In 2012, on a whim, Vincent Lynch decided to search the genome of the African elephant to see if it had extra anti-cancer genes. Cancers happen when cells build up mutations in their DNA that allow them to grow and divide uncontrollably. Bigger animals, whose bodies comprise more cells, should therefore have a higher risk of cancer. This is true within species: On average, taller humans are more likely to develop tumors than shorter ones, and bigger dogs have a higher cancer risk than smaller ones.