Gender is a cultural category. Only humans have culture (behavior guided by symbolic communication, language) . Other animals don't. have culture, so don't have gender. Gender is a linguistic binary representing the biological binary of sex. I'm thinking we should retain the gender cultural / social construct wherein women do the predominance of caring labor. This a logical socially constructed extension of instinctive sex-based behavior. We might expand the slogan to : Gender behavior is determined by sexual physiological characteristics and behaviors.