PEOPLE DOMESTICATED sheep and cattle, wheat and maize. Wasps domesticated viruses. And, just as domesticating other species helped human populations explode, so viral domestication assisted an explosion of wasps. That, at least, is the conclusion of Benjamin Guinet, an evolutionary biologist at Lyon University, in France. As he writes in the Proceedings of the Royal Society, he thinks an ancestor of a group of wasps called the Cynipoidea, which parasitise flies, corralled 18 viral genes into its genome in an act of domestication that happened 75m years ago, and that this helped the group flourish.