Analyzing adaptive strategies: Human behavioral ecology at twenty-five

Expected current adaptiveness Highest Lowest Intermediate Hypothesis generation Optimality and ESS models Informal inference Population-level models Primary hypothesis-testing methods Quantitative ethnographic observation Survey, laboratory experiment Mathematical modeling and simulation Favored topics Subsistence, reproductive strategies Mate choice, sex differences Cooperation, maladaptation a Modified from Smith.46HBE is only one of several distinct approaches to evolutionary analysis of human behavior that have developed in recent years; other prominent ones include evolutionary psychology and dual inheritance theory.Here we offer a brief comparison with these two fields.46 -49 Evolutionary psychology (EP) aims to uncover the evolved "psychological mechanisms that underpin human . . .behavior," and "the selective forces that shaped those mechanisms" 50 (see reviews [51][52][53][54] ).EP posits that human behavior is guided by specialized cognitive modules rather than "general purpose" mechanisms that work across multiple behavioral domains.It argues that these modules evolved in the EEA (environment of evolutionary adaptedness), and are designed to produce very specific outcomes that may no longer be adaptive in modern (post-paleolithic) environments.Based on these assumptions, some evolutionary psychologists [55][56][57] have actively criticized behavioral ecologists for studying adaptive patterns in contemporary nonforaging contexts, and for measuring degree of adaptation via fitness outcomes or correlates.Dual inheritance theory (DIT) views culture and genes as providing separate (but linked) systems of inheritance, variation, and hence evolutionary change.58 -63 Most DIT practitioners posit that the spread of cultural information is affected by multiple forces, including natural selection (differential fitness of culturally inherited variation), decisionmaking (based on genetically or culturally evolved preferences and constraints), and transmitter influence or prominence.They differ in the relative strengths or attention they give to these various forces.In contrast to classical forms of cultural evolutionism 64,65 and to evolutionary archaeology, 66,67 DIT practitioners posit that cultural evolution is embedded in and constrained by genetically evolved psychological propensities.They often build these assumptions into explicit mathematical models.Since cultural inheritance differs from genetic inheritance in key ways (e.g., nonparental transmission, multiple transmission events over a lifetime), the evolutionary dynamics of culture will also differ in important but analytically understandable ways.Hence, genetically nonadaptive cultural evolution is possible, and may be likely in hierarchical and modern bureaucratic societies.However, this divergence of cultural and genetic evolution can cut both ways: several DIT theorists 60,68,69 posit that mechanisms of cultural evolution often find ways of improving on adaptive outcomes compared to what can be achieved by ordinary genetic evolution plus phenotypic adaptation.Although EP, DIT, and HBE are often portrayed as competing alternatives, a case can be made for viewing them as complementary.46,48,49 Competition is fueled by different assumptions, analytical methods, and alliances with other disciplines, as well as by ordinary academic politics.Complementarity between the three styles is increasingly recognized, however, and can be fostered by taking advantage of differences in their methods of investigation (e.g., observation vs. experiment), empirical foci (e.g., psychological vs. behavioral vs. cultural), selection of constraints (cognitive, ecological, informational), time scales of adaptation, and behavioral domains (see table, above).There are limits to this complementarity, however.A behavior cannot simultaneously be the product of a genetically programmed cognitive algorithm that no longer produces adaptive results, a product of a culturally inherited meme that persists because it has a high replication rate, and a product of phenotypic adaptation that is optimally geared to local environmental conditions.Nevertheless, these hypotheses could be simultaneously true for different behavioral domains or instances.46