Evolutionary psychology looks to trace the roots of human behaviour in our past evolution. So, for example, a preference for rich and sweet foods reflects a time when food was scarce and calories needed to be found wherever and whenever possible while our phobias of snakes and spiders go back to times when we lived in close proximity to dangerous creatures. Now, a study of 266 Spanish students has confirmed earlier theories about how the sexes' reactions to infidelity reflects evolutionary pressures. The researchers found that women were more distressed by emotional infidelity whereas men were more distressed by physical infidelity. This confirms earlier theories that women look for emotional commitment (to raising their children) in men while men look for biological commitment so that they know the child they are helping to raise is theirs.
Fernandez, Ana Maria ... [et al] - Distress in response to emotional and sexual infidelity : evidence of evolved gender differences in Spanish students Journal of Psychology January 2007, 14(1), 17-24