That is what a new paper has found:
Barbara E. Stranger et al., Patterns of Cis Regulatory Variation in Diverse Human Populations. PLoS Genetics 2012. Open access.
Cis-regulatory elements are key pieces of the overall codification of the genome. The main finding of this paper is that they show almost no geographic structure, that virtually all variation in these key elements is inter-individual and not among populations.
|From Supplemental Figure 1 - PC analysis|
As you can see in the PCA plot, the inter-population variation is most subtle, almost impossible to discern with so much overlap. The lack of structure repeats for the other components.