File:Heterozygosity in Relation to Geography in America.png

English: Heterozygosity in Relation to Geography in America.

(A) Relationship between heterozygosity and geographic distance from East Africa. Populations in Sub-Saharan Africa and Oceania are marked with gray triangles and squares, respectively, and the remaining non-American populations from Europe, Asia, and northern Africa are marked with gray pentagons. Within the Americas, populations are color-coded and symbol-coded by language stock (see Figure 8). Denoting heterozygosity by H and geographic distance in thousands of kilometers by D, the regression line for the graph is H = 0.7679 − 0.00658D, with correlation coefficient −0.862. (B) The fit of a linear decline of heterozygosity with increasing distance from a putative source, considering Native American populations only. The color of a point indicates a correlation coefficient r between expected heterozygosity and geographic distance from the point, with darker colors denoting more strongly negative correlations. Across the Americas, the correlation ranges from −0.436 to 0.575, and color bins are set to equalize the number of points drawn in the four colors. From darkest to lightest, the four colors represent points with correlations in (−0.436, −0.424), (−0.424, −0.316), (−0.316, 0.494), and (0.494, 0.575), respectively.

Assuming a single source for a collection of populations, the serial founding model predicts a linear decline of genetic diversity with geographic distance from the source location. Such a pattern is observed at the worldwide level, as a linear reduction of heterozygosity is seen with increasing distance from Africa, where distance to Native American populations is measured via a waypoint near the Bering Strait (Figure 3A). To investigate the source location for Native Americans, we considered only the Native American data and allowed the source to vary, measuring the correlation of heterozygosity with distance from putative points of origin. Consistent with the founding from across the Bering Strait, the correlation of heterozygosity with geographic distance from a hypothesized source location had the most strongly negative values (r = −0.436) when the source for Native Americans was placed in the northernmost part of the American landmass.