Research questions and interests are the basis of what we call scientific discovery. Based on the present understanding, the concept of population sciences is different from the concept of demography (demography can be understood as a discipline belonging to the same group and category as ontology demography, pure demography, descriptive demography, normative demography, mathematical demography, econometric demography, empirical demography, and applied demography). According to the views of Chinese scholars, population sciences is a broad social science discipline system, which includes three branches: population theory, demography, and population sciences (Wu 2006; Lu 2004; Wu et al. 2000). The population theory herein can be understood as the axiom or basic principle of demography. Demography originated from the statistical analysis of population variables, but it is not limited to this discipline. Instead, it includes sub-disciplines such as population economics, population sociology, health demography, population ecology, population geography, history of population thought, historical demography, gerontology, etc. Demographic research in China began in the early twentieth century and recovered in the early 1970s: