Behavioral traits converge for humans and animals sharing an environment
Humans, mammals and birds that live in a particular environment share a common set of behavioral traits, according to a new study, which identifies a local convergence of foraging, reproductive and social behaviors across species. The findings, based on studying more than 300 small-scale human hunter-gatherer populations, support one of the central tenets of human behavioral ecology - that ecological forces select for various behaviors in distinct environments, driving behavioral diversity worldwide. The origin and evolution of human behavior are uncertain and debated. While some suggest that humans' unique and equally diverse cultural belief systems are the source of behavioral variation, others argue it is more a product of adaptation to local ecological conditions, which may influence behaviors in similar ways across species. Toman Barsbai and colleagues address these questions by comparing an ethnographic database encompassing 339 small human hunter-gatherer populations worldwide with the behavioral traits of their non-human neighbors to evaluate the behavioral similarity across species living together in a common locale. The analysis revealed that human foragers, mammal and bird species show high levels of similarity across various behavioral traits, including diet composition, child-care duties and community organization. For example, in places where hunter-gatherer populations have social classes, more birds and mammals exhibit notable social hierarchies. According to Barsbai et al., this convergence appears to result from pressures of the local environment and indicate that environmental conditions may play an important role in shaping the behaviors of humans and other animals in similar ways. "Barsbai et al. show convincingly that ecological factors explain much variation in human behavior, but so too does cultural history," write Kim Hall and Robert Boyd in an accompanying Perspective, noting that it is a mistake to understate the deeply entwined role of culture on behavior. "So far, we do not have a complete theory that predicts when culture will override fitness maximizing ecological adaption and vice versa," say Hall and Boyd. "That will be the challenge for the next generation of social scientists as we move beyond an 'either/or' view and toward a fully integrated evolutionary theory of human behavior."
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