A smallpox-like virus that hopped from snakes to wild gerbils seems to have taken a snippet of the snake's DNA with it. Pieces of DNA called retroposons copy themselves, and the copies insert into new locations. Researchers report that a retroposon found in the rodent tateropox virus most likely jumped from the carpet viper, an extremely poisonous African snake that lives in the same territory as the Kemp's gerbil, from which the virus was isolated. See this week's Proceedings of the National Academy of Sciences USA.