Anthropological enquiry suggests that all societies classify animals and plants in similar ways. Paradoxically, in the same cultures that have seen large advances in biological science, practical knowledge of nature has dramatically diminished. Here we describe historical, cross-cultural, and developmental research on the ways in which people ordinarily conceptualize organic nature (folk biology), concentrating on cognitive consequences associated with knowledge devolution. We show that the results of psychological studies of categorization and reasoning from ‘standard populations’ fail to generalize to humanity at large. The populations most commonly used in studies by psychologists (Euro-American college and university students) have impoverished experience of nature, and this generates misleading results about knowledge acquisition and the ontogenetic relationship between folk biology and folk psychology. We also show that groups living in the same habitat can manifest strikingly distinct behaviours, cognitions, and social relations relative to it. This has novel implications for environmental decision making and management, including commons problems.