Polygamy is about sex, whereas monogamy is about love.
No group-living nonhuman primate is monogamous, and adultery has been documented in every human culture studied- including those in which fornicators are routinely stoned to death. In light of all of this bloody retribution, it's hard to see how monogamy comes "naturally" to our species. Why would so many risk their reputations, families, careers- even presidential legacies- for something that runs against human nature? Were monogamy an ancient, evolved trait characteristic of our species, as the standard narrative insists, these ubiquitous transgressions would be infrequent and such horrible enforcement unnecessary. No creature needs to be threatened with death to act in accord with its own nature.
There are 80,000 prostitutes in London alone and what are they, if not bloody sacrifices on the alter of monogamy
…each woman is a wonderful world unto herself. And monogamy? It’s like choosing to live in a single town and never traveling to experience the beauty, history, and enchantment of all the other unique, wonderful places in the world. Why does love have to limit us? Perhaps it doesn’t. Only fear is restrictive. Love is expansive. And I wonder, since fear of enmeshment impels us to avoid commitment and fear of abandonment makes us possessive, what type of evolved relationship can emerge once those wounds are healed?
Monogamy is not a choice, it is a responsibility of a genuine human.
Monogamy is faith in the faithless
The daddy-at-home theory posits that concealed ovulation evolved to promote monogamy, to force the man to stay home, and thus to bolster his certainty about his paternity of his wife's children. The many-fathers theory instead posits that concealed ovulation evolved to give the women access to many sex partners and thus to leave many men uncertain as to whether they sired her children.
Polygamy is a luxury of the cave-people, and monogamy is an existential responsibility of the civilized society.
Confusing monogamy with morality has done more to destroy the conscience of the human race than any other error.
Straight couples don't have to be monogamous to be married or married to be monogamous. Monogamy no more defines marriage than the presence of children does. Monogamy isn't compulsory and its absence doesn't invalidate a marriage.