FIGURE 3. Phenotypic variability versus distance from Africa.
From the following article:
The effect of ancient population bottlenecks on human phenotypic variation
Andrea Manica, William Amos, François Balloux & Tsunehiko Hanihara
Nature 448, 346-348(19 July 2007)
doi:10.1038/nature05951
Relationship between mean phenotypic variability (corrected for climate) for male skulls and distance from the putative African origin (represented by the centroid of likely origins). The solid line represents the best fit from the regression.