In this blog post, we will examine the debate over whether rape is an adaptive behavior in the context of evolutionary biology, focusing primarily on critical perspectives on this issue.
Recent news reports frequently cover sexual crimes, particularly rape cases. In South Korea, too, sexual crimes have long been treated as a major social issue, and such crimes continue to occur steadily. So why do people commit rape? Generally, it is often thought to be the result of a failure to properly regulate violent tendencies and sexual impulses. However, there are also studies that interpret this from the perspective of evolutionary biology. Notably, in ‘A Natural History of Rape’, co-authored by Professor Randy Thornhill, it is argued that male rape behavior is an adaptive behavior that evolved to increase the likelihood of reproductive success. This claim has faced significant criticism not only from the humanities and social sciences but also from the general public, and it has long been a subject of debate within evolutionary biology itself. In fact, ‘Darwin’s Table’ selected “Is Rape an Adaptation?” as its first topic and held a lively discussion on the matter. So, is rape truly an adaptive behavior, as Thornhill claims? I believe it is a stretch to view rape as an adaptive behavior. Rather, I think it is more reasonable to interpret rape as a byproduct of the failure to adequately control human sexual desires and impulses.
Before discussing whether rape is an adaptive behavior or not, we first need to examine the concept of “adaptation.” In evolutionary biology, adaptation refers to a trait formed as a result of natural selection. In a population with diverse variations, if a specific trait is better suited to the environment than other traits and thus provides an advantage for survival and reproduction, that trait is passed on to the next generation more frequently. When this process is repeated over a very long period, the proportion of individuals possessing that trait increases; this is referred to as the result of natural selection. In other words, an adaptation refers to a trait that has been selected by natural selection over a long period of time because it is advantageous for survival and reproduction. Therefore, to say that rape is an adaptive behavior implies that the act of rape was selected because it provided an advantage for survival and reproduction over the course of a long evolutionary process. Let us now examine the problems with this claim.
Thornhill argued that rape is a behavior directly selected by natural selection over a long evolutionary process, specifically an adaptive behavior by which males who have difficulty finding mates increase their chances of reproductive success. One of his arguments is that a significant number of rape victims are young women of childbearing age. In other words, by targeting women capable of pregnancy, men increase their own chances of reproductive success. However, this explanation fails to account for sexual violence against victims who are not of childbearing age. In fact, sexual violence against children and the elderly continues to occur, and ‘Darwin’s Table’ notes that child victims account for a significant proportion of such cases. Since victims who are not of childbearing age cannot become pregnant, these cases demonstrate the limitations of explaining rape as an adaptive behavior aimed at reproductive success.
Furthermore, Thornhill argued that human rape behavior could also be an adaptive behavior, citing the fact that male scorpion flies possess specific organs that enable forced copulation. However, this logic is not sufficiently persuasive. This is because behaviors observed in specific animals or insects cannot be directly applied to humans. Humans differ significantly from other animals not only in physical structure but also in cognitive abilities, social norms, and cultural environments. Therefore, it is inappropriate to generalize examples from specific animals to explain human behavior. Just as the fact that most animals do not commit rape cannot serve as evidence that human rape is not an adaptation, the existence of organs that facilitate forced copulation in some animals does not constitute evidence that human rape is an adaptive behavior.
Another reason why it is difficult to view rape as an adaptive behavior is that rape crimes continue to occur even among people who have spouses.
Historical statistics show that a significant number of rapists were married, and this pattern remains largely unchanged today. Furthermore, if we exclude minors from the analysis, the proportion of offenders with spouses is likely to be even higher. Additionally, an examination of the socioeconomic backgrounds of rapists reveals that it is not merely those who struggle to find a spouse who commit these crimes; a significant number are economically stable or hold high social status. In other words, even people who have secured a spouse and are in an environment where they can reproduce stably commit rape. In fact, in such cases, rape is highly likely to lead to social punishment and family breakdown, which could work against them in terms of survival and reproduction. Considering these points, it is difficult to view rape as an adaptive behavior.
Furthermore, counterarguments can be raised against each of the pieces of evidence presented above. A prime example is the question of how to explain rape committed by married individuals who already have a spouse. As noted earlier, the fact that people with spouses commit rape makes it difficult to explain rape as an adaptive behavior. A counterargument to this is that even if a person has a spouse, if they can pass on their genes to more women through rape, they can ultimately produce more offspring, which is advantageous for reproduction. However, this argument has the limitation of viewing rape solely through the lens of reproduction and considering only the moment the act occurs. In reality, if a married person commits rape and is caught, there is a very high probability that their family will break up or that they will lose their spouse, and social punishment and economic losses will follow. These consequences can actually lead to the loss of a stable reproductive environment; therefore, it is difficult to view this behavior as advantageous from the perspective of survival and reproduction.
Another counterargument exists: adaptation is the result of natural selection over a long history of evolution, and most human traits were shaped in environments that predate modern civilization. Therefore, the argument goes, we must consider the possibility that the act of rape was selected by natural selection in past environments rather than in modern society, and it is inappropriate to judge whether it is an adaptation based on today’s social environment or statistics. Indeed, since the pace of environmental change is very rapid in modern society, it is difficult to conclusively determine whether a trait is adaptive or not based solely on current behavioral patterns. However, it is also difficult to view rape committed by married individuals as a new phenomenon unique to modern society. Cases of married individuals committing rape have existed for a long time and are not a behavior unique to a specific era. Therefore, modern statistics serve merely as a reference for explaining this phenomenon, and it is difficult to refute this argument simply because modern data was used.
If rape is not an adaptation, how should it be interpreted? As mentioned earlier, I believe it is more convincing to understand rape as the result of a failure to adequately control strong sexual impulses. Craig T. Palmer, co-author of ‘The Natural History of Rape’, also suggested that rape may be a byproduct of strong human sexual desire. In other words, this interpretation views rape not as a behavior that evolved for survival and reproduction, but rather as a behavior that arises in the process of satisfying one’s own sexual desires. From this perspective, sexual violence against women who are not in their fertile period, rape committed by married individuals, and cases where economically and socially stable individuals commit rape can all be explained as behaviors aimed at satisfying their own sexual desires.
The debate over whether rape is an adaptive or non-adaptive behavior has been ongoing for a long time. Moreover, because rape goes beyond mere scientific discussion and is closely linked to ethical and moral issues, it continues to generate significant controversy. Even researchers who argue that rape is an adaptive behavior do not deny the fact that rape is a serious crime. They argue that understanding the evolutionary origins of rape can help develop more effective prevention strategies. However, when we synthesize the various pieces of evidence examined so far, there are quite a few cases that are difficult to explain if rape is interpreted as an adaptive behavior. Rather, I believe it is a more realistic and effective approach to understand rape as behavior stemming from a failure to control sexual impulses and desires, and to develop prevention, education, and social response measures from this perspective.
