"Little Foot" is the most complete ancient human in the fossil record. The researchers said that the skeleton has a history of about 3.67 million years and is a member of Australopithecus, from an elderly woman. However, how it adapts to the broader picture of ancient human evolution and which species it belongs to has caused fierce debate among competing research teams.
This specimen, officially named StW 573, was discovered in Fontaine Cave system in Staercke, South Africa in 1988. Ronald clarke, a paleoanthropologist at the University of the Witwatersrand, and his team have carefully released it from rock materials buried for millions of years in the past 20 years.
Today, Clarke and his colleagues provide a long-awaited analysis of this skeleton in four papers, which are being reviewed by the Journal of Human Evolution and published on the bioRxiv preprint server. They said that according to the age of the sediments near the fossils, Little Foot lived about 3.67 million years ago, about 1 10,000 years earlier than previously thought. The relatively small figure and specific skull characteristics indicate that it may be an elderly woman with a brain capacity of 408 cubic centimeters, which is about 1/3 of that of modern people.
"Little Foot" obviously suffered forearm trauma in early life, and its relatively long legs indicate that it may walk upright instead of shuttling between trees.
According to earlier data, many paleoanthropologists believe that "Little Foot" is a member of Australopithecus africanus. This is a confirmed upright walking family, living from 3.3 million to 265,438+million years ago. Many other South African samples, including some from the same cave, were designated as this species.
However, Clark believes that many features distinguish "Little Foot" and at least a dozen other fossils nearby from Australopithecus africanus. The former includes a larger, flatter face and wider orbital distance, larger canine teeth and front incisors, larger maxilla and slightly convex forehead. Clark said that the difference in tooth wear showed that australopithecus africanus was omnivorous, while Little Foot and his close relatives were vegetarians most of the time. This shows that about 3 million years ago, there should be two kinds of ancient humans living near the above caves.
Clark thinks that the feature of "small feet" is the most matching feature with Prometheus Australopithecus proposed by anthropologist Raymond Dart in 1948. Dean Falk, an evolutionary anthropologist at Florida State University who was not involved in the work, said Clark's views were "very convincing". If Clark is right, it means that "everyone has mixed two species into one" before. Falk said that knowing that they are actually separate helps to find out which species in this area gave birth to later species, thus filling some gaps in chemistry.
However, this division quickly aroused the opposition of paleoanthropologist Lee Berger of the University of Witwatersrand and paleoanthropologist john hawkes of the University of Wisconsin-Madison. In a paper published in the American Journal of Natural Anthropology a few days ago, they suggested that Prometheus' definition of Australopithecus is not clear, so it should not be used for classification. Berger further stated that the age of the above fossils could not be as long as Clark's team claimed. He believes that its skull has been distorted for millions of years and cannot be accurately measured unless a large-scale reconstruction work is carried out.
William Jin Beier, a paleoanthropologist at Arizona State University, also disagreed with Clark's conclusion. He believes that the next step should be to analyze hundreds of other Australopithecus fossils found in South Africa and East Africa, and calculate how much changes may occur between a species. After that, researchers can determine whether the "little feet" are beyond this range. If so, it may indeed be called a unique species. (Zong Hua)