In this blog post, we will examine whether evolutionary psychology can indeed be considered a science, based on various criteria from the philosophy of science.
Evolutionary psychology is a field of study that seeks to understand human psychology from an evolutionary perspective. It is primarily based on evolutionary biology and cognitive psychology, particularly computational theories of the mind and the modular hypothesis. Computational theories of the mind view cognition, emotion, and thought as information-processing or computational processes, and regard the brain as the organ that performs this information processing. Furthermore, the modular hypothesis explains that a significant portion of the mind is composed of modules, each performing a specific function. These mental modules are viewed as evolved psychological mechanisms formed over a very long period of time; given the pace of human evolution, it is believed that modern humans possess psychological mechanisms very similar to those of their distant ancestors.
Evolutionary psychology uses these psychological mechanisms to explain a wide range of phenomena, from habits repeated in daily life to behaviors common to all of humanity. For example, many people tend to prefer window seats when they go to a café. This is explained by the fact that, in order to survive on the African savanna during prehistoric times, humans evolved to prefer locations that offered a wide field of view and allowed them to scan their surroundings without being easily exposed. At first glance, the interpretation that behaviors we take for granted are the result of evolved psychological mechanisms is fascinating. However, upon closer reflection, doubts arise. Is this explanation really accurate? Is it a scientifically validated theory, or does it remain merely a hypothesis? Furthermore, can evolutionary psychology itself be considered a science?
It is not easy for anyone to clearly define the criteria that distinguish science from non-science, nor the prerequisites that a scientific claim must meet. Therefore, in this article, we will examine whether evolutionary psychology can truly be considered a science based on five generally accepted criteria.
First are logic, rationality, and accountability. Not everything that is logical is science, but anything lacking in logic cannot be considered science. This includes consistency; without logic, it is difficult for any evidence or proof to hold up. Furthermore, all claims and theories must be evaluated rationally, and the burden of proof lies with the person making the claim.
Evolutionary psychologists primarily develop their explanations based on three concepts: the theory of natural selection, adaptation to the environment, and byproducts. First, natural selection is the theory that individuals possessing traits suited for survival have an advantage in survival and reproduction over those who do not. Therefore, evolutionary psychology explains most phenomena in terms of the ultimate goals of survival and reproduction. However, this raises another question: Is the unit of natural selection the gene, the individual, the population, or some other level?
*Darwin’s Table* addresses this issue in detail. For example, if someone is willing to sacrifice themselves for another person, where does this behavior originate? Darwin proposed the theory of group selection, an evolutionary mechanism in which individuals sacrifice themselves for the group. In contrast, George C. Williams argued that traits that exist for the benefit of the group are unlikely to evolve in the long term because they are likely to disappear rapidly within the group during the process of natural selection. He viewed altruistic behavior as having evolved because it ultimately brought greater benefits to the individual.
Furthermore, Robert Trivers explained that in situations where there is a possibility of future reciprocation, helping others is actually beneficial, and that this reciprocal altruism can evolve. Stephen Jay Gould argued that evolution occurs at various levels—including the cellular, organ, individual, population, and species levels—while David Sloan Wilson proposed, through a new group selection model, that the number of altruistic individuals could increase. In response, Richard Dawkins explained that cooperative behavior is also the result of evolution as a strategy for genes to spread more copies of themselves. Conversely, Gould criticized this perspective as “gene reductionism.”
As such, it has been suggested that natural selection can occur at the individual level, the population level, and even at the gene or cellular level. If so, is the multilevel selection theory, which encompasses all these perspectives, the correct answer? If it is, it is currently difficult to clearly determine which of these levels takes precedence—or even whether the multilevel selection theory itself is correct. Therefore, natural selection must be viewed as a theory encompassing multiple hypotheses, and it is difficult to conclude that evolutionary psychology, which is based on it, has been sufficiently validated in terms of logical soundness and reliability. Some might argue that since species with a survival advantage have survived thus far, this debate is unimportant. However, just because this has been the case so far does not mean it will necessarily continue to be so in the future. Therefore, efforts are needed to establish the theory through more rigorous verification.
Second, we must avoid falling into the trap of reductionism. Psychologist Richard Wiseman distributed a copy of a newspaper to each participant and asked them to count all the photographs published in it. However, on page 2, he had written in very large letters: “Stop counting. There are a total of 43 photographs in this newspaper.” Yet not a single participant noticed this. People committed the error of focusing so intently on the detailed task of counting the photos that they failed to see the bigger picture. In this way, reductionism refers to the way of thinking that the whole is the sum of its parts, and that the whole can, in turn, be reduced to its parts.
One of the primary arguments used to criticize evolutionary psychology is precisely this reductionist fallacy. As we saw earlier, because evolutionary psychology is based on natural selection, it tends to explain most phenomena in terms of the goals of survival and reproduction. However, this approach also gives rise to various contradictions.
For example, evolutionary psychologists Randy Sonhill and Craig T. Palmer argued that rape could be an adaptive strategy that increases men’s reproductive success. However, the rape hypothesis includes explanations such as “a mechanism evolved to make women feel pain when raped” as well as the claim that “a mechanism evolved to make humans perceive rape as evil.” So, does the existence of a mechanism regulating rape behavior mean we should not condemn rape? Or does the existence of a mechanism that leads us to morally condemn rape mean we must condemn it?
Common sense suggests that men who commit rape are likely to be perceived as immoral, and women will avoid such men. In that case, men who do not commit rape might actually have a reproductive advantage. Ultimately, this approach allows any phenomenon to be explained within the framework of survival and reproduction, and even two mutually contradictory claims can be explained simultaneously. This is precisely why the fallacy of reductionism arises.
Third are reproducibility or repeatability and inductive infallibility. Even if a theory is verified through the scientific method—involving observation, hypothesis formulation, experimentation, and replication—there is always the possibility that bias and error may creep into the process and interpretation. Therefore, it must be demonstrated that the same results can be repeatedly reproduced, and all available evidence must be considered together. If one selects only certain evidence and excludes the rest, one is bound to fall into inductive error.
Let’s look at an example. The book *The Old Toolbox* introduces an interesting experiment. This experiment is based on the hypothesis that humans have evolved to avoid contact with outsiders because such contact carries the risk of exposure to new pathogens, and that this psychological defense mechanism has given rise to out-group aversion and ethnocentrism.
Evolutionary psychologist Jason Faulkner and his colleagues showed one group a slide emphasizing the dangers of bacteria and viruses, while showing another group a slide emphasizing the risks of electric shock or traffic accidents. When they subsequently surveyed opinions for and against the immigration of foreign workers, the group exposed to the risks of pathogens showed a higher rate of opposition. Based on this, they interpreted the results as supporting the hypothesis. But is this result alone truly convincing?
The explanation that people are wary of outsiders due to the possibility of exposure to new pathogens is certainly persuasive. However, this may not be the only reason for such wariness, and it is entirely possible that other factors played a greater role. For example, inter-tribal warfare could also have been a significant factor. At that time, there were few opportunities for contact with distant tribes, so interactions likely occurred primarily between neighboring tribes. If so, just how significant were the differences in pathogens between neighboring tribes? On the other hand, since inter-tribal warfare occurred frequently, it is also possible that this led to the development of a mindset of wariness toward outsiders. In that case, can we definitively conclude that the same results would have been obtained if, in the experiment, materials emphasizing the dangers of war had been presented instead of bacteria and viruses?
Of course, the same results might indeed have emerged, and pathogen factors might have had the greatest influence on the formation of in-group favoritism. However, this is merely a single case, and in evolutionary psychology, it is not difficult to find examples like this where reproducibility and inductive infallibility are difficult to sufficiently verify.
Fourth is falsifiability. Karl Popper, a leading philosopher of science of the 20th century, argued that “for a theory to be scientific, it must be falsifiable, refutable, and testable.” If a claim is true, there must also be a possibility that it could be falsified. For example, if your mother says a package will arrive tomorrow at 3:00 p.m., but the package does not actually arrive at 3:00 p.m., then that claim is proven false. In other words, it is falsifiable. On the other hand, concepts such as the theory of Yin-Yang and the Five Elements—which cannot be empirically verified or refuted—are difficult to falsify.
Let’s revisit the example of rape mentioned earlier. Evolutionary psychology explains that rape is a strategy advantageous for reproduction. To falsify this, let’s propose the opposing proposition: “Rape is not advantageous for reproduction.” In reality, committing rape can brand a person as immoral and put them at a disadvantage when seeking a mate. Therefore, one could argue that rape does not aid in reproduction. However, this can also be explained within the logic of evolutionary psychology. Ultimately, both opposing claims can be explained by evolutionary psychology.
As another example, evolutionary psychology sometimes explains homosexuality as an evolutionary adaptation. If so, it should also be possible to refute its opposites—heterosexuality and celibacy. However, heterosexuality can be explained as the behavior most directly advantageous for reproduction. Ultimately, it becomes possible to have two contradictory explanations coexist simultaneously. For this reason, there are quite a few claims in evolutionary psychology that are difficult to refute.
Fifth are predictability and the potential for advancement. A scientific theory must be able to predict events with a degree of accuracy that goes beyond chance, and when errors are revealed through falsification, it must be able to advance by proposing a new hypothesis that is superior to the existing explanation and proving it.
In falsificationism, there is a concept known as “refined falsificationism.” This means that a hypothesis must have a higher degree of falsifiability than competing hypotheses. For example, consider the hypothesis that “the force acting between all objects is inversely proportional to the square of the distance between them” and the hypothesis that “the force acting between planets in the solar system is inversely proportional to the square of the distance between them.”
The first hypothesis encompasses the second. Therefore, any instance that falsifies the second hypothesis also falsifies the first. However, not every instance that falsifies the first hypothesis necessarily falsifies the second hypothesis as well. For this reason, we say that the first hypothesis is more falsifiable than the second. Science advances when a new theory with greater falsifiability than existing theories emerges.
Conversely, the practice of adding new assumptions as a stopgap measure or partially modifying existing theories to avoid falsification is called an “ad hoc” theory modification. For example, consider the hypothesis that “All crows are black.” If a crow that is not black were discovered in Seoul, this hypothesis would be falsified. If, to avoid this, the hypothesis were modified to state, “All crows not in Seoul are black,” this would be an ad hoc modification of the theory. Falsificationism views such regressive methods of theoretical modification as undesirable.
So, can evolutionary psychology continue to develop as a science? Evolutionary psychology explains various phenomena by applying theories of adaptation to the environment and byproducts, based on natural selection. For example, since suicide is difficult to view as a behavior that directly benefits survival and reproduction, it is sometimes interpreted as an adaptation to the social environment or a byproduct that emerged during the evolutionary process. If such an explanation were to be falsified, would evolutionary psychology be able to propose a new, bold theory—one that is more persuasive than adaptation to the social environment but difficult to accept based on current common sense?
The same question arises regarding predictability. Could anyone have predicted, from a past perspective, that the issue of suicide would become as socially serious as it is today? Furthermore, to what extent can evolutionary psychology alone accurately predict new social phenomena that will emerge in the future?
Of course, behaviors or tendencies that aid survival and reproduction may be predictable to some extent based on the body of research accumulated to date. However, since changes in the social environment and their various byproducts can have an impact just as significant as natural selection, the scope of what is actually predictable is inevitably very limited.
So far, we have examined evolutionary psychology from five perspectives. It is clear that evolutionary psychology is a discipline that offers fascinating explanations for various human behaviors and everyday phenomena. However, when we synthesize the various arguments presented to date, there remain unresolved issues that prevent us from definitively classifying it as a science.
Furthermore, as evolutionary psychology is a relatively young field, it is highly likely that diverse research and debates will continue in the future. Indeed, there are many researchers and readers who show great interest in evolutionary psychology, and related research continues to accumulate. We look forward to seeing its scientific validity and explanatory power continuously evaluated and developed through more rigorous research and repeated verification in the future.
