The Red Queen_ Sex and the Evolution of Human Nature - Matt Ridley [15]
One more technical term is essential: meiosis, which is simply the procedure by which the male selects the genes that will go into a sperm, or the female selects the genes that will go into an egg. The man may choose either the 75,000 genes he inherited from his father, or the 75,000 he inherited from his mother, or, more likely, a mixture. During meiosis something peculiar happens. Each of the 23 pairs of chromosomes is laid alongside its opposite number. Chunks of one set are swapped with chunks of the other in a procedure called recombination. One whole set is then passed on to the offspring to be married with a set from the other parent: a procedure known as outcrossing.
Sex is recombination plus outcrossing: this mixing of genes is its principal feature. The consequence is that the baby gets a thorough mixture of his four grandparents’ genes (because of recombination) via his two parents (because of outcrossing). Between them, recombination and outcrossing are the essential procedures of sex. Everything else about it – gender, mate choice, incest avoidance, polygamy, love, jealousy – are all ways of doing outcrossing and recombination more effectively or carefully.
Put this way, sex immediately becomes detached from reproduction. A creature could borrow another’s genes at any stage in its life. Indeed, that is exactly what bacteria do. They simply hook up with each other like refuelling bombers, pass a few genes through the pipe, and go their separate ways. Reproduction they do later, by splitting in half.5
So sex equals genetic mixing. The disagreement comes when you try to understand why genetic mixing is a good idea. For the past century or so, traditional orthodoxy held that genetic mixing is good for evolution because it helps create variety, from which natural selection can choose. It does not change genes – even Weismann, who did not know about genes and referred vaguely to ‘ids’, realized that – but it throws together new combinations of genes. Sex is a sort of free trade in good genetic inventions, and thus greatly increases the chances that they will spread through a species and the species will evolve. ‘A source of individual variability furnishing material for the operation of natural selection,’ Weismann called sex.6 It speeds up evolution.
Graham Bell, a British biologist working in Montreal, has dubbed this traditional theory the ‘Vicar of Bray’ hypothesis after a fictional sixteenth-century cleric who was quick to adapt to the prevailing religious winds, switching between Protestant and Catholic rites as the ruling monarch changed. Like the flexible vicar, sexual animals are said to be adaptable and quick to change. The Vicar of Bray orthodoxy survived for almost a century; it still survives in biology textbooks. The precise moment when it was first questioned is hard to pin down for sure. There were doubts as far back as the 1920s. Only gradually did it dawn on modern biologists that the Weismann logic was profoundly flawed. It seems to treat evolution as some kind of imperative, as if evolving was what species exist to do – as if evolving were a goal imposed on existence.7
This is of course nonsense. Evolution is something that happens to organisms. It is a directionless process that sometimes makes an animal’s descendants more complicated, sometimes simpler, and sometimes changes them not at all. We are so steeped in notions of progress and self-improvement that we find it strangely hard to accept this. But nobody has told the coelacanth, a fish that lives off Madagascar and looks exactly like its ancestors of 300 million years ago, that it has broken some law by not evolving. The notion that evolution simply cannot go fast enough, and its corollary that a coelacanth is a failure because it did not become a human being, is easily refuted.