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Are We Hardwired? The Role of Genes in Human Behavior, William R Clark and Michael Grunstein, Oxford University Press, 2000, pp. ix +322, £16.99.

The short answer to the question posed by the title is, it seems, yes and no. At least 50 per cent of our behaviour is, according to the authors, determined by our genes but our environment also has a significant role. It is not a simple situation since our genetic hardwiring is usually the result of the interaction of several genes often on different chromosomes. Few, if any, behaviours are controlled by a single gene. So, although each gene involved is inherited in a Mendelian manner this polygenic inheritance interacting with the environment results in the wide range of behaviour patterns we actually observe in human populations. Understanding just how our behaviours are determined is clearly going to be a long term project which in a real sense has only just begun.

The authors have chosen to approach the problem by first demonstrating beyond all doubt that human behaviour has a significant inherited component by starting with a chapter on twin studies. They then examine the evolutionary origins of behaviour starting with a pond dwelling protozoan, Paramecium, followed by a soil-inhabiting roundworm, Caenorhabditis elegans, a sea-slug, Aplysia californica, and the fruitfly, Drosophila melanogaster. As the organisms become more complex so too do their behaviours but in all these cases laboratory studies have shown that while the environment is not without a modifying effect much of their behaviour is genetically determined, i.e. is hardwired. It seems that in many cases the genes for behaviour are very similar in these organisms, and indeed in ourselves. As the most complex organism on Earth Homo sapiens may well have more genetic-environmental interactions than other animals. However we do seem to share genes for behaviour with them which is not surprising since evolution tends to conserve systems which work.

Having arrived at H. sapiens the authors discuss the genetics of aggression, eating disorders, and substance abuse in some detail. But when they get to the really controversial subject of the inheritance of intelligence they seem reluctant to commit themselves. Instead of intelligence they prefer “human mental function” while admitting that, whatever we call it, it has a clear genetic component and indeed Francis Galton is credited with being the first to suggest that variation in mental traits might be inherited. There is the usual criticism of IQ tests for not being perfect (what is?). Yet much of this chapter is about IQ tests and on page 233 they state “We can provide a secure and culturally enriched environment that will allow each child to optimize his or her innate abilities, but we cannot fundamentally alter these abilities.” So maybe IQ tests are not so bad after all.

The final chapter “Genes, the environment, and free will” asks whether or not we do in fact make our own decisions about anything. We like to think we do but, they ask, where in the nature versus nurture debate does free will come in? If our behaviour is totally hardwired or totally environmental or any mixture of the two, free will would seem to disappear. The authors suggest that modern chaos theory may provide an answer which would allow us to believe that people are indeed responsible for their own actions. Perhaps so, perhaps not.

This is a most interesting book worth reading by anyone interested in human behaviour. Some parts are better than others, some seem to have been airbrushed with political correctness. For some reason the authors have added an appendix “A Brief History of Eugenics”. This is not without interest and is rather more balanced than many such accounts. I wonder, however, why it is there? Was it to add a spoonful of political correctness to offset the fact that much of the book’s contents suggest that, in a general sense, the early eugenicists were on the right lines?

John Timson