A Brave, 



New, 

 Healthy 

 World? 



* r^ By accident, we may be 



^ entering an era of unprecedented 

 1— ( genetic good health 



o 



Pjj by Steve Jones 



The study of human genetics began 

 with a fear for the future. Frances Galton, 

 Charles Darwin's cousin, argued in his 

 book Hereditary Genius (1869) that 

 people of innate merit — the geniuses of 

 his title — were having too few children, 

 and that, as a result, the human race was on 

 the edge of decline. 



Many Utopian and antiutopian novels 

 trace their vision of the future directly to 

 biology. Aldous Huxley's Brave New 

 World owes much to his family's scientific 

 ambiance — his brother was the biologist 

 Julian Huxley, and his grandfather 

 Thomas Henry Huxley was known as 

 "Darwin's Bulldog." H. G. Wells — whose 

 Utopia appeared in The Shape of Things to 

 Come — ^himself wrote, with Julian Hux- 

 ley, a textbook on evolution; and George 

 Bernard Shaw, author of Back to Methuse- 

 lah, appeared on public platforms with 

 Galton. 



In true Victorian style, no sooner was 

 the idea of evolution accepted than there 

 was a call to interfere with it, in this case 

 by controlling human mating. Nobody 

 needs reminding of what the eugenics 

 movement led to. Many of Hitler's crimes 

 were part of a misplaced attempt to control 

 the biological future of the human race. 



Geneticists' views have changed 

 greatly over the last century. Galton's 

 sweeping concerns about the future have 

 been replaced by a more realistic focus on 

 the risks of inbom disease. The last few 

 years have seen many triumphs in the di- 

 agnosis and treatment of genetic illness, 

 and there is the promise of many more to 

 come. 



But with these advances has come a 

 new concern. Perhaps our ability to inter- 

 fere with our genes may — as the eugeni- 



cists feared — change the evolutionary out- 

 look for the worse. Are such anxieties jus- 

 tified; and was Galton right? 



Most human biological evolution, like 

 that of any other species, depends on mu- 

 tations that can occur as genes pass from 

 parents to offspring. Some of these are bet- 

 ter than what went before and become 

 more common; others are worse and fail to 

 survive. This process, natural selection, is 

 the driving force of adaptive evolution. 



Another important — but often ne- 

 glected — agent is genetic drift, or evolu- 

 tion by accident. Particularly in small and 

 isolated communities, genes become com- 

 mon or rare at random, as those who carry 

 them have, by chance, more or fewer chil- 

 dren than average and are hence more or 

 less successful in passing on their genetic 

 heritage. 



It is hard to predict just what the fore- 

 cast for mutation or natural selection 

 might be. One thing, though, is sure. Bar- 

 ring some disastrous reduction in the num- 

 ber of people around, evolution by acci- 

 dent no longer has much force. Twenty 

 thousand years ago, there were only as 

 many people in the world as there are in 

 New York today. Society was based on 

 small bands or isolated villages, and mar- 

 riages were within the group. For most of 

 history, everyone had to marry the girl (or 

 the boy) next door, because there was no 

 choice. 



Few people now live in small or iso- 

 lated communities. The change began 

 thousands of years ago and will take thou- 

 sands more to complete (although it has 

 accelerated during the past century). This 

 will have not only a long-term effect on 

 our biology but also an immediate influ- 

 ence on genetics — not on the number of 

 geniuses, but on the incidence of disease. 



Inherited disease is certainly common 

 enough. About two out of every three 

 people reading this article will die for rea- 

 sons connected to the genes they carry. 

 Many of the genes involved — including 

 those connected with cancer and heart dis- 

 ease — ^kiU later in life, after the reproduc- 

 tive years and too late for natural selection 

 to have much effect. 



About one person in thirty, though, is 

 bom with a gene that takes its toll rela- 

 tively early. Such problems have become 

 more important, in the West at least, as in- 

 fectious diseases are controlled {see "Bac- 

 teria Break the Antibiotic Bank," page 39, 

 and "On Darwin, Snow, and Deadly Dis- 

 eases," page 42). The genes that underlie 

 many inherited diseases are recessive; 

 they show their effects only when a carrier 



has two copies, one from each parent. 



The commonest inbom diseases among 

 people of African and of European ances- 

 try — sickle-cell anemia and cystic fibro- 

 sis, respectively — are of this kind. Others 

 are more local, but are painfully familiar to 

 people from the affected regions. In 

 Cyprus, for example, one inherited blood 

 disorder, beta thalassaemia, or Cooley's 

 anemia, is so common that treating all the 

 children involved is likely to soak up half 

 the entire health budget within ten years. 

 As tteatments are developed for other dis- 

 eases, many societies will face the prob- 

 lem of paying for them. 



Both cystic fibrosis and sickle-cell ane- 

 mia can now be treated, and those affected 

 may survive to have children of their own. 

 Tests to determine whether a fetus is at 

 risk of genetic disease are now used in 

 many parts of the world, so that the num- 

 ber of children bom with these conditions 

 is dropping. But not everyone has access 

 to the tests, and some choose not to termi- 

 nate a pregnancy even when the test is 

 positive. What will the balance be be- 

 tween the increased numbers of damaged 

 genes passed on by survivors and those 

 lost by selective termination of preg- 

 nancy? Are we meddling with biology 

 without realizing what we are doing? 



Perhaps, but the effects of genetic tech- 

 nology pale before those of social change. 

 We are in the middle of one of the most 

 dramatic events in evolutionary history: 

 the human race may be entering an era of 

 unprecedented genetic good health — a bi- 

 ological Utopia reached by accident. 



At the heart of this new age is a change 

 in mating pattems. Frances Galton himself 

 showed what this can do to genes. He 

 looked at a simple inherited character, the 

 surname. Just like a gene, a sumame is 

 passed down through generations (albeit 

 through only one parent) and, also like 

 genes, names do odd things in small popu- 

 lations. 



In Switzerland, for example, everyone 

 in a mountain village may have the same 

 sumame, while everyone in another vil- 

 lage a few miles away shares a different 

 name. This is not because Schmidts sur- 

 vive in one place and Eisens in another. In- 

 stead it happens at random. Within each 

 hamlet there has, over the years, been an 

 accidental loss of names as some men 

 have no sons. Eventually, different names 

 take over in each place. The process is in- 

 evitable: even if each of the villages 

 started out (as they probably did) with a 

 slightly different set of names, the effects 

 of random loss mean that the differences 



72 Natural History 6/94 



