Sunday Times, 17 June 2012
Nicky and Louise are 30-year-old identical twins. They are attractive, competent women and, as you would expect, have a lot in common — taste in food, drink and clothes, and a commitment to exercise. They avoid dangerous sports, cigarettes, drugs, and gambling. As identical twins have exactly the same genes, there you have it, proof positive, it’s all in the genes.
Except it isn’t. Nicky has had five men in her life, Louise 25. Even though they like the same kind of men and both enjoy sex and have orgasms, their attitudes are utterly different. Aged 15, they discovered that their father had kept a secret mistress for years. Nicky took it badly; Louise didn’t, and, at that point, their sexual trajectories diverged.
But why? The short answer is that identical twins aren’t identical and our genes are not our destiny. Tim Spector is a professor working in genetic epidemiology at King’s College, London. He made the headlines and outraged many “sex counsellors” when he announced in 2009 that the G-spot (a zone of special erotic sensitivity in women) did not exist.
He also used to think genes were the heart of the matter. “Until three years ago,” he writes, “I was one of the many scientists who took the genecentric view of the universe for granted…But I had a nagging doubt that we were missing something.”
But why? The short answer is that identical twins aren’t identical and our genes are not our destiny.
Spector is not alone in experiencing a Damascene conversion from gene-centrism, but with this eminently readable book he is the first successfully to explain the issue to the general reader. In 1993 he started the UK Twins Registry of 11,000 twins, which is now one of the best databases of its kind in the world. Identical twins are one of the gold standards of genetic research; they have the same genomes, therefore any variations or similarities in them provide evidence of the influence of the genes. Spector’s doubts emerged as the variations revealed by his database became ever more apparent.
These variations need not be minor, they may be a matter of life and death. Twins Peter and Nigel, for instance, were ready to celebrate their 42nd birthday together when Peter hanged himself. Depression ran in the family but, although identical, only one of the pair seemed to have inherited the trait. Even conjoined twins such as Ladan and Laleh in Iran exhibited striking differences. Laleh liked computer games, Ladan liked praying; Ladan was left-handed, Laleh right-handed. They died in the operation to separate them in 2003. Doubtless, if they had lived apart, they would have diverged even further. The point here is that identical twins do not prove the power of the gene, they define its limitations.
Now, full disclosure — I have a dog in this fight. In the 1990s, while writing a book on genetics, I became baffled by the arguments of the gene-centrists. Following Richard Dawkins, who insisted we were lumbering robots operated by our genes, the gene-centrists claimed that our genomes did almost everything and that whatever remained could be explained by the “environment”, an entity that remained undefined. This position was riddled with unfounded assumptions and contradictions but, whenever I pointed this out, the scientists merely looked at me pityingly. Anyway, just to say, thanks, Spector, for backing me up.
The defeat of the gene-centrists began with the over-hyped publication of the human genome in 2000. This was, it was claimed, “the book of life” — it isn’t — and was to be the prelude to a revolution in medicine — so far, no. The first sign there was something wrong was the revelation that we have only about 23,000 genes, half as many as a tomato, and only a quarter as many as, in our vanity, we thought we had. The second sign was that the gene-centrists’ belief in the simple link between genotype and phenotype (organism) was naive; vast complexity was the harsh (but, for me, consoling) reality.
Following Richard Dawkins, who insisted we were lumbering robots operated by our genes, the gene-centrists claimed that our genomes did almost everything
One genetic fundamentalist claim after another collapsed — there is no gene for homosexuality, none for alcoholism and so on. It is probably true to say that the phrase “gene for” is usually meaningless. This is partly because many genes are involved in almost any trait, but, more important, it is because (as Spector surmised) there was something missing.
What was missing is now called epigenetics, a concept whose importance can scarcely be overstated. The gene-centric view was that the gene produced a protein that went on to build an organism. In fact, we now know not only that some genes can produce several proteins, but also that this mechanism can be turned on and off by processes of which, not long ago, we knew nothing. The gene, in other words, is not the last word and may not even be the first. It is certainly not in complete control of anything.
The implications are staggering. The first is that twins may not be identical because these processes (the most common is called methylation) could have happened to them in the womb. Second, the sins of the grandparents can be visited upon the grandchildren. Spector has cases of one generation’s starving and binge-eating during postwar austerity resulting in obesity two generations later. In other words, what you do in life may affect the genomes of your offspring.
This book concludes with a list of four genetic dogmas that have been overthrown: genes are not our essence; our genetic inheritance can be changed; environmental events can be “remembered” by cells; and what happens in your life can affect later generations. Or, to put it bluntly, almost everything you’ve been told about genetics is wrong.
The list also, potentially, settles the old, stale and often irrational argument about nature v nurture. What epigenetics demonstrates is not a simple division between humans and their environment (the underpinning of much of the illogic spouted by the scientists I met in the 1990s), but rather a flow of indecipherably complex interactions, a ballet of cells that, in some ways, matches the flowing, dancing world of particles and forces discovered by the physicists beneath the surface of matter.
This is not simply a book of ideas, it is also a book of stories, most astounding, many heartbreaking. Flo and Kay, for example, were an incredibly rare case of “idiot savant”, identical twins who found peace in the American television quiz show Pyramid. When it ended, they found further consolation in the idea of being buried with memorabilia of the show’s host Dick Clark. There are twin sisters, one of whom has frequent orgasms and one who didn’t have one until she was 42. There is a twin who conspires, unsuccessfully, to have her identical twin murdered. Most alarmingly, there is the story of a substance in almost all plastic that may epigenetically alter our genomes. If proved, that, I imagine, will make the euro meltdown look like a very small disaster indeed.
Spector will get you through many dinner parties. But, much more importantly, he will show how a certain kind of scientific fundamentalism collapsed under the burden of its inability to explain the world as it is — complex, flowing, changing — rather than as they would like it to be — simple and clear. Read him.