In this blog post, we will examine the argument that rape can be viewed as an evolutionary adaptation, along with the counterarguments, and consider whether rape can be explained solely from a biological perspective.
Can rape be viewed as an adaptive strategy?
Historically, humans—both men and women—have produced offspring through sexual intercourse based on mutual consent. This has been accepted as a fundamental principle in human society, not only today but also in the past. However, as situations arose where consent for sexual intercourse was not obtained or where some men monopolized reproductive opportunities, there came to be men who were unable to produce offspring. Consequently, some have proposed the view that the act known as “rape” should be understood as a strategy for passing on one’s genes.
Some adaptationists argue that this strategy is a form of “adaptation.” In evolutionary biology, adaptation refers to traits or behaviors formed as a result of natural selection. Here, natural selection refers to the process by which, among individuals of the same species, those better adapted to the environment survive and produce offspring.
If rape were indeed an adaptive strategy, the behavioral traits that lead to rape should have consistently provided a reproductive advantage and thus become widespread across generations. However, in reality, those who commit rape constitute only a tiny fraction of society as a whole. Therefore, I believe it is difficult to conclusively label rape as an adaptation based on this point.
In response to this argument, adaptationists would counter that one cannot determine whether something is an adaptation simply based on the number of individuals who engage in the behavior. In particular, they argue that since humans are heavily influenced by social norms and laws, even if an instinct exists, it may not manifest in behavior. Society defines rape as a serious crime, and those who commit it face not only legal punishment but also social condemnation and exclusion. Therefore, they argue that even if rape were an adaptation, its actual incidence might appear low due to social sanctions.
They also cite wartime situations as an example of this. Historically, there have been repeated reports of soldiers from victorious nations committing sexual violence against women from defeated nations during certain wars. Adaptationists sometimes interpret this phenomenon as evidence that a tendency toward rape is latent in humans.
The social environment is also an important factor in adaptation
Before refuting the arguments of these adaptationists, it is necessary to reexamine the meaning of “adaptation.” As explained earlier, adaptation is the result of natural selection, and natural selection presupposes the element of “environment.” The environment refers to the natural and social conditions and situations that surround organisms and influence them directly or indirectly.
Humans are quintessentially social animals. Therefore, the environment that influences humans includes not only the natural environment but also the social environment. Social norms, laws, and ethics can also be viewed as part of the environment to which humans must adapt. From this perspective, the fact that the number of people who commit rape is extremely small can be interpreted as evidence that humans have adapted to the social environment as well.
Furthermore, it is difficult to categorically assert that sexual violence in wartime—as cited by adaptationists—is necessarily behavior aimed at reproduction. In modern war studies, wartime sexual violence is often analyzed as a violent act serving various purposes, such as dominating the opposing group, instilling fear, inflicting humiliation, and demonstrating power. Therefore, it is a stretch to directly link these cases to evidence of adaptive strategies for reproduction.
Can examples from the animal kingdom be applied directly to humans?
However, adaptationists argue that we must focus on the fact that human genes were formed through a very long evolutionary process. Modern humans emerged approximately 300,000 years ago, and even before that, the human lineage had been evolving over a long period of time. The point is that, within this long history of evolution, humans are also beings that share a continuum with other animals.
Furthermore, if rape is defined as forced copulation without the female’s consent, they argue that similar behavior is observed in animals other than humans. The macaque is a case in point. Since female macaques tend to allow copulation only with males that provide food, some males who are not selected may attempt forced copulation.
Furthermore, male meerkats are known to use a structure called the pectoral shield to carry out this behavior. Adaptationists argue, based on such examples, that rape can also be a reproductive strategy.
However, this argument merely generalizes the behavior of certain animals to the entire animal kingdom. Just because forced copulation appears as a reproductive strategy in a specific species does not mean we can conclude that similar behavior in all animals serves the same purpose.
Let’s examine the once-controversial cases involving seals and penguins. In the video, a seal exhibits sexual behavior toward a penguin and eventually eats it. If the seal’s behavior were intended for reproduction, this outcome would be difficult to explain. Furthermore, if the goal were reproduction, it would be far more advantageous to target a seal of the same species rather than a penguin, which is a different species.
This case demonstrates that it is difficult to immediately generalize behaviors observed in specific animals as reproductive strategies. Furthermore, the fact that such behavior occurs even between animals of different species suggests that rape cannot be explained solely by the concept of adaptation.
Counterarguments to the Claim That Rape Is a Last-Resort Reproductive Strategy
However, adaptationists will counter that rape is an adaptation in that it serves as a strategy to preserve male genes. In particular, they argue that since men who commit rape are unable to obtain consent for sexual intercourse from women, rape can be viewed as a last resort for producing offspring. From the perspective of evolutionary biology—where the primary goal of animals is to pass their genes on to the next generation—this implies that males who are rejected by all females attempt to pass on their genes by force.
However, there are several contradictions in this argument. According to adaptationists, rapists should be highly likely to be individuals who have failed to mate—in other words, those who are relatively unattractive. If so, the majority of actual rapists should exhibit such characteristics. Taking this to an extreme, people with disabilities or serious illnesses—who are likely to be assessed as significantly less sexually attractive than the general population—should make up the majority of rapists.
However, actual criminal cases do not align with these predictions. A significant number of rapists are individuals who exhibit no particular distinguishing features based solely on their appearance or social behavior. This demonstrates that the claim that rape is a last resort for reproduction alone cannot sufficiently explain the actual phenomenon.
Furthermore, the fact that rape is not an adaptation can be confirmed by examining the characteristics of the victims. For humans to produce offspring, pregnancy must result from sexual intercourse with a woman of childbearing age. Therefore, if rape were solely an adaptive strategy for reproduction, the majority of victims would have to be women of childbearing age.
However, the actual patterns of sexual violence do not align with this prediction. Victims come from a wide range of age groups, including children and the elderly. Furthermore, a significant number of male victims are also reported. These facts demonstrate that the act of rape cannot be explained solely as an adaptive behavior aimed at producing offspring. Today, it is generally understood in criminology and psychology that sexual violence is a crime resulting from a complex interplay of factors, including not only sexual desire but also the exercise of power, the desire for dominance, aggression, the need for control, and social factors.
Taking these pieces of evidence together, it is difficult to view the act of rape as merely an adaptation for procreation. This view is supported by the fact that only a very small fraction of people commit rape, and by the fact that, for humans—who are social animals—the social environment is just as important a factor as the natural environment when discussing adaptation. Furthermore, while forced mating may appear as a reproductive strategy in some animals, this cannot be directly applied to all animals or to humans. Additionally, the characteristics of actual sexual violence perpetrators and the distribution of victims also suggest that it is difficult to view rape as merely a behavior intended to pass on genes.
Therefore, I believe it is difficult to explain rape solely through the concept of “adaptation” as defined in evolutionary biology. In particular, humans are not beings who simply follow instinct; they are social animals who live within the framework of reason and social norms. Consequently, to understand the act of rape, it is necessary to take a comprehensive approach that incorporates not only biological perspectives but also various academic disciplines such as psychology, sociology, and criminology.
