Fig. 2.

Counting genealogical and genetic ancestors from the source populations for an admixed individual. a) Pedigree of an admixed individual. Ancestors can be from source populations or from the admixed population itself. Ancestors from the source populations can be both genealogical and genetic ancestors (solid color), or genealogical ancestors only (striped). Along each genealogical line that reaches a source population, we count the most recent ancestor (dark color). b) Counting genealogical ancestors from source populations. For the pedigree in a), this panel goes back in time from an admixed individual in generation g (circled), on each line stopping when a source population is reached. The number of individuals from source 1 is 4 (red), and the number from source 2 is 3 (blue). c) Counting genetic ancestors from source populations. As in b), we traverse all admixed individuals in the pedigree, irrespective of genetic ancestry status. However, if a source-1 or source-2 ancestor is not a genetic ancestor, then that individual is not tabulated. Note that for ease of interpretation, the figure contains a higher number of genealogical but nongenetic ancestors than is likely in real pedigrees.