The ratio of a child’s index and ring fingers goes hand in hand with their family’s earnings, a major study suggests, owing to an unconscious evolutionary influence in utero.

Known as the Trivers–Willard hypothesis, it posits that women prenatally adjust their sex hormones to invest in either daughters or sons depending on maternal status, meaning poorer mothers will focus on feminising their fetuses while wealthier mothers will androgenise their children.

Previous research has found a positive correlation between high prenatal oestrogen and long index fingers, and high prenatal testosterone and long ring fingers; however, this is the first study to relate the phenomenon to wealth.

The team, led by evolutionary biologist Professor John Manning of Swansea University, examined the results of a large multi-ethnic, multinational online survey conducted in 2005 (the BBC Internet Study).