Following comets

an inferior hand of genes. Fetuses are today commonly screened for genetic disorders and this service will no doubt expand. An American company has devised a one-inch chip carrying 400,000 DNA fragments, which will allow the entire human genome to be screened for an average of four alleles per gene. The difference between eliminating the undesirable and promoting the advantageous is becoming too subtle even for ethical hair-splitting. Those who reject the lot as contrary to God’s will are the descendants of the sanctimonious bigots who sought to prevent the application of effective treatments for leprosy and syphilis, when these became available earlier this century. Nor can one argue that the new genetic techniques signal a return to the malign eugenics of earlier days, for they will be driven not by the state or any other authority but by the aspirations of individual citizens. Silver makes a genuflection in his subtitle and epigraph to Aldous Huxley, while rejecting any comparisons with the dystopia of Brave New World. But as the technology will always be exacting and expensive, genetic enhancement will remain the prerogative of the rich. So in time two populations will emerge, which Silver calls the GenRich and the Naturals, who will seldom intermarry. The genetic distance between the two groups will widen until they are no longer able to interbreed and evolution will have been given a sharp nudge. This (like the entire book) is vastly entertaining stuff, but biologists will perceive the weakness in Silver’s jeu d’esprit: almost all diseases, and certainly all mental and physical attributes, are clearly enough multigenic and interact in complex and uncertain ways with the environment. Silver believes that science will in time get to grips with all such problems; his prediction will send shivers up many spines but not, I suspect, those of geneticists. Silver unexpectedly stops short of the last frontier — the conquest of mortality. Whether this emerges from the study of telomeres or the mutation in progeria or from some other, unforeseen direction, it is surely likely to overwhelm the human species long before the designer babies start to pop out of the womb. Meanwhile, to banish the unpleasing vision of a genetic aristocracy poring over the DNA stud-book, just as the inbred nineteenth-century nobility of Europe immersed itself endlessly in the Almanach de Gotha, remember the report once given by a cavalry officer on one of his high-born subordinates: “Personally, I would not breed from this officer.”