A recent study of 740 first-time pregnant mothers in the UK shows that a mother's diet at conception can affect the gender of the baby.
The researchers found 56% of women with the highest energy intake around the time of conception had boys, compared to just 45% among women with the lowest energy intake. The average calorie intake for women who had sons was 2,413 a day, compared to 2,283 calories a day for women who had girls. Women who had sons were also more likely to have eaten a higher quantity and wider range of nutrients, including potassium, calcium and vitamins C, E and B12. They were also more likely to have eaten breakfast cereals.
The evolutionary guess is that when times are lean, a daughter will more consistently yield descendants than a son. (thx, meg)