A lot of the early stigmas and taboos about diet, clothing, and hygiene emerged from ritualized practices intended to prevent disease and promote human health. The lack of understanding meant the ritual divorced itself from the real best practices over time. But prohibitions on eating shellfish and chopping off the foreskin of your dick and keeping menstruating women out of the house were ultimately primitive efforts at avoiding food poisoning, curbing the spread of STIs, and managing the bloody mess of periodic period flow.