While there is no way to determine a precise point at which the human species became distinct from their proto-simian ancestors, the earliest known human ancestor has been identified as Ardipithecus ramidus, or Ardi for short. Ardi, a female of her species, lived approximately 4.4 million years ago and was discovered in 1992 in the Afar Rift of Ethiopia by Gen Suwa.
The human family tree is far older than some people might believe, and Ardipithecus is just the most recently discovered ancestor. In 1974 Australopithecus afarensis was discovered, better known as Lucy. Lucy was also found in Ethiopia, in the same region as Ardi, leading some scientists to offer conjecture that Lucy may be a distant relative or descendant. Either way, if the evidence presented is reliable, then it's possible that all humans would be able to trace their lineage back to that same region in Ethiopia. Ardi may not have been the first of her kind, but she's the first that modern science has discovered, making her the oldest known human ancestor and the closest to the root of that family tree yet found. Anthropologists continue searching for the fossil remains of human ancestors, hoping that a full progression of human evolution can be firmly established.