Why on earth do humans and innumerable other organisms go to the trouble of sexual reproduction. Think about all of the preening and flirting we exert in order to obtain it, not to mention the relationship factors and potential baby-making that may go along with it when it finally happens. To evolutionary biologists, it's an extremely inefficient design compared to asexual reproduction since we squander so many resources for sex, and they're only now figuring out why sex exists.
The BBC reports that researchers at Indiana University have found the strongest evidence to date for why sex evolved. While evolutionary biologists have long posited that sexual reproduction developed as a way to strengthen generational gene pools (known as the Red Queen Hypothesis), "there has been little hard evidence for it."
The Indiana researchers were able to demonstrate that genetic resiliency via sexual reproduction in round worms. By engineering an experimental group of round worms to sexually reproduce and another to reproduce asexually and testing their resistance to a bacterium, they found that the sexually reproductive round worms "fared well over the 20 generations, while all animals that cloned themselves died quickly." In addition, the bacterium was allowed to co-evolve alongside those generations of round worms, which further underscores the importance of sexual reproduction and that genetic reshuffling to combat the increasingly aggressive bacterium.
In 2004, a pair of evolutionary biologist also from Indiana University called into question the Red Queen Hypothesis since humans and other species have more sex than necessary to evade parasites. Doing it every day, as opposed to every now and then, doesn't jolt our genetic complexity. "If you are a parent who has survived to reproduce you probably have a good gene combination, so shuffling them about is not going to benefit you," one of the researchers told the BBC.
So even though this newest study offers more hard evidence that sex is good for us, it doesn't explain why, when reproduction and parasitic invasions are moot points, we're still driven to pursue it.