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New Human Ancestor Species May Have Lived Alongside 'Lucy'

May 27, 2015 04:14 PM EDT
Pictured: The holotype upper jaw of Australopithecus deyiremeda found on March 4, 2011. (Photo : Yohannes Haile-Selassie / copyright Cleveland Museum of Natural History)

A new human ancestor species dating back 3.3-3.5 million years ago may have lived alongside "Lucy," the famous hominin species, according to new research, allowing scientists to more accurately paint the human family tree.

Upper and lower jaw fossils were discovered from the Woranso-Mille area of the Afar region in Ethiopia, and have recently been assigned to the new species Australopithecus deyiremeda.

Meanwhile, Lucy is the best-known example of Australopithecus afarensis, and is believed to have lived from 2.9 million years ago to 3.8 million years ago. This would mean both Lucy's species and the new hominin species walked the Earth at about the same time. This is the most conclusive evidence for the contemporaneous presence of more than one closely related early human ancestor species prior to three million years ago.

Though, A. deyiremeda differs from Lucy's species in terms of the size and shape of its thick-enameled teeth and the robust architecture of its lower jaws. In addition, the anterior teeth are also relatively small, indicating that it probably had a different diet.

"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," lead author Dr. Yohannes Haile-Selassie, curator of physical anthropology at the Cleveland Museum of Natural History, said in a statement. "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."

Conversely, scientists have long argued that there was only one pre-human species at any given time between three and four million years ago, eventually giving rise to another new species over the course of evolution. At least, that's what the fossil record indicated until the end of the 20th century, researchers say. That's when fossils such as Australopithecus bahrelghazali from Chad and Kenyanthropus platyops from Kenya, both from the same time period as Lucy's species, were discovered.

And now, the new species A. deyiremeda may be added to that list. Analyses from regional geology, radiometric dating, and new paleomagnetic data estimate that this new possible human ancestor is between 3.3 and 3.5 million years old.

This discovery has important implications for our understanding of early hominin ecology. It also raises significant questions, such as how multiple early hominins living at the same time and geographic area might have used the shared landscape and available resources.

The new species is described in more detail in the journal Nature.

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