- Not Applicable ()
Species belonging to Darwinulidae, a family of ostracods – tiny crustaceans around 1 mm in length – reproduce asexually, i.e. completely without using sex. Fossil records show that this has been happening since at least 100 million years ago. This means that every individual alive today is an almost exact clone of a previous individual from the Cretaceous Period. The only genetic differences are due to genetic mutations in the intervening period and their evolution has therefore been extremely slow.