Chain
April 23rd, 2005, 10:46 PM
Searched the authoress in Science mag. FR poster may have copied it from current hardcopy of "Science".
http://www.freerepublic.com/focus/f-news/1389975/posts
http://www.sciencemag.org/cgi/search?volume=&firstpage=&DOI=&author1=Elizabeth+Culotta&author2=&titleabstract=&fulltext=&fmonth=Oct&fyear=1995&tmonth=Apr&tyear=2005&hits=10&sendit.x=44&sendit.y=9
Archaic Genes in Modern People?
Science Magazine | 2005-04-22 | Elizabeth Culotta
Posted on 04/23/2005 8:30:41 PM PDT
MILWAUKEE, WISCONSIN--About 1200 researchers gathered near the shores of Lake Michigan here from 5 to 9 April to discuss early Englishmen, the birth of modern humans, and Stone Age weapons.
In the past 15 years, a flood of genetic data has helped propel the Out of Africa theory into the leading explanation of modern human origins. DNA from mitochondria (mtDNA), the Y chromosome, and ancient humans each suggest that the ancestors of all living people arose in Africa some time after 200,000 years ago, swept out of their homeland, and replaced archaic humans around the globe without mixing with them. But at a genetics symposium, two independent groups presented data from the X chromosome hinting that modern humans interbred with other human species: The teams found possible traces of archaic hominids in our genes. "Just as the Y and mtDNA data seemed to have settled it, the new data revive the question [of interbreeding]," says Stanford University's Joanna Mountain, co-organizer of the symposium. "The controversy is not settled." Geneticists Makoto Shimada and Jody Hey of Rutgers University in Piscataway, New Jersey, presented an intriguing haplotype--a set of genetic mutations inherited together--that appears to have ancient roots in Asia rather than Africa. Shimada sequenced a 10.1-kilobase noncoding region in 659 individuals from around the world. Overall, the genetic variations were most frequent in Africa, just as expected if our ancestors were a subset of ancient Africans who migrated out of that continent. But one rare variant, appropriately named haplotype X, appeared in nine individuals from Europe to Oceania but was entirely absent in Africa. Shimada estimated that the haplotype arose 1 million years ago,
long before the modern human exodus from Africa. "Haplotype X is difficult to explain by the recent African origins model," says Shimada. "It's very old, it's rare, and it is widespread outside of Africa."
In independent work, geneticist Michael Hammer of the University of Arizona in Tucson offered a similar example. Hammer and postdoc Dan Garrigan identified a 2-million-year-old haplotype in the RRM2P4 region of the X chromosome that is common in East Asia but vanishingly rare in Africa. Their work, published 2 months ago in Molecular Biology and Evolution, raises the possibility that the haplotype arose in very ancient Asian populations, presumably of Homo erectus, an ancient human once found across Asia. "This is what you'd expect if you had introgression" between modern humans and H. erectus, Hammer said.
But at this point several other explanations are possible. Hey of Rutgers acknowledges, for example, that haplotype X may be present in Africa but was missed by spotty sampling in that continent. "Simply observing those [examples] is not sufficient to rule out one model or another," cautions Mountain. "What you need is 10 or 50 loci--one or two is not sufficient." Hammer, for one, thinks that these preliminary data do "speak to some archaic admixture. The few [loci] we've done so far are so suggestive that it gives me great excitement to continue sequencing more loci."
http://www.freerepublic.com/focus/f-news/1389975/posts
http://www.sciencemag.org/cgi/search?volume=&firstpage=&DOI=&author1=Elizabeth+Culotta&author2=&titleabstract=&fulltext=&fmonth=Oct&fyear=1995&tmonth=Apr&tyear=2005&hits=10&sendit.x=44&sendit.y=9
Archaic Genes in Modern People?
Science Magazine | 2005-04-22 | Elizabeth Culotta
Posted on 04/23/2005 8:30:41 PM PDT
MILWAUKEE, WISCONSIN--About 1200 researchers gathered near the shores of Lake Michigan here from 5 to 9 April to discuss early Englishmen, the birth of modern humans, and Stone Age weapons.
In the past 15 years, a flood of genetic data has helped propel the Out of Africa theory into the leading explanation of modern human origins. DNA from mitochondria (mtDNA), the Y chromosome, and ancient humans each suggest that the ancestors of all living people arose in Africa some time after 200,000 years ago, swept out of their homeland, and replaced archaic humans around the globe without mixing with them. But at a genetics symposium, two independent groups presented data from the X chromosome hinting that modern humans interbred with other human species: The teams found possible traces of archaic hominids in our genes. "Just as the Y and mtDNA data seemed to have settled it, the new data revive the question [of interbreeding]," says Stanford University's Joanna Mountain, co-organizer of the symposium. "The controversy is not settled." Geneticists Makoto Shimada and Jody Hey of Rutgers University in Piscataway, New Jersey, presented an intriguing haplotype--a set of genetic mutations inherited together--that appears to have ancient roots in Asia rather than Africa. Shimada sequenced a 10.1-kilobase noncoding region in 659 individuals from around the world. Overall, the genetic variations were most frequent in Africa, just as expected if our ancestors were a subset of ancient Africans who migrated out of that continent. But one rare variant, appropriately named haplotype X, appeared in nine individuals from Europe to Oceania but was entirely absent in Africa. Shimada estimated that the haplotype arose 1 million years ago,
long before the modern human exodus from Africa. "Haplotype X is difficult to explain by the recent African origins model," says Shimada. "It's very old, it's rare, and it is widespread outside of Africa."
In independent work, geneticist Michael Hammer of the University of Arizona in Tucson offered a similar example. Hammer and postdoc Dan Garrigan identified a 2-million-year-old haplotype in the RRM2P4 region of the X chromosome that is common in East Asia but vanishingly rare in Africa. Their work, published 2 months ago in Molecular Biology and Evolution, raises the possibility that the haplotype arose in very ancient Asian populations, presumably of Homo erectus, an ancient human once found across Asia. "This is what you'd expect if you had introgression" between modern humans and H. erectus, Hammer said.
But at this point several other explanations are possible. Hey of Rutgers acknowledges, for example, that haplotype X may be present in Africa but was missed by spotty sampling in that continent. "Simply observing those [examples] is not sufficient to rule out one model or another," cautions Mountain. "What you need is 10 or 50 loci--one or two is not sufficient." Hammer, for one, thinks that these preliminary data do "speak to some archaic admixture. The few [loci] we've done so far are so suggestive that it gives me great excitement to continue sequencing more loci."