Reading8_WhySex - Why sex is worth losing your head for 40...

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40 | NewScientist | 13 June 2009 PIC CREDIT HERE Why sex is worth losing your head for For nearly a century sex has been biology ’s biggest mystery, says Nick Lane . Now it’s becoming clear not only why it evolved, but when
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S EX is the ultimate absurdity. Forget the hormonal rushes, the sweat and contorted posturing. Forget about the heartache, the flowers, the bad poems and the costly divorce, just think about the biology. It’s nuts. Cloning makes far more sense. A clone, after all, just quietly gets on with copying itself. And since every clone can produce more clones, cloning produces far more offspring. There is no need for males – a waste of space, as hard-line feminists and evolutionists agree. What’s more, each clone has a combination of genes that has already been found fit for purpose. Sex, by contrast, randomly mixes genes into new and untested amalgams. And the horrors of sex don’t end there. There is the problem of finding a mate, and fighting off rivals. Not to mention the risk of picking up horrible diseases like AIDS and all sorts of selfish replicators that exploit sex to spread themselves through the genome. All this made sex the “queen of evolutionary problems” in the 20th century, taxing some of the finest minds in biology. The issue isn’t just explaining why almost all plants and animals engage in sex. It is also explaining why the life forms that ruled the planet for billions of years and remain by far the most abundant – the bacteria – manage fine without it. That suggests that the ubiquity of sex among complex organisms has something to do with their ancient evolutionary history, not just the recent more past. Could there be some deep connection between the evolution of sex and the evolution of complex cells more than a billion years ago? As you were probably taught at school, the seemingly obvious answer to the question, why bother with sex, is that sex generates variation, the raw material for natural selection. As environments change, sexual species can therefore evolve and adapt faster. In reality, though, most individuals live in an environment very similar to that of preceding generations. And if some start reproducing by cloning, the clones – being equally well adapted to the environment – should rapidly drive the sexuals to extinction by dint of producing far more offspring competing for the same resources. Sure, sex should be an advantage in the long term, over thousands and millions of years, but evolution doesn’t work like that. It doesn’t plan ahead. And the environment rarely changes enough in the short term, over years and decades, to favour sex. Not so fast, argued the great evolutionary biologist Bill Hamilton. The environment that really matters is on the inside, he said. Parasites lynch us from within, and evolve so
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Reading8_WhySex - Why sex is worth losing your head for 40...

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