and All That

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1 and All That For sociobiology, see E O Wilson s 1975 Sociobiology: The New Synthesis. Since humans are evolved organisms, our evolutionary history must be relevant to understanding our differences and similarities. There are three problems with studying human evolution: 1. Humans are poor experimental animals: While the field data on humans is rich, acquisition of experimental data is impeded by our longevity and by ethical considerations. 2. Humans are evolutionary orphans: the comparative method fails because our closest relatives are all extinct. 3. Changing environments: environmental differences weaken the link from selective history to current utility. Behaviours can be adaptive now for reasons other than those for which they evolved. Phenotypic development depends on a matrix of resources. Changes in social or physical environments can lead to new phenotypes (examples of human height and bonobo use of signlanguage). So, it s unsafe to assume either adaptive or phenotypic stability. Adaptationist conceptions of evolutionary history underestimate the interconnection of an organism s properties. When is a feature a trait or only part of a trait? Fineness of grain. Adaptation and development are distinct issues. Genetic determinism ignores environmental influences, and so ought properly to be restricted to instinctive behaviour (of which there is little for humans). Dawkins et al, while not genetic determinists, are incautious in their choice of words. The Thornhills rape example isn t dependent on genetic determinism, but is still false. Some adaptations require appropriate environmental cues for their development. Evidence of developmental stability (insensitivity to the environment) isn t evidence for an adaptation because: 1. Conservatism of developmental system. 2. Evolution buffers valuable traits against environmental disturbance. 3. Hereditary diseases are stable but aren t adaptive. Much confusion caused by heat of debates about social Darwinism, conservative and liberal. Summary: two barriers to the application of evolutionary theory to humans. 1. Misapplications. 2. Intrinsic problems noted above The Wilson Program Facultative versus obligate behavioural adaptation. Conditional versus unconditional behavioural rules. There are as many behavioural differences as morphological differences. Behavioural traits are as heritable, and have similar histories. They satisfy the standard requirements for natural selection variation and heritability. Example: selection of female coyness and male promiscuity is based on relative costs of reproduction, especially in mammals. Application to humans. However, there are two cautionary notes: Theotodman@lineone.net Page 1 of 6

2 1. Human sexuality is very different from that of other mammals, and isn t so closely related to reproduction. 2. Sexual behaviour may be a primate inheritance rather than a human adaptation. Mosaic (independent) versus connected traits. The latter can t change without profound developmental or phenotypic changes to the whole organism. Skin colour is an example of the former. Lung number is an entrenched trait, so isn t a specific adaptation in any one type of organism. There are some mosaic behavioural traits; behavioural modules. But, in general, human behaviour is not mosaic. There are general controlling mental mechanisms. We have to choose the right level of granularity of analysis. A change in the controlling mechanisms would have many more consequences than to a particular behaviour From Darwinian Behaviourism to Darwinian Psychology The accepted wisdom is to focus on general psychological mechanisms, not at specific behaviours. The cognitive revolution claims that behaviour is caused by a small set of cognitive mechanisms which develop as the individual grows to maturity. There is an analogy with the cognitive revolution for social behaviour. A small number of cognitive mechanisms have evolved to cause all behaviours. Alexander claimed that many human behaviours are responses to specific situations and so are not adaptations. Yet, they can still be understood adaptively as the result of adaptive mechanisms. Genuinely diverse behaviours are the result of the same learning rule selected for by natural selection. This operates within certain bounds, and it requires a research program to confirm. Surprising behaviours often turn out to be confirmations of the theory on closer investigation. An example of behaviour that seems to refute, but actually confirms the hypothesis. The avunculate system in which (because of endemic female promiscuity) a male is more sure of his genetic relation to his sister s children than to his wife s and so provides for the sister s children at the expense of his own. There are four problems with this idea: 1. The system should be unstable due to defecting female offering faithfulness towards high-resource males. S & G find this an unconvincing argument because females would be constrained by social custom not to defect. However, this counter-argument shows that social custom is a sufficient answer to the avunculate trait (so an adaptive explanation isn t required). 2. Fitness isn t (linearly, or at all, depending on the society) related to economic resources. 3. We need to know the space of available alternative behaviours. 4. There s no significant correlation between behaviour and fitness. The data is ambiguous between two hypotheses: (a) existence of adapted mechanisms for resource distribution sensitive to degrees of kinship. (b) Human resource distribution is made on the basis of unspecialised cognitive and emotional structures widely used in other activities. Theotodman@lineone.net Page 2 of 6

3 Failures to maximise fitness in human societies may be aberrations caused by novel environments; but if these counter-examples (eg. drug abuse) can be dismissed as aberrations, so may the successes of theory Evolutionary Psychology and its Promise Behavioural adaptations (qua adaptations) should be stable, but human culture is diverse. Within-group genetic differences swamp mean between-group genetic differences. However, this is the opposite of what we find in culture, which is much more uniform within than between groups. So, must deduce that evolved human nature only places the broadest constraints on cultural life. Differences between groups are due to variations in cultural rather than biological resources. Evolutionary theory is restricted to explaining how hominids developed the ability to transmit culture and to be moulded by it. The above conclusion is resisted by Evolutionary Psychologists for two reasons: 1. Cultural differences are less profound than alleged. 2. Diversity does have an evolutionary explanation: a single mechanism may generate diverse behaviours. Chomskian linguistics: a paradigm case for Evolutionary Psychologists. Human language is less diverse than seems at first sight, and is highly constrained by a language acquisition device. The setting of various switches explains the diversity of natural languages. The nature / culture dichotomy is inappropriate to language development; both are relevant. Evolutionary Psychologists don t think of the mind as a general-purpose computer, but adopt a modular theory of mind. Darwinian algorithms evolved information-processing mechanisms. Fodor s modules are: 1. Domain-specific. 2. Mandatory. 3. Opaque (their internal processes are not consciously accessible). 4. Informationally encapsulated. Evolutionary Psychologists identify Darwinian algorithms using the technique of adaptive thinking to infer the adaptation from the organism s evolutionary ecological context. There are 4 tasks for the Evolutionary Psychologist: 1. Identify the adaptive problem. 2. Discover correlations between human sense experience / capability and human knowledge capability (eg. detection of water or nutritional-value). However, some evolutionary problems may be adaptively insoluble: adaptive solutions have been developed for 3-D vision because of the existence of sharp-edge cues, but there are no analogous cues available for medium-term weatherforecasting! Theotodman@lineone.net Page 3 of 6

4 3. Construct an information-processing design that could solve the adaptive problem. Then, evaluate competing designs according to optimality modelling. The adaptive hypothesis is that the organism will use the most advantageous design to solve the adaptive problem. 4. Test for the existence of the hypothesised mechanism. Many a beautiful theory has been overthrown by an ugly fact! 13.5 Evolutionary Psychology and its Problems The central idea of Evolutionary Psychology is to look for the effects of natural selection in psychological mechanisms that explain our behaviour, rather than in that behaviour itself. Selection is very likely indeed to have been one of the forces shaping our cognitive systems. However, there are 2 problems: 1. Failure of the nostrum selection solves problems posed by the environment to adapt the lineage to that environment to fit most relevant instances of adaptive change in human psychology. 2. Premature commitment to the modularity of mind thesis. Because the social environment and the genetic lineage change together, evolutionary change driven by the environment isn t adaptive. The example of the Machiavellian intelligence hypothesis no invariant environment. Grain problem for Evolutionary Psychology; what are the problems that are out there in the environment? For example, is mate-choice a single domain / problem or a bundle of related problems? Adaptations may not be explained by the problem to which the adaptive trait is supposed to be a solution. In our example, we require a single cognitive device responsible for mate-selection for this to be a single-domain problem. It s the existence of the module that would explain why we have a single problem rather than a bundle of problems. Evolutionary Psychologists should be just as cautious of accepting the modular theory of mind as they admittedly are of the general purpose computer model. Specialised mechanisms are subject to exploitation in a hostile world. Language acquisition is an unfortunate paradigm to choose, because it is highly co-operative in game theoretic terms (in contrast to the zero-sum games that involve pure conflict; what I win, you lose). This is atypical; a resource-sharing module would be more likely to be manipulated. There are further doubts whether evolution even predicts a modular mind: 1. While language acquisition and perception do seem to develop with too little information available for general-purpose learning to be responsible (the poverty of stimulus argument), so that we can argue that they are specifically adapted, we can t extrapolate this to all skill acquisition. Learning to drive a car or learning to play chess are complex procedures, but there cannot be any purpose-built mechanism for their acquisition. 2. We find some logically trivial tasks (eg. the Watson card-selection test) very difficult in some domains but relatively easy in others. This is the exact opposite of the poverty argument. So, there is no need for a social exchange module. There is no need for special mechanisms for Theotodman@lineone.net Page 4 of 6

5 computationally simple tasks, only for complex ones like motion determination. In mate selection, the difficult elements are age and status determination, but these are generally useful functions which aren t specific to mate selection. 3. Many important problems can t be solved by modular mechanisms. Fodor (in The Modularity of Mind) argues that the pragmatics of language won t work in a modular fashion, because of the intentions (what is implied) behind what is stated. Knowledge of intentions would break the encapsulation constraint. Perceptual mechanisms have reliable rules of thumb, but it s not convincing that there are any such rules in other domains. Hence, encapsulation is the real problem for modularity. Summary: there are two basic errors in Evolutionary Psychology: 1. An over-simplified view of the relationship between the evolving population and its environment, and 2. A too-hasty acceptance of the modularity of mind hypothesis. These are linked problems. Societies change their environments, so there are no stable psychological problems to which natural selection can grind out a solution. Arms race the adaptationist heuristic needs to accommodate an evolving environment. Cognitive adaptation often transforms the environment rather than being an accommodation to it. Hence, it is no use just assuming that the environment poses problems and looking for solutions. Human groups have been their own worst enemies for a long time. This complicates the adaptationist heuristic because: 1. The population structure is not constant and is affected by cognitive changes. 2. Altruistic behaviours that would be selected against in a single population can be adaptive in a segregated population Memes and Cultural Evolution Generalise biological evolution into a wider explanatory scheme to include cultural change; differential fitness, variation and heritability apply to ideas, which can be viewed as replicators in competition. Memes. Dawkins claims that an account of meme lineages, their phenotypic effects and their environment is an account of human culture. Sterelny and Griffiths are highly sceptical of this claim. They agree that memes are in competition, can be copied and may have effects affecting their transmission, but have 3 objections: 1. For cumulative biological selection, the mutation rate must be low, to avoid disruptive noise, but not so slow as to produce sterility of variation. These are grubby details of biology, not to be expected elsewhere. 2. What and how does meme-theory explain anything? Natural selection is a hidden hand theory, explaining what looks like design without needing a designer. But, the social world does have designers. Economics is a hidden hand theory, but isn t evolutionary. Theotodman@lineone.net Page 5 of 6

6 3. Survival of the fittest is tautological for memes, because there is no independent method of verifying their fitness other than survival. For biological evolution, fitness is expected fitness, not actual reproductive success. So, we can predict success for biological organisms from their morphology, behaviour and ecological circumstances (in the appropriate model). This is not the case for memes (other than, maybe, scientific ideas). Page 6 of 6

Sociobiological Approaches. What We Will Cover in This Section. Overview. Overview Evolutionary Theory Sociobiology Summary

Sociobiological Approaches. What We Will Cover in This Section. Overview. Overview Evolutionary Theory Sociobiology Summary Sociobiological Approaches What We Will Cover in This Section Overview Evolutionary Theory Sociobiology Summary 7/22/2007 Sociobiological Approaches.ppt 2 Overview Total focus on internal aspects of personality