Members of the genus Homo include living humans (Homo sapiens) and a number of extinct nonaustralopith species that lived as early as 2.8 million years ago and as late as around 50,000 years ago. The species in this genus are distinguished from australopiths by more obligate bipedality, relatively larger brain size, and tool making.

The nearly complete skeleton of a young Homo erectus, KNM-WT 15000, known as the “Nariokotome boy” and also the “Turkana boy” was discovered by Kamoya Kimeu on the west side of Lake Turkana, Kenya (across the water from Koobi Fora) in the early 1980s.
Image credit  Alan Walker.

While the earliest members of the genus (Homo rudolfensis and Homo habilis) did not have noticeably larger brains, they had developed a stone tool technology known as the Oldowan. It was also a member of this genus, Homo erectus, that left Africa for the first time and reached Eurasia around 1.8 million years ago. Some researchers assign the earliest members of this species from Africa to a different species known as Homo ergaster. However, most researchers prefer to include all of the African and Eurasian forms into a single species, Homo erectus. There is also a consensus that Homo erectus gave rise to modern humans via intermediate populations up to its emergence around 300,000 years ago.

Modern humans living today are distinguished from all of their ancestors by culture (e.g., symbolic behavior), language, and a much more sophisticated technology. Extinct species such as Homo neanderthalensis were behaviorally and anatomically more human-like than their predecessors, and recent advances in genetic studies show that modern Eurasians retain a small percentage of Neandertal genes. The fact that modern humans were able to occupy every habitable area of the world in the last 40,000 years resulted in the extensive cultural and behavioral variation that we see today.

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