A multinational group of anthropologists has described a new human ancestor species that lived in what is now the Afar region of Ethiopia about 3.3 – 3.5 million years ago, overlapping in time with the famous Lucy’s species, Australopithecus afarensis.

The fossil specimens of Australopithecus deyiremeda were found in the Woranso-Mille Paleontological Project study area located in the central Afar region about 325 miles (520 km) northeast of Addis Ababa and 22 miles (35 km) north of Hadar (Lucy’s site).

The type specimen of the species is an upper jaw with teeth discovered on March 4, 2011, on top of a silty clay surface at the Burtele area of Woranso-Mille. The paratype lower jaws were also surface discoveries found on March 4 and 5, 2011.

The combined evidence from radiometric, paleomagnetic, and depositional rate analyses yields estimated ages of 3.3 – 3.5 million years.

According to the scientists, the new hominin differs from Australopithecus afarensis in terms of the shape and size of its thick-enameled teeth and the robust architecture of its lower jaws. The anterior teeth are also relatively small indicating that it probably had a different diet.

“The new species is yet another confirmation that 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,” said Dr Yohannes Haile-Selassie of the Cleveland Museum of Natural History, lead author of a paper published in the journal Nature.

“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.”

Anthropologists have long argued that there was only one pre-human species at any given time between 3 and 4 million years ago, subsequently giving rise to another new species through time. This was what the fossil record appeared to indicate until the end of the 20th century.

However, the naming of Australopithecus bahrelghazali from Chad and Kenyanthropus platyops from Kenya, both from the same time period as Lucy’s species, challenged this long-held idea.

Although a number of researchers were skeptical about the validity of these species, the announcement by Dr Haile-Selassie of the 3.4 million-year-old Burtele partial foot in 2012 cleared some of the skepticism on the likelihood of multiple early hominin species in the 3 to 4 million-year range.

The discovery of Australopithecus deyiremeda 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.

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Yohannes Haile-Selassie et al. 2015. New species from Ethiopia further expands Middle Pliocene hominin diversity. Nature 521, 483-488; doi: 10.1038/nature14448