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The Genetic Record

The DNA Test Was Built Not to See You

You were told a DNA test proves you are “roughly three-quarters West African.” The company that produced that number wrote, in its own published methods, that the test was designed to look only for sub-Saharan Africa — and to leave North Africa out of the analysis entirely. A test built not to see you cannot tell you who you are not.

The admission

The study behind the “West African” statistic says, in its own words, that it excluded North Africa from the analysis.

The most-cited source for the “African Americans are 73–80% West African” figure is a 23andMe study published in the American Journal of Human Genetics in 2015. It is the paper the number comes from. And in its own Methods section, describing how it measured “African ancestry,” it states the limit plainly.

“Our estimates of African ancestry specifically aim to infer ancestry of sub-Saharan Africa and does not include ancestry from North Africa.”
— Bryc, Durand, Macpherson, Reich & Mountain, “The Genetic Ancestry of African Americans, Latinos, and European Americans across the United States,” American Journal of Human Genetics 96(1):37–53 (2015), Methods — PMC4289685

Read it twice. The test that is used to tell you that you are “only West African” was designed to measure sub-Saharan ancestry and to leave North Africa out. That is not a critic’s objection. It is the study’s own stated limitation. A number produced by a method that excludes North Africa cannot be used to rule North Africa out. The Empire of Morocco is North Africa. The one place the treaty class comes from is the one place the test was built not to look.

The gap

Forty percent of the maternal line has no match in the database at all.

In 2006, a peer-reviewed study in BMC Biology compared African-American maternal DNA (mtDNA, the line passed mother to child) against the reference database of sub-Saharan African lineages. Roughly forty percent of the African-American maternal lineages had no match — they could not be sourced to the sub-Saharan groups the test was built around. Four in ten maternal lines the “West African” story cannot account for. The test cannot find what it was not built to look for.

Source: Ely, Wilson, Jackson & Jackson, “African-American mitochondrial DNAs often match mtDNAs found in multiple African ethnic groups,” BMC Biology (2006).
The record

Three entries, all from the laboratories’ own published papers.

None of these were written to help you. Each is the scientists’ own record — the admission of what the test excludes, the gap it leaves, and the deepest human lineage on earth surfacing in a South Carolina man the panels had never accounted for.

2015
23andMe writes the exclusion into its own methods
The study that produced the widely repeated “West African” percentage states that its estimates “specifically aim to infer ancestry of sub-Saharan Africa and does not include ancestry from North Africa.” The most-cited number about who you are was generated by a method that, by design, could not see the place the treaty class comes from.
Source: Bryc et al., AJHG 96(1):37–53 (2015), PMC4289685, Methods.
2006
Forty percent of the maternal line: no match
Comparing African-American mtDNA to the sub-Saharan reference set, roughly 40% of maternal lineages returned no match. The story that everyone descends, wholesale, from a handful of West African source populations does not survive the maternal data.
Source: Ely et al., BMC Biology (2006).
2013
The oldest paternal line on earth, found in a South Carolina man — missing from every panel
The deepest branch of the human paternal tree, haplogroup A00, was identified in an African-American man from South Carolina (Mendez et al. 2013). It is older than the timeline the field had treated as settled, and it was absent from every reference panel until his sample forced a new branch onto the tree. It is a plain demonstration that the panels were incomplete at the very root — that the reference sets do not contain everything, and never did.
Source: Mendez et al., “An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree,” AJHG 92:454–459 (2013).
What this proves — and what it does not

This does not claim a DNA test proves you are Moroccan. It shows the test used to call you “only West African” was built not to see North Africa — so it cannot rule it out.

Be exact, because the exactness is the strength. The genetic record here is not offered as proof of Moroccan ancestry — that rests on the documentary record: the treaty, the census, the laws that named the class. What the genetic record proves is narrower and unbreakable: the instrument used to erase the question was built to exclude the answer. The “West African” statistic cannot refute North African descent, because by its makers’ own admission it never measured it. The deepest lineage on earth sat outside the panels until a South Carolina man’s sample put it there. And forty percent of the maternal line has no home in the database at all. You were not measured and found to be someone. You were measured with a ruler built not to reach you.