Selectionists deal directly with the artifacts in the archaeological record and consider the human behaviors producing them, or the decisions, values, and norms standing behind those behaviors, as unavailable to a scientific approach. This gives selectionism a certain appealing simplicity and clarity, though much current evolutionary inquiry in archaeology, by contrast, seeks to investigate precisely those sectors of the human experience declared out of reach by selectionists. One emerging tradition of analysis emphasizes processes of cultural transmission, including the roles of learning and decision making. Another focuses on investigating the population-level consequences of environmental variability on variability in human behavior. Both typically require forming and evaluating mathematical models, often in forms suggested by population genetics, in the first case, or by evolutionary ecology, in the second.
Cultural Transmission/Dual-Inheritance Theory
This first of two families of current approaches - related to selectionism by its interest in cultural transmission and therefore in history - is based on an analogy between cultural transmission and genetic transmission. Using formalisms modified from population genetics, Luigi Luca Cavalli-Sforza and Marcus Feldman gave mathematical interpretations to processes in cultural evolution that are analogous to the forces of mutation, selection, migration, and drift in evolutionary biology. This entailed a change in focus from the cultural evolutionist’s interest in long-term trajectories of cultural systems to consideration of the fates of single traits, where a trait is ‘‘the result of any cultural action (by transmission from other individuals) that can be clearly observed or measured on a discontinuous or continuous scale.’’
To apply these forces to culture change, some have to be redefined. Selection, for example, can occur on two levels: cultural selection, entailing adoption of a trait by individuals, and natural selection, which refers to the consequences of that decision on Darwinian fitness. Likewise, cultural transmission is much more varied than genetic transmission since it can be vertical (parents to offspring, as in genetic transmission), oblique (parental generation to offspring generation), or horizontal (within generation). Another important difference between cultural and biological transmission modulates the rate of culture change: cultural transmission may be ‘one to many’ (which can result in rapid change), ‘many to one’ (ordinarily quite conservative), or anywhere in between. These differences make it possible for cultural transmission and selection to result in fixation of behaviors that are detrimental to Darwinian fitness - for example, smoking cigarettes in many portions of the world, or female genital mutilation in North Africa.
Robert Boyd and Peter Richerson, their students and colleagues have broadened and modified this strategy of analysis. They recognized that selection among alternative behaviors is often biased by factors such as the frequency of that behavior in the population, or the prestige of individuals using alternative behaviors; such biases can have significant effects on the course of culture change. A number of archaeologists (e. g., Bettinger and Shennan) have adopted portions of this approach, for example, to model how population size affects rate of culture change, or to infer processes of cultural transmission from the pattern of changing numbers of variant ceramic or projectile point designs through time.
Cultural transmissionists, selectionists, and historical linguists are also beginning to adapt phylogenetic tree - and network-building methods from evolutionary biology and from the study of the history of manuscripts (see Figure 2). These methods provide rigorous tools for investigating the history and pattern of branching and blending within various cultural domains, and also make it possible to control for common origin in assessing cross-cultural hypotheses of functional relationships (thus, overcoming ‘Galton’s problem’). Phylogenetic approaches also make it possible to ask questions about the stability of co-occurrence and co-evolution of traits over long time spans. Do cultures have a stable ‘core’ of relatively unchanging characteristics or are all characters equally subject to change? By their macro-scale and their ability to consider many characters simultaneously, these approaches begin to return us to some of the same interests that motivated the earlier cultural evolutionists.
Behavioral Ecology
Human behavioral ecology (HBE) is the second of the principal contemporary approaches to applying evolutionary theory in archaeology. Archaeologists working in this tradition assume that people (and other animals) have evolved to strive for success in, and make reasonably intelligent decisions about, matters such as maximizing rate of food intake, defense of resources, and so forth, to the extent that these are connected with Darwinian fitness. They use tools
Swati S43 Xhosa S41 Ngoni S45 Zulu S42
Figure 2 This phylogenetic tree was built using data on linguistic cognates among 68 Bantu-speaking cultures in Africa. Then the presence of cattle was mapped onto this tree, along with an inference concerning the ancestral states of cattle-keeping among the hypothetical ancestral populations determined during the construction of the language-based tree. Ancestral states for matriliny and patriliny were also mapped onto this tree (not shown) and then a computer program compared these two phylogenies. The results supported the conclusion that populations adopting cattle-keeping lose matriliny, while controlling for the influence of shared history among the populations in the sample. Reprinted from [Holden CJ and Mace R (2005) ‘The Cow is the enemy of Matriliny’: Using phylogenetic methods to investigate cultural evolution in Africa. In: Mace R, Holden CJ, and Shennan S (eds.) The Evolution of Cultural Diversity: A Phylogenetic Approach, p. 223, Figure 12.3. London: UCL Press] with permission from [Thomson Learning].
Derived in zoology and evolutionary ecology, which were in turn strongly influenced by approaches in economics, to examine the extent to which predictions based on these assumptions are borne out in the archaeological record. Decision making is usually assumed to be based on rational choice among alternative models, in conjunction with individual learning and innovation, and in the context of limited and costly information and various constraints in possible courses of action. HBE is related to sociobiology, though that field takes a more direct interest in reproductive success through its use of kin selection and other models that measure Darwinian fitness directly, rather than analyzing nonreproductive behaviors presumed to be related to fitness.
Behavioral ecologists explain behavioral variability through time, or within a population at a given point in time, by reference to relevant aspects of environmental variability (broadly defined to include the social environment). Traditional problems include explaining change in group size, sharing/exchange, land tenure/resource defense, prey choice/diet breadth, and settlement pattern. Although these problem domains may on first glance seem narrow, they are certainly broad enough to allow researchers in this tradition to study some of the most important transitions in human history - for example, the transition from foraging to agriculture and animal domestication. Recent HBE models, moreover, increasingly grapple with more social and even symbolic phenomena. One such development is the use of signaling theory, which suggests that self-interested individuals can be expected to engage in individually costly but frequently group-beneficial signaling behaviors, with such behaviors becoming more socially conspicuous in proportion to an individual’s ability to produce them. Rebecca Bliege Bird and Eric Alden Smith suggest that costly (honest) signaling explains puzzles including unconditional generosity (for example, in feasting), pursuit of risky big game for public consumption, ostentatious commitment to religion, artistic skill, monumental architecture, and so on.
World History
