How Long Have Humans Been on Earth?
Modern humans have existed for roughly 200,000 years. The species to which humans belong, Homo sapiens, is the only species of human alive today. However, all species in the genus Homo are technically humans. This includes Homo habilis, the oldest undisputed species in the genus at 2.2 million years old.
Evidence suggests that both Homo sapiens and Homo habilis originated in Africa. The evolution of the genus coincided with a change in climate that resulted in cooler worldwide temperatures. Modern humans differ from older species of human by lighter skeletal structures, larger brains, weaker jaws, reduced brow ridges, flatter faces and high, nearly vertically oriented foreheads. All species within the Homo genus are primates that walk on two legs and possess very large cranial volumes relative to body size.