New Fossils Indicate Early Branching of Human Family Tree
 
By   JOHN NOBLE WILFORD
              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 Africas 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 1470s face and show what its teeth and lower jaw were like,  Dr. Meave Leakey said this week, At last we have some answers.         
  The real crux of matter, said Susan C. Antón of New York University, a  member of the team, is how the discovery shapes the interpretation of  1470s place in the early world of Homo. These fossils are anatomically  like 1470, and we now have some teeth, she said. We are more certain  that 1470 was not a one-off, and not everything 1470 is big.        
  In their first formal report, 
Dr. Leakey and her colleagues wrote in the journal Nature, These three specimens will greatly aid the reassessment of the systematics and early radiation of the genus Homo.        
  They, however, chose not to assign the fossils to any existing or new  species until more analysis is conducted on contemporary hominids. The  1470 specimen was two million years old; the new face and fragmentary  jaw are 1.9 million to 1.95 million years old; the better-preserved  lower jaw is younger still, at 1.83 million years old.        
  Fred Spoor, a member of the discovery team who directed the laboratory  analysis, said in a news teleconference that the research showed clearly  that human evolution is not this straight line it was once thought to  be. Instead, East Africa, he said, was quite a crowded place, with  multiple species with presumably different diets.        
  Dr. Spoor is a paleoanthropologist at University College London and the  Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.  The lab work was supported by the institute. The fieldwork was financed  by the National Geographic Society, and the dating of the fossils,  mainly by Craig S. Feibel of Rutgers University, was supported by the  Leakey Foundation.        
  Although a few specialists in human origins questioned whether the still  sparse evidence was sufficient to back the new conclusions, Ian  Tattersall of the American Museum of Natural History in New York City,  who was not involved in the new discovery, concluded, This new material  certainly substantiates the idea, long gathering ground, that multiple  lineages of early Homo are present in the record at Koobi Fora.        
  Dr. Tattersall continued, And it supports the view that the early  history of Homo involved vigorous experimentation with the biological  and behavioral potential of the new genus, instead of a slow process of  refinement in a central lineage.        
  Bernard Wood of George Washington University, who has studied the early Homo fossil record, wrote in 
a companion article in Nature, In a nutshell, the anatomy of the specimens supports the hypothesis of multiple early Homo species.        
  Dr. Wood then weighed the pros and cons of placing the new fossils with  the species H. habilis, first discovered in 1964, or a separate and  controversial parallel species known as H. rudolfensis, to which 1470  has often been tentatively assigned. H. erectus emerged around the same  time, joining the other two species in Africa.        
  Chris Stringer of the Natural History Museum of London, who had no part  in the research, agreed that it looked as if the new discoveries  confirm the distinctiveness of 1470 and therefore confirm the  existence of a distinctive kind of early human around 1.8 to 2.0 million  years ago. But he noted that there remain many uncertainties about  the 1470 fossil and whether it might still be just a large specimen of  Homo habilis.        
  Another problem, Dr. Stringer said, is that in the last three decades,  as the number of fossils attributed to habilis has grown, it has become  unclear how to define what is and is not a member of that Homo species.  Determining if the new fossils belong to rudolfensis or habilis, he  said, would depend on ongoing comparisons with the original fossil  assemblage at Olduvai Gorge in Tanzania, where the first and many other  habilis and contemporary specimens have been excavated.        
  An assessment of recent finds at Olduvai as well as the 1470 fossil, by  Ronald J. Clarke of the University of Witwatersrand in Johannesburg, was  published recently in a special issue of The Journal of Human  Evolution.        
  So where do we go from here? Dr. Wood asked in his commentary. More  work needs to be done using the faces and lower jaws of modern humans  and great apes to check how different the shapes and the palate can be  among individuals in living species.        
  All in all, the state of hominin affairs that paleoanthropologists are  left with is neatly summed up in the title of Dr. Woods article,  Facing Up to Complexity. He concluded with the prediction that by  2064, 100 years after Leakey and colleagues description of H. habilis,  researchers will view our current hypotheses about this phase of human  evolution as remarkably simplistic.