In this blog post, based on the concept of adaptation in evolutionary biology, we will examine the debate over whether rape is an adaptive behavior shaped by natural selection, as well as the various perspectives on this issue.
Darwin proposed the theory of evolution and argued that evolution occurs through natural selection. Based on this, the field of “evolutionary biology” developed, and “adaptation” is one of its most important concepts. The concept of adaptation in evolutionary biology differs in meaning from the everyday use of the term—that is, the process of gradually becoming accustomed to a new environment. Evolutionary adaptation refers to a genetic trait that enables an organism to survive and reproduce more effectively. While almost no biologist since Darwin has denied the mechanism of natural selection itself, debates over the extent to which natural selection applies continue to this day. One of the most contentious debates is whether the human mind and behavior have also evolved through natural selection; a prime example of this is the question, “Is rape an adaptation?”
Those who argue that rape is an adaptive behavior shaped by natural selection (adaptationists) oppose the conventional view that rape is merely an act of violence or a learned cultural behavior; instead, they contend that rape may have served the function of increasing men’s reproductive success. In particular, they suggest that it may have evolved as a means of species reproduction for men who face difficulties in finding mates. Adaptationists argue that they are not making a value judgment—such as “Is rape right?”—but rather a factual judgment: “Is rape an adaptive behavior?” They also contend that understanding rape from an evolutionary biological perspective may actually help prevent rape crimes.
Those who oppose the claim that rape is an adaptive behavior can be broadly divided into two groups. The first group argues that rape itself is not an adaptive behavior, but rather a byproduct of vigorous sexual activity—that is, adaptive behavior aimed at species reproduction. Since they view rape as fundamentally a sexual act rather than a violent one, they can be considered the passive opposition. The second group consists of anti-adaptationists who refute the very basis of the claim that rape is an adaptive behavior; they represent the active opposition.
The arguments of anti-adaptationists can be summarized into three main points. First, they argue that if rape were an adaptation that benefits species reproduction, it would be difficult to explain why the proportion of non-reproductive-age women among rape victims is not significantly different from that of reproductive-age women. Second, they point out that some claims made by adaptationists—such as that reproductive-age women suffer greater harm than non-reproductive-age women, and that child sexual abuse is relatively less severe—do not align with actual research findings. Third, they counter that concluding human rape behavior is also an adaptation based solely on the fact that certain organs enabling forced copulation exist in some insects is an excessive generalization and an overinterpretation.
Furthermore, anti-adaptationists argue that cases such as male-on-male rape, incestuous sexual violence, and sexual violence against children are difficult to fully explain through adaptation theory alone. Therefore, it is considered more reasonable to view rape as a byproduct of vigorous sexual activity. Furthermore, they argue that rape cannot necessarily be viewed as an adaptation, pointing out that various traits in organisms can be shaped not only by natural selection but also by various evolutionary processes and environmental factors.
I, too, would like to place greater weight on the argument that rape is not so much an adaptive behavior for human reproduction as it is a result heavily influenced by cultural, social factors, and learning. However, before discussing this, it is necessary to establish clear criteria, as there is significant debate regarding the appropriate standards and measurement methods for distinguishing between what is an adaptation and what is not.
As explained earlier, an “adaptation” is a “genetic trait that enables an organism to survive and reproduce more effectively,” while “rape” refers to “a crime involving the forced sexual act against another person’s will.” Since the definition of rape is relatively clear, it is appropriate to focus our discussion on the concept of adaptation.
There are several reasons to oppose the claim that rape is an adaptive behavior. One of these is that violence plays a far greater role than sexual desire in the psychological underpinnings of rape. According to ‘Men Who Rape: The Psychology of the Offender’ by criminal psychologist Nicholas Groth, rapists can be broadly classified into three types: anger-driven, power-driven, and sadistic. The first type, the anger-driven rapist, aims to humiliate and insult the victim and destroy their self-esteem, often accompanied by severe violence and verbal abuse. For them, rape is a means of expressing their anger through violence rather than an act for procreation. The second type, the power-driven rapist, seeks to render the victim helpless in order to feel a sense of dominance, authority, conquest, and power. This, too, is far removed from procreation. The third type, the sadistic rapist, derives sexual arousal from the act of aggression itself, and their motivation differs from that of the anger-driven rapist. If rape were viewed as an adaptive behavior, sexual mechanisms would have to be central; however, actual research in criminal psychology emphasizes that rape is more closely related to violence, the desire for power, and the desire for domination.
In response, adaptationists might counter, “If rape were unrelated to adaptation, it would be difficult to explain why it has persisted from ancient times to the present.” Indeed, the concept of rape can be traced back through very ancient history. Greek and Roman mythology features examples—such as the story of Zeus and Europa—that, from a modern perspective, evoke notions of coercion and power dynamics. Furthermore, there are numerous records spanning antiquity, the Middle Ages, and the modern era documenting women as victims of sexual violence during wars. As such, rape has repeatedly appeared throughout human history, and based on this, some argue that it may have been an adaptive behavior.
However, it is a logical leap to conclude that rape is an adaptation simply because it has persistently existed throughout human history. Rape is not the only phenomenon that has existed alongside human history. Artistic activities such as music and visual arts have also been with humanity for a long time, but this does not mean that all artistic activities can be categorically defined as biological adaptations. Similarly, it is difficult to conclude that rape is an adaptive behavior based solely on the fact that it has existed for a long time. Rather, it may be more reasonable to interpret rape as having been used throughout history as an effective means of violence to dominate and subjugate others.
Adaptationists also cite rape in wartime as another piece of evidence. The fact that organized and large-scale sexual violence occurred during World War II and in various armed conflicts since then has been confirmed by diverse historical records and investigations by international organizations. Furthermore, cases of sexual violence being used as an organized instrument of war were reported during the Balkan conflicts of the 1990s and the Rwandan genocide. Even today, in regions affected by armed conflict, sexual violence is treated as one of the war crimes condemned by the international community. Furthermore, there have been reports of increased sexual violence targeting socially vulnerable groups during large-scale disasters or situations where social order collapses rapidly. Adaptationists argue that, based on these examples, the reproductive drive intensifies in extreme situations where human survival is threatened, leading to rape; they claim this serves as evidence that rape is an adaptation rooted in sexual mechanisms.
However, the mere fact that rape increases during war or social unrest is insufficient to conclude that it is an adaptation for reproduction. A closer look at the characteristics of the victims reveals that a significant number are not only women of childbearing age but also children and the elderly—that is, women who are not of childbearing age—and sexual violence against men is also consistently reported in various conflict zones. Furthermore, sexual violence occurring during war is often interpreted as strategic violence intended to humiliate enemy forces, destroy communities, and spread fear, rather than being motivated by reproduction. In fact, modern international law and the International Criminal Court define wartime sexual violence as a war crime and a crime against humanity, which supports the interpretation that sexual violence is not merely a reproductive behavior but a means of exercising power and violence. Therefore, it is more convincing to understand rape occurring in situations of war and disaster as a manifestation of violence arising from extreme human stress and the collapse of social norms.
In conclusion, the argument that rape is not an adaptation is more valid than the argument that it is. Understanding rape as a criminal act involving a complex interplay of power, domination, and violence, rather than as a biological adaptation for species reproduction, is more consistent with the findings of modern criminal psychology, social sciences, and jurisprudence. Therefore, rather than categorizing rape as an adaptive behavior shaped by natural selection, it is more reasonable to view it as a violent crime resulting from the combined influence of social, cultural, and psychological factors.
