In 1949 Simone de Beauvoir passionately described women's enslavement to what she called the ‘outside forces’ of their reproductive biologies. ‘Woman is of all mammalian females’, she wrote,

These crises are fundamentally linked to endocrine systems; for de Beauvoir, puberty, ovulation, menstruation, pregnancy, childbirth and menopause all demonstrate the ways in which ‘the species’ takes hold of women's bodies through the actions of sex hormones. Women's lives are a profound struggle against this ‘imperious’ process. ‘Not without resistance’, she argues, ‘does the body of woman permit the species to take over; and this struggle is weakening and dangerous’ (de Beauvoir 1988: 59). Unlike men (whose endocrine systems do not create significant crises), a woman must strive to maintain a hold on her individuality and resist her ‘enslavement’ to the demands of biological reproduction, which are, physiologically at least, of no benefit to her (de Beauvoir 1988: 62–4).