The human race would be 400,000 years old
It is difficult to date certain important events on the phylogenetic tree of life as the paleontology data often come to the upside.Thus, the recent discovery of a fossil hominin in Ethiopia has led researchers to age at least 400,000 years of the date of the emergence of the genus Homo.
Towards the end of 1974, a team of thirty Ethiopian, American and French co-led by Donald Johanson (paleoanthropology), Maurice Taieb (geology) and Yves Coppens (paleontology) led excavations near Hadar in Ethiopia when some of them fell on the fossilized remains of a geological formation outcropping along the Awash River. This course is now world famous water rises in the Ethiopian plateau, flows north into the Great Rift Valley and the Afar depression and empties into Lake Abbe, near Djibouti.
What had thus discovered the researchers? Nothing less than the fragments of the skeleton of an Australopithecus afarensis Lucy. This hominin lived there about 3.2 million years. Until now it was thought that the genus Homo had emerged a little less than a million years later with Homo habilis, whose direct descent from Australopithecus afarensis was not established. But now an international team of anthropologists and geosciences specialists, led by members of the Institute of Human Origins founded by Donald Johanson at the State University of Arizona (USA), has release two high profile publications in the journal Science.
A missing link between Australopithecus and Homo?
Paleoanthropologists from Arizona State University (ASU) are exploring the region Geraru-Ledi, near Hadar, since 2002. One of the goals of shipments they conducted was to find fossils of hominins corresponding to y a little-known period of 3 to 2.3 million years before present. There is actually very little information on the evolution that then leads the genus Australopithecus (which contains several species and not just the part which was Lucy) to the genus Homo. One can imagine the excitement that invaded in January 2013 the Ethiopian Chalachew Seyoum when he fell, as he says in the video above, a lower jaw fragment bearing fossilized teeth. The doctoral student in paleoanthropology immediately understood that he held in his hands a fossil hominin.
LD 350-1 cataloged under the code, it could be dated because it was between two layers of sediments containing volcanic ash. Radiometric method based on argon isotopes 40 / argon 39, supplemented by other dating methods, has shown that the hominin that came from this jaw fragment was aged 2.75 to 2.8 million years.
The real surprise came when the director of the Institute of Human Origins, William H. Kimbel, examined more closely LD 350-1 with colleagues including Brian Villmoare of the University of Nevada (Las Vegas States States). The presence of thin molars, premolars symmetric and uniformly proportioned jaw is a hallmark of the genus Homo that particular found in Homo habilis there are 2 million years. The slope of the chin that betrays the jaw fragment, however, is a primitive ape-like feature that is observed in Australopithecus. The conclusion of Kimbel is clear: "This is an excellent example of a transitional fossil at a critical period of human evolution."
The appearance of a result of climate change?
But there is more, LD 350-1 allows to push at least 400,000 years the birth of the genus Homo, as the oldest known fossilized fragments previously went back only about 2.3 million years. Certainly, there is still much work to do to get a more complete picture of this species and to answer basic questions: What does it eat? She used stone tools? The research will continue.
Other fossils in the Ledi-Geraru region were also found and dated. They allow you to get an idea of the time environment there are between 2.84 and 2.58 million years. While around Hadar lived there 3 million years monkeys, elephants and giraffes more characteristics of an environment where meadows and forests alternate, 200,000 years later we find around Ledi-Geraru fauna and flora signaling a drier period. It is reminiscent of the Serengeti with existing gazelles and zebras, or the Kalahari. New and many species of mammals have also emerged quickly. This intense period of apparent speciation may have been caused by climate change affecting East Africa at the time, but it's hard to tell if he actually played a role in the emergence of Homo .
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