Virgin births

1 WHAT ARE THEY AND WHICH SPECIES HAVE THEM?

Virgin births occur when an unfertilised egg divides and develops, eventually producing a full-blown adult. It is a type of asexual reproduction, also known as parthenogenesis, and it’s more common than you might think. Many invertebrates, including aphids, water fleas and some bees and scorpions, reproduce this way, but the phenomenon also occurs in some vertebrates. Komodo dragons, hammerhead sharks and turkeys are known to produce virgin births, too.

2 WHY WOULD YOU WANT TO REPRODUCE THIS WAY?

As some women might be inclined to tell you, there are many reasons to do away with males. In female-only species, every adult member can produce offspring, which means the population can grow faster than species with both sexes. Energy isn’t wasted looking for love or reproducing, freeing up resources to concentrate on other things, such as finding food or dodging predators. It can also be a way to bulk up the population when numbers are scarce.

3 DOES IT PRODUCE ONLY FEMALES?

Remarkably, no! It all comes down to sex chromosomes, which are the chunks of DNA that determine whether an embryo develops into a male or female. In some birds, reptiles and fish, females have both male and female sex chromosomes, which means they can theoretically produce both sons and daughters by parthenogenesis. In practice, boa constrictors seem to have only female virgin births, while pit vipers and turkeys seem to have only male ones. No one knows why.