Molecular Anthropology

The Y chromosome, which determines male sex, does not undergo recombination along most of its length. Instead, it passes intact from father to son. A man's Y chromosome, therefore, is a more-or-less exact copy of the one possessed by his father, grandfather, great-grandfather, and so on back through time. Like any other DNA segment, it may mutate, and any changes it accumulates are faithfully passed along as well. Two brothers are likely to have exactly the same Y chromosome sequence. Two men whose last common male ancestor was ten generations ago, however, are likely to have slightly different sequences. Comparison of the sequences of two Y chromosomes, therefore, can show how closely related two males are.

Skulls from a Neandertal (left) and an anatomically modern human Cro-Magon (right). Molecular anthropologists analyze modern and ancient DNA to determine how the Neandertal is related to modern humans.

Y chromosome analysis has been used to track migration of human populations, and to study the relatedness of modern populations. For instance, Jews and Palestinian Arabs derive from a common ancestral population that lived in the Middle East about 4,000 years ago. Recent studies have linked the ancestors of American Indians to several small populations in Siberia, confirming the predominantly Asian origin of American Indians and refining the understanding of their migration history. Many other similar studies have been performed, providing an increasingly clear (and complex) picture of human migration and mixture.