This AlterNet article on “The Virtues of Promiscuity” discusses the evolutionary benefits of female promiscuity; that is the contributions “slutty” behavior makes toward the fitness of a species. Here’s a choice quotation:
Even evolutionary psychologists, stout defenders of the meat-for-fidelity model, are beginning to acknowledge the benefits of women’s “slutty” behavior. University of Texas psychologist David Buss gives the most credit to what he terms “mate insurance,” a backup replacement in case the male partner doesn’t survive.