Old dad plus young mother equals son

Ageing sugar daddies seeking a male heir for their fortune should get hitched pronto to that young popsie. British scientists have found that women who marry men much older than themselves have a greater chance of having a boy as their first child.

"The age difference between parents predicts the sex of the first child," said John Manning and colleagues at the School of Biological Sciences at the University of Liverpool.

A study of 301 families, with age differences ranging from husbands 15 years older to nine years younger than their wives, found that where the husband is younger, or up to five years older, a daughter is the likeliest first child. On average, men are two years older than their wives.

The researchers, whose work is reported in the science journal Nature, are stumped for the reason: "We don't know why, but that is the case in our data," said Professor Manning.

Certainly, some maternal effect does exist. Studies found that after war and periods of hardship, when the age difference in marriages tends to increase, more boys are born.