In this blog post, we will examine from various perspectives whether rape could be an evolutionarily adapted behavior.
When Randy Schonehill’s A Natural History of Rape was published about ten years ago, it drew immense attention. The claim that rape, a major social problem, is evolutionarily ingrained—that is, an adaptation in humans—sparked heated debate not only among women’s groups but also among scholars studying evolutionary theory. Through this article, I wish to present my perspective on this matter. To state my position upfront, I agree that rape can be considered an adaptation. The reason this question of whether rape is an adaptation garners such significant attention likely stems from the perception of rape as a crime driven by impulsive sexual desire, coupled with the ambiguity surrounding the term ‘adaptation’ itself. I will begin by clarifying the concept of adaptation within evolutionary theory.
The dictionary definition of ‘adaptation’ refers to responding appropriately or becoming suitable for specific conditions or environments. In evolutionary terms, adaptation does not mean an individual quickly adjusting to a particular environment, but rather that over multiple generations, the proportion of individuals possessing genetic factors advantageous in a changed environment increases to some degree. To explain it more clearly, the adaptation discussed here does not refer to the act of wearing thicker clothes when temperatures drop. Rather, it describes how, over many generations of persistently falling temperatures, individuals possessing traits advantageous for maintaining body heat survive more frequently because they are better suited to the given environment.
Furthermore, this phenomenon of adaptation, or survival of the fittest through natural selection, ironically results from genetic diversity. All living beings, including humans, possess dozens of chromosomes, even something as small and insignificant as a fruit fly. During reproduction, a mechanism mixes dozens of genes with a mate’s. While every gene is inherited from parents, the traits that manifest cannot be said to be entirely identical to the parents’ traits. The importance of this genetic diversity can be simply illustrated with an example. If a species were to evolve over time through extreme adaptation or the mechanism of survival of the fittest, it would become incapable of coping with other environmental changes after sufficient time had passed. Therefore, while the mechanism of survival of the fittest is important, a broad gene pool is essential to support it. This is evident from the fact that diverse species have survived for hundreds of thousands of years on Earth, where the environment has continuously changed.
Among the arguments against the view that rape is an adaptation, some have suggested that since rape is never a trait advantageous in a specific environment, it should be eliminated through natural selection. This can be explained through the importance of genetic diversity and the significance of passing genes to the next generation, as discussed earlier. Rape acts as an excellent reproductive means for individuals struggling with species propagation to leave offspring. Leaving offspring means passing one’s genes to future generations. Whether those genes are beneficial or useless to future generations is not something an individual or a species can judge. In other words, an individual passing on its genes is important from the perspective of genetic diversity, regardless of whether the trait is superior or inferior.
One reason discussions on whether rape is adaptive are so sharply polarized is that, from a modern societal perspective, rape constitutes a serious crime and carries extremely negative social stigma. However, when debating the adaptiveness of rape, social judgments must be excluded. Social judgments can vary with the times. Moreover, the adaptiveness of a specific trait is independent of time or era. That is, if a trait is adaptive, it could have emerged through adaptation to a specific environment in the past. Similarly, its elimination due to another environmental change could also be considered adaptation. Therefore, the current existence of a trait cannot be the sole measure to determine its adaptiveness. According to this, if punishment for rapists and the socially negative view persist, this could lead to a decrease in rapists. If this environment continues over many generations, the concept of rape itself could potentially disappear. If this were to occur, it would provide the strongest argument for claiming rape is adaptive.
There is an interesting statistic regarding rape: the pregnancy rate from rape is approximately twice as high as the pregnancy rate from consensual intercourse. This could support the notion that rape is not merely an act to satisfy sexual desire but a genuine act for procreation. This statistic is also highly controversial. First, the credibility of the data is enhanced because the survey on consensual sex targeted couples who consistently had sex without contraception for the purpose of pregnancy. Furthermore, since reporting rape is difficult for victims due to societal stigma, it can be expected that the actual difference in pregnancy rates is likely even greater.
Many people refute the idea that rape is adaptive by citing child sexual abuse, same-sex rape, or rape of women beyond childbearing age. However, when considering the proportions, rape targeting women of childbearing age is overwhelmingly more common. Therefore, the aforementioned cases can be explained as byproducts or side effects of rape.
It was mentioned that social judgments must be excluded when discussing whether a specific trait is adaptive. Therefore, arguing that rape is adaptive does not equate to defending rape as a justifiable act. Of course, rape is a grave crime that must never be committed. However, the trait of rape has clearly contributed significantly to genetic diversity from the past to the present. Had we not secured this genetic diversity through such means, humanity might not have survived catastrophic disasters like deadly pandemics of the past and could have become extinct. In conclusion, diverse genes hold greater value than specific traits superior to others in a given environment, simply by virtue of their diversity. And the trait of rape has contributed to that genetic diversity.
