253W Poster - Population Genetics
Wednesday June 08, 9:15 PM - 10:00 PM

Authors:
Lily Agranat-Tamir; Jazlyn A Mooney; Noah A Rosenberg

Affiliation: Stanford University, Stanford, CA

Keywords:
Population history

In a genetically admixed population, admixed individuals possess ancestry from the various source groups. Studies of genetic admixture in admixed human populations frequently estimate ancestry components corresponding to fractions of individual genomes that trace to specific ancestral populations. However, the same numerical ancestry fraction can represent a wide array of admixture scenarios. Using a mechanistic model of admixture, we characterize admixture genealogically: how many distinct ancestors from the source populations does the admixture represent? We consider the number of ancestors both in terms of genealogical ancestors of an admixed individual chosen at random and genetic ancestors, those genealogical ancestors who contribute to the genome of the modern admixed individual. We apply our mathematical results to the African-American population, estimating for individuals chosen at random from this population the numbers of genealogical and genetic ancestors originating from the source populations. The results provide insight both on how many of the genetic ancestors of a typical African-American might have been forcibly displaced to the Americas in the Transatlantic Slave Trade and on how many separate European admixture events might have contributed genetic ancestry to the genome of a typical African-American individual.