Sexual reproduction that involves two partners is far less efficient than self-fertilization — at least, from the perspective of evolution. So why did creatures like humans ever start having sex with each other? According to a new study, we did it to fight parasites. We spoke with the researchers to discover what this says about sex.
Biologists at the University of Indiana found some of the most convincing evidence yet that the evolutionary driver of sexual reproduction is a need to avoid death by parasites. The basic logic is that, if an organism reproduces asexually, then the genetic variation of its species as a whole will slowly grind to a halt, and it becomes increasingly likely that a parasite that can kill one member of the species can wreak havoc on the entire population. (For proof of that, just look at bananas.)