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The earliest known primate skeleton has been found by palaeontologists, a 55 million-year-old tree-dwelling creature that lived in what is now central China.
Its fossil was discovered by a team from Beijing's Institute of Vertebrate Paleontology and Paleoanthropology, led by Ni Xijun. Xijun had been alerted to the existence of the fossil several years ago by a farmer in Hubei Province, who found it in a quarry that used to be a lake and which has been the source of a number of important fish and bird fossils from the Eocene Epoch.
Dubbed Archicebus achilles*,* it represents a vital piece of evidence in tracking how modern primate species evolved.
It belongs to the branch of the evolutionary tree that leads to modern monkeys, apes and humans, but close to the point where the apes and monkey are believed to have split into two seperate groups.
It was a tiny creature about the size of a human hand, and weight between 20 and 30 grams, making it slightly smaller than the smallest primate currently extant -- the pygmy mouse lemur. Its features, though, were more monkey-like -- a long tail, hands, feet and teeth like a monkey, and with a small head with small eyes.
The feet in particular were intriguing, as they contain both monkey-like attributes (like a long metatarsal) but also the long, big toes with nails found in other primates. It suggests that features that were thought to be evolutionarily advanced, and unique to modern monkeys and apes, are actually very primitive, and one of the earliest sets of features to evolve. It even seems to suggest that, while modern humans came from Africa, modern primates first arose in Asia.
The Archicebus achilles fossil is approximately seven million years older than the next-oldest primate fossils found up to this point, Darwinius and Notharctus.
Those specimens, however, are related more to the most distant branches of the primate family tree that includes modern lemurs.
The prevailing idea of primate evolution had had our ancestors looking close to modern monkeys, including in size, with smaller creatures diverging towards the lemurs. This discovery up-ends that assumption.
Analysis of the fossil was a multinational effort involving experts from the Carnegie Museum of Natural History in Pittsburgh, Northern Illinois University, Northwestern University, the American Museum of Natural History in New York and the European Synchrotron Radiation Facility in Grenoble. The latter facility was used to scan the fossil at a high resolution in order to build a detailed 3D-model rather than investigating it directly and potentially damaging it. The discovery and study of the fossil is detailed in the study published in Nature. "Archicebus marks the first time that we have a reasonably complete picture of a primate close to the divergence between tarsiers and
Xijun said. "It represents a big step forward in our efforts to chart the course of the earliest phases of primate and human evolution."
This article was originally published by WIRED UK
