they may do this is by hunting large mammals. From a purely economic point of view, hunting a large antelope makes much less sense than putting out a dozen or so traps, but a successful kill with all the attendant dangers is far more impressive. Dunbar draws a comparison with chivalric tales of medieval Europe when aspiring young men had to prove their worth by performing difficult tasks such as killing dragons, rescuing sleeping beauties, etc. Risk-taking tasks have the advantage that they are difficult to cheat and thus provide a good demonstration of one’s fitness to father somebody’s children.

Geoff Miller has suggested that the evolution of the human brain was driven mainly by the demands for sexual advertising – both to catch a prospective mate and hang on to them in the face of subsequent competition. A modern male can do this by making his partner laugh – an activity which triggers endorphin release. A study has shown that women are more likely to smile or laugh than man, and more likely to do so in response to men. But unfortunately for any aspiring female comedians, men are more likely to laugh in response to other men. While this may reflect a male-dominated society, Dunbar thinks it is far more likely to be a way women access the relative merits of their current partner against other males that happen to be on the scene. A man’s ability to make a woman laugh may be as good a test of fitness as any other.

Men and women differ considerably in the way they learn accents: men will tend to pick up the regional working-class accent; women by contrast tend to pick up a more neutral middle-class accent, the so-called Received Pronunciation or RP. One explanation is that women can improve their reproductive chances by hypergamy, or marrying up the social scale, whereas less well-off men need to be seen to belong in their environment in order to tap into the social network. Being poor with the wrong accent is a disasterous state of affairs.

But this is changing and a survey of dating agencies and personal ads show that women now want “new men” rather than rich but otherwise unreconstructed men; this is a reflection of the greater economic independence of women, and that the general levels of wealth and comfort are far higher now than they were in earlier times. With less pressure on hypergamy, Dunbar feels that women will eventually abandon RP and adopt the regional accents of men.

Sexual selection can lead to intense selection for males possessing certain traits, causing them to proliferate. This, according to Geoff Miller, was what led to the second phase of brain expansion in humans: a need to keep ones mate entertained.

Dunbar extends this theory to invoke the role of language in making people laugh, in turn triggering endorphin release.

While the ideas proposed in this chapter might not have been the main driving force behind language and large brains, they might have been valuable components that were added into the system as it developed and indeed may have driven them to levels beyond what might have occurred on the social bonding model on its own.

Chapter 10. “The Scars of Evolution”.
This final chapter summarises the work and ends with a few cautionary tales. In particular teleconferencing seems less effective if there are more than four participants. While this limitation came about from the number of people that could stand in a circle and hear each other, it seems to have become hard wired into our brains. Finally there was the case of a medium-sized company which happened to have 150 employees. The company began to struggle when it moved into new premises without a tea room, where much of the synergy that had made the company so successful in the past had been generated.


Aiello L C & Dunbar R I M (1993): "Neocortex Size, Group Size and the Evolution of Language", Current Anthropology, Vol 34, No 2 (April 1993) pp. 184-193.

Baxter S (2002): “Evolution”, Gollancz.

Bickerton D (1990): “Language and Species”, University of Chicago Press, USA.

Diamond J (1997): “Guns, Germs and Steel”, Chatto and Windus.

Dunbar R I M (1996): “Grooming, Gossip and the Evolution of Language”, Faber and Faber, London Boston.

Jaynes J (1976): “The Origin of Consciousness in the Breakdown of the Bicameral Mind”, Mariner Books, USA.

McBrearty S (2007): “Down with the Revolution”, in Rethinking the human revolution, McDonald Institute Monographs, University of Cambridge.

McBrearty S & Brooks A (2000): “The revolution that wasn’t: a new
interpretation of the origin of modern human behaviour”, Journal of Human Evolution (2000) 39, 453–563.

Mithen S (2005): “The Singing Neanderthal”, Weidenfeld & Nicholson.

Wells S (2002): “The Journey of Man: A Genetic Odyssey”, Penguin.

© Christopher Seddon 2009

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