Scientists have pinpointed a mutation that gives sheep big butts — big, hard, glorious butts. A callipyge sheep has a bottom made of muscle, not fat, due to a changed DNA letter. The Duke University geneticist who discovered the mutation, Randy Jirtle, said that some humans might share the trait: “They’d have relatively large rear ends, and absolutely no fat — like sprinters.” Just like Solid Gold, the first sheep with the trait, born two decades ago. His descendants are called “callipyge” from the Greek for “beautiful buttocks.” In another story about mutating bottoms, scientists at Cornell have discovered that disabling a gene can turn a tomato from round to pear-shaped. Without the gene, appropriately named OVATE, a fruit will grow more at the top, leading to a long neck and bulbous base. The missing gene is likely to be the reason that squash, eggplants, and, well, pears are shaped as they are. Most wild fruit are round, and it is suggested that humans bred elongated fruit for aesthetic reasons. You betcha.