Life's Twisted Plotline

Sometime within the next few months we shall have a rough first draft of the complete human genome. This is routinely reported as an event of medical and perhaps ethical significance. I believe it is more than that. I believe it is the greatest intellectual moment in history. Bar none. Some may protest that a human being is more than his or her genes. I do not deny it. There is much, much more to each of us than a genetic code. But until now, human genes were an almost complete mystery. We will be the first generation to penetrate it.

The genome is a sort of autobiographical record, written in "genetish," of all the vicissitudes and inventions that have characterized the history of our species and its ancestors since the dawn of life. Genes have already told us that we are the closest relatives of chimpanzees; that the common ancestor of fruit flies and people was a 600 million-year-old segmented worm with the ability to learn; that the Basques are as unrelated to other Eurasians as their language implies and may be descended from indigenous European hunter-gatherers. Genes can even tell us a bit about "LUCA," the Last Universal Common Ancestor of all life, a single-celled microbe that lived about 4 billion years ago.

Unlike other autobiographies, the genome contains stories about the future as well as the past. Among the genes are clear messages about what will happen to your body as you age, a few of which we can already read. There is a gene, for example, that can alter your susceptibility to Alzheimer's disease elevenfold, depending on whether its 334th letter is G or A.

The idea of the genome as a book--longer than 800 Bibles yet so small that there are trillions of copies inside each one of us--is not even a metaphor. It is literally true. A book is a piece of digital information, written in linear, one-dimensional and one-directional form and defined by a code that transliterates a small alphabet of signs into a large lexicon of meanings through the order of their groupings. So is a genome.

It was genes that prescribed my shape, gave me five fingers on each hand and 32 teeth in my mouth, laid down my capacity for language and defined about half of my intellectual capacity. When I remember something, it is they that do it for me, switching on the neurochemical system that stores the memory.

Where does this leave free will? The answer, according to some, is that free will comes from society--from our culture and nurture. By this reasoning, freedom equals the parts of our nature not determined by our genes, a sort of flower that blooms after our genes have done their tyrannical worst. We can rise above our genetic determinism, they insist, and grasp that mystic flower, freedom.

But that only replaces genetic determinism with social determinism, which to my mind is even bleaker. It came as something of a surprise to me to reread Aldous Huxley's Brave New World and discover that there is almost nothing about genetics in it. In the book, alphas and epsilons are not bred; they are produced by chemical adjustment in artificial wombs followed by Pavlovian conditioning and brainwashing, then sustained by opiate-like drugs. In other words, the quintessential 20th century dystopia owes nothing to nature and everything to nurture--an environmental, not a genetic, hell. It is hard to tell who caused more suffering: the extreme genetic determinists who ruled Germany in the 1930s or the extreme environmental determinists who ruled Russia at the same time.

Yet the myth persists that genetic determinism is a more implacable kind of fatalism than social determinism. In practice, this is not proving true. Dyslexia and shyness both have a large innate component; recognizing this has led to better therapies, not callous fatalism. Nor does genetic determinism undermine responsibility. To the extent that you act in character, you are responsible for your actions; yet acting in character is merely expressing the many determinisms that caused your character. We have a paradox. Unless our behavior is random, it is determined. If it is determined, then it is not free.

We can resolve the paradox in part by distinguishing determinism from predictability. The weather is deterministic, but it is not predictable. Like the weather, we are a complex amalgam of feedback systems: genes in our brains switch on in response to our behavior as well as vice versa. Perhaps freedom lies in expressing your own determinism, not somebody else's. As the psychologist Lyndon Eaves has put it, "Would you rather be pushed around by your environment, which is not you, or by your genes, which in some sense is who you are?" Give me nature over nurture anytime.

Ridley is the author of The Red Queen, The Origins of Virtue and, most recently, Genome, from which this was adapted