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The search for the direct ancestor of modern man is one of the great problems of science. Many species of hominin have been proposed over the years and a newly discovered species Australopithecus sediba has been claimed as the parent of all humans alive today. However, tests have shown that this hypothesis is highly improbable and that the search for our direct ancestor must continue.
Scientists have widely agreed that hominins known as Australopithecusare our most likely ancestors. Australopithecus afarensis was found in the 1970s, and the first discoveries of this hominin come from the famous "Lucy". However, in 2008, experts discovered evidence of another member of the Australopithecus family, who was a distant relative of Lucy, who looks like a monkey.
Australopithecus sediba, of which two fossils are shown on the left and right, would have been a species in transition between older Australopithecus, such as Lucy in the middle and later Homo species. Image compiled by Peter Schmid with the kind permission of Lee R. Berger. ( CC BY-SA 3.0 )
Discovery of a new species
The 9-year-old son of the famous paleoanthropologist Thomas Berger has unearthed the jaw bone and other bone fragments of a hitherto unknown species in the Mapala Cave in South Africa. This provoked an international sensation and immediately Berger and his colleagues claimed that the new hominin whom they named Australopithecus sediba , after a local word for the source , was the direct ancestor of the anatomically modern man.
It was determined that the discovery was two million years old and that its unique set of advanced monkey-like features gave the claims some credibility. According to a Discover Magazine blog, this statement has also revived "an old idea that the roots of human evolution were in South Africa".
However, not all academics were convinced, "mainly because the numbers did not seem to add up," reports Cosmos Magazine. According to the Science Advances study, the Australopithecus sediba fossils "postdate the first homo of 800 000 years". It meant that the dating of Australopithecus sediba was all wrong if it had to be our ancestor. The species first discovered by Berger's son was considerably younger than the first evidence we had of the Homo kind.
Matthew Berger moments after the Australopithecus sediba clavicle was discovered at the Malapa site. Photo of Lee R. Berger ( DC BY-SA 3.0 )
was Australopithecus sediba our ancestor?
The discovery of the new species in South Africa has given rise to much debate, especially as many other discoveries of Australopithecus sediba were made at Mapala Cave. Many studies have been published on the hominins fossils found in the Mapala Cave, but according to Discover Magazine, none of them has reached "definitive conclusions, except by leaving the door open to its long-standing ancestor potential ".
The majority of researchers have not accepted the fact that humans are descended from the species found in South Africa because hominin remains are younger than the oldest fossils in the United States. Homo kind. For many, it was not logical to claim that remains younger than the oldest Homo could be from his ancestor.
Fossil casts Australopithecus afarensis (left), Homo Habilis (center), and Australopithecus sediba (right). ( Matt Wood, UChicago )
Very unlikely to be our ancestor
The controversy led a team at the University of Chicago to develop a test to determine, once and for all, whether the evidence showed that: Australopithecus sediba was the ultimate origin of modern man. Under the direction of lead researcher Andrew Du Ph.D., they developed statistical models calculating the probability that this kind of Australopithecus was the ancestor of later humans. After testing several hypotheses, they established that Berger's theory of human origins was highly improbable.
According to Science Advances, the University of Chicago team discovered that it is unlikely that the fossil horizon of an ancestor is at least 800,000 years younger than that of the descendant (about 0.09% on average) . This meant that the fossils were just not old enough to come from our progenitor, as many had suspected.
However, that will not solve the controversy. Even the lead author of the study is cited by Inverse as "stating that it is" difficult for science to conclusively resolve a debate ".
In the end, Lucy is the best candidate
Science Daily quotes Zeresenay Alemseged, PhD, Professor of Biology and Anatomy and Anatomy Donald M. Pritzker of the University of Chicago and co-author of the study:
"Given the timing, the geography and the morphology, these three pieces of evidence make us think of a better candidate than the sediba.We may disagree about the morphology and the different characteristics of a fossil, but the degree of confidence that can be attributed to the analyzes of the chronological data presented in this article make our argument a very strong argument ".
The exhibition "Hidden Treasures of Ethiopia" at the Houston Museum of Natural Science presents a model of "Lucy". ( Jason Kuffer / CC BY NC ND 2.0 )
In recent years, many other discoveries seem to reject the idea that the fossils found in Mapala Cave originated from our ancestor. These include the discovery of Homo Nadeli which was also discovered by a team led by Berger. Then there is the discovery in the north-east, Ethiopia, of a fossil dating from nearly 3 million years ago and which is considered by some to be the oldest vestige of a member of the Homo kind.
The statistical study of the American university shows that Australopithecus sediba , probably lived after the emergence of our first ancestors, up to a million years ago. This recent discovery, particularly in Ethiopia, virtually eliminates the possibility that the hominin species found in South Africa in 2008 is our ancestor. It means that Australopithecus afarensis , or "Lucy" is the most likely candidate to be our ancestor, but even that is not certain.
Top image: Skull of Hominid 1 (MH1) from Malapa of South Africa, named "Karabo". The combined fossil remains of this juvenile male are designated as holotype for Australopithecus sediba. Source: CC BY-SA 4.0
By Ed Whelan
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