Study: Did Parasites play a role in the evolution of sex?

Posted by admin on December 14 2009 Add Comments

It’s almost hard to believe, but there is a new theory that suggests that sex between humans may have evolved as a defense against parasites. It sounds a bit far-fetched, but below is the hypothesis that scientists are currently discussing and recently published in the July 09 issue of American Naturalist.

The theory presented in the study:

One hypothesis is that parasites keep asexual organisms from getting too plentiful. When an asexual creature reproduces, it makes clones—exact genetic copies of itself. Since each clone has the same genes, each has the same genetic vulnerabilities to parasites. If a parasite emerges that can exploit those vulnerabilities, it can wipe out the whole population. On the other hand, sexual offspring are genetically unique, often with different parasite vulnerabilities. So a parasite that can destroy some can’t necessarily destroy all. That, in theory, should help sexual populations maintain stability, while asexual populations face extinction at the hands of parasites.

Enter Potamopyrgus antipodarum, a snail common in fresh water lakes in New Zealand. What makes these snails interesting is that there are sexual and asexual versions. They provide scientists with an opportunity to compare the two versions side-by-side in nature.

“The rise and fall of these female-only lineages was surprisingly fast and consistent with the prediction of the parasite hypothesis for sex,” Jokela said. “These results suggest that sexual reproduction provides an evolutionary advantage in parasite rich environments.”

Read the full text for more information

Are you confused by this theory? Yeah, we are too. But if this theory does hold up, then it is just one more example as to how some parasites are beneficial to the human body. Of course, we all know that if you have parasites in your intestines, you want to get them out as soon as you possibly can.