Adam's Curse: a future without men
Bryan Sykes Bantam Press, 310pp, £18.99
ISBN 0593050045
In his poem "Tortoise Shout", D H Lawrence asks: "Why were we crucified into sex?/Why were we not left rounded off, and finished in ourselves . . . ?" Bryan Sykes has a ready answer: survival. Sykes, professor of human genetics at Oxford, explains that those species which replicate with two sexes are more durable, more genetically varied, better able to withstand parasites than those - such as dandelions, greenfly and whiptail lizards - which propagate without sex.
You may well ask whether it is possible to discuss sexual reproduction and the war between the sexes without jokey asides. The answer, to judge from Adam's Curse, is "no". Embarked on the laudable endeavour of explaining why the human male is on its way to extinction because of mutational deterioration of its distinctive Y chromosome, Sykes cannot resist nudge-nudge remarks. "Impressing females is a costly business, as many of you know," he quips, as he describes the efforts of the male of many species to cajole or coerce females into accepting their sperm.
Archness is a forgivable if irritating sin in a science writer. Complex new discoveries in a rapidly advancing speciality such as genetics require translation for the general reader. Anthropomorphism is a favourite aid. Richard Dawkins got away with it in The Selfish Gene, imputing to a bundle of DNA ambitions and emotions recognisable to the human beings reading the book. Sykes helps the medicine to go down by personifying genes.
The separation of the sexes, he says, has arisen "from a deliberate ploy by the nuclear genes to limit the damage caused by the two warring cytoplasms following the sexual fusions which the nuclear genes themselves require to exchange DNA". The result of the "ploy" is a "peace treaty", the evolution of the double-chromosomed organisms "needed to protect and deliver the fragile gametes of the male sex to the eggs of the female, well-supplied with cytoplasm".
Cytoplasm? The uninformed reader needs the Shorter Oxford English Dictionary definition: "the protoplasm of the cell as distinct from the nucleus". No matter. Sykes's main point is as clear as it was in his excellent earlier book, The Seven Daughters of Eve, in which he discovered among Europeans seven groups whose genetic origins are traceable, through their mitochondrial DNA, to seven women who lived as long as 45,000 years ago. (Mitochondrial DNA, he explained, is the only bit of the human DNA that is passed purely from female to female.)
Adam's Curse concerns the ingredient that is unique to the male, the Y chromosome. As it is transmitted only through the male line, it leaves a genetic trail through which male ancestors can be traced, especially as surnames are passed through paternal inheritance. For a start, Sykes collected the DNA of scores of men named Sykes and found their Y chromosome matched his and that many of them came from Yorkshire. Thus he was able to trace his own Y chromosome back to a 13th-century Yorkshireman, Henri del Sike. Through similar genetic detective work, Sykes traces the chromosomal roots (and Viking infusion) of the several million descendants of Clan Donald to Somerled of Argyll, who died in 1164 in an attack on the Isle of Man. He then shifts his search to the origins of the prolific Mongolian chromosome and finds that 16 million men carry the Genghis Khan chromosome, trumping the Somerled chromosome 30 times over.
A moral begins to emerge, which feminists will quickly grasp. The Y chromosome is the conqueror's chromosome; its agent is testosterone, with concomitant aggression, promiscuity and patrilineal succession. Those with power pass on more Y chromosomes than those without, because they take the most women. Sykes plausibly traces this male tendency to pillage, plunder and rape to the dawn of agriculture. Once hunter-gatherers gave way to farmers, power resided in those with the most land and the most sons, and women were enslaved as housekeepers and breeders. In short, Sykes argues, Adam's Curse is the Y chromosome that behaves badly and enslaves the feminine.
That's the bad news. The good news - at least to the carriers of mitochondrial DNA (women) - is that the Y chromosome is doomed. Male infertility is increasing as sperm counts decline and the chromosome itself atrophies. Sykes calculates that there will only be another 5,000 generations, or 125,000 years, before sexual selection disappears and the human race relies on unisex reproduction by females. Not clones. Rather, female eggs fertilised by the nuclear chromosomes of another female and implanted by in-vitro fertilisation. In the longer run, to be sure, this development threatens the extinction of the human species.
But Sykes is concerned with the medium term. Unchauvinistically, he welcomes the lifting of Adam's Curse. When sperm no longer fight one another for access to eggs, he says, the "destructive spiral of greed and ambition fuelled by sexual selection diminishes, and the sickness of our beautiful planet eases". Sounds good, although some may feel that 125,000 years is a long time to wait.
Brenda Maddox is the author of Rosalind Franklin: the dark lady of DNA (HarperCollins)
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