Geographic structure of human genetic variation: medical and evolutionary implications

The geographic structure of human populations can be summarized by two numbers, 85 and 15, and two key-words, Continuous Genetic Change, and outliers. 85 and 15 % of the global variation represent, on the average, the genetic differences within and between populations, respectively; Continuous Genetic Change, CGC, characterizes most of the differences between groups at different geographic scales; and outlier populations, or genetic isolates, generated by different types of barriers to gene flow, punctuate with peaks the clinal landscape. The presence of this patterning, probably consistent across the genome with some exceptions, has several biomedical and evolutionary implications. However, its origin and evolution is only partially understood, and the geographic distribution of genetic variation at selectively important genes is still poorly investigated. Major efforts in these directions, as well as in the study of potential population outliers, will be of great importance to better define and predict the implications and future evolution of our geographic structure.