Yeah polygamy doesn't even work well to produce more offspring according to the people who have examined the numbers in its mid-nineteenth century heyday. There's so much more BS involved that it's not even effective apparently and it turns out that boosting the population was just a cover story anyway. The unpaired males you mention are a problem in the fundamentalist communities who still follow this practice--which is not legally or socially endorsed (never was in the USA), making it that much more complicated of course.

There have been a couple Dark Horse episodes ruminating on evolution and monogamy--off the top of my head Bret discusses it with Louise Perry and Bridget Phetasy. I've also heard JBP wade in on the subject from time to time citing the long-term emotional involvement required to raise stable children. Pretty unique in the animal world. Are we just animals? Are we not? Such a fine line sometimes.

Lots to philosophize about!