Researchers from Italy and the UK have uncovered further genetic details of how the slave trade and conquest of the Americas have affected the genetic makeup of American populations, as they report in Nature Communications this week.
"In the past, people have been comparing a European sample and an African sample," University of Oxford's Cristian Capelli tells the Los Angeles Times. "We tried to see if within these populations there was additional information that was missed."
Using a haplotype-based ancestry identification approach, the investigators characterized the genetic heterogeneity of 1,414 people from different parts of Europe and Africa and grouped them in 78 clusters that corresponded broadly with geographical origin. For instance, African individuals formed 33 clusters, with Yoruba individuals from Nigeria forming their own cluster and Mandenka individuals from Senegal forming two clusters. European individuals, meanwhile, formed 37 clusters.
The researchers then compared the genomes of some 2,500 admixed individuals from the Americas to these clusters. From this, Capelli and his colleagues could gauge the ancestry of the American populations at a finer scale. For example, they report that Caribbean populations have higher levels of African ancestry than South American ones — Barbadians have an estimated 0.87 African ancestry, especially Yoruba, while Maya have none.
They also observed smaller genetic signatures of Basque ancestry in South America and French ancestry in one African-American individual.