Last year 23andme’s research team published a major landmark study titled “Genetic Consequences of the Transatlantic Slave Trade in the Americas“. Arguably the largest DNA study to examine African ancestry in the Americas! Covering a wide span of the Afro-Diaspora, incl. also several thousands of African Americans. Highly interesting therefore. The research approach of this study consists of combining genetic data obtained from 23andme customers with Trans-Atlantic Slave Trade patterns. Which is practically the same approach I have been using ever since I started my AncestryDNA survey in 2013. This study by 23andme is even including Cape Verdean samples as a control group! Which is something I have done as well in all my research sofar.1 Since I have recently finished my survey findings based on 23andme results (2018/2019 version) it should be useful to compare notes.
23andme’s 2020 study
- Genetic Consequences of the Transatlantic Slave Trade in the Americas (Micheletti et al., 2020)
- Supplemental Data Micheletti et al, 2020
- Table S7. Mean Ancestry Composition for the Research Cohort (main source for comparison)
My own survey findings based on 23andme and AncestryDNA results
- Afro-Diaspora AncestryDNA results: A Comparison (Fonte Felipe, 2016)
- Update: Afro-Diasporan AncestryDNA Survey (part 1) & part 2) (Fonte Felipe, 2018)
- 23andme’s African breakdown put to the test: Afro Diaspora edition! (Fonte Felipe, 2021)
Table 1 (click to enlarge)
In this blogpost I will compare my own research findings (based on regional admixture) with 23andme’s study from 2020. In fact much of the data contained in 23andme’s study (based on the 2018 version of Ancestry Composition) is consistent with my own. As demonstrated above in Table 1. Which features the African breakdown for African Americans on 23andme (scaled to 100%).2 Despite smaller sample size on my part actually very similar outcomes. Providing mutual corroboration. The study’s main findings of lower Senegambian and higher Nigerian ancestry than expected for African Americans are in line with what I had already established in my 2015 survey. Based on AncestryDNA test results for 350 African Americans. As well as more recently in my 23andme survey. See also:
- 350 African American AncestryDNA results (2015)
- 200 African American 23andme results (2018/2019 version)
Within the remaining part of this blog post I will discuss the following:
- Why do so many African Americans have Nigerian ancestry?
- Ancestral implications of “Nigerian” go beyond modern-day borders
- Domestic Slave Trade from mostly Virginia spreading Bight of Biafra lineage
- Lower Senegambian than expected because of less reproduction?
- Substructure according to state origins
- African breakdown for other parts of the Afro-Diaspora
- Mostly in agreement with historical expectations
- Overlap & differences with my own survey findings
- Regional diversity and substructure
- Confirmation of Upper Guinean Founding Effect?
- Discordances & limitations of 23andme’s study
- Afro-descended samples taken from migrants underrepresent wider variation in countries of origin
- Central African IBD disproportionately high when contrasted with regional admixture from Central Africa
- Sex-biased admixture: multiple & context-dependent historical narratives!
- Exciting future prospects: personalized 23andme results featuring African IBD specified according to ethnic groups Continue reading