It’s called “Intelligence: A Unifying Construct for the Social Sciences” by Richard Lynn & Tatu Vanhanen.

Available formats: hard cover, paper cover or e-book (pdf).

From the webpage about the book:

“Differences in intelligence help to explain all kinds of phenotypic social phenomena as well as the persistence of social inequalities in the world. Environmental factors affecting such phenomena vary from case to case, but intelligence reflecting the evolved human diversity remains the same explanatory factor across all phenotypic social phenomena. This means that it provides a unifying theoretical construct for the social sciences. Unfortunately social scientists have not yet realized that most problems explored in social sciences are phenotypic phenomena depending on both genotypic and environmental factors and that intelligence is a powerful genotypic common explanatory factor.”

[Webpage].

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