Matt Ridley

standardized: They were then replaced by the Acheulian technology of Homo erectus, which consisted of hand axes and teardrop-shaped stone devices.

Again, nothing happened for a million years and more, until about 200,000 years ago when there was a sudden and dramatic expansion in the variety and virtuosity of tools at about the time that Homo sapiens appeared: From then on there was no looking back: Tools grew ever more varied and accomplished until the invention of metal: But it comes too late to explain big heads; heads had been swelling ever since 3 million years ago. 1e Making the tools that erectus used is not especially hard.

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Everybody could do it, presumably, which is why it was done all over Africa. There was no inventiveness or creativity going on: For a million years these people made the same dull hand axes, yet their brains were already grossly large by ape standards: Plainly, the instincts of manual dexterity, perception of shape, and reverse engineering from function to form were useful to these people, but it is highly implausible to account for the enlargement of the brain as driven entirely by an enlargement of these instincts: The first rival to the toolmaking theory was 'man the hunter. ' In the 1960s, starting with the work of Raymond Dart, there was much interest in the notion that man was the only ape to have taken up a meat diet and hunting as a way of life: Hunting, went the logic, required forethought, cunning, coordination, and the ability to learn skills such as where to find game and how to get close to it. All true, all utterly banal: Anybody who has ever seen a film of lions hunting zebra on the Serengeti will know how skillful lions are at each of the tasks mentioned above: They stalk, ambush, cooperate, and deceive their prey as carefully as any group of humans ever could. Lions do not need vast brains, so why should we? The fashion for man the hunter gave way to woman the gatherer, but similar arguments applied. It is simply unnecessary to be capable of philosophy and language to be able CO dig tubers from the ground. Baboons do it just as well as women. 19

Nonetheless, one of the most startling things to come out of the great studies of the !Kung San people of the Namib desert in the 1960s was the enormous accumulation of local lore that hunter-gatherer people possess—when and where to hunt for each kind of animal, how to read a spoor, where to find each kind of plant food, which kind of food is available after rain, which things are poisonous and which medicinal. Of the !Kung, Melvin Konner wrote, ' Their knowledge of wild plants and animals is deep and thorough enough to astonish and inform professional botanists and zoologists: 'zo Without this accumulated knowledge it would not have been possible for mankind to develop so rich and varied a diet, for the results of trial-and-error experiments would not have been cumulative but would have had to be relearned every genera-

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The Red Queen

Lion. We would have been limited to fruit and antelope meat, not daring to try tubers, mushrooms, and the like. The astonishing symbiotic relationship between the African honey guide bird and people, in which the bird leads a man to a bees ' nest and then eats what remains of the honey when he leaves, depends on the fact that people know because they have been told that honey guides lead them to honey. To accumulate and pass on this store of knowledge required a large memory and a large capacity for language. Hence the need for a large brain.

The argument is sound enough, but once more it applies with equal force to every omnivore on the African plains. Baboons must know where to forage at what time and whether to eat cen-tipedes and snakes. Chimpanzees actually seek out a special plant whose leaves can cure them of worm infections, and they have cultural traditions about how to crack nuts: Any animal whose generations overlap and which lives in groups can accumulate a store of knowledge of natural history that is passed on merely by imitation: The explanation fails the test of applying only to humans. 21

THE BABY APE

The humanist might be feeling a little frustrated by this line of argument. After all, we have big brains and we use them: The fact that lions and baboons have small ones and get by does not mean that we are not helped by our brains. We get by rather better than lions and baboons. We have built cities, and they have not: We invented agriculture, and they did not. We colonized ice-age Europe, and they did not. We can live in the desert and the rain

'forest; they are stuck on the savanna. Yet the argument still has considerable force because big brains do not come free. In human beings, 18 percent of the energy that we consume every day is spent in running the brain. That is a mighty costly ornament to stick on top of the body just in case it helps you invent agriculture, just as sex was a mighty costly habit to indulge in merely in case it led to innovation (chapter 2). The human brain is almost as costly an THE INTELLECTUAL CHESS GAME

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invention as sex, which implies that its advantage must be as immediate and as large as sex 's was.

For this reason it is easy to reject the so-called neutral theory of the evolution of intelligence, which has been popularized in 22

recent years mainly by Stephen Jay Gould:

The key to his argu-

ment is the concept of 'neoteny '—the retention of juvenile features into adult life: It is a commonplace of human evolution that the transition from Australopithecus to Homo and from Homo habilis to Homo erectus and thence to Homo sapiens all involved prolonging and slowing the development of the body so that it still looked like a baby when it was already mature. The relatively large brain case and small jaw, the slender limbs, the hairless skin, the unrotated big toe, the thin bones, even the external female genitalia—we look like baby apes.2'

The skull of a baby chimpanzee looks much more like the skull of an adult human being than either the skull of an adult chimpanzee or the skull of a baby human being. Turning an ape-man into a man was a simple matter of changing the genes that affect the rate of development of adult characters, so that by the time we stop growing and start breeding, we still look rather like a baby: 'Man is born and remains more immature and for a longer period than any other animal, ' wrote Ashley Montagu in 1961. 24

The evidence for neoteny is extensive. Human teeth erupt through the jaw in a set order: the first molar at the age of six, compared with three for a chimp. This pattern is a good indication of all sorts of other things because the teeth must come at just the right moment relative to the growth of the jaw. Holly Smith, an anthropologist at the University of Michigan, found in twenty-one species of primate a close correlation between the age at which the first molar erupted and body weight, length of gestation, age at weaning, birth interval, sexual maturity, life span, and especially brain size: Because she knew the brain size of fossil hominids, she was able to predict that Lucy would have erupted her first molar at three and lived to forty, much like chimpanzees, whereas the average