Women Not as Faithful as Gorillas
http://www.technewsworld.com/story/science/gorilla-chimp-testicle-sperm-37952.html

Male chimpanzees have evolved huge testicles and sperm counts for their body size. Among gorillas, females mate only with a dominant male, and accordingly, gorillas' testicles are tiny. Human testicles are somewhere in between in size.

University of Chicago researchers have determined the size of men's testicles has evolved based on the infidelity of women.

Researchers led by Bruce Lahn found in promiscuous species such as chimpanzees, competition for mating privileges does not end with sex, as once inside the female, sperm must battle those of a rival to be the one that fertilizes the egg.

To maximize their chances of fatherhood, male chimpanzees have evolved huge testicles and sperm counts for their body size.

Among gorillas, however, females mate only with a dominant male, and accordingly, gorillas' testicles are tiny.

Human testicles are somewhere in between in size, suggesting while women are not as promiscuous as female chimps, neither are they as faithful as the female gorilla.

The study was published Monday in the journal Nature Genetics.