Native American Ancestry in African Americans

Many people in the United States of America have a family tradition of Native American ancestry. There is a new paper about detecting minority components in autosomal DNA. That is the stuff that comes from all eight great grandparents. The paper says that on average African American samples from a scientific dataset contain about 0.4% native ancestry. What is 0.4%?

Well, let us say the current generation was born about 1950. That was the date popular with my first anthropology teacher. Then let us call the average generation about 25 years.

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At generation 9 (or 8 generations back) there are 256 ancestors. One of these is on average about 0.39% of ones autosomal ancestry. That is close to the roughly 0.4% found by researchers. The finding indicates then that 1 in 256 of the average African American’s ancestors we Native American. If you are an African American genealogist and wish to go after that family story of Native Heritage, be of good cheer. There is likely some truth in the story.

Source

Maples, B. K., Gravel, S., Kenny, E. E., and Bustamante, C. D. (2013). RFMix: A discriminative modeling approach for rapid and robust Local-Ancestry inferenceThe American Journal of Human Genetics, 93(2):278-288.

Abstract

Local-ancestry inference is an important step in the genetic analysis of fully sequenced human genomes. Current methods can only detect continental-level ancestry (i.e., European versus African versus Asian) accurately even when using millions of markers. Here, we present RFMix, a powerful discriminative modeling approach that is faster (∼30×) and more accurate than existing methods. We accomplish this by using a conditional random field parameterized by random forests trained on reference panels. RFMix is capable of learning from the admixed samples themselves to boost performance and autocorrect phasing errors. RFMix shows high sensitivity and specificity in simulated Hispanics/Latinos and African Americans and admixed Europeans, Africans, and Asians. Finally, we demonstrate that African Americans in HapMap contain modest (but nonzero) levels of Native American ancestry (∼0.4%).