Kanazawa (2004) suggests that there is a negative association between social class and reproduction because lower-class individuals, who tend to have lower general intelligence, have greater difficulty employing evolutionarily-novel modern contraception. I derive three hypotheses from Kanazawa's theory: 1) There are no class differences in the numAber of desired children; 2) The effect of sexual activity on reproduction is weaker among the more intelligent; and 3) The interaction between sexual activity and intelligence is stronger among men. The analyses of the U.S. General Social Surveys support all three hypotheses.
Kanazawa (2004a) proposes that the human brain may have difficulty comprehending entities and situations that did not exist in the ancestral environment, and, as one empirical demonstration of this Savanna Principle, Kanazawa (2002) shows that people who watch certain types of TV shows are more satisfied with their friendships, suggesting that they may have difficulty distinguishing TV characters from real friends. In an entirely different line of research, Kanazawa (2004b) advances an evolutionary psychological theory of the evolution of general intelligence, which proposes that general intelligence evolved in order to handle evolutionarily-novel problems. The logical convergence of these two separate lines of research leads to the prediction that the human difficulty in dealing with evolutionarily-novel stimuli interacts with general intelligence, such that the Savanna Principle holds stronger among the less intelligent than among the more intelligent. Further analyses of the U.S. General Social Survey demonstrate that less intelligent men and women may have greater difficulty separating TV characters from their real friends than more intelligent men and women.
Domestic violence severely decreases women's health and well-being, thus the question of why many battered women stay with their abusive mates is puzzling. I offer possible evolutionary logic behind battered women's decision to stay, by suggesting hitherto unrecognized potential reproductive benefits of staying in abusive relationships. The logic suggests that battered women should have more sons than daughters. A recent study indeed suggests that battered women may have more sons than other women.