We here in the Boston area have been referring to the “black Irish” as far back as I can remember.
I had an Irish friend who looked Hispanic.
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Did he look like someone from Latin America or from Spain? The article is theorizing that original Irish ancestors came from Spain, not Latin America.
The “black Irish” are more likely to be the result of the many Spanish sailers who were wrecked on the Irish shores when the Spanish Armada was destroyed. Catholic Ireland welcomed Catholic Spaniards. England was not so kind.
Regarding the red heads, what about the Neanderthal genes that have been suggested conferred that trait?