A paleoanthropological surprise
Beneath the ruins of a medieval Georgian fortress, a discovery re-wrote the story of early human migration. Archaeologists began excavating the fortress of Dmanisi in the 1930s. In 1983, their work on the medieval cellars turned up something unexpected: the tooth of an extinct rhinoceros. This find, along with other animal fossils, dated the layers beneath the fortress to the Early Pleistocene, around 1.8 million years ago. The next year, primitive stone tools surfaced, confirming an ancient hominin presence.
The first hominin fossil, a lower jaw, was found in 1991. This was followed by a series of remarkable discoveries, including five hominin skulls and over a hundred post-cranial fossils. These remains, dated between 1.77 and 1.85 million years old, represent the earliest hominins found outside of Africa. The hominins are classified as Homo erectus, sometimes using the subspecies name Homo erectus georgicus.
The five Dmanisi skulls show a startling range of physical traits. Their cranial capacity varies significantly, from as low as 546 cubic centimeters in Skull 5 to 775 cc in another—a range that overlaps with the more primitive Homo habilis. Skull 5, the most complete, combines this small braincase with a large, forward-projecting face and massive teeth, a mix of features previously unseen in a single early Homo individual.
One species, many faces
The variation among the Dmanisi skulls, all found in the same location and time period, challenges how paleoanthropologists classify early human fossils. If these skulls had been discovered in different locations across Africa or Asia, they might have been assigned to separate species, such as Homo habilis, Homo rudolfensis, and Homo erectus.
The Dmanisi population suggests that what were once considered distinct species might actually be examples of variation within a single, evolving lineage of Homo erectus. This evidence supports the idea that early Homo was one species that spread from Africa across Eurasia, diversifying in appearance as it adapted to new environments. The Dmanisi individuals were smaller than classic Homo erectus, standing around 145 to 166 cm tall, with a mix of anatomical features. They had modern-looking legs and spines adapted for long-distance walking and running, but their arms were more similar to those of earlier australopithecines.
The environment they inhabited was a temperate mix of forests and grasslands, populated by a diverse range of animals. Fossils found alongside the hominins include saber-toothed cats, Etruscan wolves, giant cheetahs, bears, and extinct species of giraffe and elephant. The hominins were both hunters and prey. They manufactured over 10,000 simple stone tools of the Oldowan tradition, the earliest known type of stone tool industry. These flake tools and choppers were used for tasks like butchering animal carcasses.