Sex selection and the shortage of women: is science to blame? - Richard Dawkins - RD.ne... - 0 views
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what if we are dealing with a human society in which cultural traditions over-ride the genetic imperatives (yet another example, this time not necessarily a benign one, of ‘rebelling against the selfish genes’). What if the religion of a country fosters a deep-rooted undervaluing of women? What if there is an ancient culture of despising women, whether for religious or otherwise traditional or economic reasons? In past centuries such cultures might have fostered selective infanticide of newborn girls. But now, what if scientific culture makes it possible to know the sex of a fetus, say by amniocentesis or ultrasound scanning? There is then an obvious temptation selectively to abort female embryos, which could have far-reaching and probably pernicious social consequences. I'll refrain from gloating over the possibility of Taliban-inspired woman-hating societies going extinct for lack of women.
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The Guardian has a report today on ‘sex selection of babies’, which is described as a ‘scourge’ of the developing world.
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Unnatural Selection by Mara Hvistendahl charts how the trend towards choosing boys over girls, largely through sex-selective abortions, is rapidly spreading across the developing world. While the natural sex ratio at birth is 105 boys born for every 100 girls, in India the figure has risen to 112 boys and in China 121. The Chinese city of Lianyungang recorded an astonishing 163 boys per 100 girls in 2007. The bias towards boys has been estimated to have caused the "disappearance" of 160 million women and girls in Asia alone over the past few decades. The pattern has now spilled over to Azerbaijan, Georgia and Armenia, the Balkans and Albania, where the sex ratio is 115/100. The unnatural skewing towards male populations has become so pronounced in recent decades that Hvistendahl, a writer for Science magazine, says it has given rise to a new "Generation XY". She raises the possibility that with so many surplus men – up to a fifth of men will be single in northwestern India by 2020 – large parts of the world could become like America's wild west, with excess testosterone leading to raised levels of crime and violence.
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In nature, the balance of males and females is maintained by natural selection acting on parents. As Sir Ronald Fisher brilliantly pointed out in 1930, a surplus of one sex will be redressed by selection in favour of rearing the other sex, up to the point where it is no longer the minority. It isn't quite as simple as that. You have to take into account the relative economic costs of rearing one sex rather than the other. If, say, it costs twice as much to rear a son to maturity as a daughter (e.g. because males are bigger than females), the true choice facing a parent is not "Shall I rear a son or a daughter?" but "Shall I rear a son or two daughters?" So, Fisher concluded, what is equlibrated by natural selection is not the total numbers of sons and daughters born in the population, but the total parental expenditure on sons versus daughters. In practice, this usually amounts to an approximately equal ratio of males to females in the population at the end of the period of parental expenditure. Note that the word 'decision' doesn't mean conscious decision: we employ the usual 'selfish gene' metaphorical reasoning, in which natural selection favours genes that produce behaviour 'as if' decisions are being made.