I got that information from SciShow's video on Monogomy. You could watch the video, just search SciShow Monogamy on youtube or even google and it should be the first hit. By the way, thanks for not turning this into a huge trolling argument but an actual informative conversation. And I agree, that polygamy isn't wrong, but according to my source it's the primitive default for nature. What people want to do for themselves is fine, I'm not judging, but from nature's standpoint, polygamy=primitive.