Everyone knows that having a boy or girl depends on whether the man's sperm has a Y chromosome. British scientists found in their research that the chance of sperm carrying a Y chromosome is determined by genes; that is to say, if a man has more sisters, his partner will have a greater chance of giving birth to a girl in the future. The findings were published in the latest issue of the British Journal of Evolutionary Biology.

Researchers from the University of Newcastle in the UK conducted a statistical survey on the history of 927 families in Europe and North America, with a total number of more than 550,000 people. The results showed that men with more brothers are more likely to have sons, and men with more sisters are more likely to have daughters. It can be seen that the ability to give birth to a boy or a girl is likely to be inherited from the father.

The researchers said that this conclusion can also help us solve a mystery: after World War I, on average, there were two more boys than girls for every 100 births. In a war, a father who is prone to giving birth to a boy has a smaller chance of having all his sons killed in battle, and is more likely to pass on the gene for giving birth to a boy; while a father who is prone to giving birth to a girl has fewer sons. Once his son is killed in battle, his ability to give birth to a daughter will be reduced. It cannot be inherited.