By Matt Ridley.

HarperCollins; 344 pages; $26 (from March 2000). Fourth Estate; £18.99

THESE are interesting times to be a biologist. Biology is rapidly becoming as “hard” a science—in all senses—as physics. Until recently, biologists had to accept that they did not really know what makes life tick. The shapes of a few molecular cogs were known, but not how these all fitted together, or how many of them there were.

Now, that is changing. Already, the first complete lists of genes for entire organisms have been compiled. These lists, known as genomes, reveal the number of cogs. When they have been read and interpreted, they will also explain how the cogs fit together, and thus how living things work. Next year, or the year after that, the most interesting list of all should be completed: humanity's. “Genome”, therefore, is impeccably timed. Matt Ridley's idea is to choose a single feature—usually a gene—from each of the 23 pairs of human chromosomes and turn it into the material for a chapter of a book. That would not have worked had the whole list been in: on average, there will be 4,000 genes per chromosome to choose from. On the other hand, even two or three years ago, not enough genes would have been identified for him to have been able to choose 23 appropriate to the stories he wanted to tell.

For, in truth, Mr Ridley, a former science editor of The Economist, clearly picked the stories first, and then looked for suitable genes as an excuse to write about them. One can forgive him this, for the stories are fascinating, and their links to the genes in question usually close enough to show how much the new genetic knowledge will eventually revolutionise the subject.

All the big themes are covered: life and death; self-interest and politics; fate and free-will; disease, prevention and cure. And, inevitably in a book on genetics, sex.

Some stories stretch back to the time of man's last common ancestor with the rest of life—that of the 5SRNA gene, on chromosome one, for example. This gene produces part of the biochemical cog known as a ribosome. Ribosomes, in turn, churn out the proteins of which all living things are made. That gives the author an excuse to speculate about what the common ancestor was like, and to introduce the idea that RNA, DNA's neglected molecular cousin, is the older and more fundamental molecule of the two.

Other stories are about more contemporary events—as with a discussion of the ramifications of PRP. This is the gene for a protein which, when it misbehaves, causes bovine spongiform encephalopathy (in cows), Creutzfeldt-Jakob disease (in people) and paranoid dissimulation syndrome (in politicians, civil servants and others).

For this is not just a book about biology. It is also about the ramifications of biology, its interactions with the rest of human society and, in particular, the ascent of Darwinism into the human sciences.

That is a touchy subject, particularly with members of the older school of psychologist and sociologist (and with quite a few biologists, too). Mr Ridley, however, usually manages to avoid triumphalism, especially in the delicate arena of genetics and behaviour. There is the odd dig at those more purblind environmental determinists who, while rejecting the application of a genetic straitjacket to human behaviour, happily apply a cultural straitjacket instead. But mainly, he challenges the false distinctions between mind and body, behaviour and anatomy, and environment and heredity.

The point is that neither nature nor nurture is in overall charge. The brain affects the rest of the body, for sure. But the body also affects the brain. Genes will do nothing unless activated, and activation is frequently in response to environmental stimulation. People learn. Yet it is the genetically determined architecture of their brains which permits that learning to occur. And while the influence of inheritance, albeit limited, might seem obvious to a layman, it has been hard for the experts to absorb. For them, calculating its ramifications may be more difficult than teasing out the constituents of matter.


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