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The family tree of our ancestors became even more complicated this week with the announcement of a new ancient species of hominin from the Afar region of Ethiopia. The international research team, led by the Cleveland Museum of Natural History, have named their new species Australopithecus deyiremeda, and have dated the remains as being between 3.3 and 3.5 million years old. This age means that Australopithecus deyiremeda would have lived alongside the more familiar species, Australopithecus afarensis, of which the most famous specimen is ‘Lucy’.
The fossils at the centre of this story were discovered in the Woranso-Mille area of the Afar region in Ethiopia, at a site about 22 miles north of the location where Lucy herself was discovered. The first bones of this new species were found in 2011 and to date consist of upper and lower jaw bones plus teeth. These differed sufficiently from the other hominins of the same age that its discoverers assigned them to a brand new species; Australopithecus deyiremeda, placing them as a close relative of Australopithecus afarensis. The major difference between this new species and Lucy’s relatives is the far thicker tooth enamel and robust lower jaw of Australopithecus deyiremeda. This is highly suggestive that this latest hominin was eating very different things to its evolutionary cousins, probably far tougher foods which required the strengthening of the jaw and teeth. Without further skeletal remains however, it is impossible to deduce too much about this new species and its behaviours.
This find is nevertheless highly significant because it reveals the unsuspected complexity of early human evolution. It was long thought that there was only one species of ancestral human living between 3 and 4 million years ago, but this idea has been challenged in the last few decades with the naming of several new species, and more controversially the discovery of less conclusive fossil remains that seem to differ significantly to Australopithecus afarensis. Now the addition of Australopithecus deyiremeda to our family tree adds yet more evidence to the argument that throughout hominin evolution the world has been host to numerous, overlapping species. It also reopens the question of which of these early species is our direct ancestor.
Reference: Haile-Selassie, Y., et al. 2015. New species from Ethiopia further expands Middle Pliocene hominin diversity. Nature. doi:10.1038/nature14448
Featured Image: Casts of the fossil material from Australopithecus deyiremeda. Credit: Laura Dempsey @ Cleveland Natural History Museum