Cinderella effect

In evolutionary psychology, the Cinderella effect is the alleged higher incidence of different forms of child-abuse and mistreatment by stepparents than by biological parents. It takes its name from the fairy tale character Cinderella. Evolutionary psychologists describe the effect as a remnant of an adaptive reproductive strategy among primates in which males frequently kill the offspring of other males in order to bring their mothers into estrus, and give the male a chance to fertilize her himself. There is both supporting evidence for this theory and criticisms against it. Evolutionary psychologists Martin Daly and Margo Wilson propose that the Cinderella effect is a direct consequence of the modern evolutionary theory of inclusive fitness, especially parental investment theory. They argue that human child rearing is so prolonged and costly that "a parental psychology shaped by natural selection is unlikely to be indiscriminate". According to them, "research concerning animal social behaviour provide a rationale for expecting parents to be discriminative in their care and affection, and more specifically, to discriminate in favour of their own young".