[Thot Leader]

If you don't like the "foreign DNA causes an autoimmune response that affects women's brains" argument, consider the following. Viral infections that may be subclinical (i.e. no obvious, lasting symptoms) such as all the herpes viruses (Epstein Barr, CMV, HSV1 etc.) have now been linked to neurodegenerative diseases like Alzheimer's and MS. So, the more a girl fucks around, the more pathogens she's stacking up for life, and these pathogens are shown to cause brain damage, so there's that.

Also, and this may be pseudoscience, but I've heard that women produce less and less oxytocin with each successive sex partner, meaning her capacity to pair bond with future mates decreases with each cock she takes.