Evolutionary genetics and cultural traits in a ‘body of theory’ perspective

The chapter explains why evolutionary genetics - a mathematical body of theory developed since the 1910s - eventually got to deal with culture: the frequency dynamics of genes like “the lactase gene” in populations cannot be modeled correctly without including social transmission. The body of theory requires specific justifications, for example meticulous legitimations of describing culture in terms of traits. It is an immensely valuable scientific instrument, not only for its modeling power but also for the amount of work that has been necessary to build, maintain, and expand it. To demonstrate such patrimony, and to emphasize the importance and accumulation of statistical knowledge therein, this paper tells a brief history of evolutionary genetics, explaining also the probabilistic nature of genotypes, phenogenotypes and population phenomena. Although evolutionary genetics is actually composed by distinct and partially independent traditions, the most important mathematical object of evolutionary genetics is the Mendelian space, and evolutionary genetics is mostly the daring study of trajectories of alleles in a population that explores that space. The ‘body’ is scientific wealth that can be invested in studying every situation that happens to turn out suitable to be modeled as a Mendelian population, or as a modified Mendelian population, or as a population of continuously varying individuals with an underlying Mendelian basis. Mathematical tinkering and justification are two halves of the mutual adjustment between the body of theory and the domain of culture. Some works in the current scientific literature overstate justification, misrepresenting the relationship between body of theory and domain, and hindering interdisciplinary dialogue.