Understanding the genetic architecture of phenotypic variation in natural populations is a fundamental goal of evolutionary genetics. Wild Soay sheep ( Ovis aries ) have an inherited polymorphism for horn morphology in both sexes, controlled by a single autosomal locus, Horns . The majority of males have large normal horns, but a small number have vestigial, deformed horns, known as scurs; females have either normal horns, scu...