1997: Resources, attractiveness, family commitment; reproductive decisions in human mate choice. Ethology 103,681-699. AbstractAccording to recent evolutionary theory, males and females have been selected for different kinds of mate preferences as behavioral adaptations in our ancestral past. These psychological algorithms, however, are open to ecological/cultural changes in the contemporary societies and, as a consequence, there are permanent tradeoffs between the possible behavioral outputs in mate choice. Using 1000 lonely heart advertisements, we made an attempt to provide a detailed analysis of traits males and females offer and demand in the 'bargaining' of reproductive values. Striking differences between the sexes have been found in many of the 42 measured traits associated with physical attractiveness, financial condition, occupational status, domestic virtues, length of relationship, and marital status. We have revealed not only that females were more likely than males to prefer resources in mates, and that females offering cues of physical attractiveness made higher demands than those who did not, but the better physical conditions the females offered, the greater the financial and occupational status they required in potential mates. Similarly, males increased their reproductive success through choosing females of greatest reproductive value: the more resources they had, the greater the demands they made about the potential partner's physical attractiveness. Surprisingly, women valued traits associated with family commitment of potential partners more than cues of resources, which is regarded as an adaptive answer to a particular cultural condition. A remarkable trade-off in males between direct and indirect methods of paternal investment has been found; the fewer resources they had, the more traits indicating domestic virtue they offered. Contrary to cultural powerless hypothesis, women with higher status valued resources in mates even more than lower-ranked women. Males seeking short-term mates demanded physical attractiveness more, and female seeking short-term mates prefered mates with many resources, compared with those pursuing long-term mating. In the context of long-term mating, both sexes placed a greater emphasis on cues of family commitment rather than on those of resources and physical condition. Finally, it was found that as both males and, surprisingly, females age, they prefer relatively younger mates than themselves.