Many features distinguish modern humans from the nonhuman apes. however, only two of these features define hominins. why? correct answer(s) drag appropriate answer(s) here the evolution of hominins involved several different changes that happened at different times. only two of these features evolved early enough to apply to all the hominins. proper taxonomic groups are always defined by the traits that are shared among members of the group but not found in closely related species. these two traits arose in the common ancestor of all hominins, but are not found in the nonhominin apes. proper taxonomic groups are always defined by the traits that all members of the group share.