In this blog post, we’ll examine the debate over whether rape can be viewed as an adaptive behavior from the perspective of evolutionary biology, along with the evidence supporting this view.
Desert foxes and Arctic foxes are both foxes, but they look very different. One of the most notable differences is that desert foxes have very large ears, while Arctic foxes have very small ears. They likely originated from a common ancestor with a similar appearance. However, in the hot desert, individuals with large ears that could effectively dissipate heat had a survival advantage, whereas in the cold Arctic, individuals with small ears that minimized heat loss had a survival advantage. Individuals with a survival advantage were also more likely to reproduce successfully, and as a result, the trait of “ear size” was passed down through generations, leading to the desert foxes and Arctic foxes we see today.
The examples of the desert fox and the Arctic fox are frequently used in middle and high school biology classes to explain natural selection. Since being presented as the key principle driving evolution in Darwin’s ‘On the Origin of Species’, natural selection has been regarded as one of the most important concepts in evolutionary biology as a whole. However, the debate over what exactly constitutes an “adaptation”—a result of natural selection—continues to this day.
Among these debates, the question of whether the human mind and behavior have also evolved through natural selection is particularly intense. The “rape debate” featured in ‘Darwin’s Table’ is a prime example of this. Over the question, “Is male rape behavior an adaptation?” scholars who support adaptationism (hereinafter referred to as the “Dawkins team”) and those who are critical of it (hereinafter referred to as the “Gould team”) are locked in a fierce confrontation. The Dawkins team argues that rape is essentially a sexual behavior and an adaptive behavior that increases a man’s chances of reproductive success. In contrast, the Gould team argues that rape is not an adaptation but a violent act intended to dominate and subjugate the other person; even if it is a sexual behavior, they claim it is merely a byproduct of sexual desire.
Like the Dawkins Team, I believe that rape is an adaptation. That is, rape is fundamentally a sexual behavior—not merely a byproduct of sexual desire, but an adaptive behavior that increases a man’s chances of reproductive success. In the following text, I will present evidence supporting this position, examine the logic of the opposing view, and explore its limitations.
First, to understand that rape is fundamentally a sexual behavior, we need to examine the nature of “sex” itself. According to Richard Dawkins’ ‘The Selfish Gene’, males and females have evolved by adopting different reproductive strategies. In most animals and plants, male gametes are much smaller and more numerous than female gametes. In the past, when gametes were roughly similar in size, those that were slightly larger than other cells held more nutrients, giving them a reproductive advantage. Conversely, gametes smaller than average were highly motile and thus more likely to fuse with nutrient-rich gametes. As this selection process repeated, gametes gradually diverged into larger or smaller, more agile forms, eventually becoming the female egg and the male sperm, respectively.
Because of this reproductive strategy chosen by males, they generally tend to mate with as many females as possible. However, unlike many other animals, human females do not clearly signal their fertility, such as through ovulation. Consequently, it is difficult for men to accurately determine a partner’s fertility, which can lead to a relatively lower reproductive success rate.
If a man finds himself in a situation where it is difficult to secure normal mating opportunities, the pressure to reproduce may become even greater. Viewed in this evolutionary context, rape can be interpreted as a behavior representing the extreme manifestation of a man’s reproductive drive.
On the other hand, there is also a perspective that views rape not as a sexual act but as a violent act. From this perspective, sex is merely a means to an end and is essentially viewed as an act of violence intended to dominate and subjugate the other party. However, two counterarguments can be raised against this claim.
The first concerns sexual violence occurring in wartime. Historically, there are documented cases where sexual violence during war was used as a means to undermine the morale of the enemy. However, this alone is insufficient to explain the origins of wartime sexual violence. Rather, war can be viewed as an extreme situation where social order has collapsed, providing conditions that are, to some extent, similar to the primal environments in which human evolution took place. The fact that sexual violence occurs frequently in such environments could serve as grounds for interpreting rape as behavior linked to human instinct. In other words, it may be a more natural explanation to view it as behavior that already existed being strategically utilized in the specific context of war.
Second is dating violence. This particularly refers to sexual violence committed after using alcohol or drugs to impair the victim’s ability to resist. In the past, certain cocktails were nicknamed “lady killers,” but this is neither an official term nor a medical concept and is now considered an inappropriate expression. Furthermore, there is insufficient evidence to suggest that any specific alcoholic beverage is directly linked to sexual crimes. However, in reality, sexual violence involving alcohol or drugs continues to occur, and some perpetrators use these means to make it difficult for the victim to resist. If rape were simply an act of violence, there might be little need to resort to such methods. This suggests that rape cannot be fully explained by violence alone.
So, why can rape be viewed as an adaptation rather than a mere byproduct of sexual desire? An adaptation refers to a trait directly selected through natural selection, while a byproduct refers to a result that arises incidentally during the evolution of another trait. Although the boundary between adaptations and byproducts is often unclear, Dawkins’ team interprets rape as an adaptive behavior in males. To understand this, we need to revisit the debate on rape presented in ‘Darwin’s Table’.
Dawkins’ team cites two main reasons for arguing that rape is an adaptation. First, a significant proportion of rape victims are women of reproductive age. Second, certain animals possess physical characteristics that facilitate forced copulation. For example, male scorpion flies have specific structures that aid in forced copulation, and based on this, the team argues that human rape behavior may also be a product of adaptation.
Gould’s team directly refutes this argument. First, they point out that actual victims of sexual violence span a wide range of age groups—including not only women of childbearing age but also children, adolescents, and the elderly. Therefore, they argue that the claim that rape evolved solely for the purpose of reproduction cannot sufficiently explain this diverse range of victim profiles. Furthermore, they argue that concluding that the same evolutionary process applied to humans simply because certain animals possess organs that facilitate forced copulation constitutes the fallacy of hasty generalization.
It is possible to counter these rebuttals from Gould’s team. It is indeed true that rape victims span a wide range of age groups. However, this fact alone does not necessarily lead to the conclusion that rape is not an adaptation. This is because the environment in which evolution took place is very different from modern society. Humans live in a civilized society governed by social order and laws, where rape is defined as a serious crime and is subject to strong social condemnation and legal punishment. This social environment can also influence the behavior of perpetrators. Therefore, the adaptationist position holds that there are limitations to determining evolutionary origins based solely on the patterns of crime observed in modern society.
Furthermore, one cannot conclude that human rape behavior is an adaptation based solely on the example of male macaques. However, the fact that adaptations related to forced copulation have been identified in other animals suggests the need to investigate the possibility that related evolutionary mechanisms exist in humans as well. In fact, in 2000, behavioral ecologists Randy Thornhill and Craig Palmer raised the possibility that rape might be an evolutionary adaptation and presented various hypotheses in their book ‘A Natural History of Rape’. However, this hypothesis has faced significant criticism since its publication and is still not accepted as a consensus theory in the fields of evolutionary biology, psychology, and criminology. Therefore, while it is possible to present this as a hypothesis, it should not be accepted as a verified fact.
A key point in this debate is that the question of whether rape is a byproduct of sexual desire or an adaptation directly selected by natural selection remains unresolved. To determine this, we must be able to verify which behaviors were actually advantageous for reproductive success in the early environments where humans evolved. From an adaptationist perspective, it is believed that males facing difficulties in finding a mate could have employed various strategies. They might have continuously sought out new partners or persistently courted them; attempting forced intercourse regardless of the other person’s consent could also have been a possibility. Adaptationism argues that if such situations recurred, the latter behavior could have increased reproductive success and thus become subject to natural selection.
On the other hand, counterarguments have consistently been raised, stating that this explanation alone cannot fully account for all instances of rape observed in actual human societies. In modern evolutionary psychology and criminology, the view is widely discussed that rape is not caused by a single factor but rather results from the complex interplay of various factors, including sexual desire, the desire for power and dominance, aggression, sociocultural environments, and individual psychological traits. Therefore, it is also necessary to consider that the research findings accumulated to date are insufficient to categorize rape solely as an adaptation or a byproduct.
Taking all of this into account, whether rape is an adaptation remains a matter of debate in evolutionary biology and evolutionary psychology. While some researchers suggest that rape may be an adaptive behavior selected by natural selection to increase reproductive success, others argue that it is a byproduct of sexual desire or aggression, or the result of a complex interplay of factors such as the desire for power and dominance, as well as sociocultural factors. Therefore, it is difficult to say that any one position has been definitively proven.
It is natural for people to find this debate distasteful. However, it is important to note that exploring the evolutionary origins of a behavior is entirely distinct from ethically justifying that behavior. The fact that researchers are investigating the possible evolutionary background of a specific behavior does not mean that the behavior is permissible or justified. In fact, rape is a serious crime in all societies today that violates an individual’s right to bodily autonomy and human rights, and it is subject to strict legal punishment.
Therefore, the evolutionary biological discussions surrounding rape must be viewed as an academic endeavor aimed at understanding the origins of human behavior. While such research can serve as a reference for gaining a deeper understanding of human behavior and developing crime prevention and response strategies, it should not be used to explain all causes of rape based solely on specific hypotheses, nor should it be used as grounds to diminish social and ethical responsibility. Efforts to objectively analyze the act of rape from various academic perspectives and the social principle of defining it as a clear crime and protecting victims are not conflicting values; rather, they are values that must be upheld together.
