This essay explores the universal cognitive bases of biological taxonomy and taxonomic inference using cross-cultural experimental work with urbanized Americans and forest-dwelling Maya Indians. A universal, essentialist appreciation of generic species appears as the causal foundation for the taxonomic arrangement of biodiversity, and for inference about the distribution of causally-related properties that underlie biodiversity. Universal folkbiological taxonomy is domain-specific: its structure does not spontaneously or invariably arise in other cognitive domains, like substances, artifacts or persons. It is plausibly an innately-determined (...) evolutionary adaptation to relevant and recurrent aspects of ancestral hominid environments, such as the need to recognize, locate, react to, and profit from many ambient species. Folkbiological concepts are special players in cultural evolution, whose native stability attaches to more variable and difficult-to-learn representational forms, thus enhancing the latter's prospects for regularity and recurrence in transmission within and across cultures. This includes knowledge that cumulatively enriches (folk expertise), overrides (religious belief) or otherwise transcends (science) the commonsense ontology prescribed by folkbiology. Finally, the studies summarized here indicate that results gathered from “standard populations” in regard to biological categorization and reasoning more often than not fail to generalize in straightforward ways to humanity at large. This suggests the need for much more serious attention to cross-cultural research on basic cognitive processes. (shrink)