Sex Ratio Bias in India

Sometimes boys are worth more, sometimes girls are worth more. In an evolutionary sense. Or, more correctly, the value of a certain sex … as an offspring … can be measured in fitness terms. Fisher noted this and hypothesized this was the explanation for the 50-50 sex ratio we usually see. As one sex becomes more rare, it becomes more valuable, and thus parents (mothers, perhaps, usually) bias towards that sex. Then the disparity goes away and thus the differential value goes away.Of course, the truth is that we don’t actually see the 50-50 sex ratio all the time … many species of organisms have a highly biased sex ratio. Many have a highly biased ratio in adults, much more biased than in offspring. This sort of thing varies quite a bit. But what about humans, and what about the report that Indian girl-boy ratios at ‘all-time low’ … Continue reading

Why is There no Birth Control Pill for Men?

i-fc0baa42c324cefa8495fdb0044234b2-dice.jpg Why is there no Birth Control Pill for men?This latest “Ask a ScienceBlogger” question will certainly engender a wide range of responses from the Scienceblogs.com team. Answers may address physiology, endocrinology, pharmacology, economics, and other areas of scientific thinking and practice. The answer I’d like to propose can be summed up in two closely linked words pilfered from the question itself: Continue reading

Macaque Mothers Favor Their Sons

Blogging on Peer-Reviewed Research

The Trivers Willard Hypothesis predicts that under certain conditions, individuals will bias their investment in offspring differently depending on the sex of the offspring. It is believed that this can be as extreme as infanticide or as subtle as providing different amounts of breast milk.

A new study by Katherine HInde finds that macaques may do this. However, I think this may be counterintuitive.

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Whitey Bulger and the Evolution of Sex Bias in Investment in Offspring

imageMost of you won’t know who Whitey Bulger is. He is actually on the FBI’s ten most wanted list. He may have been spotted in Italy last Spring, and the FBI is just now asking for assistance from anyone who knows where he might be. (That’s not gonna work.)Whitey was top dog in Boston’s Winter Hill gang. His brother was a Senator for the Commwealth of Massachusetts, and served as Senate President for several years.It is said that Whitey was an FBI informant, and that his handler, FBI Special Agent John Connolly, tipped Whitey off that he was about to be indicted on racketeering charges. No problem. Whitey had left stashes of cash in safe deposit boxes all around the world, in preparation for the day he had to go on the lam. So he took off in 1995, and the FBI has not been able to catch up. Special Agent Connolly is pulling a ten year vacation in the stir.I remember when Whitey disappeared, and ever since then, I’ve used him almost annually in lecture material describing the Trivers-Willard hypothesis. It goes like this: Continue reading