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Revision as of 08:10, 9 July 2007
Humanity was believe to have shared a last common ancestor with chimpanzees approximately 5 million years ago at the dawning of the Pliocene epoch.
Our bipedalism is what evolutionary biologists believe has led to our larger brains and ability to use tools. Walking on two legs frees up both hands to use tools. The ability to use tools resulted in an evolutionary pressure to become more intelligent which has resulted in an increase in brain volume. It is believed that our ancestors developed bipedalism about 4 million years ago. Lucy, an Australpithicus is fully bipedal at 3.7 million years ago, indicating that the trait evolved sometime before that. Her brain size is only slightly larger than a modern chimpanzee, indicating more time was needed for the Southern Ape to develop into modern man.
The Genus Homo
By the end of the Pliocene, anthropologists and evolutionary biologists recognize a species that is classified in our genus, Homo. Homo habilus or handy man used stone tools and it is believed that they had a primitive form of language. Their brain size was half again that of a chimpanzee but still only slightly more than a third of a modern human. Some scientists consider Homo habilus to be a late variety of Australopithecus but Homo habilus was an indication that evolution was getting closer to modern man
By the beginning of the Pleistocene, Homo ergaster, what many consider to be the first true human formed. He had a brain capacity almost two thirds of modern man, used more advanced tools, and may have had the ability to control fire. Homo ergaster or Homo erectus may have been the first humans to radiate out of Africa about 1.8 million years ago. Around 800,000 years ago humans took on a much more modern appearence. Their brain capacity was around 90 per cent that of modern man, with broad overlap. They used spears and handaxes, wore clothes, cooked their own food, and may have buried their dead. Homo heidlebergensis which is sometimes classified as late Homo erectus or early Homo sapiens lived during this time between 800,000 and 500,000 years ago. It is believed that he is the last common ancestor between modern man and Neanderthals.