The Dmanisi skull, also known as Skull 5 or D4500, is one of five skulls discovered in

Dmanisi Dmanisi ( ka, დმანისი, tr, , az, Başkeçid) is a town and archaeological site in the Kvemo Kartli region of Georgia approximately 93 km southwest of the nation’s capital Tbilisi in the river valley of Mashavera. The hominin ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...

and classified as early ''

Homo erectus ''Homo erectus'' (; meaning "upright man") is an extinct species of archaic human from the Pleistocene, with its earliest occurrence about 2 million years ago. Several human species, such as '' H. heidelbergensis'' and '' H. antecessor' ...

''. Described in a publication in October 2013, it is estimated to be about 1.8 million years old and is the most complete skull of a

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus ''Australopithecus'' that encompasses the extant species ''Homo sapiens'' (modern humans), plus several extinct species classified as either ancestral to or closely related ...

'' species,Skull suggests three early human species were one : Nature News & Comment
/ref> and the first complete adult

hominin The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos) and in standard usage excludes the genus ''Gorilla'' (gorillas). The ...

skull of that degree of antiquity. According to researchers, the discovery "provides the first evidence that early ''Homo'' comprised adult individuals with small brains but body mass, stature and limb proportions reaching the lower range limit of modern variation." The skull has been the cause of a paleontological controversy that is still ongoing as of 2017: many hominin fossils thought to be from different species such as ''

Homo rudolfensis ''Homo rudolfensis'' is an extinct species of archaic human from the Early Pleistocene of East Africa about 2 million years ago (mya). Because ''H. rudolfensis'' coexisted with several other hominins, it is debated what specimens can be confide ...

'' or ''

Homo habilis ''Homo habilis'' ("handy man") is an extinct species of archaic human from the Early Pleistocene of East and South Africa about 2.31 million years ago to 1.65 million years ago (mya). Upon species description in 1964, ''H. habilis'' was highly c ...

'' may not have been separate species at all. Rather, they may have been a single evolving lineage.

Discovery of the skull

In 1991, Georgian scientist David Lordkipanidze found traces of early human occupation in the cave at

: a hamlet and an

archaeological site An archaeological site is a place (or group of physical sites) in which evidence of past activity is preserved (either prehistoric or historic or contemporary), and which has been, or may be, investigated using the discipline of archaeology and ...

about southwest of the country's capital,

Tbilisi Tbilisi ( ; ka, თბილისი ), in some languages still known by its pre-1936 name Tiflis ( ), is the capital and the largest city of Georgia, lying on the banks of the Kura River with a population of approximately 1.5 million pe ...

. Since then, five early hominin skulls have been discovered at the site. Skull 5, found in 2005, is the most complete specimen of them all. After further analysis, it was coupled with its

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

(D2600) found 5 years earlier. The final analysis of the discovery took many years and was only published in 2013.

Description of the skull

Despite a brain volume the size of a large

Australopithecus ''Australopithecus'' (, ; ) is a genus of early hominins that existed in Africa during the Late Pliocene and Early Pleistocene. The genus ''Homo'' (which includes modern humans) emerged within ''Australopithecus'', as sister to e.g. ''Australopi ...

male, () all the characteristics of

are clearly visible on Skull 5. The

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or sku ...

sizes of the other Dmanisi skulls are between and . The cranial superstructures of Skull 5, which are prominent and massive, suggest that it was probably a male. Its face is one of the largest of any human ancestor discovered to date. The

zygomatic arch In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomat ...

es are massive with the right one displaying many traces of deformations, probably due to fractures and injuries. Researchers estimate that the height of the individual was between and and his weight between and .

Dating

Until the 1980s, scientists assumed that

hominins The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera '' Homo'' (humans) and '' Pan'' (chimpanzees and bonobos) and in standard usage excludes the genus '' Gorilla'' (gorillas). The ...

had been restricted to the African continent for the whole of the

Early Pleistocene The Early Pleistocene is an unofficial sub-epoch in the international geologic timescale in chronostratigraphy, being the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently estimated to span the time ...

(until about 0.8 Ma), only migrating out during a phase named Out of Africa I. Thus, the vast majority of archaeological effort was disproportionately focused on Africa.Lahr, M.M., 2010. “Saharan Corridors and Their Role in the Evolutionary Geography of ‘Out of Africa I’”. In: A. Baden et al. (Eds.), Out of Africa I: The First Hominin Colonization of Eurasia. Springer Netherlands, 27–46. The Dmanisi archeological site is the earliest hominin site out of Africa and the analysis of its artifacts showed that some hominins, chiefly the ''

Homo erectus georgicus The Dmanisi hominins, Dmanisi people, or Dmanisi man were a population of Early Pleistocene hominins whose fossils have been recovered at Dmanisi, Georgia. The fossils and stone tools recovered at Dmanisi range in age from 1.85–1.77 million y ...

'' had left

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

as far back as 1.85 million years ago. All of the 5 skulls are roughly the same age. Consequently, the paleontological significance of the

dating Dating is a stage of romantic relationships in which two individuals engage in an activity together, most often with the intention of evaluating each other's suitability as a partner in a future intimate relationship. It falls into the catego ...

of the Dmanisi skulls is major. It is worth noting that it was not associated with the discovery of skull 5, but with another specimen found at the same site, the Dmanisi Skull 3, also known as D2700.

Controversy and significance of the discovery

The Dmanisi skulls, especially Skull 5 with its comparatively tiny brain compared to other skulls found at the site, suggests that the earliest species of the genus ''

'' were actually subspecies of the species ''erectus''. The variation in

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

of all the Dmanisi skulls is so large that had they been discovered on different archaeological sites, they most likely would have been classified as different species. However, all Dmanisi skulls have the same age and have been found at exactly the same place. Faced with the wide variation between Skull 5 and the other Dmanisi skulls, Georgian and University of Zurich researchers were prompted to examine normal variations in modern human skulls and chimpanzees skulls. They found that while they looked different from one another, the great variations among all Dmanisi skulls were no greater than those seen among modern people and among chimpanzees. Consequently, it was entirely possible that such a discrepancy could be found in ''Homo erectus''. This discovery led the scientists to suggest that two species of early hominins, ''

'' and ''

'', were actually both ''

''. This is an ongoing debate among the scientific community.

List of Dmanisi 5 specimens

The five Dmanisi skulls are named: * D2280 (skull 1) * D2282/D211 (skull 2) * D2700/D2735 ( skull 3) * D3444/D3900 ( skull 4) * D4500/D2600 (skull 5)

References