Humans have evolved along with chimpanzees from a common ancestor over the last 6 million years, primarily in Africa. Several distinct species of humans evolved over this period. Modern humans emerged as a distinct population approximately 100,000 years ago.
For most of the last 6 million years, modern humans' ancestors lived alongside different hominid species that were closely related but that represented separate lineages. While it is never possible to identify with certainty a specific fossil specimen as a direct ancestor, it is possible to identify candidate species that clearly illustrate the transition between ancestral hominids and modern people. One likely ancestor of modern humans was Australopithecus afarensis, popularly known as "Lucy," who lived in Africa around 3 million years ago. A likely descendant of A. afarensis was the earliest recognized species of human, Homo habilis. H. habilis is believed to be an ancestor of the very successful and diverse Homo erectus, which thrived between approximately 1.5 million and 100,000 years ago.
The immediate predecessor of anatomically modern humans was likely to have been an ancestor of Neanderthals as well. For tens of thousands of years, the two species of humans lived in proximity to each other, with Neanderthals finally going extinct sometime prior to 25,000 years ago and leaving modern H. sapiens as the last species of human.