Some 18 million years ago, an ancestor of mouse-eared bats ‘stole’ genetic material from an ancient virus related to Ebola. The swiped genetic sequence — a gene called VP35 — has remained largely intact in the bats despite the passage of time, a new study finds. The research also sheds light on the gene’s possible function in bats, suggesting that it may play a role in regulating the immune system’s response to threats.