Molar enamel is thicker among frugivorous extant Old World monkeys and apes than among their folivorous close relatives. Furthermore, species that have the thickest molar enamel reportedly eat fruits, seeds, and nuts that are so hard that they cannot be broken by their sympatric thinner-enameled relatives. Species with relatively thick enamel show no tendency toward a terrestrial feeding pattern. Members of the Ramapithecinae, the stock which probably gave rise to Pliocene-Recent hominids, had very thick molar enamel. This suggests that they ate hard seeds, nuts, and fruits previously available only to arboreal rodents and forest-floor pigs. There is no reason to believe that these anatomical features had to evolve in non-rain-forest environments, as others have argued.