Ancestry Testing and DNA: Uses, Limits – and Caveat Emptor

Ancestry Testing and DNA: Uses, Limits – and Caveat Emptor

Council for Responsible Genetics
Volume 22, Issue 3-4 (July-August 2009)
Pages 16-18

Troy Duster, Professor of Sociology
New York University

Direct consumer use of DNA  tests for ancestry tracing has taken off in the last five years, and we are not just talking about probes for first-generation genetic lineage as in the “Who’s your daddy?” tests popularized on daytime television.  Since 2002, nearly a half-million people have purchased tests from at least two dozen companies marketing direct-to-consumer kits.  The motives for testing range from the desire for ancestral links to those who lived on other continents five-hundred plus years ago to a more modest interest in reconstructing family histories.  For many African-Americans, the quest to find a link to regions and peoples of sub-Saharan Africa can take on a spiritual or even messianic quest, at least partially explained by the fact that the Middle Passage across the Atlantic during the slave trade explicitly and purposefully obliterated linguistic, cultural, religious, political and kinship ties.  The 2006 PBS television series, African American Lives, brought this quest into sharp relief.  First celebrity and later ordinary Blacks were mesmerized by stories of DNA matches that claimed to reveal or refute specific ancestral links to Africa, to Native American heritage, and surprising to some, East Asian or European populations.

In sharp contrast, CBS’ 60 minutes aired a dramatic segment in the fall of 2007 (October 7) that portrayed a direct and sharp challenge to the claims-making about such ancestry testing.  The segment began with Vy Higgensen, an African-American woman from New York’s Harlem triumphantly affirming her connection to “new kin” (one of whom was a white male cattle rancher from Missouri).  But as the program unfolds, we see a disturbing cloud of doubt drift over the last part of the segment that ends with a less than subtle hint at specious claims.  A first test from the company African Ancestry, claims that Higgensen is linked to ancestors in the Sierra Leone, the Mende people.  She rejoices. “I am thrilled!  It puts a name, a place, a location, a people!”  But then she is shown the results of a second test, from another company, Relative Genetics, which claims that she instead has a genetic match to the Wobe tribe of the Ivory Coast.  She seems unruffled.  Yet a third test, from Trace Genetics, claims that her ancestors are from Senegal, the Mendenka.  Now she seems agitated, visibly concerned, confused – and most certainly disappointed that what began as a definitive match to a particular group or region of Africa has now turned into a “you pick which one you want to believe” game.

What can DNA tell us about our genetic lineage, and where does it fall short? What explains Vy Higgensen’s multiple results from different testing sites? Flawed methodology? Partial truths hyped as definitive findings? Did the testing companies use different methods or deploy different reference populations – or both?…

…There is a yet more ominous and troubling element of the reliance upon DNA analysis to determine who we are in terms of lineage, identity, and identification. The very technology that tells us what proportion of our ancestry can be linked, proportionately, to sub-Saharan Africa (ancestry-informative markers) is the same being offered to police stations around the country to “predict” or “estimate” whether the DNA left at a crime scene belongs to a white or black person. This “ethnic estimation” using DNA relies on a social definition of the phenotype (the observable physical or biochemical characteristics of an organism, determined by both genetic makeup and environmental influences). That is, in order to say that someone is 85 percent African, we must know who is 100 percent African. Any molecular, population, or behavioral geneticist who uses the term “percent European” or “percent Native American” is obliged to disclose that the measuring point of this “purity” (100 percent) is a statistical artifact that begins not with the DNA, but with a researcher adopting the folk categories of race and ethnicity…

Read the entire article here.

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