Humans and domesticated animals tend to show variation in eye color unlike in wild animals whose eye colors is usually fixed. It is however not known when this variation in eye color emerged in the evolution of the genus Homo and domesticated animals. From previous research, we know however that the emergence and fixation of variants in both coat, plumage and eye coloration started during the early stages of domestication in the Neolithic. Eye coloration in humans is known to be continuous having numerous shades ranging from different shades of light blue to dark brown. The very rare cases of eye coloration in wild animals is associated with maturation with age as seen in birds and some instances of sexual dimorphism (certain duck species). Who knows perhaps in humans it is a case of sexual selection with blue and green eyed individuals preferred more as mates than brown eyed individuals.
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