Two terms, sex and gender, must be separated here. The “Manichean fallacy” (either/or logical error) has for centuries warped our perception of human nature. While from ancient times societies have divided humanities into two categories by their “sex” – male and female – modern science has revealed that each of us contains both “male” and “female” hormones and physical traits, in varying proportions. As the human body matures (let us say in the teen years), the predominant hormones are physically “encouraged” to manifest, in hair growth, breast tissue growth, and other physical manifestations. During this same time period, the social “roles” (our “gender expectations”) are encouraged and/or discouraged by society’s “expectations” of behavior – boys should like sports, girls should like sewing, etc. These sociological pressures, along with the physiological pressures of hormonal chemistry, not only force us into the false duality, but actually prevent the paradigm from being questioned. The result is a perpetual divide, being challenged in modern times by cultural/economic Feminist movements and studies, and by a gradual acknowledgement of transgender, homosexuality, and "curious" lifestyles and explorations. Scientists have been able to measure changes in hormonal productions brought on by sociological changes in the acceptance of these gender variations.