In a lab in Kansas, Aracely Lutes has created a new species of all-female lizard that reproduces by cloning itself. There wasn’t any genetic engineering involved; Lutes did it with just a single round of breeding.

This feat stands in stark contrast to the slow pace at which species usually arise. Here’s the typical story: different populations become separated in some way, whether by space, time, predators, sexual preferences, or an inability to understand one another. Differences gradually build up between them, until they can no longer produce fit and fertile offspring. Voila – where there was once one species, there are now two.

There are exceptions to this recurring tale of slow divergence. Different species sometimes mate to create hybrids, whose genomes are a mash-up of those of their parents. These individuals are often infertile (think mules) or weak. But in rare cases, they survive and prosper. For example, there is a hybrid bat from the Caribbean that combines the genomes of three separate species, one of which is now extinct. Other mammals including the red wolf and stump-tailed macaque might also be ...