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October 18, 2013

Cranium D4500 was found during the 2005 excavation season at Dmanisi. It was recovered from the bottom layers of Block 2, just above the basaltic bedrock. D4500 belongs to the same individual as mandible D2600 (which was recovered in 2000). It represents the fifth individual found at Dmanisi, and is referred to as "Skull 5", published now in Science on 18th October 2013.

Dmanisi Skull 5 is an exception with its fossilization history, as it remained virtually undisturbed over the 1.77 million years that have passed since its death. It represents the world’s first completely preserved adult hominid skull from the early Pleistocene (1.77 million years ago).

The Skull 5 individual probably had a long and eventful life. Its big teeth are worn down to stumps, such that it suffered from tooth root infections. Its deformed right cheek bone testifies a badly healed fracture. The left mandibular joint is deformed as a consequence of a chronic arthritic inflammation.

Skull 5 provides the unique opportunity to study the morphology of an entire adult cranium with its associated mandible and teeth, and to document anatomy previously unknown for early Homo.

Skull 5 shows a combination of features hitherto unknown for early Homo. It has the smallest braincase of all Dmanisi individuals (546ccm; about 1/3 of an adult modern human), but the largest and most protruding face, and the biggest teeth. Hence it considerably expands the range of morphological variation seen at Dmanisi. Together with the four Dmanisi individuals found earlier, it provides first insights into patterns of variation in a paleopopulation (ancient population) of early Homo.

Variation in the Dmanisi paleopopulation is substantial, but it does not exceed the range of variation seen in modern human and chimpanzee populations. Dmanisi thus shows that paleopopulations of early Homo exhibited significantly more diversity than typically assumed. Accordingly, the diverse early Homo fossils from Africa probably represent a single species, and it is less probable that they reflect species diversity. 

The Dmanisi individuals share many morphological traits with the earliest known Homo fossils from Africa (2.3-1.75 million years), and also with later Homo representatives from East Asia (1.6-1.2 million years). This indicates continuity of a single evolving lineage of early Homo across continents and over time. A sensible species name for this lineage is Homo erectus.