History Files


Prehistoric World

Just Who was Homo Georgicus?

Edited from Talk Origins, 1 August 2005



Discovered in 2001 at Dmanisi in Georgia, the skull's estimated age is 1.8 million years. Specimen D2700 consisted of a mostly complete skull in exceptionally good condition, including a lower jaw (D2735) found about a metre away and thought to belong to the same individual.

At around 600cc (cubic capacity), this was the smallest and most primitive hominid skull ever discovered outside of Africa until Homo floresiensis' recent discovery.

Two other skulls had earlier been found at the same site in 1999. D2280 was an almost complete braincase with a brain size of 780cc. D2282 was a cranium which included many of the facial and upper jaw bones, with a brain size of about 650cc. A lower jaw, D211, had also been discovered in 1991, and another lower jaw, D2600, in 2000.

Although the brain size of D2282 (650cc) was smaller than any erectus fossil then known, and close to the average Homo habilis brain size, Gabunia et al. (2000) pointed out the many similarities of D2280 and D2282 to Homo erectus fossils such as WT 15000 and ER 3733. Their final conclusion was that D2280 and D2282 were both Homo ergaster or something very similar.

At 600cc, new discovery D2700 is even smaller than D2282, and appears more primitive. Vekua et al. (2002) list many characteristics in which it resembles ergaster (or erectus), and also a number in which it resembles the habilis skull ER 1813.

However, the differences between the three Dmanisi skulls were not considered great enough to justify placing them in different species. However, in a later paper, all these specimens were assigned to the new species Homo georgicus, using the fossil D2600 as a type specimen (Gabunia et al. 2002). The same paper also estimated the height of georgicus from a foot bone at about 1.5 m (4'11").

In April 2005 a newly published paper gave details of a fourth skull (D3444) and jawbone (D3900) belonging to the same individual discovered at Dmanisi. This skull was unusual in that it had lost all but one tooth, and most of them had been missing for a number of years. This suggests that the individual might have required considerable support from his companions to survive. (Lordkipanidze et al. 2005; April 2005 National Geographic).

The implications for evolution

It has always been thought that the first hominid to leave Africa was Homo erectus, and that this had happened after erectus had attained the modern body shape and full adaptation to bipedalism shown in the Turkana Boy fossil.

The discovery of the Dmanisi skulls, particularly D2700, raises the possibility, suggested by Vekua and his colleagues, that the Dmanisi hominids might have evolved from habilis-like ancestors that had already left Africa. That in turn would cause re-evaluation of theories about why hominids first left Africa.

It seems most probable that this time there was no "Out of Africa"-style migration but that these early humans initially underwent range expansions in African-like environments that were familiar to them, rather than making pioneering moves into the unknown. The known conditions of the time support this view perfectly, as sweeping plains linked Africa to Central Asia.

Resembling as they do Homo erectus/Homo ergaster and Homo habilis, and containing a mixture of traits from all three species, it's hard to imagine a more convincing series of transitional fossils.



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