Chapter 1 introduces the evolutionary modernization theory and outlines major hypotheses to be tested in the following chapters. Evolutionary Modernization theory updates the Classic modernization by modifying the classical theory’s one-sided emphasis on cognitive factors and by integrating Emotional and experiential factors in explaining cultural change. Socioeconomic development causes major cultural change not just by influencing people’s cognition but also by directly affecting people’s sense of existential security. The increased sense of existential security followed by rapid economic growth and the absence of war brought a value shift from giving top priority to economic and physical security toward greater emphasis on free choice, environmental protection, gender equality and tolerance of gays. This in turn led to major societal changes such as a surge of democratization around 1990 and the legalization of same-sex marriage. Yet this intergenerational value shift transforms the societies’ prevailing values with long time-lags because a society’s values are shaped by its entire historical heritage, and not just its level of existential security.