Karen, Further to the articles you posted on 'races', here's an interesting one from the Wall Street Journal. For a subject of this nature, it's a little ancient (10 September 1993) but still largely correct as far as I know.
Keith <<<< STRANDS OF TIME by Jerry E. Bishop Variations in DNA fragments hint that some American natives may hail from Polynesia St. Louis -- Douglas C. Wallace can see the future in a tiny strand of DNA. . . . But he also can peer deep into the past. He has looked back more than 100,000 years to the first humans in Africa. And recently, as a gathering here of science reporters, he painted a picture of prehistoric migrations emerging from DNA that is exciting anthropologists. The scene depicts groups of prehistoric, intrepid mariners moving, not out of Siberia as anthropologists have long assumed, but out of Southeast Asia across the Pacific into the Americas 6,000 to 12,000 years ago. If this picture is accurate, it makes many American Indians distant cousins of the Polynesians. Dr. Wallace's crystal ball is a unique fragment of DNA hidden in every human cell. This clairvoyant DNA is distinct and separate from the long strings of DNA that house almost all human genes in the cell nucleus. It resides, instead, in an outlying compartment called a mitochondrion. Hence its name: mitochondrial DNA, or simply mtDNA. The mtDNA contains a mere 37 genes compared with the 50,000 to 100,000 genes in nuclear DNA.* And these few mtDNA genes are devoted largely to the mitochondria's principal job of producing chemical energy for the thousands of second-by-second chemical reactions in a cell. Yet, astonished medical researchers are finding that defects in this snippet of DNA can cause human disease. And, to the surprise of anthropologists, mtDNA is turning into a kind of biological Rosetta stone for decoding human origins. Loud Ties, Deep Theories Few scientists studying mtDNA are probing deeper -- and risking more -- than Doug Wallace, a professor of genetics and molecular medicine at Emory University in Atlanta. . . . Clearly, mtDNA has become Dr. Wallace's consuming, almost obsessive interest. . . . Yet this detour into anthropology via mtDNA isn't without controversy. Dr. Wallace, for example, subscribes to the much-publicized "Eve hypothesis," in which a reading of mtDNA indicates modern humans originated in Africa 100,000 to 200,000 years ago. Some anthropologists retort that mtDNA is an unreliable clock for timing human evolution, and that the fossil evidence shows modern humans evolved much earlier than mtDNA indicates.** But it is another strange property of mitochondria that unexpectedly thrust the young scientist into the study of human origins. Humans inherit two copies of the nuclear genes, one from each parent. But only the mother's mitochondrial genes are passed on to the child for reasons still not fully understood. Thus, every person's mtDNA is descended in a direct line through female ancestors. There isn't any DNA from the father's side of the family mixed in to confuse the line of descent. This phenomenon of maternal inheritance had been seen in animals but it was a young Doug Wallace who showed it occurred in humans in a series of experiments in 1979 at Stanford University in Palo Alto, Calif. Dr. Wallace . . . saw in this maternal inheritance a way to tell how closely groups of people are related. As mtDNA is passed down from mother to daughter, innocuous alterations or mutations are bound to occur. Over a few thousand years, groups of people who live together and intermarry will accumulate distinctive patterns of these mutations. Continental Divide In 1981 Dr. Wallace headed a Stanford research team that found that ethnic groups could be identified and linked to their continent of origin by the mutation patterns in their mtDNA. Moreover, by determining how often these telltale mutations occurred, it was possible to calculate how long ago certain groups stopped intermarrying and separated, each going off to develop its own unique pattern of mtDNA mutations. "Each continent had a different pattern" of mtDNA mutations, Dr. Wallace recalls of his research findings. Africans had mtDNA variations that distinguished them from Asians who, in turn, had variations that distinguished them from European-American Caucasians. "That's when I knew we had an anthropological story," he says. . . . Dr. Wallace began studying the mtDNA of Native Americans in the mid-1980s in hopes of resolving a long-raging debate over when prehistoric peoples entered the Americas. The presumption long has been that the ancestors of Native Americans came from Siberia. But anthropologists have argued for year over how many, and when, such migrations occurred. The mtDNA analyses are showing that the ancestors of the Amerinds, who comprise most Native Americans, entered the Americans in a single migratory wave 20,000 to 40,000 years ago, Dr. Wallace and his Emory colleagues . . . reported last year. This puts humans in the Americas long before a fluted stone-spear point -- the oldest American tool ever found -- was dropped by a prehistoric dweller near Clovis, N.M., 11,000 years ago. The researchers also found that ancestors of the Navajo, Apache and other members of a Native American group, known collectively as the Na-Dene, are latecomers; they entered the continent in a second migration a mere 5,000 to 10,000 years ago, the research indicates. Polynesian Links? To their surprise, however, the researchers found that native Siberians lack one peculiar mutation that appeared in the Amerinds 6,000 to 10,000 years ago. This raises the question of where, if not from Siberia, this mtDNA originated. It turns out, Dr. Wallace says, that this particular mutation pattern is also found in aboriginal populations in Southeast Asia and in the islands of Melanesia and Polynesia. This hints at what may have been "one of the most astounding migrations in human experience," he says. A group of ancient peoples moved out of China into Malaysia where they became sailors and populated the islands of the South Pacific. Then some 6,000 to 12,000 years ago these ancient mariners made it to the Americas. "I don't know how they came," Dr. Wallace says. "They either came across the Pacific to Central and South America or they went up the east coast of Asia and across the northern Pacific to Alaska and Canada," he says. He already is examining mtDNA samples from natives of the Kamchatka Peninsula north of Japan to see if there is any mtDNA trace of these ancient sailors. >>>> *(KH -- we now know that there are only about 30,000 human genes.) ** (KH -- the apparently contrary evidence is now reconciled by supposing that some catastrophe occurred about then which caused a severe bottleneck down to a few hundred individuals.) ---------------------------------------------------------------------------- ------------ Keith Hudson, General Editor, Handlo Music, http://www.handlo.com 6 Upper Camden Place, Bath BA1 5HX, England Tel: +44 1225 312622; Fax: +44 1225 447727; mailto:khudson@;handlo.com ________________________________________________________________________
