Lineage Fitness Theory and the Lineage Manipulation and Mutualism Mechanism: Bridging Evolutionary Social Sciences & Cultural Evolution

Ryan Nichols

Department of Philosophy, California State University Fullerton

Lineage fitness theory aims to improve integration of cultural evolution with evolutionary psychological and social sciences by explaining the onset and maintenance of key traditions as products of gene-culture co-evolutionary selection of a mechanism. The lineage fitness hypothesis is deduced from inclusive fitness theory, corresponding middle-level evolutionary hypotheses, and stated assumptions pertaining to cumulative culture. The lineage manipulation and mutualism mechanism refers to the causal processes by which ancestors exploited intra-lineage cumulative cultural traditions to marginally raise their fitness by partially controlling inputs to evolved psychological modules of descendants. This caused increases in rates of co-descendant survival, in welfare tradeoff ratio amongst distant co-descendants, and led to manipulation of mating preferences and behaviors of co-descendants. Unique predictions of this theory that are not entailed by kin selection theory are identified. The posterior probability of this theory is raised by attention to studies demonstrating effects of cultural traditions on patrilineal investment, and by a case study of Han Chinese culture and genomics. A Bayesian argument noting several limitations concludes the discussion by affirming (only) that the lineage fitness hypothesis merits further investigation by experts.