IT’S a puzzler almost as old as the one about the chicken and the egg.
But now Sheffield researchers have cracked the question – why do some animals, such as seahorses, leave taking care of young to the males rather than the females?
University of Sheffield experts found the role reversal was caused by an imbalance in the numbers of males relative to females.
Dr András Liker, Marie Curie Research Fellow from the university’s department of animal and plant sciences, said: “Sex-role reversal has been a formidable puzzle for evolutionary biologists ever since Darwin.
“Our study is the first supporting the idea that sex ratio plays an important part in the evolution of role reversal.”
The researchers studied birds where sex roles were reversed and found there was a higher ratio of males to females, compared with the usual situation where females care for offspring.
It is thought that, because the male birds found it harder to find a mate, it benefited them to look after the young.
Their findings were reached with the universities of Bath and Veszprém in Hungary, and have been published in a journal.