What do Homo erectus, Homo habilis and Homo rudolfensis all have in common? A recent study suggests that they may all be members of the same species. An eight-year study of a set of fossils first discovered in 2005 in the Republic of Georgia (see below) is rethinking the way that scientists may classify some of our early Homo ancestors.
The fossils in question are all skulls of early members of the Homo genus. They have been dated to between 1.77 and 1.85 million years ago. One of these skulls, called Skull 5, is remarkably well preserved, and contains the jaw features typically associated with Homo habilis , but the brow ridges of Homo erectus. So where do these two species fit in the human evolution story? Below is a copy from one of my books, Inquiry into Life (14e).
But studying the variation in the Georgian fossils, some archeologists are now thinking that what was once believed to be characteristics that defined the differences between H. habilis and H. erectus may simply be representative of variation in individuals within a single species. Furthermore, it is possible that H. rudolfensis, which predated H. habilis and H. erectus, may also be a member of this same species.
There remains a considerable amount of work to be done before the scientific community accepts the idea that these groups represent a single species. However, for the longest time the evolutionary history of our species has been cloudy. Recent studies of Neandertals and Denisovans is challenging our views of how our species interacted with other members of our genus. When coupled with the information being presented by the Georgian fossils, these discoveries demonstrate that we developing a better understanding of where to look for important fossil evidence. If the hypothesis presented by this study is validated, then the human evolutionary tree may be a lot less complicated than we originally thought, which may in turn help us better understand not only how our species evolved, but how it moved across the globe.
For more resources, see the links below:
- Slideshow of the discovery provided by Science
- ScienceFriday podcast on the discovery
- Research article: A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo
David Lordkipanidze, Marcia S. Ponce de León, Ann Margvelashvili, Yoel Rak, G. Philip Rightmire, Abesalom Vekua, and Christoph P. E. Zollikofer
Science 18 October 2013: 342 (6156), 326-331. [DOI:10.1126/science.1238484]
- NY Times article (John Nobel Wilford): “Skull Fossil Suggests Simpler Human Lineage“
- BecomingHuman.org – an interactive exploration of human evolution.
Editor’s Note: Updated on 10/30 – we incorrectly indicated that the distribution of H.habilis and E. erectus overlapped on the diagram.