Å·±¦ÓéÀÖ

“The key question to ask in distinguishing the earliest human ancestor from the apes is what are the characters that set them apart from the apes? Various characters have been proposed, such as enlarged brains, reduced sexual dimorphism, upright bipedal walking, enamel thickness and reduced premolar honing. The first two can be discounted immediately, for increased brain size occurred late in human evolution, after 2 million years ago, and sexual dimorphism remained high for about as long. Thick enamel on the teeth is common to most hominines, but as we have seen, it was also widespread in fossil apes. The same is true of reduced honing, which is present in several lineages of fossil apes. The only character we are left with to distinguish human ancestors is bipedalism, but we have to ask, is this enough? Could not some fossil apes with no connection with human ancestry have experimented with bipedal walking?”