Christopher Ryan is the coauthor of "Sex at Dawn: How We Mate, Why We Stray, and What It Means for Modern Relationships."
I agree with his main idea that he supports in his book with lots of historic, biological and sociological facts:
Monogamy is like vegeterianism. You can choose to do it, it can be healthy, good, and right for you. But it is not for everyone, and it is not a "default" mode of a human being.
Click to view
longer (1 hour) TED talk:
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Sullivan has thoroughly debated Sex at Dawn and its provocative findings on nonmonogamy -
here,
here,
here,
here,
here,
here,
here,
here,
here,
here,
here,
here,
here and
here.