Worms conceived via sexual reproduction are apparently endowed with a bolstered immune system that helps the creatures fight off deadly parasites.
In contrast, worms forced to reproduce asexually (self-fertilization) often succumb to bacterial infections and die.
According to researchers at the University of Indiana, the amorous worms are living proof sex evolved because it allows various organisms to reshuffle their genes and stay ahead of parasites and other harmful bacteria.
"We found [in the lab] self-fertilizing populations of C. elegans were rapidly driven extinct by the co-evolving parasites, a result consistent with the Red Queen Hypothesis," explained lead scientist Levi Morran, an evolutionary biologist at the University of Indiana in the US.
"Sex helped populations adapt to their co-evolving parasites, allowing parents to produce offspring that were resistant to infection and ultimately avoid extinction."
Curtis M. Lively, co-author of the above-mentioned study, said he believes the amorous worms may go a long way towards explaining the widespread existence of sex in the context of evolution.
"The Red Queen Hypothesis predicts sex should allow hosts to evade infection from their parasites, whereas self-fertilization may increase the risk of infection.
"[And in fact], sex [did] help [the] populations adapt to their coevolving parasites, allowing parents to produce offspring that were resistant to infection and ultimately avoid extinction. Coevolution with the pathogen not only favored sex over self-fertilization, but also allowed sex to be maintained throughout the experiment," he added.
It should be noted that the notion of sex between two organisms has long trouble evolutionary biologists, as it often involves the production of males - which don’t directly produce any offspring.
Theoretically, self-fertilization may seem a far more efficient means of reproduction, but as the above-mentioned study illustrates, sexual cross-fertilization helps keep a species one evolutionary step ahead of parasites and extinction.