- 18:00 27 May 2015 by Penny Sarchet
Casts of the jaws of Australopithecus deyiremeda (Image: Laura Dempsey/Cleveland Museum of Natural History)
Lucy had company. Her species of Australopithicus was not alone in the neighbourhood some 3.2 million years ago – they lived alongside at least one other type of early human.
For decades, palaeoanthropologists have been debating whether Lucy’s species, Australopithecus afarensis, was the lone hominin living in eastern Africa at the time.
Now Yohannes Haile-Selassie of the Cleveland Museum of Natural History in Ohio and his colleagues have identified a new species they callAustralopithecus deyiremeda. It lived in what is now the central Afar region of the East African Rift Valley around 3.3 million years ago, only 35 kilometres north of known Australopithecus afarensis sites.
Haile-Selassie says his team has found A. afarensis bones at the same site as their new species. “I’m pretty sure that those two species did actually overlap not only in time but also in space,” he says.
The new hominin has been identified from jaw and tooth specimens. Compared with Lucy’s species, Australopithecus deyiremeda had a more robust jaw and thicker tooth enamel, suggesting they may have eaten tougher, more abrasive food.
That makes sense, says Louise Humphrey of the Natural History Museum in London. “The presence of more than one hominin species in close chronological and spatial proximity would suggest differences in resource exploitation, including food preferences and the way in which food items were accessed,” she says.
A jumble of hominins
The discovery seems to confirm that more than one type of Australopithecusexisted in the area that is now Ethiopia before our Homo lineage appeared –perhaps as early as 2.8 million years ago .
It might also settle an ongoing dispute about how to interpret a wide variation seen in A. afarensis bones, with some saying the differences are too great for it to have been just one species.
“If Haile-Selassie is right, I think it’s only reasonable to conclude that some unknown number of Australopithecus afarensis skeletal remains actually belong to this new species instead,” says John Hawks at the University of Wisconsin-Madison. “This means that everything that has been written about variation, function and the anatomy of Australopithecus afarensis from fragmentary remains must now be in doubt.”
But Tim White of the University of California argues that more evidence is needed before we can conclude that there were two species of early humans in the area at the time. He thinks all the variation seen – even in the latest find – could just be diversity within Australopithecus afarensis. “Darwin recognised that anatomical variation within a biological species is normal,” he says.
Journal reference: Nature, DOI: 10.1038/nature14448