On Sat, 30 Nov 2002, Karen Watters Cole <[EMAIL PROTECTED]> forwarded:
>Geneticists Track More of Earliest Humans' First Itineraries >By Nicholas Wade, NYT, 11.12.02 @ >http://www.nytimes.com/2002/11/12/science/social/12ORIG.html ><http://www.nytimes.com/2002/11/12/science/social/12ORIG.html> >EXCERPTS: >…(1) 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. > >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. This article was taken apart on the the paleoanth group I inhabit. The reporter has dumbed down the details to the point of error, although it does not alter the larger thrust of the researchers' claims: there are not, in fact, only three mtDNA lineages in northern siberia, and in fact the" lineages" are really mutation lines, which are not mutually exclusive. A single individual may carry several. They do, however, tend to group into clusters which are commonly found together in individuals, and the three cited do not cluster together, but are found in two separate clusters, A in one, C & D in the other. Among the other types found in siberia is most interestingly the X haplotype, which is otherwise almost exclusive to the americas. What the original research was actually saying was that the frequency of the appearance of these particular types is enhanced in the north, which may be due to their structure, which is in fact rather inefficient in the primary purpose of processing ATP, so that some energy is constantly lost to heat throughout their activity. Thus no matter what process is being undertaken by the cell, a little heat "tax" is always deducted, not just in those dedicated heat-producing activities undertaken by more efficient mitochondria. -Pete Vincent
