DNA research helps understand how the Americas were first populated

Brad Lepper

Source - http://www.dispatch.com/news/20170402/archaeology-dna-research-helps-understand-how-americas-were-first-populated

Human history is written in our DNA.

Biological anthropologists Connie Mulligan, of the University of Florida, and Emoke Szathmary, of the University of Manitoba, consider how genetics informs our current understanding of the population history of the Americas in the latest issue of the American Journal of Physical Anthropology.

The ancestors of American Indians diverged from their Eurasian source populations sometime after 40,000 years ago. These people entered Beringia, the large land mass that connected Asia to North America during the Pleistocene Epoch, but could not move into North America because massive glacial ice sheets blocked their way.

For perhaps as much as 15,000 years, they were isolated on America’s doorstep.

During this period, several distinctively American genetic lineages became established. Four of these, identified by the letters A, B, C and D, occur across North and South America. A fifth, X2a, is restricted to North America.

We know these lineages developed during the extended layover in Beringia because they have been identified in the DNA of the most ancient American Indian human remains yet discovered.

Once the climate began to warm around 16,000 years ago, the glaciers began to recede and the various groups living in Beringia moved southward initially along the Pacific Coast in “a single, rapid expansion into the Americas.”

The quickness of this dispersal of many small groups into the vast and varied environments of two continents accounts for most of the subsequent diversification of languages and cultures that we see in the historic era.

In a paper published last year in Current Opinion in Genetics & Development, Pontus Skoglund and David Reich, both with Harvard Medical School, cite evidence for a small “Australasian” genetic signature among the first Americans, which they refer to as “Population Y.” But it’s not yet clear when this distinctive DNA was introduced into the indigenous American gene pool.

Skoglund and Reich acknowledge that sorting out the population history of the Americas will require “information from anthropology, linguistics, archaeology and sociology.” It is especially important to involve contemporary American Indians in that process because “their perspectives have been underrepresented in these studies in the past.”

Mulligan and Szathmary suggest that one reason American Indians might have been reluctant to become involved in genetic research is that the results commonly are framed in ways that many find “threatening to their identity and interests.”

As an example, Mulligan and Szathmary suggest that the use of the term “migration” to describe the initial movement of peoples from Asia into the Americas can be interpreted to imply that indigenous Americans are simply another immigrant population with no special rights to the lands their ancestors were the first to discover.

Mulligan and Szathmary suggest we stop using the word “migration” to describe a process that involved “occupation over several millennia of a consolidated Asian-American land mass, where people differentiated from their source populations, evolving the molecular genetic markers that identify their descendants today as ‘American.’ ”

What they’re proposing isn’t a matter of arbitrary political correctness, but instead reflects the simple truth that “words matter in conveying respect for the populations whose history we study.”