Background: The amount and distribution of genetic diversity in and among human populations are primarily determined by our recent evolutionary past. Since the Mid-Pleistocene, about 700 000 years ago, our evolution has been dominated by population expansions coupled with admixture, recurrent genetic interchange (gene flow), and local adaptation.
Objective and hypotheses: To understand the evolutionary factors influencing present-day genetic variation in humans.
Method: Phylogeographic analysis, ancient DNA, and analysis of fossil data.
Results: An accurate and cross-validated reconstruction of recent human evolutionary history is estimated.
Conclusion: Admixture and gene flow tend to increase genetic diversity within populations and reduce differences between. Although we make much of our population differences, humans are one of the most genetically homogeneous species on the planet despite our global distribution. Because much of the gene flow in our species has been constrained by geographic distance throughout much of our evolutionary history, the best predictor of the degree of genetic differentiation between any two populations is simply their geographic distance from each other. Skin color, race, and other cultural classifications are not good predictors of molecular genetic differentiation. Local adaptation to physical factors (such as UV radiation) and biological factors (such as infectious diseases) tends to increase diversity between populations. This differentiation is not related directly to geographic distance, but rather relates to the geographic distribution of the environmental factor or factors leading to natural selection for local adaptation. Many of these local adaptations represent trade-offs between various traits and are responsible for most of genetic diversity that is of clinical importance.
01 Oct 2015 - 03 Oct 2015