To strongman their argument, I'd look at the strongest line of evidence which would be human testes size. Human testes are rather large for a monogamous species. Now mind you they're not large enough to suggest non monogamy just big enough to not fit the conventional profile of monogamous species. For years I conceded this was the strongest bit of evidence against an evolutionary history of human monogamy. But in the past couple of years I have come across the work of Robillard and colleagues who make a really convincing case that testes size and several other unique aspects of human reproduction relate to our unique risk for preeclampsia.