The Edinburgh Geologist
Issue no 29

Enigma of the big brain 

by Bill Baird

Most people think of the human brain as having gradually increased in size as man developed from primitive ancestors. In general terms this can be accepted as a true statement of the palaeoanthropological evidence. One of our earliest hominid ancestors Australopithecus afarensis who lived 3 million years ago had a skull with a brain capacity [brain size] of only 450cc (these figures are sometimes estimates, when they are based on the cranial capacity of reconstructed skull cavities). Some 2 million years ago Homo habilis had a brain size of some 750cc. By 1.5 million years ago Homo erectus had a brain size of some 1000cc and by the time of Swanscombe man 250,000 years ago brain size had grown to 1300cc. Modern man has a brain of some 1280 to 1360cc. In the face of it then, a steady progression. This increase may have been linked to increasing manual dexterity and also perhaps the use of language and increased social interaction. One of the resulting changes in human behaviour has been the increase in the size of the social grouping from a simple family group, to a clan, then to the extended tribe and eventually a nation. 

However, like all rules there are exceptions. In the case of human brain size these seem to defy evolutionary theory and in terms of progress lead us in a circle. If we accept that an increase in brain size is necessary for human social and technical skills then it should follow that the larger the brain the more dextrous and socially skilled the owner. How then do we explain the Neanderthals, with an average brain size of 1600cc for males, which is greater than that of modern man? This race, widespread in Europe, the Middle and Near East from over 100,000 to 35,000 years ago seems to be an exception to the rule. They have left little of significance in the way of artifacts, either tools or ornaments. In terms of social skills and ability to operate as a group, larger than that of the extended family, to the advantage of the race, they seem to have been a woeful failure. Cro-magnon man with a slightly smaller brain seems to have absorbed them or destroyed them with little difficulty. 

You might think the Neanderthals were a race with other problems, which so hindered evolutionary progress, that the handicaps outweighed the advantage of the big brain. Perhaps there was an unknown handicap, but what if the Neanderthals were not alone in having a larger brain than modern man? What if in South Africa at the end of the last ice age there were a people, the ancestors of the present Bushmen, with huge brains? A few thousand years ago this clearly recognizable modern race had individuals with brain sizes approaching and perhaps sometimes exceeding 2000cc. 

It is important here to enter a note of caution. Brain size in modern man is given as an average of just over 1300cc for men and lOOcc less for women. But the minimum and maximum are lOOOcc to 2000cc. Widely quoted examples of this variation are Anatole France weighing in at lOOOcc and Jonathon Swift at double that. Any individual within the minimum and maximum limits can show all the abilities of skill and even genius or be of subnormal mental development. In other words, within a fairly wide range, brain size is not a direct measure of intelligence. The link between brain size and intelligence does exist but it is not absolute. The correlation factor is quoted as 0.3 to 0.35. There is some evidence to suggest that density and network activity within the brain is equally or even more important than absolute size. However, it is obvious that historically a clear indication of human progress is increased brain size linked to dextral and social skills. So when then does a big brain become a handicap? What is the nature of that handicap? How indeed do we measure intelligence? If intelligence tests are set by people of normal brain size, what relevance might they have to an individual with a brain one third bigger than the individual who set the test. It is only 50 years since just such flawed tests, carried out in the USA, proved that the American Negro was mentally incapable of competently flying combat aircraft. 

It is interesting to speculate on the significance and uses of larger than normal human brains. If we believe in evolution as a non-reversible process then there must have been some significant advantage, however short term, of the linkage to its continued increase in size. 

Imagine an environment where human numbers had not significantly reduced the once huge numbers of edible species of food animals and plants. Where the climate was reasonably kind and the threat of predators, both animal and other humans, was low. Where there was time to ponder on the song and flight of birds, to watch the rising and setting of the sun, moon and stars. To listen to the wind and rain, watch some things grow and others die, to be overwhelmed by the beauty of this wondrous earth with all its riches. It is pleasing to think that these might have been some of the pastimes of our big brained ancestors. However, that time, if it ever existed has gone forever, so where do we go from here? Can we draw any understanding of our present situation and compare it to the lives and thoughts of previous races? 

For what it is worth I make a suggestion which I believe has the hallmark of simplicity and practicality. It may be that the increase in brain size was only a benefit when it achieved maximum social conformability with greatest manual dexterity. Anything further was a positive irrelevance. At the optimum stage of racial, national or social groupings the human race can operate almost like the social insects. We can use manual skills to manufacture weapons or dam rivers. We can defend our territories to the death, at the command of an accepted individual or elite. We can create power and circulate it for use throughout a nation. With our size ofbrain we can either manage to operate adequately on our own or combine to operate as a super organism like the ants or termites. 

With a bigger, more complex brain, I suggest that we become different. We become knowing, questioning and immensely aware of our position in and links with the environment. 

Not for nothing does Homo sapiens network computers, set up think tanks and hold group brain storming sessions. We have little to learn from the ants, I believe that we are ourselves becoming a social organism. We should not look back on our ancestors with disdain for their primitive life but forward with apprehension to our facade of a modern life. 

Further Reading

Ankney, C.D. 1992. Differences in Brain Size. Nature, 358, 532. 

Ankney, C.D. 1992. The brain size/IQ debate. Nature, 360, 292. 

Becker, B.A. 1992. Differences in Brain Size. Nature, 358, 532. 

Bledt D.A. 1992. Brain size differences. Nature, 359, 182. 

Brand, C.R. 1992. Sizing-up the brain. Nature, 359, 768. 

Chen Tiemei, Yang Quan & Wu En 1994. On the Antiquity of Homo sapiens in China. Nature, 368, 55-56. 

Eiseley, L. 1959. The Immense Journey. Vintage Books, New York. 

Elliot Smith, G. 1917. The Endocranial Cast of the Boskop Skull. Proceedings of the Manchester Literary and Philosophical Society, 15-16. 

Haughton, S.H. 1917. Preliminary note on the ancient human skull remains from the Transvaal. Transactions of the Royal Society of South Africa, 6, 1-13. 

Holloway, R.L. 1973. Endocranial capacities of the early African hominids. Journal of Human Evolution, 2, 449. 

Keith, A. 1925. The Antiquity Man. Vol. 1. Williams and Norgate Ltd, London. 356-376. 

Krantz, G.S. 1968. Brain size and hunting ability in earliest man. Current Anthropology, 9, 450. 

Leaky, E. 1982. The Making of Mankind. Sphere books Ltd, London. 

Lewis-Williams, D. 1991. Bushmen. Struik, Cape Town. 

Lynn, R. 1992. Brain Size Differences. Nature, 359, 181. 

Maddox, I. 1992. How to publish the unpalatable. Nature, 358, 187. 

Morrison, R. 1991. The Voyage of the Great Southern Ark. Ure Smith Press, Australia, 301-321. 

Pilbeam, D. 1988. In: Origins. The Darwin College Lectures. A.C. Fabian (ed). Cambridge University Press, 108- 114. 

Rushton, J.P. 1992. Differences in Brain Size. Nature, 357, 532. 

Rushton, J.P. 1992. The brain size/IQ debate. Nature, 360, 292. 

Schluter, D. 1992. Brain Size Differences. Nature, 359, 181. 

Shackley, M. 1980. Neanderthal Man. Duckworth Gerald and Co. Ltd, London. 

Singer, R. 1958. The Boskop 'Race' Problem. Man, 232, 173-178. 

Stringer, C. and Gamble, C. 1993. In Search of the Neanderthals. Thames and Hudson, London. 

Tattersaal, I. et al. (eds.) 1988. Brain. In: Encyclopedia of Human Evolution and Prehistory. Garland Publishing, New York and London, 98-105. 

Tobias, P. 1994. Ad Hominidae: The Future of South Africa's Ancient Past. Optima, 40. 

Tsai, F.C.S. 1992. Brain size differences. Nature, 359, 181-182. 

van Valen, L.M. 1992. Sizing-up the brain. Nature, 359, 768. 

Watson, L. 1986. Earthworks. Hodder and Stoughton, London. 

Wills, C. 1993. The Runaway Brain: The Evolution of Human Uniqueness. Basic Books, New York. 

Wilson, M.L. 1993. The 'strandloper' concept and its relevance to the study of the past inhabitants of the southern African coastal region. Annals of the South African Museum, 103, 293-382. 

Wilson, M.L. 1994. Lyall Watson and the 'Strandlopers'. The Digging Stick, 7, 7-9. 

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