FAQ of Evolutionary Psychology进化心理学的常见问题

http://www.anth.ucsb.edu/projects/human/epfaq/evpsychfaq_full.html 2011-10-26 The Evolutionary Psychology FAQ Last updated September 8, 2004. This FAQ is written and maintained by Edward Hagen, formerly of the Center for Evolutionary Psychology, University of California, Santa Barbara, and now at the Institute for Theoretical Biology in Berlin. The FAQ assumes a basic knowledge of genes and natural selection. Its purpose is to outline the foundations of evolutionary psychology. These foundations are extremely robust (though not beyond criticism). The status of specific hypotheses (e.g., mate selection preferences, cheater detection modules) is more debatable, and will not be discussed in detail here. In addition, I address many of the common misconceptions about evolutionary psychology. This FAQ draws upon the work of many individuals. Comments and criticisms regarding it are welcome: e.hagen@biologie.hu-berlin.de. A Russian translation of this FAQ is also available. Frequently asked questions:  What is evolutionary psychology?  What is the EEA and why is it important? (general answer)  What is the EEA? (detailed answer)  Isn't it true that we can't know what happened in the distant past, so the EEA concept is useless?  Why is the EEA equated with the Pleistocene?  Why couldn't humans have evolved during the last 10,000 years?  What is an adaptation?  What is a psychological adaptation?  What about spandrels?  What is domain specificity and why is it necessary?  What is a module?  How can we identify psychological adaptations?  Why are adaptations not for the good of the species?  Why are genes selfish?  Do selfish genes mean selfish people?  Why is the heritability of adaptations generally zero?  How can evolutionary psychologists talk about adaptations without talking about specific genes?  Are there enough genes to build psychological adaptations?  What about 'plasticity'?  What about learning?  What about gene-environment interactions?  Are evolutionary psychologists primarily interested in what makes humans different from other animals?  Is evolutionary psychology just a politically correct version of sociobiology?  Is evolutionary psychology another form of genetic determinism?  Is evolutionary psychology racist?  Is evolutionary psychology sexist?  Is evolutionary psychology a form of Social Darwinism?  Is rape an adaptation?  If my 'genes made me do it', am I still responsible?  Do evolutionary psychologists think that everything is an adaptation?  Why do some people hate evolutionary psychology?  More thoughts on Evolutionary Psychology and political (in)correctness  What are your politics? (Translation: Doesn't evolutionary psychology have a crypto conservative political agenda?)  Does evolutionary psychology have any problems?  References and other reading  What do you do? What is evolutionary psychology? In the three and a half centuries since William Harvey proved that the purpose of the heart is to pump blood, physiologists have revealed the functional organization of the body in blinding detail. Their discoveries demonstrate beyond question that the structure of the body serves survival and reproduction. Further, there is near unanimity among biologists that this functional structure is a product of natural selection. In our century, psychologists have developed powerful techniques that conclusively demonstrate that cognition, too, has structure. Evolutionary psychologists are betting that cognitive structure, like physiological structure, has been designed by natural selection to serve survival and reproduction. Evolutionary psychology focuses on the evolved properties of nervous systems, especially those of humans. Because virtually all tissue in living organisms is functionally organized, and because this organization is the product of evolution by natural selection, a major presumption of evolutionary psychology is that the brain, too, is functionally organized, and best understood in evolutionary perspective. It is clear that the body is composed of a very large number of parts, and that each part is highly specialized to perform a specific function in service of the survival and reproduction of the organism. Using the body as a model for the brain, it is a fair guess that the brain, too, is composed of one or more functional parts, each of which is also specialized to facilitate the survival and reproduction of the organism (we'll get to genes in a bit). Thus, according to evolutionary psychology, neural tissue is no different from any other tissue: it is functionally organized to serve survival and reproduction. This is the foundational assumption of evolutionary psychology. Because vision, hearing, smell, pain, and motor control are indisputable functions of the nervous system that clearly have utility for survival and reproduction, this assumption has a high degree of face validity. Further, these examples suggests that the brain may best be conceived not as an organ with a single function, but rather as composed of a large, and potentially vast number of functional parts. Evolutionary biologists refer to the functional components of organisms as 'adaptations'. Evolutionary psychologists often refer to brain functions as psychological adaptations, although they are not qualitatively different from other adaptations. The functional organization of the body has been elucidated primarily by the direct examination of morphology. A detailed analysis of the structure and composition of our organs and tissues has resulted in an excellent understanding of their purpose. Unfortunately, this has not been the case with the brain. The gross morphology of the brain appears to have little connection with its functional properties. Although we have a fair understanding of nerve cells--the primary constituents of neural tissue--the properties of the brain clearly come from higher order assemblages of such cells, not just the cells themselves. This is just as true of organs like the heart as it is of the brain. Because nerve cells can rapidly change state (e.g., their firing rate), because such state-changes involve little energy, and because they can be well insulated from their neighbors, it is possible for a nerve cell to be in one state, whereas some of its close neighbors may be in completely different states. This is in marked contrast to, say, muscle cells. If one muscle cell is involved in a contraction, then nearby cells almost certainly are as well. Neural tissue is quite different. Even the individual states of nerve cells in a network depend critically on the topology of the network itself. Further, assemblages that are actually distinct may have a complex three-dimensional distribution that can be very difficult to untangle. These properties of neural tissue make it exceedingly difficult to "see" the morphology of neural assemblages--with few exceptions, the network topology of virtually our entire brain is currently "invisible." It exists at a scale above the individual cell, but well below that which can be teased apart with any imaging technology currently available. Until recent decades, much of our immune system was similarly "invisible." Evolutionary psychology offers one way around this technological limitation. If researchers had a sound basis for proposing brain functions a priori, they could then seek indirect evidence that brains in fact have these functional properties. Philosophers and scientists had long wondered why living things are made up of an amazing array of beautifully designed mechanisms, an organization which non-living things completely lack. Why is it that entities that reproduce manifest overwhelming evidence of design, but entities that don't reproduce are utterly devoid of the same? As Darwin and Wallace first perceived, the association of reproduction and design is not accidental. Evolution by natural selection is currently accepted as the only process whereby entities can acquire functional properties. Functional organization is the consequence of the reproductive feedback that characterizes natural selection. If a population of reproducing entities (hereafter organisms) varies in some trait, if the variations can be passed on to offspring, and if, as a consequence of possessing a particular variant, an organism produces more offspring on average than organisms that lack that variant over evolutionary time, then the population will come to consist solely of organisms possessing the reproductively efficacious variant trait. In this way, populations of organisms will tend to acquire traits that facilitate reproduction and lose traits that hinder reproduction. We now know that what is passed on to offspring is a large DNA molecule that is further partitioned into numerous sections called genes. Because the structure of this DNA is intimately bound up with the structure of the organism, variations in the DNA are strongly associated with variations in the organism. Changes in DNA are referred to as mutations, and result from environmental hazards such as radiation, toxins, etc. Reproduction is an enormously complex process. At any given moment in the human body, there are thousands of process that, should they fail to complete successfully, would result in death within minutes. For this reason, any given random change in the body is likely to hinder survival and reproduction, not facilitate it. There are far more ways for a mechanism to fail than there are ways to improve it. How many times has a change occurred to your car so that it got much higher than the EPA estimated miles-per-gallon rather than much lower? Thus, the vast majority of DNA mutations result in changes to the body (also called the phenotype) that hinder reproduction. Occasionally, however, a mutation occurs that results in a change to the phenotype that facilitates reproduction. Because this mutation can be passed on to offspring, and because this mutation tends to result in more offspring, the mutation becomes more frequent in the population. Over time, this process will result in organisms that have a sophisticated repertoire of mechanisms that facilitate reproduction We now have the answer to the question posed above: what functions is the brain likely to perform? If brain tissue is organized like all other tissue, it will perform precisely those functions that facilitate reproduction. More accurately, because evolution by natural selection is an historical process, and because the future cannot be predicted, the brain and body will perform functions that facilitated reproduction (note the past tense). Whether they currently do so will depend on how closely the present resembles the past. If we can develop an accurate picture of a species' reproductive ecology--the set of physical transformations that had to occur over evolutionary time for individuals to reproduce--we can infer those properties the organism is likely to have in order to ensure that those transformations reliably took place. Evolutionary time, the time it takes for reproductively efficacious mutations to arise and spread in the population, is often taken to be roughly 1000-10,000 generations; for humans, that equals about 20,000-200,000 years. Over the last 200,000 years, humans regularly encountered spiders and snakes, creatures whose toxins would have significantly impeded the reproduction of individuals unlucky enough to get injected with them. Over the last 100 years, humans have regularly encountered automobiles, encounters that also can seriously impede reproduction (e.g., by getting run over). Because 200,000 years is long enough for humans to evolve protective mechanisms, but 100 years isn't, we can predict that humans may well possess an innate aversion to spiders and snakes, but not to automobiles--even though far more people are currently killed by cars than by spiders or snakes. Once we have firmly established that avoiding spiders and snakes would have reliably facilitated the reproduction of ancestral humans, we can then design experiments to determine whether humans in fact possess an innate, cognitive ability to detect and avoid these animals (more on how to do this below). A major lesson of evolutionary psychology is that if you want to understand the brain, look deeply at the environment of our ancestors as focused through the lens of reproduction. If the presumptions of evolutionary psychology are correct, the structure of our brains should closely reflect our ancestral reproductive ecology. Thus, evolutionary psychology provides a method for perceiving the functional organization of the brain by studying the world--currently a far more tractable problem than disentangling neural assemblages. What is the EEA and why is it important? (general answer) The Environment of Evolutionary Adaptedness. This phrase, first coined by John Bowlby of attachment theory fame, has been the source of much confusion and controversy. First of all, the EEA is NOT a specific time or place. Roughly, it is the environment to which a species is adapted. Animals that lived in different environments or made their livings in different ways faced different reproductive problems, and that's why all animals aren't the same. Fish faced different problems than did butterflies, and as a result they have different adaptations. The EEA for any specific organism is the set of reproductive problems faced by members of that species over evolutionary time. The EEA for a particular species of fish is likely to be completely different than the EEA for a particular species of butterfly, even if those species both evolved in the same locations over the same periods of time. Each of these species faced reproductive problems that the other didn't, and thus their EEA's are different. The EEA concept is very similar to the notion of 'niche' in evolutionary biology. I have used the past tense when referring to the solving of reproductive problems because adaptations evolved over a large number of generations and are therefore "tuned" to reliable aspects of past environments (see the next section). If the environment changes, then the adaptation may be "out of tune" with the present environment and fail to properly perform its reproductive function. The EEA concept is extremely important for understanding the functional properties of organisms, including the functional organization of the human brain. As outlined in the previous section, the functional properties of organisms arise by the process of evolution by natural selection. This means that the functions that organisms have are precisely those that solved long standing, recurrent reproductive problems. Reproductive problems are all the various things organisms had to do to survive and reproduce in a particular environment over evolutionary time--find food, find mates, avoid predators, combat pathogens, etc. This observation is particularly important for understanding the functional organization of the human brain. Because we cannot (yet) directly study the wiring of the brain (except in a very few cases), we need another 'window' or set of tools for perceiving brain functions. Darwin's theory provides this window. If we can specify all the reproductive problems faced by our ancestors (i.e., if we can specify the human EEA), we can specify all the potential functions that our bodies and brains could have, in principle. With respect to the brain in particular, if we can specify all the reproductive problems involving information processing, we can specify all the possible psychological mechanisms that could have evolved. Whether humans possess any particular psychological mechanism (i.e., an ability to solve a particular reproductive problem involving information processing), becomes an empirical question. Fortunately, it is much easier to find something if you have some idea what you are looking for. Studying the past is, at present, easier than studying brain wiring. The EEA concept therefore provides a much needed tool for determining, a priori, what kinds of functions, or mechanisms, the human brain is likely to have: the human brain solves the reproductive problems posed by past environments; it allows us to do all the things we needed to do to survive and reproduce in ancestral environments--find food, find mates, detect and avoid predators and other dangerous animals, etc. We can understand the functional organization of human bodies and brains precisely to the extent that we can understand the human EEA. What is the EEA? (detailed answer) In order to understand the precise definition of the EEA, we must understand the definition of a selection pressure. Many of the misconceptions about the EEA can be avoided by adhering closely to the precise definition of the EEA derived from the theory of natural selection. As noted above, the EEA is the set of all selection pressures faced by an organism's ancestors over 'recent' evolutionary time (i.e., over approximately the last 1000-10,000 generations). To understand what a selection pressure is, we must understand how a mutation spreads in a population. It must alter the phenotype in some way that enhances reproduction (ignoring drift and other similar processes for the moment). As emphasized elsewhere in this FAQ, reproduction is an enormously complex process; that it happens at all is a near miracle. Reproduction involves a vast number of physical processes that must proceed correctly if reproduction is to be successful. Given the design of an organism, given all the physical transformations that have to take place in order to reproduce, and given ALL the environmental conditions that the organism may encounter with some non-zero probability during its life, there is a (relatively) small set of *potential* transformations of the environment--where the term environment may include aspects of the organism itself--that will enhance rather than impede reproduction. These potential reproduction enhancing transformations are called selection pressures. Stated another way, selection pressures are those aspects of the environment that can have a notable impact on the reproduction of members of a particular species over evolutionary time. The EEA of any species is the set of all features of the environment that could have had some impact on the reproduction of members of this species over recent evolutionary time. For example, let's assume that an herbivore regularly ingests a particular plant toxin, and that this toxin has a detrimental effect on sperm quality. Let's also assume that there are enzymes that can neutralize this toxin, but that the herbivore cannot produce these enzymes. The fact that the plant toxin can be neutralized by an enzyme is an example of a *potential* transformation that could facilitate the reproduction of the herbivore (because it would result in improved sperm quality). Thus, the plant toxin is a selection pressure and is therefore an aspect of the EEA of the herbivore. Should a mutation arise that produces a toxin neutralizing enzyme, this mutation will spread in the population. After many generations, all herbivores of this particular species will now be able to neutralize this plant toxin. If the plant goes extinct, the herbivores will still be able to produce the detoxifying enzyme (for many generations, at least), and this particular toxin is still considered an aspect of the species' EEA. Alternatively, if no mutation ever arose to produce a detoxifying enzyme, this plant toxin was still a feature of the species EEA. It was a selection pressure, even though no adaptation evolved to neutralize it. On the other hand, if a different toxic plant also grew in the same area as the first toxic plant, but the herbivores never ate that plant, then the second plant an