翻訳です
A 17-year investigation into a fossilized early human skeleton from Ethiopia culminated last week with 11 papers published in Science.
Detailed descriptions of the skeleton, of a fairly complete 4.4-million-year-old female, show that humans did not evolve from ancient knuckle-walking chimpanzees, as has long been believed.
The new fossils of Ardipithecus ramidus ― known as “Ardi” ― often the first substantial view of the biology of a species close to the time of the last common ancestor shared by humans and apes.
Like modern humans, Ardi could walk upright and didn’t use her arms for walking, as chimps do.
Still, she retains a primitive big toe that could grasp a tree like an ape.
Previously, the oldest near-complete skeleton of an early human was the 3.2-million-year-old Australopithecus afarensis skeleton known as Lucy, also from Ethiopia.
Because Lucy had many traits in common with modern humans, she didn’t provide much of a picture of the earlier lineage between apes and humans, says Alan walker, a biological anthropologist at Pennsylvania State University in University Park.
The new A. ramidus “is so much more important ― and strange”, he says.
The earliest Ardipithecus, A. kadabba, lived around 5.8 million years ago in Ethiopia.
The other oldest known hominids are Orrorin tugenensis, from about 6 million years ago in Kenya, and Sahelanthropus tchadensis, from at least 6million years ago in Chad (see graphic).
In addition to describing the fossils, the Science papers provide details about the geology and palaeoenvironment of the discovery site, in the Afar desert 230 kilometres northeast of Addis Ababa.
The research team, known as the Middle Awash Project, involves 70 investigators, 47 of whom are authors on the papers.
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