Final answer:
In evolutionary psychology, it is theorized that women are most jealous of emotional infidelity due to concerns over their partners' investment of emotional resources elsewhere, whereas men worry about sexual infidelity as it may compromise their paternity certainty.
Step-by-step explanation:
According to the evolutionary perspective on sex differences in mating tendencies, women are most jealous of emotional infidelity, whereas men are most jealous of sexual infidelity. This belief stems from the idea that, throughout human evolution, certain behaviors have become ingrained in the sexes due to reproductive strategies that have been conducive to passing on one's genes. The theory posits that men's jealousy evolved as a mechanism to ensure paternity security, as they can never be absolutely certain that they are the biological fathers of their partners' children without modern DNA testing.
Women, on the other hand, look for signs of emotional attachment from their partners because emotional resources invested elsewhere by her mate could mean reduced support and resources for her and her offspring. It's important to note that these tendencies are suggested by evolutionary theories and are subject to various cultural and individual factors. While some empirical studies have found support for these theories, other scholars, like Karen Horney, have criticized such biological determinism and argued that behaviors such as jealousy are largely culturally conditioned.