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Aaron P. Ragsdale is a population geneticist who develops and applies models connecting demographic history to genetic variation. A weakly structured stem for human origins in Africa by Aaron P. Ragsdale and others evaluates histories with long-lived structure and continuing exchange rather than treating all ancestral biological populations as completely isolated branches. This connects mathematical model choice to the interpretation of human ancestry. ^[ref]

Iain Mathieson is a population geneticist who studies human variation, demographic history and natural selection. His work combines modern and Ancient DNA to investigate how ancestry and selection shape observed variation. In Genome-wide patterns of selection in 230 ancient Eurasians by Iain Mathieson and others, changes across sampled past biological populations help separate historical allele-frequency patterns from a present-day snapshot. ^[ref]

Iosif Lazaridis is a population geneticist studying human history with Ancient DNA. Ancient human genomes suggest three ancestral populations for present-day Europeans by Iosif Lazaridis and others compared ancient and present-day genetic data to model distinct ancestry contributions. The result illustrates why a biological population’s history can require genetic admixture rather than a single branching tree. ^[ref]

A population geneticist studies variation in allele frequencies, its evolutionary causes and the ancestry of sampled genetic material. The work combines genetics, probability and empirical data to investigate processes including natural selection, genetic drift and gene flow. For example, comparing alternative demographic models can test whether an observed pattern is better explained by biological population separation or continuing exchange, subject to the model assumptions. ^[ref]