Fossil by fossil, scientists over the last 40 years have suspected that their models for the more immediate human family tree — the single trunk, straight as a Ponderosa pine, up from Homo habilis to Homo erectus to Homo sapiens — were oversimplified. The day for that serious revision may be at hand.
The discovery of three new fossil specimens, announced Wednesday, is the most compelling evidence yet for multiple lines of evolution in our own genus, Homo, scientists said. The fossils showed that there were at least two contemporary Homo species, in addition to Homo erectus, living in East Africa as early as two million years ago.
Uncovered from sandstone at Koobi Fora, badlands near Lake Turkana in Kenya, the specimens included a well-preserved skull of a late juvenile with a relatively large braincase and a long, flat face, which has been designated KNM-ER 62000 (62000 for short). It bears a striking resemblance to the enigmatic cranium known as 1470, the center of debate over multiple lineages since its discovery in the same area in 1972.
If the 62000 skull showed that 1470 was not a single odd individual, the other two specimens seemed to provide a vital piece of evidence that had been missing. The specimen 1470 had no mandible, or lower jaw. The new finds included an almost complete lower jaw (60000) — considered to be the most complete mandible of an early Homo yet found — and a part of another lower jaw (62000).
The fossils were collected between 2007 and 2009 by a team led by Meave and Louise Leakey, the mother-and-daughter paleoanthropologists of the Koobi Fora Research Project and members of the famous African fossil-hunting family. Dr. Meave Leakey is the wife of Richard Leakey, a son of Louis and Mary Leakey, who produced the early evidence supporting Africa’s central place in early human origins. Mr. Leakey divides his time between Stony Brook University on Long Island, where he is a professor of anthropology, and the Turkana Basin Institute in Kenya.
After looking “long and hard” for fossils to confirm the intriguing features of 1470’s face and show what its teeth and lower jaw were like, Dr. Meave Leakey said this week, “At last we have some answers.”