In this blog post, we’ll examine the main arguments that view rape from a biological perspective, along with the counterarguments, and consider together the claim that rape is an evolutionary adaptation.
There are crimes that occur relentlessly, regardless of time or place. Theft, murder, assault, and rape are prime examples. Among these, rape is considered one of the most brutal and serious crimes. When a rape occurs, society is deeply shocked, and calls to punish and prevent such crimes grow louder. In fact, every time a major incident occurs, discussions about the need to impose harsher penalties have followed. However, despite stricter penalties, rape continues to occur relentlessly.
Why does rape persist throughout human history? Some attribute the cause of rape to men’s animalistic nature, while others argue that it is triggered by women’s behavior. Meanwhile, there are studies that analyze rape from an evolutionary biological perspective. Notably, evolutionary biologist Randy Thornhill, in his 2000 book ‘A Natural History of Rape’, argued that rape can be understood as an evolutionary adaptation. The publication of this book sparked intense social controversy. Thornhill was criticized for defending crime, and fierce debates ensued even among evolutionary biologists. Some even used these claims as an opportunity to criticize evolutionary theory itself. What exactly was in the book that caused such a major social controversy? From here on, we will examine Thornhill’s arguments and consider the claim that rape is an adaptation.
Before doing so, however, we need to examine the concept of “adaptation” as used in evolutionary biology. Adaptation refers to the process by which traits that are advantageous for an organism’s survival or reproduction are passed down to subsequent generations through natural selection. When an individual with a specific genetic trait gains an advantage in survival or reproduction, that individual passes on more of its genes to the next generation than other individuals. As a result, over time, the proportion of individuals possessing that trait within the population increases. This is what is meant by “adaptation” in evolutionary biology.
Based on this concept, we can understand the meaning of the claim that “rape is an adaptation.” This claim suggests that rape may have functioned as a strategy advantageous for human survival or reproduction. Since rape involves forced sexual intercourse, this premise assumes that it was selected for reproductive rather than survival purposes. Let us now examine the claim that rape is an adaptation in more detail.
The first piece of evidence presented by Thornhill is that rape can increase the reproductive success of some men. In order for a man to pass on his genes to future generations, he must engage in sexual relations with a woman. However, even though reproduction is important, women do not readily choose to have sex. Because women must invest considerable time and energy in pregnancy, childbirth, and child-rearing, they consider various factors when choosing a mate. Strength, social status, and the ability to secure resources are typical criteria. In contrast, men who are physically small or lack competitiveness may be at a relative disadvantage according to these standards. If highly competitive men secure the majority of mates, some men may find it difficult to obtain reproductive opportunities through normal means. Thornhill argued that, in such situations, forced sexual intercourse may have provided reproductive opportunities for some men, and if such behavior actually increased reproductive success, it could have been selected for during the course of evolution.
However, based on this argument, one might conclude that men who commit rape may actually have a reproductive advantage over men who find partners through normal means. Generally, securing a mate requires significant effort and resources. Men must compete with other males, protect their mates, secure and provide resources, and establish a stable livelihood. In other words, they must invest considerable energy not only in their own survival but also in the survival and reproduction of their mates in order to gain reproductive opportunities.
Rape, on the other hand, does not require this process. Therefore, men who attempt to reproduce through rape can focus their resources more on their own survival rather than on competing for a mate. Thornhill’s ultimate argument is that this could provide a certain advantage in terms of survival and, consequently, may have offered an adaptive advantage in both reproduction and survival.
However, there are quite a few people who disagree with this argument. They cite various reasons to argue that it is difficult to view rape as a behavior advantageous for survival and reproduction. The most prominent argument is that rape is a serious social crime. They contend that committing a crime leads to punishment, which works against both survival and reproduction.
In response, those who support Shonhill’s position argue that these counterarguments do not sufficiently consider the timescale of human evolution. It is only relatively recently that rape has become subject to legal punishment and strong social condemnation. Most of human evolution took place during a time when neither states nor legal systems existed. Therefore, the relatively short period since the formation of civilization may not have been sufficient for evolution to proceed in a new direction. They argue that if society continues to impose severe penalties for rape and significantly reduce reproductive opportunities, there is a possibility that behavioral traits associated with rape will not be selected for in the long term. This explanation emphasizes that, just as long-established habits do not change overnight, evolution also occurs over a very long period of time.
Opponents counter that this explanation, too, lacks sufficient evidence. They argue that it is difficult to specify exactly how much time is required for evolution, and since a considerable amount of time has passed since rape was criminalized, we should by now be seeing a downward trend in rape rates. Some point to cases where rape crime statistics have not decreased or have even increased, demanding an explanation for this discrepancy.
However, caution is needed when interpreting these statistics. Sexual violence has long been a crime in which incidents went unreported. In the past, cases were often not reported at all; today, however, reporting rates have risen significantly due to changes in social attitudes and the expansion of victim support systems. Therefore, it is difficult to judge changes in actual incidence rates by simply comparing past and present reporting figures. For this reason, it is not easy to conclude that rape is not an evolutionary adaptation based solely on changes in the number of reported cases.
Meanwhile, some argue that even without considering sociocultural factors, rape cannot be a behavior that is advantageous for reproduction. They contend that there may be a difference in the likelihood of pregnancy between sexual intercourse resulting from rape and that based on mutual consent. Some studies have reported that sexual intercourse initiated by a woman’s consent carries a higher probability of pregnancy than intercourse that is not. However, these findings are controversial due to limitations in research methods and sample selection; conversely, other studies have shown that, under identical conditions, sexual intercourse resulting from rape may actually carry a higher probability of pregnancy. As these findings have not yet reached a consistent conclusion, they must be interpreted with caution.
Even if the findings of the first study are valid, following Thornhill’s logic, it is possible to interpret that an evolutionary advantage may still exist for males who have no reproductive opportunities through normal means, as rape offers them a chance to reproduce—albeit with a very low probability. Of course, it is important to distinguish that this explanation does not justify or condone rape; it is merely a line of reasoning presented in the context of introducing a specific evolutionary biological hypothesis.
Those who argue that rape is not advantageous for survival and reproduction also present another line of reasoning. They pose the question: “Would a woman actually raise a child conceived through rape?” The argument is that if a woman who becomes pregnant through rape terminates the pregnancy or, even if she gives birth, does not raise the child, the likelihood of the rapist’s genes being passed on to the next generation is greatly reduced. Under these circumstances, it is difficult to view rape as a strategy advantageous for reproduction.
However, the author explains that this counterargument oversimplifies human parenting behavior. Even if a child is conceived through rape, half of its genetic makeup comes from the woman herself. Many social animals, including humans, exhibit behavior in which they care not only for their own offspring but also for the young of the group. In human society as well, there are cases where women who gave birth following an unwanted pregnancy still raised the child to the end. Considering these points, it is difficult to conclude with certainty that a child conceived through rape has absolutely no chance of being raised.
Even if the mother did not raise the child herself, in early human societies—where medical technology and abortion procedures as we know them today did not exist—it is more likely that a pregnancy resulting from rape would have led to childbirth. Furthermore, in communal societies, other members of the community may have cared for the child or helped ensure its survival. Therefore, the author argues that it is difficult to conclude definitively that a child born as a result of rape would necessarily have failed to survive.
It is also argued that whether rape is an evolutionarily advantageous behavior must be assessed by comparing it under identical conditions. For example, let’s assume there are two men who are unlikely to be chosen by women. One committed rape, and the other did not. It is uncertain whether the man who committed rape will actually father a child, or whether that child will grow up to pass on his genes to the next generation. However, compared to the other man who had no reproductive opportunities, the rapist has a relatively higher chance of passing on his genes.
Assuming such situations recurred across multiple populations, it is possible that some rapists did indeed pass their genes on to future generations. Therefore, when viewed from the perspective of the population as a whole, the act of rape may have increased the likelihood of reproductive success to some extent, and for this reason, the hypothesis that it is an evolutionary adaptation can be proposed, according to the author.
In conclusion, the author believes it is possible to interpret rape as an evolutionary adaptation. Of course, this does not mean that rape is necessarily a behavior that guarantees offspring. However, if it increased the likelihood of passing on genes to the next generation—even by a very small margin—it could satisfy the conditions for adaptation as defined in evolutionary biology. From this perspective, the author argues that rape may have been selected as a behavioral trait advantageous for reproduction, and therefore, an interpretation as an adaptation is possible.
However, this interpretation by no means morally justifies or defends rape. Even if a certain behavior might have been selected through the evolutionary process, that does not mean it should be permitted in modern society. While it is possible to hypothesize that abuses of power, assault, or theft may have held evolutionary advantages in specific environments, this does not mean such acts can be socially tolerated.
Furthermore, the final part of the original text requires some revision in light of current research findings. In modern evolutionary psychology and evolutionary biology, the view that rape is an “adaptation” is not accepted as the established academic consensus. Rather, the explanation that rape is either a by-product of other evolutionary traits or a crime resulting from the complex interplay of various sociocultural and individual factors receives broader support. Therefore, it is generally accepted today that rape cannot be explained solely by a single biological nature or genetic adaptation.
We must explore ways to prevent and ultimately reduce sexual violence by studying rape not only from a biological perspective but also through various disciplines such as psychology, sociology, and criminology. Research aimed at gaining a deeper understanding of the factors that lead to rape can serve as a crucial foundation for improving systems designed to prevent crime and protect victims.
