The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Disentangling human demographic processes? …What mtDNA simulations teach us


1Genetics and Genomics Graduate Program, University of Florida, 2Department of Anthropology, University of Florida

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Gene flow has played a defining role in the population structure of modern humans. The complexity of human demographic processes makes it difficult to disentangle the effects of geneflow from the effects of other demographic processes. To address this, we simulated mitochondrial DNA (mtDNA) for 42 different parameter combinations describing modern humans migrating out of Africa, which include two possible times for the initial migration event, three sizes for the initial migrating population and seven levels of subsequent gene flow. We calculated genetic summary statistics on the simulated datasets to capture the genetic variation of each combination. We compared the summary statistics values to identify which combinations generate distinguishable differences in genetic variation. Depending on the parameter combination, one to four summary statistics could capture differences in genetic variation. Our results show that different timings for the migration (2000 vs 4000 generations ago) generated indistinguishable patterns of genetic variation. Combinations with low initial migration size (1% of the source population) generated distinguishably different patterns of genetic variation from the higher initial sizes (10% and 30%). The genetic variation from the different levels of gene flow were only distinguishable between low (4Nm<1) and high (4Nm>>1) levels of gene flow. These results suggest that despite the complexity of human demographic processes, the genetic variation of mtDNA generated in human populations is not high enough to be captured by simple summary statistics.

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