Science magazine October 8, 1999 286: 229a
To pinpoint Eve's origins, geneticists Himla Soodyall and Trefor Jenkins of the South African Institute for Medical Research and the University of the Witwatersrand in Johannesburg analyzed mitochondrial DNA (mtDNA), genetic material from the energy-producing organelles in all cells. Because after conception only the egg's mitochondria survive, mtDNA forms a continuous thread running back in time through the maternal lineage. Knowing mtDNA mutation rates, scientists can infer, by comparing DNA segments from different populations, which are the most ancient patterns.
The researchers drew blood from 100 people from two Khoisan groups and compared the mtDNA sequences with those from 50 other sub-Saharan Africans. Soodyall says the study found that some 84% of the mtDNA types they looked at were "unique" to the Khoisan and could be dated back to 120,000 years ago. This demonstrates that "some of the most ancestral signatures in mtDNA are still found in living Khoisan people," she says. The same sequences have been lost due to random mutations in other, later populations.
The findings, presented at a recent human evolution meeting at Cold Spring Harbor Laboratory in New York, complement data from the male side: Y chromosome studies had previously pegged the Khoisan among a handful of groups with Y chromosomes most closely resembling those of a common ancestor who lived in Africa 145,000 years ago (Science, 31 October 1997, p. 804). Mike Hammer of the University of Arizona, Tucson, who took part in the Y chromosome study, says the latest mtDNA work provides "important confirmation" of the team's work.
http://www.sciencemag.org/cgi/content/summary/286/5438/229a
HUMAN EVOLUTION: Y Chromosome Shows That Adam Was an African
Ann Gibbons
In the beginning, there was mitochondrial Eve--a woman who lived in Africa between 100,000 and 200,000 years ago and was ancestral to all living humans. Geneticists traced her identity by analyzing DNA passed exclusively from mother to daughter in the mitochondria, energy-producing organelles in the cell. Scientists have been searching ever since for "Adam," the man whose Y chromosome was passed on to every living man and boy. Now two international teams have found the genetic trail leading to Adam--and it points to the same time and place where mitochondrial Eve lived. Described this month at a symposium on human evolution at Cold Spring Harbor Laboratory in New York, the genetic trail is so clear that it allows researchers to compare the migration patterns of men and women tens of thousands of years ago
Science Magazine - HUMAN EVOLUTION: Y Chromosome Shows That Adam Was an African
Ann Gibbons
Science 1997 October 31; 278: 804-805.
http://www.sciencemag.org/cgi/content/summary/278/5339/804