Georgian Dmanisi archaeological discoveries - date, location, and migration debate adding to human evolution knowledge

Not only is Georgia abuzz over the opening of the renovated National Museum, but the latest discoveries in Dmanisi which may change scientists’ theories on the transitional nature of human evolution are creating a great deal of excitement. Proceedings of the National Academy of Sciences (NAS) of the United States of America published a paper on June 6 purporting to present new archaeological and geological evidence that may shift the date and geography of the beginning of human evolution. The oldest hominid may be from Eurasia (and the Southern Caucasus region in particular), not Africa, and may be an ancestor of all earlier Homo erectus. The bones unearthed in Dmanisi are similar to the oldest forms of Homo erectus, not as one would expect, an ancestor of Homo sapiens.

The previous theory of human evolution is that hominids in the form of Homo erectus emerged from Africa and migrated to Eurasia, where they then migrated back to Africa where they evolved as Homo sapiens. But if the bones in Dmanisi are Homo erectus of the earliest forms, then the theory of two-way migration changes the interpretation and debate about human evolution.

The paper presented at the NAS in America was prepared by ten American, Spanish, Italian and Georgian scientists. The scientists claim that the bones are 80,000 to 100,000 years older than the Dmanisi hominids known as “the first Europeans.” The layer of stone and bone unearthed is 1.85 million years old, which suggests that the Caucasus region was inhabited continuously over a longer period of time than previously estimated. The research shows that the Dmanisi settlement dates back to the times when Homo erectus first appeared in Africa. Thus, the Dmanisi discoveries provide the ground for a hypothesis that the oldest hominid’s evolution occurred in Eurasia, and not in Africa.

Scientists opposing this hypothesis believe that the branch of oldest hominids was forked and several types of hominids emerged simultaneously. If the “Splitters” are correct, the bones would be categorized Homo georgicus. Other opposing scientists, the “Lumpers” believe that there were several types of hominids who took a linear development, in which case the Dmanisi bones would be Homo erectus. Creationists also oppose the hypothesis, believing that hominids did not evolve, but that humans were created by God.

The unearthed bones are currently in Grenoble, France, where the inner structure will be examined with a synchrotron. Nevertheless, it is the two-way migration theory that is the focus of debate, and the Dmanisi archaeological site is of interest to international scientists.

Dmanisi is the name of the site located about 85 kilometres (53 miles) southwest of Georgia’s capital, Tbilisi, in the Kvemo Kartli region, beneath a medieval castle near the junction of two rivers. Dmanisi has been an archaeological site since the 1980s for its Bronze Age deposits. In 1991, a human jaw and teeth were found. To date, a total area of 300 square meters has been excavated.

Four hominid fossils and thousands of extinct animal bones and bone fragments, and over 1,000 stone tools were found buried between two and 4.5 meters deep. The stratigraphy of the site indicates that the hominid and vertebrate remains were laid into the cave by geological, rather than cultural, causes. Two nearly-complete hominid skulls were found and they most likely represent Homo ergaster/Homo erectus similar to the African Homo erectus from the West Turkana region (in Kenya) and possibly Hader in Ethiopia – but this is still debatable. The stone artefacts (made of basalt, volcanic material, and andesite) appear to be Oldowan chopping tools similar to tools from Olduvai Gorge in Tanzania and Ubeidiya in Israel. This has implications for the migration route – the Levantine corridor.

Post-cranial material from a partial skeleton of an adolescent individual, associated with skull D2700/D2735, and from the remains of three adult individuals, shows that the post-cranial anatomy has primitive and derived features. The primitive features include a small body, a low encephalization quotient (low brain mass) and absence of humeral torsion. The humerus is the upper arm bone between the shoulder and elbow; the more it is rotated or twisted – the amount of twist is called the torsion – the more it is ‘human’ rather than animal – i.e. the absence of humeral torsion indicates that the skeleton is closer to an animal skeleton than a human skeleton. The derived features include modern human-like body proportions and lower limb morphology indicative of the capability for long-distance travel. Therefore, the scientists who documented the find indicate that the earliest known hominids to have lived outside Africa, in the temperate zones of Eurasia, did not yet display the full set of derived skeletal features.

The UNESCO World Heritage Centre states that he palaeoarchaeological site of Dmanisi is completely authentic: several hominid individuals along with abundant remains of fossil animals and stone artefacts are well-preserved and there is no evidence of erosion and minimal weathering of hominid and artefact-bearing deposits surface. Dmanisi corresponds to all criteria defined in the International Council on Monuments and Sites (ICOMOS) comparative study for hominid sites: good chronologies; number of fossils; antiquity of finds; potential for further finds; groups of closely-related sites; and discovery and demonstration of human evolution. The ICOMOS study divides human evolution into four periods, the earliest of which is from 5 million to 1 million years BP (before the present). Among hominid sites on the World Heritage List, Dmanisi can be compared with the Atapuerca Archaeological Site in Spain and Sterkfontein Valley in South Africa. The earliest hominid remains in Atapuerca are dated from circa 800,000 BP, while Dmanisi specimens are dated to 1.75 million years ago. Dmanisi is the only European site belonging to the first period defined in the ICOMOS study.

Therefore the skeletal bones and fragments found in Georgia are consistent with the transitional nature of humans and evolutionary theory. Because the paleoanthropologists never expected to find such fossils outside of Africa, the discoveries add to the migration or geological-origin debate. Date and location, they are the issues.

http://www.nature.com/nature/journal/v449/n7160/full/nature06134.html
http://whc.unesco.org/

Ministry of Culture and Monument Protection of Georgia: http://www.mcs.gov.ge/