In this blog post, we will examine the debate over whether rape is an evolutionary adaptation from the perspective of evolutionary biology and explore various viewpoints on the matter.
Recently, the extremist armed group “Islamic State” (IS) faced strong criticism from the international community after distributing documents justifying the use of women as sex slaves and human trafficking. The documents released at the time caused widespread shock, as they even included content justifying sexual violence against minors. As such, not only organized sexual violence occurring during war or armed conflict, but also sexual violence perpetrated within close relationships—such as by family members, acquaintances, or teachers—has persisted in various forms from the distant past to the present.
Natural selection refers to the process by which individuals possessing traits advantageous for survival in a specific environment achieve greater survival and reproductive success than those without such traits, thereby passing those traits on to the next generation. According to the theory of natural selection, for adaptation to occur, first, variation must exist; second, that variation must confer an advantage in the environment; and third, that trait must be inherited by offspring. Adaptation refers to characteristics in which an organism’s form or function is suited to the environment, thereby aiding the survival of the individual and the species, or the result of such characteristics being formed through the evolutionary process. Among various variations, traits advantageous for survival and reproduction are passed down to future generations through natural selection. In evolutionary biology, adaptation is generally explained as the result of natural selection.
‘Darwin’s Table’ is a book that explores various topics through discussions among scholars representing diverse perspectives in evolutionary biology. In this book, adaptationists and anti-adaptationists present differing views on the topic, “Is male rape behavior an adaptation?” Cosmedis, an adaptationist, raises the possibility that rape is a behavior that has been selected by natural selection over the course of a long evolutionary history. He introduces the hypothesis that rape is one form of adaptive behavior that increases men’s reproductive success, explaining that this does not in any way imply moral justification but is merely an attempt to scientifically understand how such behavior arose. Another adaptationist, Pinker, also argues that this understanding can help solve social problems. In contrast, anti-adaptationist Coin criticizes the presented data for failing to sufficiently support this hypothesis. He argues that statistics regarding the victim’s age or fertility status do not meaningfully support the hypothesis that rape is an adaptation for reproduction, and that solutions proposed on this basis also lack sufficient scientific grounds.
I believe that rape is an evolutionary adaptation. However, before explaining the evidence for this, there is one point I want to make clear. Natural selection does not operate according to ethical standards. Nature merely selects traits and behaviors that are advantageous for survival and reproduction; it does not judge whether they are morally right or wrong. When many people hear the phrase “rape is an adaptation,” they tend to think, “How can such behavior be an adaptation?” or “Bad behavior couldn’t possibly have been selected through evolution.” However, natural selection operates based on the criteria of survival and reproduction, not ethics. Therefore, saying that rape is an adaptation does not mean that such behavior is morally justified; rather, it refers to the possibility that it was subject to natural selection in specific environments of the past. In past societies where labor was a vital resource, reproduction held great significance, and it is plausible that the behavior of some men who were unable to secure reproductive opportunities was subject to natural selection because it ultimately contributed to reproductive success. Furthermore, the fact that there have been repeated historical reports of a sharp increase in sexual violence during times of war is also cited as evidence supporting this perspective. In other words, behaviors that were previously suppressed emerge in situations where social norms and legal controls are significantly weakened.
Some may counter that rapists do not consciously act with the purpose of reproduction. However, there is also the view that humans have evolved to engage in various instinctive behaviors aimed at species preservation and reproduction. From this perspective, rape is sometimes interpreted as an act committed by individuals who are unable to satisfy their reproductive urges through normal means.
Recognizing rape as an adaptation does not mean acknowledging that rape is a justifiable or proper behavior. It merely discusses the possibility that it is a result of natural selection, which operates primarily around reproduction and survival. However, in current evolutionary biology, there is no academic consensus on the hypothesis that rape is an adaptation selected by natural selection in humans. While some researchers propose the adaptation hypothesis, others argue that rape is not an adaptation but rather a byproduct of other psychological traits or the result of significant sociocultural factors. Therefore, this issue remains a subject of ongoing debate in evolutionary biology. I fully agree that rape is a crime that is morally unacceptable and subject to strict legal punishment in modern society. However, considering the evidence presented above, I believe that rape is a behavior that may have been influenced by natural selection in past environments conducive to survival and reproduction.
