Economist.com | Human evolution

Don't put money on it and don't speculate about you or your friend's personal circumstances - the difference is miniscule. Also, don't believe the evolutionary biologist's armwaving.

"Single mothers are more likely to have daughters...

...According to Karen Norberg, of the National Bureau of Economic Research in Cambridge, Massachusetts, they can. In a review of data from almost 60,000 American families, Dr Norberg found that the chance of a woman giving birth to a boy rather than a girl is higher if she has been living with a man before the child was conceived. To be specific, for parents who were living together, boys were born 51.5% of the time, while when the parents were not cohabiting only 49.9% of births were male. This difference may seem small, but statistically it is highly significant, which suggests it is the result of evolution. Dr Norberg's paper was published this week in the Proceedings of the Royal Society."

Economist.com | Human evolution