Men and women select different ideal heights

The first research on men and women's different natural selection was done in Sweden. Short women and men of average height are more successful at reproduction, according to the study.

Gert Stulp, with colleagues from Groningen, Amsterdam and Cambridge University, studied the number of children born to brothers and sisters in a large-scale American database containing data on thousands of residents of Wisconsin born in 1937 or 1938.

"It turned out that by taking the height of just one person, we could predict whether his or her sibling would produce many or few children. Shorter individuals have a higher chance of becoming an uncle or aunt through their sister, while individuals of average height are more likely to have nephews and nieces via their brother."

The gender difference relating to body height was clearly visible.

However, some of the traits that are helpful to one sex but a hindrance to the other cannot be quite so easily switched off, he said. Short parents tend to produce short daughters and short sons. This benefits the reproductive success of the daughters, but not that of the sons.

It is still unclear why shorter women have more children.

"In general, the earlier a woman has her first child, the more children she will have. Women with a genetic tendency to have children at a young age also appear to have a genetic tendency to be short. But whatever the reason, evolutionary processes still seem to be alive and kicking in modern society," Stulp said.