Lynch’s team — working with African and Asian elephant skin cells from the San Diego Zoo in California — found similar results. They also discovered more than a dozen TP53 copies in two extinct species of mammoth, but just one copy in elephants’ close living relatives, manatees and hyraxes (a small, furry mammal). Lynch thinks that the extra copies evolved as the lineage that led to elephants expanded in size. But he thinks that other biological mechanisms are involved too.