For many of us, a world comprised entirely of men would be a dystopian nightmare or a dream come true. But for the Corbicula clams, it’s just life.

Several species of these freshwater clams are entirely male. Technically, they’re hermaphrodites because each individual produces both sperm and eggs, but the eggs don’t contribute to the next generation. When they are fertilised by sperm, their own DNA gets ejected and the resulting embryo only contains genes from the sperm. In this way, the clams produce clone “sons” that are genetically identical to them.

Like all species that have abandoned sex, the existence of these clams is a mystery. In the short-term, there are many advantages to ditching sex. An asexual animal can