3/30/2012. Two Contrasting but Complementary Evolutionary Perspectives on Human Behavior:

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1 Two Contrasting but Complementary Perspectives on Human Behavior: Psychology (EP) derived from a synthesis of biology and psychology Human Behavioral Ecology (HEB) derived from a synthesis of biology and anthropology I think these are legitimate and complementary perspectives. So do Barrett, Dunbar & Lycett (text). Psychology Human Behavioral Ecology Focus on Universals Variation/Diversity Assumed Selective How measure Adaptation? Usual study population of Adaptedness Design Criteria (re EEA) Modern societies Present Reproductive Success or Fitness Traditional societies Hunter-gatherer (foraging) society: Subsistence gained from hunting animals,fishing, and gathering edible plants in the wild, without domestication of animals or of plants (agriculture). Relatively small, simple band level of social organization. Hunting and gathering is thought to have been the only subsistence strategy employed by hominid societies for more than two million years, until about 10-15,000 years ago. The environment that humans and, therefore, human minds evolved in was very different from our modern environment. Our ancestors spent well over 99% of our species' evolutionary history living in small, nomadic bands of a few dozen individuals who got all of their food each day by gathering plants or by hunting animals. Each of our ancestors was, in effect, on a camping trip that lasted an entire lifetime, and this way of life endured for most of the last 10 million years. Cosmides & Toobey: Psychology: A Primer 1

2 Our species lived as hunter-gatherers 1000 times longer than as anything else. [Our familiar] world with roads, schools, grocery stores, factories, farms, and nation-states, has lasted for only an eyeblink of time when compared to our entire evolutionary history Agriculture first appeared on earth only 10,000 years ago, and it wasn't until about 5,000 years ago that as many as half of the human population engaged in farming rather than hunting and gathering. Natural selection is a slow process, and there just haven't been enough generations for it to design circuits that are welladapted to our post-industrial life In other words, our modern skulls house a stone age mind. The key to understanding how the modern mind works is to realize that its circuits were not designed to solve the day-to-day problems of a modern American -- they were designed to solve the day-today problems of our hunter-gatherer ancestors Cosmides & Toobey: Psychology: A Primer Cosmides & Toobey: Psychology: A Primer psychology is relentlessly past-oriented. Cognitive mechanisms that exist because they solved problems efficiently in the past will not necessarily generate adaptive behavior in the present. Indeed, EPs reject the notion that one has "explained" a behavior pattern by showing that it promotes fitness under modern conditions Although the hominid line is thought to have evolved on the African savannahs, the environment of evolutionary adaptedness, or EEA, is not a place or time. It is the statistical composite of selection pressures that caused the design of an adaptation. Cosmides & Toobey: Psychology: A Primer Key point about EEA: mismatches between modern environments and the EEA will inevitably compromise the effectiveness of human adaptations that evolved in the EEA. This compromised effectiveness is called adaptive lag. Natural Selection or Cultural Selection? The two can work hand in hand: co-evolution or biocultural evolution. 2

3 Tenets of Psychology 1. Psychological mechanisms not behaviors have been shaped by natural selection to enhance reproductive success. 2. Mechanisms have many effects ( side effects ) besides the favorable (selected) effects. And these side effects can be maladaptive. 3. The historical ecological context (EEA) in which human evolution occurred is different from the contemporary context, especially those of modern societies. 4. Therefore, a given trait may be: (a) adaptive; (b) a maladaptive side effect of an otherwise adaptive mechanism; or (c) a maladaptive interaction of an out-of-date adaptive mechanism with a new environmental context. 5. The Mind as a set of specialized modules Psychology vs. Human Behavioral Ecology Psychology Human Behavioral Ecology EP HBE Focus on Universals Variation/Diversity Assumed Selective How measure Adaptation? of Adaptedness Design Criteria (re EEA) Present Reproductive Success or Fitness Daly & Wilson 1999 vs. Usual study population Modern societies Traditional societies 3

4 Daly & Wilson 1999 Daly & Wilson 1999 Interpretative pitfalls await those who disregard the possibility of mismatch between contemporary environments and the EEA. Example: Kalick et al (1998): no correlation between attractiveness at and prior or future health status therefore a Fisher runaway effect, not a good genes effect. Blinded by beauty. But the ancestral information value of attractiveness cues [i.e., predictive of good health in the EEA] might have been obscured by modern medicine, good nutrition, or other aspects of life in 20 th -century, urban California. True evolutionary approach carves the psyche more nearly at its joints. Freud never grasped the fundamental Darwinian insight that the ultimate criterion of adaptive functional organization is its contribution to fitness. Symons (1989): measuring reproductive attainment [contemporaneous reproductive fitness] is not the test of a Darwinian approach. EPs accuse HBEs of treating inclusive fitness as a motive or objective rather than as the historical arbiter of the selective retention of attributes, and thus of imagining that evolution imparts a magic ability to find the course of action that maximizes inclusive fitness even in the face of evolutionarily unforeseen challenges. Contrast Psychology (EP) and Human Behavioral Ecology (HBE). To considerable extent EP and HBE are complementary, differing in relative emphasis placed on psychological mechanism versus manifest behavior But they diverge in other, controversial ways: 1. Use of formal models and deductive theory ( HBE) 2. Emphasis on domain-specific cognitive algorithms ( EP) 3. Relationship between psychological mechanisms and observed behavior ( EP) 4. Assertions regarding adaptive lag and adaption to past environments (EP HBE ) 5. Views on the relevance of fitness measures to analyses of contemporary behavior. (EP HBE ) 1. Use of formal models and deductive theory ( HBE) 2. Emphasis on domain-specific cognitive algorithms ( EP) fitness maximization is often a better predictor of behavioral patterns than is pursuit of any one specific goal presumably because nature is full of trade-offs, and organisms have evolved mechanisms to appropriately weigh different goals and currencies. While partitioning adaptive problems into discrete real-world problem domains (such as mate assessment, kin recognition, parental investment allocation, and threat and bluff) may carve the psyche more nearly at its joints, it is not at all clear how EP helps us analyze the myriad situations where these domains interact in determining adaptive payoffs. Need optimization and ESS models. 4

5 3. Relationship between psychological mechanisms and observed behavior. The central problem here is that behaviour is unlikely to be a simple expression of evolved psychological mechanisms, but rather a complex outcome of interaction between such mechanisms and psychological, social and cultural dynamics. In practice the EP research strategy often ends up simply ascribing behavioural patterns, or verbal statements about preferences, to hypothesized psychological mechanisms. Mate choice as example: EP studies has revealed lots about the sexual and parental cues men look for in women, and vice-versa [but little about] how they are used in the real world of mating markets and biological clocks. 4. Assertions regarding adaptive lag and adaption to past environments (EP HBE ) In practice, the evolutionary part of EP often reduces to rather vague claims about selective conditions in the EEA that may have favoured the evolution of a hypothesized psychological mechanism To the extent that our knowledge of the EEA remains sketchy, rigorous quantitative testing of precise selectionist hypotheses becomes virtually impossible, and the result can easily degenerate into adaptive storytelling. In contrast, HBE researchers begin with the assumption that evolved conditional strategies, learning biases, and social information transfer will produce adaptive outcomes, most of the time, even in relatively novel environments. pointing to the negative side of a given trade-off does not provide valid grounds for concluding that the trait is maladaptive trout example 5. Views on the relevance of fitness measures to analyses of contemporary behavior. (EP HBE ) EP researchers: fitness measures are irrelevant to evolutionary analyses of current behaviour. in our experience the fitness-maximization assumption usually comes closer to predicting observed behaviour than an assumption that fitness consequences are irrelevant. EP researchers are all too ready to assume that a given trait maximized fitness in the EEA (a truly untestable assertion) even as they find fitness measures irrelevant in the present. Cultural selection and natural selection can work to the same end Genes trait fitness Natural selection Memes trait fitness Cultural selection Meme: a unit of cultural ideas, symbols or practices, which can be transmitted from one mind to another through communication. 5