New findings in Genetics.

From what had seemed like irreversible oblivion, archaeologists and population geneticists believe they are on the verge of retrieving a record of human history stretching back almost 50,000 years.

        The record, built on a synthesis of archaeological and genetic data, would be a bare-bones kind of history without individual names or deeds. But it could create a chronicle of events, however sketchy, between the dawn of the human species at least 50,000 years ago and the beginning of recorded history in 3,500 B.C. The events would be the dated migrations of people from one region to another, linked with the archaeological cultures and perhaps with development of the world's major language groups.

        The new element in this synthesis is the increasing power of geneticists to look back in time and trace the history of past populations from analysis of the DNA of people alive today. “It is astonishing how much archaeology is beginning to learn from genetics,” Dr. Colin Renfrew, a leading archaeologist at the University of Cambridge in England, said at a conference on human origins at the Cold Spring Harbor Laboratory on Long Island.

        Geneticists believe that the world outside Africa was populated by the migration of a very small number of people who left east Africa about 50,000 years ago. These modern humans, with their more advanced and inventive culture, are thought to have displaced the archaic hominids like the Neanderthals, which had emigrated from Africa many thousands of years earlier.

        These Paleolithic populations created sophisticated stone tools and left evidence of their advanced culture in the cave paintings of southern France, dating to at least 30,000 years ago.

        Geneticists are now improving their dating methods, even though the dates are still very approximate, to the point that they can begin to correlate their findings with the archaeologists'. The geneticists' first foray into human prehistory was the famous “mitochondrial Eve” article of 1987 by the late Allan Wilson, showing that when people around the world were placed on a family tree constructed from their mitochondrial DNA, the tree was rooted in African populations, in an individual who lived about 70,000 years ago.

        Though the methodology of the paper was imperfect, its result was unchanged after the method had been corrected, and geneticists have developed a growing confidence in mitochondrial DNA dates. The first major branch points in the mitochondrial Eve tree have been called the daughters of Eve and they fall in a geographic pattern with some daughters of Eve being characteristic of Africa, some of Asia and the Americas and some of Europe and the Near East.

        Dr. Richards and his colleagues have analyzed the ancestry of the present European population by looking within the major daughter of Eve branches for sub-branches that occur both in Europe and the Near East, from western Iran through Turkey and Arabia to Egypt, because the Near East is the probable source of most of the ancestral populations that entered Europe.

        The sub-branches from each region were then dated by counting the number of mutations that had occurred in the mitochondrial DNA sequence from the beginning of the sub-branch until today. If the sub-branch was older in the Near East than Europe, it indicated a migration into Europe. By this method Dr. Richards's team was able to date the migrations into Europe. They also picked up a sizable back-migration from Europe to the Near East.

        The geneticists working on the Y chromosome may eventually be able to date migrations with similar precision. The major class of mutation on the Y is so rare that the ticks of the mutation clock are too many thousands of years apart to be reliably averaged. But a second kind of mutation occurs more rapidly and the combination of the two may make a reasonable clock.

        Analysis of the Y chromosome has already yielded interesting results. Dr. Ariella Oppenheim of the Hebrew University in Jerusalem said she had found considerable similarity between Jews and Israeli and Palestinian Arabs, as if the Y chromosomes of both groups had been drawn from a common population that began to expand 7,800 years ago.

            These genetic findings are important for us in that they prove the all human beings on earth are descendents of a single set of parents who lived not very long ago, in terms of the appearance of other species.