D4500 was recovered in 2005 from the base of layer B1y in Block 2 of the Dmanisi excavation area. It represents the same individual as mandible D2600, found 5 years earlier [4]. Skull 5 is likely associated with the postcranial elements of an adult individual with a nearly modern human body proportion. It was described in 2013 by Lordkipanidze and colleagues [5] in a publication. Skull 5 is distinguished by its large and projecting face, combined with a brain size of  (546 cm3 about one-third of a modern human). It has the smallest braincase of the Dmanisi individuals but the largest face and teeth, a combination previously unknown for early Homo. However, the detailed anatomy of its braincase, which gives clues to the brain’s “wiring”, is similar to that of the more recent early human species, Homo erectus [5][6].

Skull 5 is the first complete specimen to show evidence of how the face (including the mandible) of an adult early Homo was oriented and positioned relative to the braincase [1].

Debate on Classification

The 2013 publication [1] became controversial. The authors proposed that the specimens previously attributed to Homo ergaster should be a chronosubspecies called Homo erectus ergaster and that the Dmanisi population most likely originated from an Early Pleistocene expansion of the Homo erectus lineage from Africa. They retracted their previous designation of the Dmanisi sample as Homo georgicus [4] and reclassified the whole sample as Homo erectus ergaster georgicus, under Homo erectus ergaster [1][7]. 

H.e.e. georgicus is the first use of quadrinomial in primate taxonomy and is not recognized by the International Code of Zoological Nomenclature and thus criticized by other palaeoanthropologists [7][2]. However, Zollikofer et al. [8] countered that they used the name H.e.e. Georgicus to distinguish the Dmanisi sample as a paleodeme of the Homo erectus ergaster and that although the use of taxonomic quadrinomials is not regulated by the International Code of Zoological Nomenclature, it is not invalid.  

Schwartz et al. [2] also contested the publication’s claims that Dmanisi hominins belong to one classification and that the variation in their features is due to within-species taxic variation within the Homo erectus lineage including significant age-related and sexual dimorphism, and that it is unlikely that they belong to different classifications given the close proximity of their discovery and the short time period [1]. 

Schwartz et al. [2], countered that neither time nor place is necessarily related to systematic identity and that because the Dmanisi fossils were possibly deposited over as many as several hundred years, there was enough time for faunal migration and/or replacement. They also believe that Skull 5 (D4500/D2600) should be the holotype of a distinct species Homo georgicus as proposed by Gabunia et al. in 2002 [4]. As a result, the taxonomic status of Skull 5 and the other Dmanisi hominins remains unclear [6].