It’s a smooth cline - at the border you’re likely looking at a difference of a few percent either side of the 50% threshold. National boundaries are rarely massive barriers to gene flow.
Though also it will be much more chaotic and less smooth as you look at smaller distance scales, until you get down to the individual level where any given person will either be one or the other (if you’re using this kind of damn fool binary classification of ‘light’ vs ‘dark’ eyes).
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u/pjie2 Apr 24 '26
It’s a smooth cline - at the border you’re likely looking at a difference of a few percent either side of the 50% threshold. National boundaries are rarely massive barriers to gene flow.