Virgin birth, known to scientists as parthenogenesis, appears to be rather common in the animal kingdom. Many insects and other invertebrates are capable of switching between sexual and clonal reproduction. Among the vertebrates, virgin births have been documented in at least 80 taxonomic groups, including fish, amphibians, and reptiles. But humans and our fellow mammals provide a notable exception. So far as anyone can say—and there are a few gaps in the data, notably the platypus—no mammalian species is capable of giving birth without a father.