A surprising discovery under a medieval town
Beneath the ruins of a medieval Georgian village, archaeologists found something unexpected. The Dmanisi archaeological site, about 85 kilometers southwest of Tbilisi, was initially explored for its Silk Road-era history. In 1983, however, the discovery of an extinct rhinoceros tooth showed a much deeper past. A year later, primitive stone tools surfaced. The first hominin fossil, a mandible, was found in 1991. The finds culminated in the recovery of five hominin skulls between 1991 and 2005.
The fossils were located in sediment layers dated to between 1.77 and 1.85 million years old, making them the oldest undisputed human ancestors found outside of Africa. The collection includes four crania and five mandibles, representing a small community of early humans. These individuals lived alongside a diverse range of animals, including saber-toothed cats, giraffes, and giant cheetahs. The hominins themselves were small-bodied, standing around 145 to 166 centimeters tall, with a mix of primitive and modern features. Their legs were suited for long-distance walking, but their arms were more similar to those of earlier australopithecines.
One species, many faces
The five Dmanisi skulls show variation. They show a degree of variation, more than is typically seen within a single species of early hominin. Their cranial capacities range widely, from 546 to 775 cubic centimeters. The smallest, Skull 5 (D4500), has a braincase smaller than many Homo habilis specimens, while its facial structure is large and robust. Other skulls from the same site have larger, more globular braincases.
This diversity is such that if the skulls had been found in different locations, they would have been assigned to separate species, such as Homo habilis, Homo rudolfensis, and Homo erectus. Because they were all found together in the same geological layer, researchers led by David Lordkipanidze proposed they represent the range of variation within a single, highly variable population of Homo erectus. This idea challenges the practice of naming new species based on variations between individual fossils. The Dmanisi five suggest that what were once considered distinct branches on the human family tree are different faces of the same evolving lineage.