Blue eyes came to dominate in certain areas because those populations were geographically isolated. This allowed the recessive gene for blue eyes to be expressed with progressively increasing frequency within a limited population. Unlike early Christian paternalism, primitive Scandinavian cultures have traditionally allowed females to choose their own spouses. No doubt, blue-eyed women preferred to mate with blue-eyed men, as is still the case today. Over time, even a slight preference for blue on blue pairings would have resulted in a progressively increasing percentage of blue-eyed people.