There are two areas in the brains of monkeys that correspond precisely to these areas. The Broca-homologue is used for controlling the muscles of the monkey's face, larynx, tongue and mouth. The Wernicke-homologue is used for recognising sound sequences and the calls of other monkeys. These are exactly the non-linguistic problems that many SLI people have: controlling facial muscles and hearing sounds distinctly. In other words, when ancestral human beings first evolved a language instinct, it grew in the region devoted to sound production and processing. That sound-production and 1 0 2 G E N O M E
processing module remained, with its connections to facial muscles and ears, but the language instinct module grew on top of it, with its innate capacity for imposing the rules of grammar on the vocabulary of sounds used by members of the species. Thus, although no other primate can learn grammatical language at all — and we are indebted to many diligent, sometimes gullible and certainly wishful trainers of chimpanzees and gorillas for thoroughly exhausting all possibilities to the contrary - language is intimately physically connected with sound production and processing. (Yet not too intimately: deaf people redirect the input and output of the language module to the eyes and hands respectively.) A genetic lesion in that part of the brain therefore affects grammatical ability, speech and hearing - all three modules.11
No better proof could be adduced for William James's nineteenth-century conjecture that human beings evolved their complex behaviour by adding instincts to those of their ancestors, not by replacing instincts with learning. James's theory was resurrected in the late 1980s by a group of scientists calling themselves evolutionary psychologists. Prominent among them were the anthropologist John Tooby, the psychologist Leda Cosmides and the psycho-linguist Steven Pinker. Their argument, in a nutshell, is this. The main goal of twentieth-century social science has been to trace the ways in which our behaviour is influenced by the social environment; instead, we could turn the problem on its head and trace the ways in which the social environment is the product of our innate social instincts.
Thus the fact that all people smile at happiness and frown when worried, or that men from all cultures find youthful features sexually attractive in women, may be expressions of instinct, not culture. Or the universality of romantic love and religious belief might imply that these are influenced by instinct more than tradition. Culture, Tooby and Cosmides hypothesised, is the product of individual psychology more than vice versa. Moreover, it has been a gigantic mistake to oppose nature to nurture, because all learning depends on innate capacities to learn and innate constraints upon what is learnt. For instance, it is much easier to teach a monkey (and a man) I N S T I N C T 1 0 3
to fear snakes than it is to teach it to fear flowers. But you still have to teach it. Fear of snakes is an instinct that has to be learnt.12
The 'evolutionary' in evolutionary psychology refers not so much to an interest in descent with modification, nor to the process of natural selection itself - interesting though these are, they are inaccessible to modern study in the case of the human mind, because they happen too slowly - but to the third feature of the Darwinian paradigm: the concept of adaptation. Complex biological organs can be reverse-engineered to discern what they are 'designed' to do, in just the same way that sophisticated machines can be so studied.
Steven Pinker is fond of pulling from his pocket a complicated thing designed for pitting olives to explain the process of reverse engineering. Leda Cosmides prefers a Swiss-army knife to make a similar point. In each case, the machines are meaningless except when described in terms of their particular function: what is this blade for? It would be meaningless to describe the working of a camera without reference to the fact that it is designed for the making of images. In the same way, it is meaningless to describe the human (or animal) eye without mentioning that it is specifically designed for approximately the same purpose.
Pinker and Cosmides both contend that the same applies to the human brain. Its modules, like the different blades of a Swiss-army knife, are most probably designed for particular functions. The alternative, that the brain is equipped with random complexity, from which its different functions fall out as fortunate by-products of the physics of complexity - an idea still favoured by Chomsky - defies all evidence. There is simply nothing to support the conjecture that the more detailed you make a network of microprocessors, the more functions they will acquire. Indeed, the 'connectionist' approach to neural networks, largely misled by the image of the brain as a general- purpose network of neurons and synapses, has tested the idea thoroughly and found it wanting. Pre-programmed design is required for the solving of pre-ordained problems.
There is a particular historical irony here The concept of design in nature was once one of the strongest arguments advanced against 1 0 4 G E N O M E
evolution. Indeed, it was the argument from design that kept evolutionary ideas at bay throughout the first half of the nineteenth century. Its most able exponent, William Paley, famously observed that if you found a stone on the ground, you could conclude little of interest about how it got there. But if you found a watch, you would be forced to conclude that somewhere there was a watchmaker. Thus the exquisite, functional design apparent in living creatures was manifest evidence for God. It was Darwin's genius to use the argument from design just as explicitly but in the service of the opposite conclusion: to show that Paley was wrong. A 'blind watchmaker' (in Richard Dawkins's phrase) called natural selection, acting step by step on the natural variation in the creature's body, over many millions of years and many millions of individuals, could just as easily account for complex adaptation. So successfully has Darwin's hypothesis been supported that complex adaptation is now considered the primary evidence that natural selection has been at work.13
The language instinct that we all possess is plainly one such complex adaptation, beautifully designed for clear and sophisticated communication between individuals. It is easy to conceive how it was advantageous for our ancestors on the plains of Africa to share detailed and precise information with each other at a level of sophistication unavailable to other species. 'Go a short way up that valley and turn left by the tree in front of the pond and you will find the giraffe carcass we just killed. Avoid the brush on the right of the tree that is in fruit, because we saw a lion go in there.' Two sentences pregnant with survival value to the recipient; two tickets for success in the natural-selection lottery, yet wholly incomprehensible without a capacity for understanding grammar, and lots of it.
The evidence that grammar is innate is overwhelming and diverse.
The evidence that a gene somewhere on chromosome 7 usually plays a part in building that instinct in the developing foetus's brain is good, though we have no idea how large a part that gene plays.
Yet most social scientists remain fervently resistant to the idea of genes whose primary effect seems to be to achieve the development I N S T I N C T 1 0 5
of grammar direcdy. As is clear in the case of the gene on chromosome 7, many social scientists prefer to argue, despite much evidence, that the gene's effects on language are mere side-effects of its direct effect on the ability of the brain to understand speech. After a century in which the dominating paradigm has been that instincts are confined to 'animals' and are absent from human beings, this reluctance is not surprising. This whole paradigm collapses once you consider the Jamesian idea that some instincts cannot develop without learnt, outside inputs.
This chapter has followed the arguments of evolutionary psychology, the reverse-engineering of human behaviour to try to understand what particular problems it was selected to solve. Evolutionary psychology is a new and remarkably successful discipline that has brought sweeping new insights to the study of human behaviour in