Despite being a subscriber to the likes of Science Direct and Wiley Online Library for my Palaeo-related new release alerts, sometimes one still has to rely on more informal contacts for the necessary heads-up. And on this occasion I have my newly forged Google+ contacts Palaeontology Rocks and the wider Human Evolution community to thank for this latest blog posting.
Not a year has passed since the revelatory unearthing of Skull 5 at the famous Georgian fossil site of Dmanisi. The discovery received much coverage in the blogosphere, therefore please refer to the following sources (1, 2 and 3) for your better informed background information.
Prior to the finding, interpretations of the Dmanisi collection were at best as flaky as a Stone Age tool. Dated close to 1.8 million years ago (Ma), the original remains sported an odd “mosaic” of features. But were they suggestive of Homo erectus (“standing man”, the first to cook meat), Homo habilis (“handy man”, the first to make tools), or an altogether new species dubbed Homo georgicus (“Georgian man”, western Asia not southeast USA)?
The discovery of Skull 5 (catalogued as D4500) was major in that it apparently unified the Dmanisi fossils with those of Homo habilis in Africa and Homo erectus in Asia. Rather than being separate species, all the fossils were most likely representative of a single evolving lineage. Our family tree it seemed was in need of a pruning…
Now to the new development. Published in PLoS One last week, a study of the Dmanisi jawbones (see photo) contests the above interpretations of Skull 5. Marked shape differences in the jaws, unrelated to the size or sex of the individual who chompsed with it, are present early in growth. This, according to the authors, is evidence of difference not similarity.
What’s more, the argument is supposedly strengthened by the uncertain dating of the earth at Dmanisi. Therefore, on the grounds of the uncertain ground and the developmental differences in mandibular (jawbone) morphology (shape), more than one lineage could well be represented at Dmanisi.
Source: Bermudez de Castro, JM. et al. 2014. On the variability of Dmanisi mandibles. PLoS One 9(2): e88212