Researchers at the University of Chicago report in the January 20 issue of Nature that genes pertaining to male reproduction--those involved in sperm production, transfer and morphologyevolve much faster than their non-sexual counterparts.
Chung-I Wu, Ph.D., professor and chairman of the department of ecology & evolution at the University of Chicago, together with Gerald Wyckoff, a graduate student and Wen Wang, Ph.D., a postdoctoral fellow, argue that sexual pressure underlies this phenomenon.
"The pressure on a male to find a mate and fertilize her eggs is constant, and the stakes of success or failure are enormous," said Wu. "Presumably, genes governing male reproduction are under continuous pressure to evolve ways to outcompete other males when it comes to fathering offspring."
In previous research, Wu and colleagues found that genes related to sperm production in fruit flies, mice and rats evolved faster than other genes. In the January 20 Nature paper, Wu and his co-authors describe the accelerated evolution of male reproductive genes in man and other primates.
"That the rapid evolution is positively, not negatively driven is important," said Wu. "Positive selection indicates that the DNA changes are doing something better for the organism as opposed to something worse or nothing at all, which would be the case if the changes were just random mutations."
The title of the paper, "Rapid Evolution of Male Reproductive Genes in the Descent of Man," makes reference to Charles Darwin's book Descent of Man. "I chose this title because Darwin talks about how the drive to mate is perhaps the strongest driving force behind evolution," Wu explained. As Darwin wrote, the advantages of "conquering other males in battle or courtship, and thus leaving a numerous progeny are in the long run greater than those derived from rather more perfect adaptation to the conditions of life."