Friday, 29 May 2015

New Possible Human Ancestor Discovered

Upper jaw of Australopithecus deyiremeda
Credit: Yohannes Haile-Selassie / copyright Cleveland Museum of Natural History
New species from Ethiopia further expands Middle Pliocene hominin diversity - Nature

A great deal of religion, especially the Abrahamic religions, depends on humans seeing themselves as a special creation. The entire thrust of the Genesis origin myth, for example, is an attempt to explain why human beings are different to, and above, the rest of the animals. It went without saying to the people who invented this myth that this was simply a matter of obvious fact. It probably never even occurred to them that this was merely an assumption, just as it doesn't seem to occur to some people today.

Humans are different and special, so there must be a reason. That belief almost certainly doesn't come from the myth; the myth was very probably invented to explain the 'fact'.

The new species is yet another confirmation that Lucy's species, Australopithecus afarensis, was not the only potential human ancestor species that roamed in what is now the Afar region of Ethiopia during the middle Pliocene. Current fossil evidence from the Woranso-Mille study area clearly shows that there were at least two, if not three, early human species living at the same time and in close geographic proximity.

Dr. Yohannes Haile-Selassie,
curator of physical anthropology,
The Cleveland Museum of Natural History.
Of course, for people throughout recorded history, there has only been one type of human - modern humans. Even people who lived close to our nearest relatives, the great apes, in Africa and Southeast Asia, even they were different enough to be regarded as mere animals, not some sort of human.

But in fact, for most of our evolutionary history, this is a very unusual situation. For most of our Homo ancestry and probably for almost all of our pre-Homo history, certainly our Australopithecine history, we lived alongside several other closely related species, and may well have been able to interbreed with them.

We could certainly interbreed with our Neanderthal and Denisovan cousins until they went extinct maybe a recently as 30,000 years ago. We may even have been able to communicate with them by speech.

So, it comes as no surprise that the existence of yet another Australopithecine, named Australopithecus deyiremeda has been discovered living alongside one of the most famous hominin, "Lucy" or Australopithecus afarensis some 3.3-3.5 million years ago.

Middle Pliocene hominin species diversity has been a subject of debate over the past two decades, particularly after the naming of Australopithecus bahrelghazali and Kenyanthropus platyops in addition to the well-known species Australopithecus afarensis. Further analyses continue to support the proposal that several hominin species co-existed during this time period. Here we recognize a new hominin species (Australopithecus deyiremeda sp. nov.) from 3.3–3.5-million-year-old deposits in the Woranso–Mille study area, central Afar, Ethiopia. The new species from Woranso–Mille shows that there were at least two contemporaneous hominin species living in the Afar region of Ethiopia between 3.3 and 3.5 million years ago, and further confirms early hominin taxonomic diversity in eastern Africa during the Middle Pliocene epoch. The morphology of Au. deyiremeda also reinforces concerns related to dentognathic (that is, jaws and teeth) homoplasy in Plio–Pleistocene hominins, and shows that some dentognathic features traditionally associated with Paranthropus and Homo appeared in the fossil record earlier than previously thought.

From an evolutionary biologist's or palaeoanthropologist's point of view, the existence of yet another contemporaneous species in the same area is nothing new. The interesting thing in this discovery has to do with details of the dentition and jaw structure in that it shows they appeared in the hominin fossil record much earlier than previously thought. Like A. afarensis, this new species is a strong candidate to be the ancestor of Homo habilis and so to be our direct ancestor.

So, while creationists are still in denial about the existence of all these ancestral fossils and an increasingly clear picture of our divergence from the other African apes, our subsequent evolution, and the normalcy throughout our evolutionary history of there being several co-existing hominin and hominid species, real scientists have moved way beyond our African origins being a debated scientific hypothesis, to it being an establish fact with just the fine details now being filled in.

And not a single fossil ever discovered has been inconsistent with the science of evolution by descent with modification. This is because scientific knowledge is based on evidence, not sacred old folk-legends and fairy tales from the infancy of our species.

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