You are what your mother eats: evidence for maternal preconception diet influencing foetal sex in humans.

This is an amazing finding, supposing that it's repeatable and statistically significant.... Scientists have found that, with a bit of tongue and cheek, "you are what your mother eats." Mothers who had a high calorie diet at conception were more likely to have male children than mothers who had a lower calorie diet. There doesn't seem to be a correlation between offspring sex and energy intake *during* pregnancy, however. They conclude that this finding supports the hypothesis that males, which are apparently especially "costly," would be expected to be born in environments with higher resource quantity and quality.

This also might make sense in context of territoriality. Wilson (year?) found that territoriality in male chimpanzees evolved as a mechanism to increase a group's food supply, which correlates with greater fecundity. More food -> more male offspring -> more territoriality -> more food. An interesting feedback loop model.

Mathews, F. (2008). You are what your mother eats: evidence for maternal preconception diet influencing foetal sex in humans. Proceedings of the Royal Society.

Facultative adjustment of sex ratios by mothers occurs in some animals, and has been linked to resource availability. In mammals, the search for consistent patterns is complicated by variations in mating systems, social hierarchies and litter sizes. Humans have low fecundity, high maternal investment and a potentially high differential between the numbers of offspring produced by sons and daughters: these conditions should favour the evolution of facultative sex ratio variation. Yet little is known of natural mechanisms of sex allocation in humans. Here, using data from 740 British women who were unaware of their foetus's gender, we show that foetal sex is associated with maternal diet at conception. Fifty six per cent of women in the highest third of preconceptional energy intake bore boys, compared with 45% in the lowest third. Intakes during pregnancy were not associated with sex, suggesting that the foetus does not manipulate maternal diet. Our results support hypotheses predicting investment in costly male offspring when resources are plentiful. Dietary changes may therefore explain the falling proportion of male births in industrialized countries. The results are relevant to the current debate about the artificial selection of offspring sex in fertility treatment and commercial ‘gender clinics’.