Fascinating stuff.

"Origins, admixture dynamics and homogenization of the African gene pool in the Americas"

"AbstractThe Transatlantic Slave Trade transported more than 9 million Africans to the Americas between the early 16th and the mid-19th centuries. We performed genome-wide analysis of 6,267 individuals from 22 populations and observed an enrichment in West-African ancestry in northern latitudes of the Americas, whereas South/East African ancestry is more prevalent in southern South-America. This pattern results from distinct geographic and geopolitical factors leading to population differentiation. However, we observed a decrease of 68% in the African gene pool between-population diversity within the Americas when compared to the regions of origin from Africa, underscoring the importance of historical factors favoring admixture between individuals with different African origins in the New World. This is consistent with the excess of West-Central Africa ancestry (the most prevalent in the Americas) in the US and Southeast-Brazil, respect to historical-demography expectations. Also, in most of the Americas, admixture intensification occurred between 1,750 and 1,850, which correlates strongly with the peak of arrivals from Africa. This study contributes with a population genetics perspective to the ongoing social, cultural and political debate regarding ancestry, race, and admixture in the Americas.
Significance Statement Differently from most genetic studies, that have estimated the overall African ancestry in the Americas, we perform a finer geographic analysis and infer how different African groups contributed to North-, South-American and Caribbean populations, in the context of geographic and geopolitical factors. We also perform a formal comparison of information from demographic history records of the Transatlantic Slave Trade with inferences based on genomic diversity of current populations. Our approach reveals the distinct regional African ancestry roots of different populations from North-, South-America and the Caribe and other important aspects of the historical process of mestizaje and its dynamics in the American continent."

6 Fig. 1. Ancestry analysis of African and admixed populations of the Americas397 inferred using ADMIXTURE (K=6). (A) Vertical bar plot showing the total African,398 European and Native American proportions of the ancestry clusters (SI Appendix, Fig.399 S1 and section 2.6.1.). *The Kwa/Gur dataset includes approximately 35 ethno400 linguistic groups, predominantly from the Kwa and Gur Niger-Congo linguistic401 group(27). **The Nilotics dataset includes predominantly three ethno-linguistic groupsin Northern Uganda (Langi, Acholi and Lugbara) from the Nilotic linguistic group27 402 ;#403 the Europeans are: Iberian Population in Spain (IBS) and Utah residents with Northern404 and Western European ancestry (CEU), in this order in the ADMIXTURE bar plot;## 405 the Native Americans are: Shimaa, Ashaninka and Aymara, respectively from Borda406 et al. (in preparation); the PLCO (Prostate, Lung, Colorectal and Ovarian Cancer407 Screening) data is comprised of African-Americans from East USA. (B) Percentages of408 subcontinental African ancestry clusters. For admixed populations of the American continent these percentages are relative to the total African ancestry (i.e. the sum of the410 four African associated clusters: West-Central, Western, Southern/Eastern, Northern411 Ugandan)."