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They will, on the one hand, have sex with just about anything that moves, given an easy chance, like males in a low-MPI species. On the other hand, when it comes to finding a female for a long-term joint venture, discretion makes sense; males can undertake only so many ventures over a lifetime, so the genes that the partner brings to the project—genes for robustness, brains, whatever—are worth scrutinizing. The
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Robert Wright (The Moral Animal: Why We Are the Way We Are: The New Science of Evolutionary Psychology)