Popular academic ideas linking physiological adaptations to social behaviors are spreading disconcertingly into wider societal contexts. In this article, we note our skepticism with one particularly popular—in our view, problematic—supposed causal correlation between neocortex size and social group size. The resulting Dunbar's Number, as it has come to be called, has been statistically tested against observed group size in different primate species. Although there may be reason to doubt the Dunbar's Number hypothesis among nonhuman primate species, we restrict ourselves here to the application of such an explanatory hypothesis to human, culture‐manipulating populations. Humaninformationprocessmanagement, we argue, cannot be understood as a simple product of brain physiology. Cross‐cultural comparison of not onlygroupsize butalsorelationship‐reckoning systems like kinship terminologies suggests thatalthoughneocorticesareundoubtedly crucial to human behavior, they cannot be given such primacy in explaining complex group composition, formation, or management.