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

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

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

and classified as early ''

Homo erectus ''Homo erectus'' ( ) is an extinction, extinct species of Homo, archaic human from the Pleistocene, spanning nearly 2 million years. It is the first human species to evolve a humanlike body plan and human gait, gait, to early expansions of h ...

''. 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 ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

Homo ''Homo'' () is a genus of great ape (family Hominidae) that emerged from the genus ''Australopithecus'' and encompasses only a single extant species, ''Homo sapiens'' (modern humans), along with a number of extinct species (collectively called ...

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

hominin The Hominini (hominins) form a taxonomic tribe of the subfamily Homininae (hominines). They comprise two extant genera: ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos), and in standard usage exclude the genus '' Gorilla'' ( gorillas) ...

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 confiden ...

'' or ''

Homo habilis ''Homo habilis'' ( 'handy man') is an extinct species of archaic human from the Early Pleistocene of East and South Africa about 2.4 million years ago to 1.65 million years ago ( mya). Upon species description in 1964, ''H. habilis'' was highly ...

'' 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 recorded history, historic or contemporary), and which has been, or may be, investigated using the discipline ...

about southwest of the country's capital,

Tbilisi Tbilisi ( ; ka, თბილისი, ), in some languages still known by its pre-1936 name Tiflis ( ), ( ka, ტფილისი, tr ) is the Capital city, capital and List of cities and towns in Georgia (country), largest city of Georgia ( ...

. 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 jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

(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'' (, ; or (, ) is a genus of early hominins that existed in Africa during the Pliocene and Early Pleistocene. The genera ''Homo'' (which includes modern humans), ''Paranthropus'', and ''Kenyanthropus'' evolved from some ''Aus ...

male, () all the characteristics of

are clearly visible on Skull 5. The

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, brain-pan, or brainbox, 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 calv ...

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 (colloquially known as the cheek bone), is a part of the skull formed by the zygomatic process of temporal bone, zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the ...

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 (hominins) form a taxonomic tribe of the subfamily Homininae (hominines). They comprise two extant genera: ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos), and in standard usage exclude the genus ''Gorilla'' (gorillas), ...

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

Early Pleistocene The Early Pleistocene is an unofficial epoch (geology), sub-epoch in the international geologic timescale in chronostratigraphy, representing the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently esti ...

(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'' had left

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

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 Romance (love), romantic relationships in which individuals engage in activity together, often with the intention of evaluating each other's suitability as a partner in a future intimate relationship. It falls into the cate ...

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