Scientists have long wondered why men exist. Sex between males and females is simply not nearly as efficient as asexual reproduction. But now a group out of the UK is reporting in the journal Nature that, after looking at several years of lab-controlled procreation of the Tribolium flour beetle, they've found that sexual selection—the process by which males compete for females—helps species become fitter and more resilient to disease. "Competition among males for reproduction provides a really important benefit, because it improves the genetic health of populations," the lead researcher at the University of East Anglia says in a press release. "Sexual selection achieves this by acting as a filter to remove harmful genetic mutations, helping populations to flourish."
Such a question can be tested on this particular beetle (a pest in many a flour bag) because aside from their genes, the males don't help raise offspring, reports NBC News. In the lab, the scientists controlled the beetle's environments such that the only difference between populations was the strength of sexual selection, which ranged from intense—with 90 males competing for 10 females—to no sexual selection at all, where females were limited to one monogamous partner and thus males didn't have to compete. Seven years (and 50 generations) later, the beetles that resulted from the strongest sexual selection were in the best health and were the least likely to go extinct when inbred, Reuters reports. (Speaking of evolution, a third of Americans don't believe it exists.)