Modernity increases gender differences.

Another in a series of paradoxes:
As gendered cultural influences lessen, innate differences between men and women influence personality to a greater extent, concludes a 2008 global study spanning fifty-five cultures. It confirms previous findings based on multiple studies that gender differences in personality are smallest in the most traditional cultures and greatest in those that are the most modern, affluent and progressive.

These conclusions are "counterintuitive" to the socialization (blank slate) theory of gender differences long favored by most feminists, which has presumed that boys and girls enter the world with similar cognitive and behavioral tendencies and that subsequent personality differences are attributable to the rigid gender roles found in most cultures. The concerns of those who predicted that equal rights for women would homogenize the genders now seem unfounded.

The 2008 study and its forebears are not arguing that personality differences between men and women are only caused by genes. The current scientific consensus is that nature and nurture have roughly equal influences on the behavioral tendencies that define personality. The 2008 study also does not contend that efforts to achieve equality alone create greater personality differences, but that prosperity also plays a huge role. Fortunately, we live in a world in which progressive societies prosper and prosperous societies – excepting a few oil rich nations – are progressive.

Another bombshell contained in the 2008 study: modern cultures are mostly changing and benefiting men’s personalities, not women’s. One theory offered to explain this finding is that industrialization has increased the relative power of men and acted to enhance male personality traits – in part because the benefits of industrialization do not flow as much to women, who are more restrained by the responsibilities of child rearing.

The authors’ alternative explanation is that the struggle just to survive in non-industrialized societies suppresses gender differences in personality. Where advances in civilization have made life easier, innately influenced male personality traits such as assertiveness, dominance, risk taking and affinity for innovation have flourished. It has been well documented that as progressive governments have broadened opportunities, environmental effects matter less in success and inherited traits matter more. An analogous physical phenomenon is the greater differences in height between men and women in more affluent cultures due to better nutrition and medical care. (But progress is not uniformly advantageous for men. Gender differences in blood pressure, non-existent is some agrarian economies, are highest where modernity has liberated men’s personalities to focus on career competition.)

The rise of more egalitarian societies and the decline of institutional and cultural barriers to opportunity are forces that should eventually equalize the relative opportunity each gender has for power and wealth. But the resulting changes in men’s personalities are creating new advantages for them that seem to be acting as a counterweight to the societal forces of equalization. To cite another of the authors’ analogies, in spite of laws equalizing opportunities in competitive track and field in the U.S., a far greater percentage of men cluster at the top – have times close to the best runners of their gender – than is the case for women. Men seem to respond to greater opportunity by becoming more competitive, and the result is greater clustering at the top. As Harvard Law Professor Lani Guinier said, "it is not enough to just add women and stir." We have to do more to help women be more effective in creating social change.