Around the time our ancestors evolved modern body proportions—tall stature with long legs and short arms—they began to migrate out of Africa. The oldest well-known hominid fossils outside of Africa are 1.7 million years old and were discovered in the Caucasus Mountains of the Republic of Georgia, a region that serves as a corridor out of Africa and into the Eurasian continent. Over the last several years, scientists working there, at the Dmanisi site, have uncovered several hominid skulls and jawbones, as well as simple stone tools made by the early humans who once lived there.

Who were the first hominids to exit the continent of Africa? One leading contender is Homo ergaster, represented in this exhibition by the Turkana Boy specimen. Scientists believe this species—or one very similar—was the first hominid advanced enough to expand out of its traditional range.

Neither large brain size nor improved technology, however, seems to have been responsible for this population expansion. Rather, modern body proportions, which allowed for tireless walking over long distances in the open sun, may have been the key. Long legs ensure an efficient stride, and a tall, upright posture has two important advantages: only the head and shoulders receive direct sunlight while the entire body is exposed to cooling breezes.

The recent discoveries at Dmanisi, in the Republic of Georgia, support the idea that our ancestors did not need large brains and sophisticated tools to make the journey out of Africa. The hominids who lived at Dmanisi 1.7 million years ago had rather small brains and used very primitive stone tools. Paleoanthropologists are still studying the Dmanisi fossils to learn more about these early humans. Further research should help clarify what enabled our predecessors to leave Africa.