4. Eye color
Scientists from The University of Tromsø, Norway claim that blue-eyed men prefer blue-eyed women. According to the researchers, this is because the eye color of the future baby helps to understand if the choice was right.
Men with brown and green eyes tend not to prefer blue-eyed women.
Of course, the preferences of blue-eyed men seem quite logical. But, in fact, even if both parents have blue eyes, they might have a brown-eyed baby.