We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time.
--T. S. Eliot, Four Quartets: Little Gidding
In an age of spacecraft and deep-sea submersibles, we take it for granted that humans are intrepid explorers. Yet from an evolutionary perspective, the propensity to colonize is one of the distinguishing characteristics of our kind: no other primate has ever ranged so far and wide. Humans have not always been such cosmopolitan creatures, however. For most of the seven million years or so over which hominids have been evolving, they remained within the confines of their birthplace, Africa. But at some point, our ancestors began pushing out of the motherland, marking the start of a new chapter in our family history.
It was, until recently, a chapter the fossil record had kept rather hidden from view. Based on the available evidence--a handful of human fossils from sites in China and Java--most paleoanthropologists concluded that the first intercontinental traveling was undertaken by an early member of our genus known as Homo erectus starting little more than a million years ago. Long of limb and large of brain, H. erectus had just the sort of stride and smarts befitting a trailblazer. Earlier hominids, H. habilis and the australopithecines among them, were mostly small-bodied, small-brained creatures, not much bigger than a modern chimpanzee. The H. erectus build, in contrast, presaged modern human body proportions.
Curiously, though, the first representatives of H. erectus in Africa, a group sometimes referred to as H. ergaster, had emerged as early as 1.9 million years ago. Why the lengthy departure delay? In explanation, researchers proposed that it was not until the advent of hand axes and other symmetrically shaped, standardized stone tools (a sophisticated technological culture known as the Acheulean) that H. erectus could penetrate the northern latitudes. Exactly what, if anything, these implements could accomplish that the simple Oldowan flakes, choppers and scrapers that preceded them could not is unknown, although perhaps they conferred a better means of butchering. In any event, the oldest accepted traces of humans outside Africa were Acheulean stone tools from a site called Ubeidiya in Israel.
Brawny, brainy, armed with cutting-edge technology--this was the hominid hero Hollywood would have cast in the role, a picture-perfect pioneer. Too perfect, it turns out. Over the past few years, researchers working at a site called Dmanisi in the Republic of Georgia have unearthed a trove of spectacularly well preserved human fossils, stone tools and animal remains dated to around 1.75 million years ago--nearly half a million years older than the Ubeidiya remains. It is by paleoanthropological standards an embarrassment of riches. No other early Homo site in the world has yielded such a bounty of bones, presenting scientists with an unprecedented opportunity to peer into the life and times of our hominid forebears. The discoveries have already proved revolutionary: the Georgian hominids are far more primitive in both anatomy and technology than expected, leaving experts wondering not only why early humans first ventured out of Africa but how.
A Dubious Debut
AS THE CROW FLIES, the sleepy modern-day village of Dmanisi lies some 85 kilometers southwest of the Georgian capital of Tbilisi and 20 kilometers north of the countrys border with Armenia, nestled in the lower Caucasus Mountains. During the Middle Ages, Dmanisi was one of the most prominent cities of the day and an important stop along the old Silk Road. The region has thus long intrigued archaeologists, who have been excavating the crumbling ruins of a medieval citadel there since the 1930s. The first hint that the site might also have a deeper significance came in 1983, when paleontologist Abesalom Vekua of the Georgian Academy of Sciences discovered in one of the grain storage pits the remains of a long-extinct rhinoceros. The holes dug by the citadels inhabitants had apparently opened a window on prehistory.