The idea that men and women are fundamentally different from each other is widely accepted. And throughout the world, this has created distinct ideas about which social and physical characteristics are necessary in each gender to maintain healthy human development. However, social revolutions throughout the last century have challenged traditional ideas about not only which traits are normal and necessary for survival, but also how humans acquire them. Thanks to a new study from researchers at Case Western Reserve University, science is continuing the charge. By studying rare families in which a daughter shares the same Y chromosome as her...