Researchers have been studying the evolution of bighorn sheep in response to trophy hunting at Ram Mountain, Canada, since 1973. This population was intensively hunted until 1996, when hunting regulations increased the minimum size of the horns of rams (males) that could be shot, after which the number of rams killed by hunters each year decreased dramatically. More recently, researchers observed that, in response to the selective pressure imposed by the hunters, the average horn length of rams decreased by almost 30% between 1973 and 1996. After hunting pressure decreased in 1996, horn length rebounded, increasing by about 13%. Which evolutionary mechanism likely underlies born length in the bighorn sheep population? O genetic drift natural selection speciation inbreeding
