Sexual reproduction requires splitting a species into two sexes, only one of which will be able to produce offspring. There are some species of animals that do without males; the females simply trigger their eggs to develop into embryos without any need for sperm. All the offspring of an asexual animal can produce offspring of their own, instead of just half. So it would make sense that genes that gave rise to asexual reproduction would win out in the evolutionary race.
Clearly that hasn’t happened. The world is rife with sex. Animals do it. Plants do it. Even mushrooms do it. So evolutionary biologists have carried out a number of studies to get an answer to the question, “Why sex?”
In 2009, I wrote an essay for Science about this research. If I had been writing that essay today, I’d have focused some attention on an elegant experiment on the sex life of a humble worm. It gives a big boost to the long-floated idea that ...
