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Robin Dunbar


A new history of mankind's evolution

Book review by Anthony Campbell. Copyright © Anthony Campbell (2004).

Robin Dunbar is Professor of Evolutionary Psychology at the University of Liverpool. This short book is aimed at a non-professional audience and scores high for readability, but it is very much one man's view of how we have got where we are today. This becomes evident at the outset, when, after a brief impressionistic sketch of human origins, starting with the Australopithecines, Dunbar unequivocally dismisses the Neanderthals as a separate species, partly on the basis of recent DNA evidence. He takes the "out of Africa" hypothesis to be the settled view and does not consider any alternatives. His main focus of interest, in any case, is on the origins of modern human consciousness.

Central to his approach is the concept of "intentionality", which refers to mind states such as believing, hoping, intending and so on. There can be orders of intentionality. Simply understanding that other people have thoughts is second-order intentionality, but things can get more complicated. To use Dunbar's example, Iago had to intend [1] that Othello would believe [2] that Desdemona wanted [3] to love another for his plot to work. Moreover, we, the audience, need fourth-order intentionality to understand the play, and Shakespeare needed fifth-order intentionality to be able to write the play so as to produce the appropriate response in us.

Modern humans are capable of fifth-order and sometimes of sixth-order intentionality. Chimpanzees and other anthropoid apes can apparently manage only second-order intentionality at best, it seems, and Dunbar thinks that this is the main reason they have not acquired language. The crucial factor here is the typical group size in which the different species live. Larger group sizes in early human societies promoted the growth of larger brains, with the capacity for higher-order intentionality and ultimately the development of language.

Dunbar has an interesting discussion of the origins of language. How far back does it go, and what about our old friends, the Neanderthals? We can get some clues from comparative anatomy. The motor nerve to the tongue (the hypoglossal) emerges through a canal at the base of the skull, so it is possible to gauge its size in fossil skulls. Both the Neanderthals and the Cro-Magnons had large canals, whereas those Australopithecine skulls in which the diameter can be measured had ape-sized canals, but there are too few suitable fossils to allow us to be certain about when the change occurred. Another anatomical clue comes from estimates of the diameter of the spinal canal in the upper thoracic vertebrae. An enlargement here may be related to the fine control of breathing needed for speech; it is found in both modern humans and the Neanderthals. Taking these two measurements together, Dunbar suggests that the latest possible date for the development of at least some form of speech must be about half a million years ago.

Dunbar also looks at the development of speech from a different, and less conventional, direction. He regards speech in humans as having arisen to take the place of grooming in other primates, and thinks that in its earliest form it may have consisted of singing ("chorusing") and laughter rather than the communication of information, which came later. He constructs a rather elaborate argument to relate brain size to the amount of time that a group of hominids would have to spend on grooming in order to maintain social stability. The maximum amount of time (allowing for finding food) that monkeys and apes devote to grooming is 20 per cent of total daylight time. Once our ancestors found that, because of group size, they needed to exceed this limit, a vocal element would have been introduced. Grooming plus "chorusing" would take them to the equivalent of 30 per cent of their time, and beyond this point they required speech.

I find this is an intriguing speculation, if difficult to verify, and it prompts other thoughts. The relative absence of physical grooming, outside family or sexual contexts, in modern human societies certainly calls for comment, and it seems quite possible that part of the success of manual therapies such as osteopathy and even acupuncture may be due to the fact that they provide a setting in which physical contact between relative strangers is considered acceptable.

As language developed, more elaborate forms of culture also became possible. Chimpanzees do seem to have the beginnings of culture, but Dunbar thinks that their inability to perform at higher levels of intentionality explains why they can never acquire complex cultures of the human kind. No chimpanzee could follow the plot of Othello. And it is, he believes, this human capacity for high-level intentionality that has led to the invention of religion in every human society that we know of.

Dunbar doubts that there is any good evidence for religion or belief in an after-life among the Neanderthals. This is rather surprising, given that their average brain size was as large as ours or even a little larger. If they really lacked religion, he suggests, this may have been because their frontal lobes (needed for abstract thought) were relatively undeveloped although they had larger occipital lobes (connected with vision). This may indicate that they had a lower order of intentionality and hence less complex language than the Cro-Magnons. And, finally, if they did not have religion, their society may have been less cohesive than that of the Cro-Magnons and this may explain their failure to survive.

This is an interesting discussion and Dunbar's view of religion is similar to that of David Lewis-Williams in The Mind in the Cave, which he cites. There seem to be rather a large number of assumptions in the chain of argument, but if it is right, we face today, as Dunbar remarks, something of a dilemma. Our evolutionary success appears to have been linked with the development of religion as a cohesive social force, and there is quite a lot of evidence to show that societies which are firmly based in religion are more stable and have better psychological health than less traditional societies. Is it possible to produce these effects in a secular society, or does the rise of rationalism threaten our social stability? And does this help to explain the rise of religious fundamentalism in so many parts of the world today? Perhaps T.S.Eliot (himself a Christian) was right, though not in the way he meant, when he wrote: "Human kind cannot bear / very much reality."

6 July 2004

%T The Human Story
%S A new history of mankind's evolution
%A Dunbar, Robin
%I faber and faber
%C London
%D 2004
%G ISBN 0-571-19133-9
%P 216 pp
%K evolution
%O illustrated with line drawings

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