Cultural evolution comes of age

View Large Image | Download PowerPoint SlideI begin this book review with a confession. I have spent much of my career working on cultural evolution and I am proud of the work I have done. However, when a parent at a school function or a seatmate on a cross-country flight asks what I work on, I say evolutionary biology or human evolution. I have always felt that nobody knew about contemporary work in the field, and answering ‘cultural evolution’ led to lengthy and occasionally awkward explanations.Cultural Evolution, a terrific new book by Alex Mesoudi, should help solve this problem. In it, he gives an accessible, authoritative survey of this burgeoning field that will be useful to students, scholars from other disciplines, and the general educated reader. Mesoudi provides crystal-clear conceptual explanations of the mathematical models that underpin much of the work on cultural evolution, and skillfully links this theory to a range of empirical work. However, this is more than just an explanatory text. It also takes on the big and often controversial issues surrounding the relationships between genetic and cultural evolution and between micro- and macro-level explanations in the social sciences.The book begins with a bang. The first chapter starts with three empirical examples that support the notion that transmitted culture is crucial for understanding human behavior (from political science: immigrants from Europe come to the USA with beliefs about civic duty that strongly affect political behavior. This variation persists over multiple generations. From anthropology: behavior in economic experiments, such as the Ultimatum Game, show strong cross-cultural differences in fairness and willingness to punish. From psychology: basic assumptions that underlie people's reasoning about the behavior of others vary cross-culturally). Then Mesoudi takes on much of existing social science. Disciplines such as economics and psychology mainly ignore transmitted culture; disciplines such as sociology and anthropology focus on culture, but are non-quantitative and do not link patterns of culture to individual human psychology. The field of cultural evolution is important, Mesoudi argues, precisely because it links these two levels in a single, unified theory. There is no shilly-shallying here: his treatment is trenchant and, for this reader, convincing.Mesoudi then moves on to describe the body of work on cultural evolution that has developed over the past several decades. The central idea that unifies this field is that culture is information stored in human brains and transmitted among individuals and over time through imitation, teaching, and other forms of social learning. This means that culture is a population-dynamic phenomenon and, accordingly, there is now a rich body of theory describing the population-dynamic processes that shape cultural variation within populations—a theory of cultural microevolution. Much of this theory is based on mathematical models analogous to those used in population genetics and, as a result, this work has been difficult for many social scientists. However, Mesoudi provides an excellent non-mathematical treatment explaining how these models work and what they tell us about how social and psychological processes shape human cultures.Conceptualized in this way, cultural populations are characterized by descent with modification, and this means that phylogenetic methods can be used to reconstruct cultural histories. However, there is more horizontal transmission between lineages in cultural systems than in genetic ones, and this difference must be accounted for. Mesoudi clearly explains how cultural phylogenies can be reconstructed and then describes applications of these methods in anthropology, linguistics, and history.The second half of the book illustrates how the theory of cultural evolution can be applied to a diverse set of empirical problems. There are experiments in which laboratory cultures evolve and theory can be tested, field studies in small-scale societies in which patterns of cultural transmission are measured, and applications to economics of technological change and social learning in other animals. Mesoudi excels at providing brief, understandable descriptions of a wide range of interesting research.Cultural Evolution ends with a manifesto. Disciplines in the human sciences are curiously insular. Scholars in different disciplines propound different, contradictory explanations of human behavior, but show little interest in resolving these contradictions. They continue to do research and teach undergraduates as if the findings of other disciplines did not matter. Obviously, this is not a satisfactory situation. Mesoudi forcefully argues that the theory of cultural evolution is the solution to this problem because it provides a synthetic framework that links the properties of individuals to the dynamics of societies and, in so doing, creates a bridge between biology and the social sciences. This is heady stuff, and doubtless many readers will disagree. However, even those who do will find Mesoudi's excellent synthesis of this new field both challenging and informative.