How can you determine when and where a lineage originated? And how does the origin and spread of a lineage relate to what we think of as the origin of a population? These are rather contentious issues. According to the simplest way of thinking, current high frequency and high diversity may mark the place of origin of a lineage; but high frequency can also arise by genetic drift, and high diversity by admixture. The time can be calculated in several ways, and a wide range of mutation rates can be used, so molecular dates are much less certain than archaeological ones. In thinking about the second question, we can paraphrase the Italian geneticist Guido Barbujani: imagine that at some time in the future Indian astronauts colonise Mars, and geneticists then type their Y chromosomes. We may well find that their lineages date back to 9,000–20,000 years ago. But we would not be wise to infer that they have been living on Mars for 9,000 years.
June 01, 2008
Wise words on Y chromosome phylogeography
DENISE R CARVALHO-SILVA, TATIANA ZERJAL, CHRIS TYLER-SMITH, Ancient Indian Roots? J. Biosci. 31(1), March 2006 Link (pdf)
Labels Y chromosome