This was followed by Homo erectus and Homo ergaster, who had double the brain size and may have been the first to control fire and use more complex tools. Coordinating fine hand movements needed for tool use may have led to increasing brain capacity. Homo habilis, which used stone tools and had a brain about the size of a chimpanzee, was an early hominin in this period.

The fourth stage features the genus Homo, which existed between 1.8 and 2.5 million years ago. The second stage, around four million years ago, was marked by the appearance of Australopithecus, and the third, around 2.7 million years ago, featured Paranthropus. These humans may have been bipedal, meaning they walked upright on two legs. The first, between four and seven million years ago, consisted of the proto hominins Sahelanthropus, Orrorin and Ardipithecus. There were four main stages of human evolution. Generally, it is believed that hominids first evolved in Africa and then migrated to other areas. A comparison of the skeletal structures of gibbons, humans, chimpanzees, gorillas and orangutans.

Skeletal structure of humans and other primates. Humans and chimps then separated about 7.5 million years ago. Various divergences among apes, gibbons, orangutans occurred during this period, with Homini (including early humans and chimpanzees) separating from Gorillini (gorillas) about 8 millions years ago. Primate development diverged from other mammals about 85 million years ago. bipedalĭescribing an animal that uses only two legs for walking. hominidsĪ primate of the family Hominidae that includes humans and their fossil ancestors. The theory that hominins were forced out of the trees they lived in and onto the expanding savannah as they did so, they began walking upright on two feet. The theory that there was a near-extinction event for early humans about 70,000 years ago. The theory that improving cognitive capabilities would allow hominins to influence local groups and control resources. sexual dimorphismĭifferences in size or appearance between the sexes of an animal species. encephalizationĪn evolutionary increase in the complexity and/or size of the brain. The theory that species must constantly evolve in order to compete with co-evolving animals around them. The theory that extinctions due to environmental conditions hurt specialist species more than generalist ones, leading to greater evolution among specialists. The theory that the savannah was expanding due to increasingly arid conditions, which then drove hominin adaptation.

Human evolution timeline