Homo georgicus is a species of Homo that was suggested in 2002 to describe fossil skulls and jaws found in Dmanisi, Georgia in 1999 and 2001, which seem intermediate between Homo habilis and H. erectus. A partial skeleton was discovered in 2001. The fossils are about 1.8 million years old. The remains were first discovered in 1991 by Georgian scientist, David Lordkipanidze, accompanied by an international team which unearthed the remains. Implements and animal bones were found alongside the ancient human remains.
History[]
In 1991, an expedition to Dmanisi uncovered animal bones, stone tools and a mandible (the latter by a team led by Medea Nioradze and Antje Justus). Heads of the expedition, Abesalom Vekua and David Lordkipanidze, were alerted of this the next morning and the mandible was fully freed by the end of the day. The heads and Leo Gabunia described this fossil back at Tbilisi. They recovered it as an indeterminate hominid. Dmanisi was further excavated but hominin remains were rare. In 1997, the right third metatarsal was found in the same layer. In May 1999, more bones were found. Extended rainfall damaged remains. Gocha Kiladze found a coin-sized skull fragment. Further fragments were found when Kiladze, Vekua, Lordkipanidze, Kakha Kakhiani and the head of the 1999 expedition found disarticulate fragments that formed a whole skull. In that same year, a well-preserved skull was recovered intact.
Description[]
H. georgicus has a cranial capacity of 546-775 with an average of 631. This overlaps Homo habilis and falls below Homo erectus. Skulls 1-4 have an encephalization quotient of 2.6-3.1, similar to the former and Australopithecines and the lower end of the latter. Skull 5 has an encephalization quotient of 2.4, within the range of Australopithecus. A well-developed brow, sagittal keeling, large orbits, premolars of the upper jaw having single roots and an angulated cranial vault distinguish them from Homo habilis. Skull 5 is the only complete skull, having a large prognathic face and a small braincase. These and large teeth make for a combination previously unseen in Homo, and were previously used to split them as species; if the skull were fragmented and split between 2 localities, they would have been split. The braincase is similar to Homo erectus. Skull 5 shows that small brains and large faces and a prognathic, robust morphology are within the range of the Dmanisi specimens. They were small-brained with large brows and a stature, mass and limb proportions at the lower Homo sapiens range.
H. georgicus was smaller than Homo erectus, possibly due to being more primitive or being adapted to a different region. The limbs are comparable to Homo sapiens and sometimes to Australopithecus garhi. The absolute length of the legs is most similar to Homo than australopiths, with the leg length and the metatarsal morphology not as derived as Homo erectus, which may suggest improved walking and running was not a sudden evolution, but continued slowly through the Early-Middle Pleistocene. Humeral torsion is quite low in Dmanisi, indicating a different arm movement and orientation, further suggesting a habitual supination and a more laterally-placed shoulder girdle. H. georgicus were very capable of extended movements, and low torsion may be a basal trait in Homo. The spine is more similar to Homo sapiens and early Homo erectus than to australopithecines. Lumbar lordosis is present in these vertebrae. The facet joints and the spinal flexion range are more similar to Homo sapiens, which indicates increased compressive loads, and in-turn, capable running and long-range walking. The feet were more medially oriented, which would have distributed weight more evenly. The feet bear modern morphology. Ian J. Wallace, Brigitte Demes, William L. Jungers, Martin Alvero and Anne Su (2008) state too little is known of these elements to reconstruct the feet for sure, believing a pelvis and more pedal bones are required. An undescribed juvenile skeleton from Dmanisi that is not directly associated with adults was announced in 2016.
Classification[]
D211 was described by Gabunia and Vekua (1995) as a basal Homo erectus based on dental similarities with Homo erectus. Günter Bräuer and Michael Shultz (1996) noted basal and derived traits and included the population was derived, despite age. Antonio Rosas and José Bermúdez De Castro (1998) suggested they should be H. sp. indet. (aff. ergaster). Gabunia et al. (2000) described Skulls 1 and 2 as similar to Homo erectus and thought many traits suggest they were similar (brow, proportions, post-orbital constriction and cranial vault height and thickness). Thus, the analysis placed them into H. ex. gr. ergaster, noting that they may have been forerunners for Homo erectus and the ancestor to Homo sapiens.
Vekua et al. (2002) described Skull 3 and its mandible, finding a resemblance to Homo habilis in brain size and facial characters consitent with small Homo erectus. Gabunia, Vekua, Marie-Antoinette de Lumley and Lordkipanidze (2002) describe D2600 as a jaw with proportions differing from all other Hominins, with a mosaic of characters blended from Australopithecus, Homo erectus and early Homo. Thus, they coin H. georgicus as a descendant to Homo habilis or Homo rudolfensis, before Homo erectus emerges. Sang-Hee Lee (2005) supports that the Dmanisi hominins are the same species, but does not specify which. Lordkipanidze et al. (2006) described Skull 4 and its jaw, noting similarity to all others except, possibly, for D2600. Tehy find it to be ancestral to Homo erectus and also note the subspecies (most of which are now disused or sunken into Homo erectus). Skulls 1-4 and D2600 were analyzed by G. Philip Rightmire, Lordkipanidze and Vekua (2006) conclude they are the same species, with D2600 as tentative. They find them to be similar to Homo habilis (via size, cranial capacity) and Homo erectus in far more characters. Thus, they find primitive features to be retentions. Rightmire, Lordkipanidze and Vekua conclude the habline features are plesiomorphic and retentions, with no reason to exclude them from Homo erectus. Vekua then supported D2600 as a distinct species, though others were unsure; Vekua preferred it keep the name H. georgicus. Matthew M. Skinner, Adam D. Gordon and Nicole J. Collard (2006) compared skulls, finding sexual dimorphism of a greater expected degree, suggesting this: either they were 1 taxon with high sexual dimorphism of uncertain inclusion in Homo, or that D2600 should be split. In 2008, a more detailed analysis by Rightmire, Lordkipanidze and Adam Van Arsdale conclude an excessive dimorphism rate comparable to gorillas, as a 1 species. Lordkipanidze, Vekua, María Martinón-Torres, José María Bermúdez de Castro, Aida Gómez-Robles, Ann Mergvelashvili and Leyre Prado (2008) analyzed the teeth of Skulls 2 and 3; they find a mosaic of Australopithecus, [[Homo erectus and Homo habilis-like traits. D2600 diverges in size and root morphology, though, noting Homo habilis does have dental dimorphism. P. James Macaluso Jr. (2010) concludes Skulls 2 and 3 are the same taxon, but D2600 is tentative.
Lordkipanidze et al. (2006) describe Skull 5 as the same individual as D2600, as the same taxon as the rest with variation similar to Pan and Homo sapiens. They find orthognathics to be women or subadults and prognathics to be men. They use this to suggest that some hominid species are actually variation of known species, and, in-turn, synonymizing Homo erectus. They find it to be from a migration of Homo erectus from aAfrica, using the quadrinomial name H. erectus ergaster georgicus. Jeffrey H. Schwartz, Ian Tattersall and Zhang Chi (2014) respond, rejecting that they are the same taxon and suggest their quadrinomial name is invalid as per the ICZN. They also question their methods and how they differentiate species. They find Skull 5 should keep the name H. georgicus, stating that rejecting this idea is a "radical proposition to which few would subscribe". The other side responds in 2014, reaffirming that it is 1 species and that if what Schwartz et al. (2014) was true, 4 species would be contemporaneous, that they ignored data deliberately and that the ICZN actual has no regulation over quadrinomial names and it should not be dismissed. Skull 5 was analyzed in 2017 and compared to Paranthropus boisei, Homo sapiens and other plesiomorphs, finding that all remains are of one taxon. They question species diversity in Homo and do not refer the remains to any known species, noting a "continuum of forms". In this, they mean Skull 5 shares features with Homo habilis and 1, the largest brain, with Homo erectus; Homo erectus and Homo habilis are hypothesized to constitute of a single lineage that emerged in Africa and spread into Eurasia. They suggest the Dmanisi hominins are of an anagenetic sequence descended from Homo habilis but ancestral to Homo erectus, nearer to the base of the Homo erectus lineage and separate from Homo habilis.
Here, the Dmanisi hominins are classified as H. georgicus on the assumption that they are distinct and represent a single species. The presence of "superarchaic" genes within the genome of Neanderthals and Denisovans, shared by a small amount of modern humans in West Africa, suggests that their last common ancestor interbred with a basal species that had been living in Eurasia since at least 1.9 million years ago. They speculate that this population was likely the same as that of Dmanisi. The name Homo dmanisensis was used once by Otavio Barduzzi Rodrigues da Costa to refer to this species once, but never again.
Paleoecology[]
Technology[]
10,000 Oldowan tools are known from Dmanisi.
Society[]
Lordkipanidze believed H. georgicus used aggressive scavenging (throwing small rocks at predators to steal their game). It is also plausible power scavenging was employed in groups for protectoin, possibly leading to kinship-dependent social cooperation arising.
Paleopathology[]
Skull 4 is an individual who has no remaining teeth but one, who lived a long time after losing their teeth. Though it would have technically been possible to live by themselves, they were likely aided by group members. They may have eaten animal brains or marrow to survive. D2280 bears 4 ovular lesions on the frontal, left parietal and occipitals, which are indicative of trauma, cysts, metastatic cancer and infectious disease. Additionally, a large, shallow depression with slightly elevated boundaries and being concave so that the diploë are lacking or absent sits on the left parietal; this is very likely to be a result of a trauma injury. Two other depressions on the left side of the frontal and occipital may have arisen due to blunt force tauma, which makes intrapersonal violence plausible. The location and structure of the 4th lesion suggests a diagnosis of treponemal disease, which makes lesions on the cranium and especially the frontal common. Perimortem perforations on the occipital were caused by large carnivorous predators or scavenging birds. This mosaic of pathology makes this individual the first instance of trauma in Homo.
Paleoecology[]
H. georgicus may have been one of the first species to migrate from Africa. However, other scraps are known but cannot be confidently assigned to the species level. Dmanisi is deposited atop a thick volcanic layer radiometrically dated to 1.85 million years. Little time passed between this event and the Pleistocene sediments deposition. Paleomagnetic analysis determine the sediments are likely 1.77 million years old, deposited during the Upper Matuyama chron. Other animals discovered here reinforces this date. The hominin-bearing layer was dated to 1.81 ± 0.03 million years in 2010. This time in Georgia may have had depleted resources and a refuge of Hominins in this region. The geography would have been favorable to Hominins, who reached it through the Levantine corridor. Georgia may have been used as a sort of "foothold" before expanding outwards. Some tools found in Romania, Balkans and Spain share similar form to the ones at Dmanisi.
All of H. georgicus except for Skull 5 and its mandible (who are somewhat younger) are contemporaneous. They all lived near a lake shore that was formed through the damming of the Maashavera and Pinazauri rivers. This was a temperate environment that was relatively humid and forested (gallery and woodland, grasslands, bush lands, tree savannahs and rocky terrain with shrubs). Cold winters are also known to have taken place. This climate is probably comparable to a mediterranean climate. Most a=faunal remains suggest a predominatly forest-steppe ecosystem with some parts being full steppe and forest. Forests covered mountain highlands and ground along river channels with flat river valleys covered by steppe vegetation. Forests were probably the most widespread at Dmanisi since deer comprise 80% of all remains. Hackberries are found in association with Hominins at Dmanisi, so they likely fed on them. Pikas, lizards, hamsters, tortoises, hares, jackals, deer, large cats, bears, horses, rhinos, flightless birds, hyaenas, gazelles, antelopes, bison and giraffes are known from Dmanisi. The Dmanisi hominins may have accumulated due to carnivore activity. Beetroots, berries and fruit are known here. Most fossils are known from the 4th layer, including the Hominins. Layers 2 and 3 are less fossilferous, with almost no carnivores and no rodents or reptiles. This may be preservation bias or paleoecological changes based around aridisation during the Early Pleistocene.
Synonyms[]
- H. lantianensis
- H, yuanmouensis
- H. dmanisensis
- H. erectus ergaster georgicus (=Dmanisi)
- H. erectus gongwanglingensis (=Gongwangling)
- H. erectus chenchiawoensis (=Chenchiawo)
- H. erectus lantianensis (=Lantian)
- H. erectus yuanmouensis (=Yuanmou)
- H. erectus georgicus (=Dmanisi)
- Pithecanthropus erectus europaeus (=Sarstedt)
- Sinanthropus
Notable Specimens[]
- Kocabaş/Kocabas calvaria: A specimen once assigned to Homo erectus from Turkey, found within solid travertine stone as it was being sawed into tile-sized slabs for market. It was assigned to this species because it shares many traits. The endocranial surface bears tuberculosis, being the earliest disease in ancient people. As this is more common in black and brown people who live in northern latitudes, this specimen supports the idea that reduced ultraviolet radiation was a climatic variable and an "adaptive challenge" in ancient hominins during Eurasian migrations. It shares traits with BH-1 (such as a lack of derived Neanderthal characters), so it may be a H. georgicus.
- Sarstedt, Sst IV-V: A fragmented left parietal (IV) and a nearly complete temporal with interior (V) identified from the waterlogged gravel pit faunal assemblage near Sarstedt, lower Germany. It was tentatively dated through the similar specimens Dmanisi 3444 and Sangiran 2. Czarnetzki et al. (2007) assigned the specimen to Pithecanthropus erectus europaeus. This proposal was ignored. It is stated to have been associated with no industry, but the site carries 9 artifacts that were unearthered over 3 years; bifacially worked scrapers and discoidal cores typical of the Middle Pleistocene. They bear various degrees of patination and gravel contusions. It is unknown if they represent a single assemblage, since these features indicate different taphonomic processes. They do not aid in dating the skeletal fragments and may have originated elsewhere.
Artifacts[]
- Socotra: Valery Zhukov discovered the Oldowan tools from Socotra in 2008 near Hadibo, publishing a small Russian book in Moscow in 2014 to share the results of his finds and presenting ~100 photographs of the technology. In 2009, an expedition worked to discover more Oldowan near wasi Tharditror and Raquf village. Special attention was given to the former and the rock terraces between the sites. They discovered thousands of artifacts 2-3 kilometers northwest of Hamer Kahyuf hill in "two ancient workshops". This industry lacks cores and having mostly choppers of one and both sides. They found large scrabbles at the site as well. At Raquf, they present the same typological line, which allowed for linkage. Near Aihaft, one more site was found containing artifacts most similar to Hadibu valley. This suggests the presence of H. georgicus-like hominins on Socotra abusing the raw materials and water sources the land bridge-connected island provided. They did not report any Microlithic sites.