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MBL Senior Scientist Irina Arkhipova provides expert commentary in this article.

Biologists have understood the broad contours of the rules of inheritance for more than a century: that genes are passed down from parent to child within species. But in more recent years, they have also become aware of genes that go rogue and hop laterally between species — be they frog genes in Madagascar , or antifreeze genes found in cold-water fish like herring that . The mechanism facilitating this gene transfer has been unclear, though viruses were suspected to play a role.

In new research , researchers have identified a unique class of genetic elements as the agents responsible for shuttling certain genes between multiple species of simple invertebrates called roundworms. A jump from one worm to another may not sound like much, but the worms in question diverged many millions of years ago, making them as different at the molecular level as fish and humans. The genetic elements, called Mavericks, have been detected in a wide range of animals, both invertebrates and vertebrates, and they display many features found in the genomes of viruses. Given those properties, researchers suspect that Mavericks — and similar elements, including some not yet discovered — may have mediated horizontal gene transfers throughout the history of life.