Dozens of hypotheses have been put forward to explain this paradox. These either deal with the fact that asexuals have difficulty purging their genome from bad genes (this normally happens during a process of cell division called meiosis which asexuals do not possess) or with the fact that asexuals cannot form beneficial gene combinations as fast or as easily as sexuals can. In the first hypothesis, asexual clades will be short lived. In the second, asexuals are much less efficient at adapting to changing environmental conditions.

And this brings us to our second paradox: some animal groups have in fact managed to survive for millions of years, and this in spite of the absence of sexual reproduction. As these groups seemingly refuse to obey our evolutionary laws, some scientists refer to them as ‘ancient asexual scandals’. Only few animal groups claim this status: bdelloid rotifers, some groups of oribatiid mites, some groups of stick insects and darwinulid ostracods (Darwinulidae). There are about 2000 species of living, non-marine ostracods and only about 30 species belong to this family. Only the species Darwinula stevensoni is very common world-wide and can occur in a variety of habitats, most other darwinulid species are rare. And yes, the genus Darwinula is indeed named after Charles Darwin!