Monday, October 21, 2013

Unique skull throws human evolution theories into turmoil

By Alton Parrish via IIAI, 18 October 2013

Unique skull find rebuts theories on species diversity in early humans

Paleoanthropologists from the University of Zurich have uncovered the intact skull of an early Homo individual in Dmanisi, Georgia. This find is forcing a change in perspective in the field of paleoanthropology: human species diversity two million years ago was much smaller than presumed thus far. However, diversity within the “Homo erectus”, the first global species of human, was as great as in humans today.

Face of Dmanisi skull5, Picture: Malkhaz Machavariani, Georgian National Museum

This is the best-preserved fossil find yet from the early era of our genus. The particularly interesting aspect is that it displays a combination of features that were unknown to us before the find.



The skull, found in Dmanisi by anthropologists from the University of Zurich as part of a collaboration with colleagues in Georgia funded by the Swiss National Science Foundation, has the largest face, the most massively built jaw and teeth and the smallest brain within the Dmanisi group.

Aerial view of the Dmanisi excavation site (foreground) and medieval town, Picture: Fernando Javier Urquijo

It is the fifth skull to be discovered in Dmanisi. Previously, four equally well-preserved hominid skulls as well as some skeletal parts had been found there. Taken as a whole, the finds show that the first representatives of the genus Homo began to expand from Africa through Eurasia as far back as 1.85 million years ago.

Dmanisi skull5, Picture: Guram Bumbiashvili, Georgian National Museum

Diversity within a species instead of species diversity

Because the skull is completely intact, it can provide answers to various questions which up until now had offered broad scope for speculation. These relate to none less than the evolutionary beginning of the genus “Homo” in Africa around two million years ago at the beginning of the Ice Age, also referred to as the Pleistocene. Were there several specialized “Homo” species in Africa at the time, at least one of which was able to spread outside of Africa too? Or was there just one single species that was able to cope with a variety of ecosystems? Although the early Homo finds in Africa demonstrate large variation, it has not been possible to decide on answers to these questions in the past. 

Computer reconstruction of the five Dmanisi skulls (background: Dmanisi landscape),  Picture: Marcia Ponce de León and Christoph Zollikofer, University of Zurich, Switzerland

One reason for this relates to the fossils available, as Christoph Zollikofer, anthropologist at the University of Zurich, explains: “Most of these fossils represent single fragmentary finds from multiple points in space and geological time of at least 500,000 years. This ultimately makes it difficult to recognize variation among species in the African fossils as opposed to variationwithin species”.

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