For those of you who don’t know, all students in UNCG’s 300+ level anthropology courses are reading a book and several articles in preparation for the Harriet-Elliott events. One of these readings, John Relethford’s “Reflections of Our Past,” has a chapter on the peopling of the Americas. Traditionally, most scholars contend that the first humans entered the Americas about 15,000 years ago (or maybe a bit earlier) and came from Asia via the Bering Land Bridge that then existed between modern-day Alaska and eastern Siberia.
According to Relethford, who was writing in 2003, the genetics strongly supports an origin of Native Americans somewhere in Asia:
1. Contemporary Native Americans and northern Asians tend to have high frequencies of the Diego blood group allele DI*A (this allele is relatively rare among other populations).
2. Based on genetic distance analysis (which takes into account the relative frequency of many different genes simultaneously to look at overall genetic difference/similarity), contemporary northeast Asian populations are most genetically similar to Native Americans.
3. Native Americans share a number of mitochondrial DNA haplotypes (sections of DNA that are inherited together as a single unit) with Asian populations (some from Siberia, some from Japan and Korea).
Relethford also discusses another interesting question: how many migrations occurred? Was it a single migration event? Two? Three? More? The genetic data seem to suggest at least two separate migration events, if not more.
Finally, when did the first colonization of the Americas take place? Here, Relethford shows that the genetic data are pretty cloudy because any estimate based on a genetic clock will be affected by population size and the overprinting of multiple migrations. Indeed, Relethford suspects that “the final determination of the age of the first Americans will be settled by archaeology and not by genetics.”