Sex tricks: A cichlid Neolamprologus leleupi swimming in the southern shores of Africa's Lake Tanganyika.
Credit: Sigal Balshine
Research from the University of San Diego in the U.S. suggests that the sperm of highly promiscuous chimps is faster than more faithful gorillas. Chimps are also known to have larger testes than gorillas.
The findings may even have implications for sperm competition in humans, said Kolm, "we cannot rule out that similar mechanisms may have made humans the way they are today."
"This is one of the few [studies] that gives a good explanation for why sperm size and shape are so variable across the animal kingdom," commented Tim Birkhead, an evolutionary biologist from the University of Sheffield in the U.K., who was not involved with the study. "It shows that sperm design is shaped by natural selection to be effective in competitive situations."
Axel Mayer, an evolutionary biologist at the University of Konstanz, in Germany, agreed that the findings are both surprising and intriguing.
Of particular interest, he said, is that there appears to be no trade-off between different characteristics of sperm, such as size and speed: "It seems as if there is no selection against the evolution of 'super-sperm' that are big, numerous, long living and fast."
