The fossils of a new human-like species have been uncovered in a cave in Malapa, South Africa, an international team of scientists reports in the journal Science today.
Named Australopithecus sediba, the new species is about 1.9 million years old and reveals clues about the changes that were occurring at an important stage of early human evolution, when the human, or Homo, group first evolved.
Australopithecines, or southern apes, lived between about 1.5 and 4.2 million years ago. They shared similarities with both humans and apes, and fossils from different australopithecine species have been found in various parts of Africa.
Virtual reconstruction of the one of the A. sediba skulls © L Berger/ Science
The team, led by Professor Lee Berger of the University of the Witwatersrand, South Africa, identified the fossil remains of Australopithecus sediba which included 2 partial skeletons in very good condition, one from an adult, probably female, and one from a child, probably a boy.
Professor Chris Stringer, Research Leader in Human Origins at the Natural History Museum explains the significance of the 2 partial skeletons, 'They are extremely important additions to the fossil record of human evolution.'
'A. sediba resembles the first recognised australopithecine species A. africanus (which lived about 2.5 million years ago), in its ape-sized brain and ape-like body shape, muscular arms and powerful hands.
'A. sediba's face, teeth, pelvis and legs show more human characteristics, and this is the most human-like australopithecine yet discovered.'
The evidence for the first humans, genus Homo, comes from fossils discovered in East Africa, dated between about 1.9-2.3 million years ago. Modern humans, Homo sapiens, who evolved in Africa around 200,000 years ago, are thought to be descendants of those first humans.
At 1.9 million years, could Australopithecus sediba be an ancestor of the first humans, and therefore a direct ancestor of modern humans?
A species from the ancient australopithecine group may have led to modern humans. However, the location where A. sediba was found may be a crucial part of the story, as Prof Stringer, explains. 'These new fossils from Malapa return the spotlight to South Africa as a possible location for the postulated transition from Australopithecus to the genus Homo (humans).
'However, the sediba fossils themselves appear geologically too young to represent actual ancestors for the human-like fossils known from East Africa at around 2 million years.
'Nevertheless, the fact that experts differ over whether to classify these specimens as australopithecine or human indicates the mixed features that they display, and the fossils provide valuable clues to the evolutionary changes that led to the first members of the human genus.'
The 2 partial skeletons of A. sediba in this research were a rare find. The fossils from the child included a near-complete skull and jaw, teeth, parts of the pelvis, ribs, upper and lower legs and upper arms. Many fossils of early human relatives have been discovered but it is often only fragments of bones or teeth that are found.
The most complete ancient hominin (human-like) skeleton, from 4.4 million years ago, was Ardipithecus ramidus, or Ardi, revealed in October 2009. Ardi had a brain and body the size of a chimpanzee's as well as some human-like features such as the small canine teeth and flexible hands and wrists.
Perhaps the most famous skeleton of an early human relative belonged to the 3.2 million-year-old 'Lucy', Australopithecus afarensis, uncovered in 1974.