The amount of money a person was willing to forgo in order to give $75 to another person decreased as a hyperbolic function of the perceived social distance between them. Similar hyperbolic functions have previously been shown to describe both time and probability discounting.
The “straw man” prior expectation of the dominant social psychology paradigm is that humans should behave with perfect rationality and high ethical standards. The more modest claim of evolutionary psychologists is that humans have evolved specific adaptations for adaptive problems that were reliably present in the ancestral environment. Outside that restricted range of problems, one should not expect optimal behavior.