Perhaps not surprisingly, the multiple species of howler monkeys studied have one copy of RNase1 that is similar to the version found in non-folivorous primates and at least one copy that has undergon...Perhaps not surprisingly, the multiple species of howler monkeys studied have one copy of RNase1 that is similar to the version found in non-folivorous primates and at least one copy that has undergone rapid evolution and neofunctionalization.