Today, only one human species exist, Homo sapiens. But over the course of human prehistory as many as 15 varieties of early human walked the earth. Though the number of species and their relationship to one another are not settled, it seems clear that the earliest hominids-a term that describes all humans who ever lived-took their first step in Africa.
They were primates descended from a group of apes that also gave rise to gorillas and chimpanzees. Around 4million years ago, something in the environment led the first hominids to leave the trees and walk upright, marking the official transition to human status. These early hominids are often grouped under the name Australopiths and include Ardipithecus, Australopithecus and Paranthropus. About 3.5 to 5 feet tall, they had apelike faces, with sloping foreheads and prominent jaws, but their canine teeth were small compared with an ape’s and their hands featured long, flexible thumbs. The most famous fossil member of these early humans is the Australopithecus afarensis known as fondly as “Lucy”, whose partial skeleton was discovered in 1974. Her species, which lived in eastern Africa between 3 and 4 million years ago, is one leading candidate for being a direct candidate of Homo sapiens.
Australopithecus died out about 1.2 million years ago. By that time, their descendants, new kind of hominids, were already roaming Africa: The genus Homo, which came into existence roughly 2.3-2.5million years ago, was marked by a distinct increase in brain size. By 1.9 million years ago, these humans had tall skeleton like those today’s Homo sapiens, although their skulls still featured sloping foreheads, prominent brows, and heavy jaws.
These late species of Homo also demonstrated another similarity to modern humans:Starting around 1.8 million years ago, the first great wave of human migration occurred when adventurous members of Homo erectus trekked out if Africa and into Europe and Asia. However these hominids eventually died out and were not the direct ancestors of today’s humans. That honour falls to the first members of our own genus, Homo sapiens, who appeared in East Africa about 200,000 years ago.