" Here monogamy, there hetaerism and its most extreme form, prostitution. Hetaerism is as much a social institution as all others. It continues the old sexual freedom—for the benefit of the men. In reality not only permitted, but also assiduously practised by the ruling class, it is denounced only nominally. Still in practice this denunciation strikes by no means the men who indulge in it, but only the women. These are ostracised and cast out by society, in order to proclaim once more the fundamental law of unconditional male supremacy over the female sex. However, "

― Friedrich Engels , The Origin of the Family, Private Property and the State