The perplexing diversity of the human personality is a yet unresolved puzzle in evolutionary science. Several hypotheses exist about its ultimate and proximate explanations without discussing the temporary aspects of its evolution. I propose the agricultural trigger hypothesis that explains how, when and why the current diversity evolved. Although pre-agricultural human bands already had to have some genotypic and phenotypic variation in personality traits, this was limited by their environment and social norms. Agriculture, however, altered several aspects of ancestral life, most importantly, it loosened the strict mutual control over the behavior of fellow group members. A positive feedback loop of social division of labor and individual niche specialization, fuelled continuously by the ever growing settlement sizes, economic inequality and hierarchy, thus triggered a major personality explosion. The current state of global diversity could therefore be the result of the above process, born with the Neolithic and still running. Supporting this hypothesis I present two agent based models capturing sub-problems of the above processes. The first explores how social division of labor can result in heritable behavioral differences, and the second shows how egalitarian norms can effect behavioral diversity.
Zsóka Vásárhelyi holds a BSc and Master´s degree in Biology from the Eötvös Lóránd University, Budapest. She is doing her PhD thesis in the Theoretical Evolutionary Biology Doctoral Program of the Eötvös Lóránd University under the supervision of István Scheuring. Zsóka Vásárhelyi has been awarded a KLI Writing-Up Fellowship to complete her thesis.