“Scelza also discovered that cultures differ dramatically in how much parental investment men typically devote to their children. In cultures with heavy male parental investment, men showed an even stronger endorsement of sexual infidelity as more distressing than emotional infidelity; more than 90 percent in those cultures, such as the Himba, chose sexual infidelity as more jealousy inducing. The more investment men make, the more important it becomes for them to ensure that they are the actual genetic fathers, at least from an evolutionary perspective. In short, cultures vary in how jealous men get about a partner’s sexual infidelity, but it’s not random or arbitrary cultural variability. It is theoretically predictable variability based on how much men invest in their children, which in turn corresponds to the costs they would incur by investing in a child who might just be their rival’s.”