Menstrual blood was ambivalent in matriarchal societies—both destructive and beneficial.

Evidence

But it is especially striking that menstrual blood’s effects are linked to the ideas of cream going sour, mayonnaise that does not take, fermentation, and decomposition; it is also claimed that it is apt to cause fragile objects to break; to spring violin and harp strings; but above all it influences organic substances that are midway between matter and life; this is less because it is blood than because it emanates from genital organs; even without knowing its exact function, people understood it to be linked to the germination of life: ignorant of the existence of the ovary, the ancients saw in menstruation the complement of the sperm. In fact, it is not this blood that makes woman impure, but rather, this blood is a manifestation of her impurity; it appears when the woman can be fertile; when it disappears, she becomes sterile again; it pours forth from this womb where the fetus is made. The horror of feminine fertility that man experiences is expressed through it. — Simone de Beauvoir, The Second Sex, 338 (#expands, via linked claim)

Since the feminine principle is then considered as reaching its highest power, it is feared that it would triumph over the male principle in intimate contact. Less specifically, man shies away from finding the mother’s feared essence in the woman he possesses; he works at dissociating these two aspects of femininity: that explains why incest is prohibited by exogamy or more modern forms and is a universal law; that explains why man distances himself from woman sexually when she is particularly destined for her reproductive role: during her period, when she is pregnant, or when she is nursing. Not only does the Oedipus complex—whose description, incidentally, has to be revised—not contradict this attitude: on the contrary, it even implies it. Man guards himself against woman to the extent that she is the confused source of the world and disorder become organic. — Simone de Beauvoir, The Second Sex, 339 (#expands, via linked claim)

The little girl would not seek sterile compensations in narcissism and dreams, she would not take herself as given, she would be interested in what she does, she would throw herself into her pursuits. I have said how much easier puberty would be if she surpassed it, like the boy, toward a free adult future; menstruation horrifies her only because it signifies a brutal descent into femininity; she would also assume her youthful eroticism more peacefully if she did not feel a frightening disgust for the rest of her destiny; a coherent sexual education would greatly help her to surmount this crisis. And thanks to coeducation, the august mystery of Man would have no occasion to arise: it would be killed by everyday familiarity and open competition. — Simone de Beauvoir, The Second Sex, 1977 (#complicates, via linked claim)

Categorization

• XREF: connects to: Menstruation horrifies girls because it signifies a descent into subordinated femininity — Simone de Beauvoir, The Second Sex, 1977; Menstrual blood’s impurity derives from its link to feminine fertility, not the blood itself — Simone de Beauvoir, The Second Sex, 338; Menstrual taboos persist despite evidence too feeble to justify them — Simone de Beauvoir, The Second Sex, 420 (+2 more)

Broader Connections

• Menstrual blood’s impurity derives from its link to feminine fertility, not the blood itself #expands (0.85) — Simone de Beauvoir, The Second Sex, 338
• Menstruation horrifies girls because it signifies a descent into subordinated femininity #complicates (0.80) — Simone de Beauvoir, The Second Sex, 1977
• Incest taboos and menstruation prohibitions both express man’s fear of feminine fertility #expands (0.80) — Simone de Beauvoir, The Second Sex, 339
• Menstrual taboos persist despite evidence too feeble to justify them #complicates (0.75) — Simone de Beauvoir, The Second Sex, 420