Dmanisi Hominins: Earliest Humans Outside Africa in Georgia

The Dmanisi hominins are a group of fossil humans from the site of Dmanisi in southern Georgia, dated to about 1.77 million years ago. Their five skulls are the oldest hominin fossils known outside Africa and the most complete collection of early Homo from a single place and time. Small-brained and using simple stone tools, they showed that our ancestors left Africa earlier, and in a more primitive state, than scientists had expected.

Background: a fossil site beneath a medieval town

Dmanisi lies on a rocky promontory where the Mashavera and Pinasauri rivers meet, about 85 kilometres south-west of Tbilisi. In the Middle Ages it was a prosperous town on trade routes through the Caucasus, and archaeologists began excavating its ruins in the 1930s.

In 1983 excavators digging in medieval storage pits found the bones of extinct animals, including a rhinoceros, in the sediments below. The following year stone tools were recognised. The deposits sit on a layer of volcanic basalt, which provided a maximum age, and Georgian researchers such as the palaeontologists Abesalom Vekua and Leo Gabunia began systematic work on the early levels.

The fossils come to light

In 1991 the team found a human lower jaw, catalogued D211. Its age was debated, since many scientists doubted that humans could have reached the Caucasus so early. That changed in 1999, when two skulls, D2280 and D2282, were found. Published in Science in 2000 by Gabunia and colleagues, they resembled early African Homo erectus and were dated to about 1.7 million years ago.

More finds followed under the leadership of David Lordkipanidze of the Georgian National Museum. A massive jaw, D2600, found in 2000, was named a new species, Homo georgicus, in 2002. In 2001 the small skull D2700 and its matching jaw were recovered, with a brain of only about 600 cubic centimetres.

The fourth skull, D3444, belonged to an old individual who had lost all but one tooth well before death, as the bone of the jaws had healed and reabsorbed. The fifth and most complete, Skull 5 or D4500, was found in 2005. It fitted the large D2600 jaw and was published in Science in October 2013.

What the Dmanisi people were like

The Dmanisi hominins were small. Bones from the body suggest heights of roughly 1.45 to 1.66 metres and weights of about 40 to 50 kilograms. Their brains ranged from about 546 to 775 cubic centimetres, smaller than most later Homo erectus and close to the upper range of Homo habilis.

Their legs and feet were long and suited to walking long distances, much like later humans, but their arms and shoulders kept some more primitive features. They lived in a mix of open grassland and woodland around a lake, alongside sabre-toothed cats, wolves, giant cheetahs, hyenas, horses, deer and ostriches. Some hominin bones carry carnivore tooth marks, a reminder that they were sometimes prey.

The stone tools at Dmanisi are simple flakes, choppers and cores of the kind known as Oldowan. There are no Acheulean hand axes. Cut marks on animal bones show that the hominins butchered meat, whether by hunting or by scavenging the kills of large predators.

Dating the site

Dating relies on several methods. The basalt beneath the deposits has been dated to about 1.85 million years ago. Magnetic reversals recorded in the sediments and the types of animal fossils also constrain the age.

A 2011 study led by Reid Ferring, published in PNAS, concluded that people used the site from about 1.85 to 1.78 million years ago, with the hominin fossils in layers of about 1.77 million years. This makes Dmanisi a few hundred thousand years older than the earliest secure human sites in Europe and broadly contemporary with early Homo erectus in Africa.

The debate over early Homo

Dmanisi challenged the idea that only large-brained, long-legged hominins with advanced tools could leave Africa. Its inhabitants had small brains and simple tools, which suggests that the first dispersal happened soon after the genus Homo appeared, and perhaps before Homo erectus fully took shape.

The skulls are also remarkably varied. Skull 5 combines a tiny braincase with a large, projecting face, while D2700 is small and delicately built. In 2013 Lordkipanidze, G. Philip Rightmire and colleagues argued that, because all five lived at roughly the same time and place, these differences reflect variation within one population. If so, they suggested, several African species of early Homo might also be variants of one evolving lineage.

That conclusion is contested. Other researchers argue that the Dmanisi skulls are more varied than one species would be, or that the comparison cannot settle the status of African fossils. Most now classify the Dmanisi fossils as an early form of Homo erectus, sometimes called Homo erectus georgicus.

Myths and facts

Myth: Dmanisi proves that humans evolved in Asia. The fossils show an early presence outside Africa, not an Asian origin. Older Homo fossils and tools are known from Africa, and most researchers see Dmanisi as part of an early dispersal from there.

Fact: the toothless skull may hint at social support. The elderly individual survived for years without teeth. Some researchers suggest that others helped by sharing or preparing food, though this cannot be proved.

By the numbers

The site today

Excavations at Dmanisi have continued for decades, run by the Georgian National Museum with international partners, and the site has become a training ground for students from many countries. Visitors to the Dmanisi museum-reserve can see both the medieval ruins and the area where the fossil-bearing layers were excavated beneath them.

The original skulls are kept in the Georgian National Museum in Tbilisi, while casts are displayed in museums around the world. Besides the five skulls, the site has produced jaws and many bones from the rest of the body, belonging to at least several adults and adolescents. Together with tens of thousands of animal bones and stone artefacts, they make Dmanisi one of the richest early Pleistocene sites anywhere.

The finds also helped raise the profile of Georgian science after independence in 1991. Lordkipanidze, who directed the excavations, later became director general of the Georgian National Museum, and the Dmanisi skulls are among the country’s best-known national treasures.

Timeline

• c. 1.85 million years ago: Earliest stone tools at Dmanisi, just above the basalt.
• c. 1.77 million years ago: Hominins whose skulls survive live and die at the site.
• 1983: Bones of extinct animals found beneath the medieval town.
• 1991: The first human jaw, D211, is found.
• 1999: Skulls D2280 and D2282 are discovered and published in 2000.
• 2002: The large jaw D2600 is named Homo georgicus.
• 2005: Skull 5 (D4500) is found.
• 2013, October: Skull 5 is published in Science.

Why it matters

Dmanisi pushed the human story beyond Africa to about 1.8 million years ago and showed that the first travellers were small-brained hominins with simple tools. It also forced scientists to reconsider how much variation an early human species could contain.