Evolutionary Scenarios and Primate Natural History

Scenarios summarize evolutionary patterns and processes by interpreting organismal traits and their natural history correlates in a phylogenetic context. They are constructed by (1) describing phenotypes (including physiology and behavior), ideally with attention to formative roles of development, experience, and culture; (2) inferring homologies, homoplasies, ancestral character states, and their transformations with phylogenetic analyses; and (3) integrating those components with ecological and other ancillary data. At their best, evolutionary scenarios are factually dense narratives that entail no known falsehoods; their empirical and methodological shortcomings are transparent, they might be rejected based on new discoveries, and their potential ideological pitfalls are flagged for scrutiny. They are exemplified here by homoplastic foraging with percussive tools by humans, chimpanzees, capuchins, and macaques; homoplastic hunting with spears by humans and chimpanzees; and private experiences (e.g., sense of fairness, grief) among diverse animals, the homologous or homoplastic status of which often remains unexplored. Although scenarios are problematic when used to bolster political agendas, if constructed carefully and regarded skeptically, they can synthesize knowledge, inspire research, engender public understanding of evolution, enrich ethical debates, and provide a deeper historical context for conservation, including nature appreciation.