Dmanisi is the name of a very old archaeological site located in the Caucasus of the Republic of Georgia, about 85 kilometers southwest of the modern town of Tbilisi, beneath a medieval castle near the junction of the Masavera and Pinezaouri rivers.
Five hominid fossils, thousands of extinct animal bones and bone fragments, and over 1,000 stone tools have been found to date, buried in about 4.5 meters (14 feet) of alluvium. The stratigraphy of the site indicates that the hominid and vertebrate remains, and the stone tools, were laid into the cave by geological rather than cultural causes.
The pleistocene layers have been securely dated between 1.0-1.8 million years ago; the types of animals discovered within the cave support the early part of that range. Two nearly complete hominid skulls were found, and they were originally types as early Homo ergaster or Homo erectus. They appear to be most like African H. erectus, as in Koobi Fora or West Turkana, although some debate exists. In 2008, the lowest levels were redated to 1.8 mya, and upper levels to 1.07 mya.
The stone artifacts, primarily made of basalt, volcanic tuff and andesite, are suggestive of Oldowan chopping tool tradition, similar to tools from Olduvai Gorge, Tanzania; and similar to Ubeidiya, Israel. Dmanisi has implications for the original peopling of Europe and Asia by H. erectus, in that the path from Africa to the rest of the world may be postulated via a "Levantine corridor".
In 2011, scholars led by excavator David Lordkipanidze debated (Agustí and Lordkipanidze 2011) the assignment of the Dmanisi fossils to Homo erectus, H. habilis, or Homo ergaster. Based on brain capacity, between 600 and 650 cm, Lordkipanidze and colleagues argued that a better designation might segregate Dmanisi into H. georgicus. Further, the Dmanisi fossils are clearly of African origin, as their tools conform to mode one in Africa, associated with Oldowan, at 2.6 million years ago, some 800,000 years older than Dmanisi. Lordkipanidze argues that it must have been significantly longer ago than Dmanisi that humans left Africa.
Lordkipanidze's team (Ponzter et al. 2011) also report that given microwave textures on molars from Dmanisi suggests that the dietary strategy included softer plant foods such as ripe fruits and possibly tougher foods.
Complete Cranium: and New Theories
In October of 2013, Lordkipanidze and colleagues reported on a newly discovered fifth and complete cranium including its mandible, along with some startling news. The range of variation among the five crania recovered from the single site of Dmanisi pretty closely matches the range of variation of all the Homo skulls in evidence existing in the world about 2 million years ago (including H. erectus, H. ergaster, H. rudolfensis, and H. habilis). Lordkipanidze and colleagues suggest that, rather than considering Dmanisi as a separate hominid from Homo erectus, we should keep the possibility open that there was only one species of Homo living at the time, and we should call it Homo erectus. It is possible, say the scholars, that H. erectus simply exhibited a much larger range of variation in skull shape and size than, say, modern humans do today.
It's tricky business, retooling what we understand of evolution, and one that requires the recognition that we have very little evidence from this period so long ago in our past and that evidence needs to be reexamined and reconsidered from time to time. Since this is well out of my area of expertise, I recommend a few sources for further investigation: John Hawks's The new skull from Dmanisi amd Adam Van Arsdales' The new (wonderful) Dmanisi skull, and Jim Foley's A superb new fossil from Dmanisi, Georgia in the Panda's Thumb.
Archaeology History of Dmanisi
Before it became a world-renowned hominid site, Dmanisi was known for its Bronze Age deposits and a medieval period city. Excavations within the medieval site in the 1980s led to the older discovery. In the 1980s, Abesalom Vekua and Nugsar Mgeladze excavated the Pleistocene site. After 1989, excavations at Dmanisi were led in collaboration with the Römisch-Germanisches Zentralmuseum in Mainz, Germany, and they continue to this day. A total area of 300 square meters has been excavated to date.
Agustí J, and Lordkipanidze D. 2011. How "African" was the early human dispersal out of Africa? Quaternary Science Reviews 30(11-12):1338-1342.
Calvo-Rathert M, Goguitchaichvili A, Sologashvili D, Villalaín JJ, Bógalo MF, Carrancho A, and Maissuradze G. 2008. New paleomagnetic data from the hominin bearing Dmanisi paleo-anthropologic site (southern Georgia, Caucasus). Quaternary Research 69(1):91-96.
Gabunia L, Anton SC, Lordkipanidze D, Vekua A, Justus A, and Swisher CCI. 2001. Dmanisi and dispersal. Evolutionary Anthropology 10:158-170.
Gabunia L, Vekua A, and Lordkipanidze D. 2000. The environmental contexts of early human occupation of Georgia (Transcaucasia). Journal of Human Evolution 38:785–802.
Gibbons A. 2013. Stunning Skull Gives a Fresh Portrait of Early Humans. Science 342:297-298.
Gowlett JAJ. 2006. The early settlement of northern Europe: Fire history in the context of climate change and the social brain. Comptes rendus Palevol 5:299–310.
Lordkipanidze D, Jashashvili T, Vekua A, Ponce de León MS, Zollikofer CPE, Rightmire GP, Pontzer H, Ferring R, Oms O, Tappen M et al. 2007. Postcranial evidence from early Homo from Dmanisi, Georgia. Nature 449:305-310.
Lordkipanidze D, Ponce de León MS, Margvelashvili A, Rak Y, Rightmire GP, Vekua A, and Zollikofer CPE. 2013. A complete skull from Dmanisi, Georgia, and the evolutionary biology of early Homo. Science 342:326-331.
Mgeladze A, Lordkipanidze D, Moncel M-H, Despriee J, Chagelishvili R, Nioradze M, and Nioradze G. 2011. Hominin occupations at the Dmanisi site, Georgia, Southern Caucasus: Raw materials and technical behaviours of Europe's first hominins. Journal of Human Evolution 60(5):571-596.
Pontzer H, Scott JR, Lordkipanidze D, and Ungar PS. 2011. Dental microwear texture analysis and diet in the Dmanisi hominins. Journal of Human Evolution 61(6):683-687.