The Red Hair and Grey Eyes of the North

I found this nugget about red hair in The Ten Books On Architecture by the Roman architect Vitruvius Pollio.

[I]n the cold regions that are far away from the south, the moisture is not drawn out by hot weather, but the atmosphere is full of dampness which diffuses moisture into the system, and makes the frame larger and the pitch of the voice deeper. This is also the reason why the races that are bred in the north are of vast height, and have fair complexions, straight red hair, grey eyes, and a great deal of blood, owing to the abundance of moisture and the coolness of the atmosphere.

The writings of Vitruvius inspired Leonardo da Vinci's famous Vitruvian Man illustration.