Physical appearance, personality traits and natural selection in Europeans
Greg Cochran's theory is that just as selecting for new personality traits in wild animals that you are trying to domesticate often introduces new physical looks, the famous diversity of looks among Europeans (red and blond hair, blue, gray, and green eyes) are by-products of natural selection for new personality traits favorable to survival in Europe. Blue eyes, for example, might possibly be a by-product of selection for something like shyness.
Shy blue eyed boys
Can short genes make you shy?
Discovery that common mood disorders are inherited together may reveal genetic underpinnings
Shyness and little boy blue: iris pigmentation, gender, and social wariness in preschoolers
Dogs and More Dogs
Evolution and Domestication: Selection on Developmental Genes?
EARLY CANID DOMESTICATION: THE FARM FOX EXPERIMENT
Scientists breed cute tame foxes
Dogs of Rarotonga
Ascent of the Dog