The Dmanisi hominins represent an important discovery in paleoanthropology, influencing our understanding of early human evolution. These ancient hominins, found in Georgia, have reshaped understanding of hominin dispersals beyond Africa. Dating back approximately 1.8 million years, the Dmanisi remains provide insights into early Homo and their adaptations to new environments. Their study contributes valuable information to the narrative of human origins.
The Discovery at Dmanisi
The Dmanisi site, located in the Republic of Georgia, about 85 kilometers southwest of Tbilisi, began yielding finds in the early 1990s. Archaeological explorations of medieval village ruins in the 1980s led to the discovery of older deposits containing prehistoric animal bones. In 1983, a rhinoceros tooth was identified, indicating the site was at least a million years older than the medieval period.
The first hominin jawbone was unearthed in 1991, followed by two skulls in 1999, revealing anatomical similarities to Homo erectus. These discoveries, found beneath the medieval ruins, established Dmanisi as one of the most ancient human habitation sites in Eurasia. The archaeological layers consist of pyroclastic silt and fine sand, with hominin bones recovered from layers dated to approximately 1.77 million years ago. Stone artifacts are found throughout a 40,000-year interval, with the earliest occupations at Dmanisi securely dated to shortly after 1.85 million years ago. This consistent hominin activity indicates repeated use of the site.
Distinctive Characteristics and Tools
Dmanisi hominins exhibit a unique combination of primitive and modern-like physical features. Their brain sizes averaged about 631 cubic centimeters, considerably smaller than later Homo erectus and about half the size of a modern human brain. Despite their smaller braincases, their postcranial skeletons, including the length and morphology of their legs, suggest adaptations for long-range walking and running, similar to later hominins.
Significant variability is observed among Dmanisi individuals. Five well-preserved skulls, known as Dmanisi Skulls 1-5, along with over a hundred postcranial fossils, have been recovered. For instance, Skull 5 stands out with its large, prognathic face and the smallest braincase among the Dmanisi specimens, yet this variation falls within the range expected for a single species. This morphological diversity has fueled discussions about species classification.
The stone tools found at Dmanisi are simple, Oldowan-like artifacts, similar to those found in East Africa. These tools primarily consist of simple cores and flakes, produced using direct hard hammer percussion. Dmanisi hominins utilized locally available volcanic rocks, such as basalt and andesite, for tool production, demonstrating an opportunistic approach. These basic tools suggest subsistence strategies like butchering animals, evidenced by cut marks on bones, and possibly processing plants or woodworking.
Reshaping Early Human Migration
Dmanisi discoveries have altered previous understandings of the “Out of Africa” dispersal, pushing back the timeline for hominins leaving Africa. Before Dmanisi, theories suggested a later migration around 1.0 million years ago, possibly requiring advanced Acheulean tools or larger brains. However, Dmanisi fossils, dated between 1.85 and 1.77 million years ago, demonstrate that early Homo with simpler Oldowan technology were capable of extensive dispersals.
This early date and primitive tool technology challenged the notion that advanced technological innovation was a prerequisite for hominins to migrate from Africa. Dmanisi evidence indicates that biological and ecological factors may have played a prominent role in driving these early movements. The presence of Homo in the southern Caucasus at such an early date suggests that Eurasia was occupied even before Homo erectus appears in the East African fossil record. This highlights that relatively small-brained hominins, equipped with basic stone tools, adapted to new environments outside of Africa.
Unraveling the “Homo” Lineage
Dmanisi finds have ignited debate regarding the classification of the early Homo genus. The morphological variation among Dmanisi skulls, particularly Skull 5, has led to discussions about whether they represent a single, highly variable species or multiple distinct species. Initially, some researchers hypothesized more than one hominin taxon at the site, with one massive jaw (D2600) designated as a new species, Homo georgicus.
However, later analyses proposed that all five skulls likely belong to the same species, exhibiting variations related to age and sexual differences. This interpretation suggests that what were once considered distinct species, such as Homo habilis and Homo rudolfensis, might represent the variation within a single widespread Homo lineage. This challenges traditional views of early Homo diversity and taxonomic splitting, implying a more unified evolutionary path for early humans across Africa and Eurasia.