Walsh, D. M.

Darwin’s discovery of descent with modification was inaugurated by a shift in perspective that Ernst Mayr (1975) has dubbed “population thinking.” Darwin realized that the explanation of the fit and diversity of organic form should be approached as a question about the constitution of populations. Rather than ask how individual organisms come to acquire their remarkable features—their complexity, their functional integration, their exquisite adaptedness to their conditions of existence—we should ask how populations come to comprise such individuals.