Not necessarily, though it's a popular inculcation.
No doubt you've read the flip side(s) of that presumption, of late..

Given homo-sap's penchant for crafting illusions that support our fav acquired 'truths', along with all those duelling gods - I suspect that pigmentation and physiognomy, the accident of geographical origin/climate - are so evident visually: why, a preacher could make most Anything out of it.

(Me? I dunno; there just ain't much traditional-lore I find too comfortable these days, given our Record to date.)