It's common knowledge that the ancestors of today's NativeAmericans were northern Siberian tribes that pushed into the NewWorld around 15,000 years ago via the land bridge across theBering Strait. But it's not necessarily so.A likelier scenario, published in today's Proceedings of theNational Academy of Sciences (PNAS) states that "Virologic andgenetic studies relate Amerind origins to the indigenous people ofthe Mongolia/Manchuria southeastern Siberian region."A co-author of the PNAS paper, Robert Biggar, told BioWorldToday, "In my opinion, this is probably the first time virology hasled genetics."Epidemiologist Biggar is the international AIDS coordinator in theNational Cancer Institute's viral epidemiology branch. He and hisRussian and American collaborators tracked a harmless retrovirusfrom the Amazonian jungles through the Arizona desert all the wayback, some 15,000 years, to the steppes of Mongolia.In 11 of the 38 Amerindian tribes whose blood they analyzed, theyfound the human T cell lymphotrophic virus type II (HTLV-II). Butin 10 Siberian ethnic groups studied, the viral RNA sequences werenot present.Whence The Virus In Pre-Drug Amerindians?HTLV-II inhabits the blood of drug-users who share needles, alongwith a better-known related retrovirus, HIV-1. Blood samples fromthose Amerindian tribes were collected in the 1970s by the paper'sco-author, geneticist James Neel of the University of Michigan."At that time," Biggar told BioWorld Today, "those Indians hadhad almost no contact with the outside world, yet they had thehighest HTLV-II prevalence in the world _ and obviously noHIV."Looking at the geographical picture, Biggar pointed out "thatHTLV-II seropositivity is not found just in the Central AmazonianIndians; it's also in the Guaymi of Panama, the Seminoles ofFlorida, the Pimas and Navahos of Arizona," _ in all, 11 groups."This is too widespread to have started in one place, thenpropagated throughout the Amerindian community." Ergo, it musthave been endemic among those who come across that land bridge15,000 years ago. (See BioWorld Today, Feb. 2, 1994, p. 1.)Which makes it, Biggar concluded, "a virus of extreme antiquity.And that means that retroviruses have been infecting Homo sapiensfor at least 15 millennia, and probably long before that. And thatopens a new area of research to us in the field of human biology.The more so, because drug use is an obviously new phenomenon."HIV," Biggar continued, "is obviously a different animal. It mayhave come into the human biosphere relatively recently, becauseman has had such difficulty coping with it. In contrast, HTLV-II ispretty damn benign; it has adapted to man, and man to it." Headded, "I'm not saying that the AIDS virus won't end up just asbenign, but we don't have 15 millennia to find out."Then serendipity stepped in. A virologist named William Hall, atThe Rockefeller University in New York, happened upon theHTLV-II in the blood of Mongol people in Central Asia.An anthropological geneticist, Rem Sukernik, at the Siberian branchof the Russian Academy of Sciences in Novosibirsk, (also a co-author) provided Biggar with 459 blood samples from CentralAsian indigenous people, drawn between 1974 and 1993.In the mitochondrial DNA of these samples, medical geneticistNeel, uncovered another blood-line link between the Mongolianethnic groups of the far southeastern part of Siberia and the NewWorld Amerindians. (Mitochondria, the cytoplasmic organelles thatsupply the cell's energy, have their own non-nuclear DNA,inherited through the maternal line only.)Neel found up to four mitochondrial haplogroups (gene variantslabeled A, B, C and D) in 18 Amerindian tribes, and three among96 Mongolian individuals, but none of the critical "B" type in the10 northern Siberian tribes.What's more, the PNAS paper presents evidence that thosenortheastern Siberians reached the access ramp to that land bridgeonly a few thousand years ago, whereas the big push into Alaskatook place long before that.As for whether the Mongols supplied the founder effect for themitochondrial haplotypes and/or the HTLV-II remains to bedetermined. "Maybe the Mongols also got the virus from someother group," Biggar speculated, but added, "It's also quite clearthat these are nomadic people that have nothing to do with drug use,and they are not injecting themselves."Meanwhile, he observed, "Bill Hall made another trip back toMongolia this fall. I don't know what his results are. He's activelypursuing it, and I envy his resources. It would be great toinvestigate some of the indigenous peoples, who are probablyMongol in origin, as are the New World inhabitants."Neel told BioWorld Today, "The origin of the American Indian hasbeen a chestnut, a prime bone of contention, for years. Most of theattention in the past has centered on Eastern Siberia."So if this is really incorrect, if his ancestors came from farthersouth, and the Siberians moved in later, that gives us a newpopulation to compare precisely with the American Indian, andaccount for some of the discrepancies in blood types." n
-- David N. Leff Science Editor
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