The Boule gene, first discovered in humans in 2001, is linked to sperm production in humans and, the study says, is likely responsible for making sperm in every other sexual animal too (quick human genetics overview).

The sperm-production gene is apparently so critical to life that it hasn't changed since every animal's common evolutionary ancestor—likely just a blob of cells—arose some 600 million years ago, the researchers conclude.

The study team discovered that the gene is found in a wide range of sexually reproducing creatures, including flies and humans.

This means that Boule is found in all the evolutionary lineages that have branched off from that common ancestor, according to study leader Eugene Xu, a professor of obstetrics