Out of Africa
Modern humans were the first hominids to populate the entire globe, after leaving Africa about 100,000 years ago. But we were not the first hominids to exit Africa. Some of our relatives began leaving that continent at least 1.8 million years ago--long before Homo sapiens evolved. Who were these first migrants? Some of our best fossil evidence for early hominid migrations comes from the Caucasus, which serves as a corridor from Africa and the Middle East into northern Eurasia. Discoveries there suggest the first hominids to leave Africa had only simple tools and relatively small brains.
Deep Under Dmanisi
Beneath the ruined medieval town of Dmanisi, in the Republic of Georgia, scientists have discovered remains of ancient rhinoceroses, saber-toothed tigers and, most remarkably, several early humans. The hominid remains are about 1.8 million years old--the oldest well-documented sample of human fossils found outside of Africa.
The First Emigrants?
Who were the first hominids to leave Africa? One leading contender is Homo ergaster. The tall body form of Homo ergaster allowed for tireless walking over long distances in the open sun. Long legs ensure an efficient stride, and a slender build allows for more efficient cooling.
The hominids of Dmanisi, however, seem to have been rather short-statured. If it turns out some had body proportions unlike those of Homo ergaster, scientists will have to reevaluate current theories about how and why hominids migrated from the continent of their origin.
Layers of bone fill the tooth sockets of a well-preserved skull from Dmanisi, showing that all but one of the teeth were lost some years before the individual died. To find soft foods that could be eaten without chewing, this hominid may have received help from others--an early example of the caring behavior typically associated with modern humans.
Artifacts found at Dmanisi--a core, a chopper and a cutting flake--are quite crude, resembling the earliest African stone tools. Apparently, hominids did not need more sophisticated technology to leave Africa and move north, as researchers once assumed.
Examine the Evidence: Dmanisi skull
Scientists have long thought the tall and relatively slender Homo ergaster was the first hominid to leave Africa, and certain fossils from Dmanisi have features in common with Homo ergaster. Yet the adult Dmanisi skull has been said to resemble slightly older, small-brained hominids from Africa. The skulls from Dmanisi are puzzlingly varied in their size and anatomical details, so more than one species may have lived in this region 1.8 million years ago.
Researchers digging at Dmanisi, in the Republic of Georgia, have unearthed hundreds of animal fossils. Like the hominids found at the site, species such as short-necked giraffes and ostriches originated in Africa. Some time before 1.8 million years ago, these adaptable creatures migrated north into the Caucasus, where they encountered Eurasian wolves and saber-toothed cats.
Predators and Providers
Carnivores such as saber-toothed cats may have helped provide meat for hominid families by killing prey and leaving parts of the carcass behind.
A large mandible, found in 2000, is much bigger and more robust than the other lower jaws known from Dmanisi, and it suggests the individual was longer-faced. This has been confirmed by a very distinctive matching cranium, discovered in 2005.