We know that many reptiles like crocodiles can choose the sex of their offspring by controlling the temperature their eggs are incubated at. And now it has been revealed that human mothers might also have some influence on whether they have a girl or a boy, not by controlling temperature but by whether or not they enjoy a bowl of cornflakes for breakfast.
That's what researchers from the University of Exeter here in the UK found when they carried out a survey of over seven hundred expectant mums who didn't know whether they were carrying a boy or a girl. By asking them about what they ate around the time of conception, Fiona Mathews discovered that women who ate at least one bowl of cereal a day were more likely to have boys than women who frequently skipped breakfast.
59% of women eating a good breakfast had boys compared to 43% of those who didn't eat cereal every day.
And this sort of thing has been noticed before. During wartime and times of stress, like the 9-11 bombings, there have been increases in the number of girls born compared to the number of boys.
In fact there is a global down turn in the number of boys being born, although it's only about a tenth of a one percent since the 1970s, it still adds up.
We don't know exactly what it causing these differences but it could be something to do with the body's way of dealing with tough times. The theory is that when there is plenty of food around, the best choice is to have boys since big strapping healthy males are best at producing their own offspring.
But when resources are limited, and mothers are going hungry, it is better to have females, since weedy males aren't much use. It is also possible that when a population has been affected by a disaster, like war, the quickest way to rebuild numbers is to have lots of females since ultimately they limit the number of children in the next generation.