How could genetic drift explain differences in the genotype frequencies among the caucasian and aborigine populations?

Genetic drift occurs when there is no random mating across a population. This causes a change in allelic frequency due to a random sampling of the population.

As the aboriginal population explored the earth, a small part of the population became geographically isolated either due to continental drift and climate changes. As the isolated population grew bigger, they established their own gene pool. This resulted a change in genotypic frequencies from that of the aboriginal population.