Scientists have discovered a human gene with a remarkable double life: it appears to play an important role in brain cells while still retaining the ability to jump around the genome. Called BC200, the gene evolved millions of years ago from a mobile piece of DNA known as a transposon, but unlike most genes that arose this way, it never lost its mobility. Researchers even found BC200 embedded inside a human poxvirus, suggesting it may have jumped from infected skin cells into the virus.