In 1987, a group of molecular geneticists at the University of California at Berkeley offered support for the idea that anatomically modern humans arose fairly recently in Africa, then spread out and colonized the world. The geneticists analyzed genetic samples of 147 women whose ancestors came from Africa, Europe, the Middle East, Asia, New Guinea, and Australia. By estimating the number of mutations that had taken place in the mithochondrial DNA (mtDNA) of each of these samples, the researchers concluded that
A. everyone alive today has mtDNA that descends from a woman (dubbed Mitochondrial Eve) who lived in sub-Saharan Africa around 200,000 years ago and that her descendants left Africa no more than 135,000 years ago.
B. everyone alive today has mtDNA that descends from a woman (dubbed Mitochondrial Eve) who lived in Asia around 50,000 years ago and that her descendants left Asia 100,000 years ago.
C. establishing a genetic clock to model human evolution is reliable only when focusing on 50,000 years into the past.
D. everyone alive can count the Neandertal of western Europe as their ancestor.
E. Neandertals coexisted with modern humans in the Middle East for at least 2,000 years.
Question 2
According to mtDNA analyses, when did the first modern humans leave Africa?
A. 2 m.y.a.
B. 1 m.y.a.
C. over 735,000 years ago
D. 535,000 years ago
E. no more than 135,000 years ago
A molecular clock.
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