We sort of know all this, but what is important is that white skin and blue eyes gained an advantage that encouraged rapid intermarriage. This led to a huge expansion of that particular variation throughout perhaps a third of the global population. By that i mean that plausibly a third of the population may have Caucasian genetics as part of their blend.
That advantage is still observed and is actually likely to sustained. Caucasian culture has been dominant and available globally for only a short time and this allows for mixed marriages with all other identifiable groups to the disadvantage of any two other choices. This looks to be a small thing but the quickest way to join into the dominant culture is as a grandchild retaining a quarter of the genetics of a grandparent. This process substantially absorbed the Eastern native population and is slowly absorbing small ethnic groups everywhere anyway today.
In this manner a dominant culture genetically absorbs multiple hybrid strains preferentially to any minority group..
An international team of researchers as headed by Harvard University’s Dr. Iain Mathieson put forth a study at the 84th annual meeting of the American Association of Physical Anthropologists recently stated.