[ErrantX]

That may be the case; but it doesn't affect the theory. What's important is reducing the standard deviation from the average number of sexual partners.

Or to put it another way; to reduce the outliers who take a disproportionately high number of lovers. It is logical that this would hamper the "global" spread of disease.

This particular theory is saying that the way to do that is to reduce the opposite form of outlier - the sexual conservative.