Was talking to Dave about if Egyptians were black. Started looking through DNA migration records. Don’t know the answer yet, but the records are pretty interesting. This is from the New York Times, it’s probably locked in their archives now.
Geneticists Track More of Earliest Humans’ First Itineraries
by NICHOLAS WADE
OLD SPRING HARBOR, N.Y. — Through the wizardry of modern genetics, it is possible to reconstruct the travels of the earliest humans as they moved out from their ancestral home in northeast Africa and spread around the globe. More details of these historic itineraries emerge each year, many at an annual conference of population geneticists and archaeologists at the Cold Spring Harbor Laboratory on Long Island.
Geneticists can track these emigrations because of the train of errors that slowly accumulates in certain regions of the DNA. After a population splits, the people who go east will clock up a different set of errors from those who venture west.
From the population splits implied by these error patterns, geneticists can reconstruct family trees of different lineages in the grand genealogy of humankind, and even assign rough dates to the branch points.
At this year’s conference, which ended last week, Dr. Peter Underhill of tanford showed how scholars could begin to link the data in the genome’s archive with historical events. Anatolia, the ancient name for Turkey, has long been a corridor for armies and peoples traveling between Europe and Asia.
Dr. Underhill, who has reconstructed the worldwide tree of the Y chromosome, has been analyzing the various Y chromosome lineages present in today’s Turkish population. He has found one lineage whose ancestors may have carried the agricultural revolution from Anatolia to Europe during the Neolithic era, 8,000 to 3,000 years ago. Anatolians with another lineage may be descendants of the Bronze Age Hattic culture, he said.
Curiously the Seljuk Turks, who wrested Anatolia from the Byzantine Empire in the 11th century, have left only a faint genetic signal of their presence, Dr. Underhill said. Though the conquerors imposed their language and culture over a wide region, an army of a mere 40,000 made little genetic difference to a population that had already reached 12 million by Roman times.
Just as the Y chromosome tracks the movement of men, an element called mitochondrial DNA, inherited only through the egg, traces the journeys of women. Dr. Douglas Wallace of the University of California at Irvine long ago defined and named the principal mitochondrial lineages. Only three of the 20 or so lineages, designated A, C and D, are found in northern Siberia. Given that northern Asia is essentially a big plain with no obstacle but freezing cold, Dr. Wallace wondered why none of the other lineages had made it to the far northeast.
He now believes, he said at the meeting, that the three mitochondrial lineages carry an altered form of an energy metabolism gene that may improve the body’s resistance to cold. This could explain why A, C and D are the principal lineages found in Native Americans: their ancestors, being better adapted to life in northern Siberia, would have discovered the Beringian land bridge to Alaska before it was submerged at the end of the last ice age.
Most of the available evidence suggests there was only one emigration of modern humans from Africa, a small group that left some 40,000 to 50,000 years ago and populated first Asia and then Europe. But some geneticists think there may have been an earlier exodus of people who traveled by boat along the southern Asian coasts, eventually reaching Australia. The people of Australia and Papua New Guinea are dark skinned and somewhat different from most other Asians and Europeans.
To test the idea of a southern route, Dr. James F. Wilson of University College London compared the DNA of the Dravidian-speaking, dark skinned aboriginal tribes of southern India with that of New Guinea highlanders to see if the two might be part of the same exodus. The first gene he looked at suggested they were related, but further study showed otherwise.
The distinctiveness of New Guineans could be from long-term drift, not a different route out of Africa," he said. Drift is the geneticist’s term for the random change that takes place between generations as some genetic variants become more common and others get rarer or disappear altogether.
Though natural selection is the familiar driver of evolution, drift is particularly important in small, isolated populations, like those of the first humans to leave Africa. So far it has been hard to pinpoint genes shaped by selection, most of the known examples being gene variants that confer resistance to malaria. But using new tests, scientists are finding quite a few genes that have undergone selective pressure, suggesting that drift was far from being the only shaper of early populations.
Dr. David Reich of the Whitehead Institute in Cambridge, Mass., described an ingenious method to recognize recently selected genes, based on the length of the unchanged DNA that the beneficial mutation drags along with it between generations.
A different method was described by Dr. Mark Stoneking of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. He figured that genes that differ widely among ethnic groups have probably been under selective pressure because of different diets, parasites, diseases or climates confronted by their owners.
With this approach Dr. Stoneking has found a gene that has three major variants: one dominates in Europeans, one in Africans and one in Asians. The gene, known as F13B, codes for part of Factor XIII in the cascade of blood-clotting proteins. It is not known why it should have different common forms in the three major population groups.
A broader approach, made possible by a large-scale DNA sequencing program, was discussed by Dr. Benjamin Salisbury of Genaissance Pharmaceuticals in New Haven. He too looked for genes whose variant forms have very different frequencies among races by decoding some 4,000 genes in 82 people.
Dr. Salisbury said he had found many such genes, including one that is absent from Africans and Europeans but found in 88 percent of Asians. He declined for commercial reasons to identify the gene. Genes under intense selective pressure are of great interest because those selected for disease resistance may pinpoint new targets for drug development. Other selected genes may define what it means to be human.
Linguists and geneticists last year discovered a human gene called FOXP2 which differs in two essential places from the equivalent gene in chimpanzees. The gene seems to underlie the articulation of rapidly spoken language. It must be of great importance because a single version is found in all humans. It came to light because several members of a large London family with a damaged version of the gene have severe difficulties with spoken language.
The discovery of this language gene, which seems to have arisen sometime within the last 100,000 years, lends support to a bold idea advanced by Dr. Richard Klein, an archaeologist at Stanford. He has noted the sudden appearance in the archaeological record about 50,000 years ago of many sophisticated activities, like art, long distance trade and intricate implements.
Anatomically modern humans first emerged some 130,000 years ago, and those of 50,000 years ago appear no different. So Dr. Klein believes some neural and cognitive change, most probably the development of language, occurred in Africa around this time, before the exodus to the rest of the world.
Dr. Klein describes himself as being in ‘a minority of one’ among experts on the period but notes that archaeologists tend to favor culture, not genes, to explain their findings. At last week’s meeting his opponents argued that many modern behaviors appeared well before 50,000 years ago.
“One does not need to resort to a genetic black box; it’s more likely that we are seeing a response to climate change” said Dr. Alison Brooks of George Washington University.
Dr. Sally McBrearty of the University of Connecticut described a 70,000-year-old crosshatched object recently found in the Blombos cave on the coast of South Africa as “the smoking gun” evidence that the people of that time were capable of symbolic representation.
Dr. Klein, who could not make a scheduled appearance at the conference, said in a telephone interview that the new finds had not changed his views. Similar artifacts, like mineral pigments, are known from pre-50,000-year sites in Europe, he said. But the makers of the artifacts were Neanderthals, who are not generally thought of as modern.
Before 50,000 years ago the evidence for modern behavior is rare and the dates are disputable, Dr. Klein said. After 50,000 years ago, neither is the case.
The FOXP2 gene cannot be dated precisely because it is universal. But other language genes yet to be found might be more helpful in deciding when language was acquired. “This is the only test of my theory, in the genome,” Dr. Klein said.