In this blog post, we will examine the claim made in evolutionary psychology that “rape is an adaptation” and the evidence supporting it, and we will review this perspective by focusing on the debate surrounding it.
Has the human body looked the same since the beginning of time? Of course, we cannot know exactly what prehistoric humans looked like. However, most biologists would answer “no” to this question. The reason is that many biologists accept evolution through natural selection—that is, the process of adaptation. According to this view, the human body changed in ways that were advantageous for survival and reproduction as it adapted to the natural environment, eventually taking on its present form. Of course, there are still people today who believe in creationism. Creationism is the view that all living things, including humans, were created by a supernatural being. However, in modern biology, the theory of evolution is the most widely accepted, based on a variety of scientific evidence. Therefore, the main debate in biology today is not whether adaptation exists, but rather which traits or behaviors can be explained as adaptations. While not all human behavior can be viewed as an adaptation, there is an argument that more behaviors than expected can be explained from an evolutionary perspective. If so, can the unethical act of rape also be explained within the framework of adaptation?
In ‘Darwin’s Table’, various scholars present differing viewpoints on this topic. At the center of the discussion is ‘The Natural History of Rape’, written by Randy Thornhill and Craig T. Palmer. Opponents criticize the book’s logical limitations and lack of evidence, while proponents acknowledge that some aspects need refinement but argue that its basic logical structure holds up. In this article, I intend to examine the arguments presented by the proponents.
First, let’s focus on why people commit rape. While some offenders may derive pleasure from the act of breaking taboos itself, it is difficult to view such cases as the norm. A commonly cited reason is to satisfy one’s sexual desires. If so, how are sexual desire and adaptation related? To understand this, we must first consider why sexual desire exists. The general explanation in evolutionary biology is that the reason many organisms, including humans, possess sexual desire is ultimately related to reproduction. Sexual desire is a biological mechanism designed to ensure the transmission of one’s genes to the next generation. From this perspective, attempts are made to interpret rape as a behavior related to reproduction as well.
This naturally raises the question: How does this differ from the claim that “rape is a byproduct of sexual desire”? In this regard, one might first ask, “Why is rape committed by women far rarer than rape committed by men?” The byproduct theory posits that, given the existence of sexual desire, anyone has the potential to commit rape. Therefore, to explain the fact that the majority of rapists are men, one must assume that men have a much stronger sexual desire than women. However, the issue of simply comparing male and female sexual desire remains a highly complex research topic, and it is difficult to draw a definitive conclusion. Therefore, it has been argued that there are limitations to explaining gender differences in rape based solely on differences in sexual desire.
So how does the adaptation theory explain the phenomenon that men commit rape more frequently than women? From this perspective, the focus is on the fact that the biological costs borne by men and women differ when reproduction occurs through rape. While women bear the burdens of pregnancy, childbirth, and child-rearing, men incur relatively fewer direct biological costs. Adaptation theory explains that this difference may have created distinct selective pressures over the course of evolution. Consequently, this theory suggests the possibility that men and women have developed different evolutionary strategies.
How, then, does the adaptation theory explain the various types of rapists? Rapists may be unmarried or married, and their ages and social backgrounds vary widely. Proponents of the byproduct theory often raise the counterargument: “How do you explain rape committed by a married man who already has a spouse?” They point out that there are cases where married men commit rape even though they can already produce offspring through normal sexual relations. Therefore, they argue that such behavior is the result of excessive sexual desire rather than reproduction.
However, adaptive theory attempts to interpret this as well within the framework of reproductive strategy. It posits that even a man with a spouse can spread his genes more widely if there is a possibility of gaining additional reproductive opportunities. In other words, adaptation theory suggests that, from an evolutionary perspective, certain selective pressures may have been at work whenever reproductive opportunities increased, regardless of whether a man had a spouse. While it cannot be concluded that this explanation accounts for all actual human behavior, adaptation theory develops its argument based on this logic.
Many of those who oppose the claim that “rape is an adaptation” approach the topic of rape primarily from an ethical standpoint. Of course, rape is a very serious crime and an act that can never be tolerated. However, scholars who advocate for adaptation theory argue that whether a behavior is ethical and how that behavior was shaped evolutionarily are separate issues. In other words, studying the evolutionary origins of a behavior is a discussion on an entirely different level from justifying or defending that behavior.
Furthermore, some argue that human morality itself is also a result of adaptation. If human morality is indeed a product of evolution, one might wonder whether morality and the act of rape are not contradictory. However, this issue is also a topic currently being actively debated in evolutionary psychology and evolutionary biology. It is widely accepted that both genetic factors and cultural learning influence human morality and cooperative behavior, and it is difficult to explain these phenomena based on any single factor alone. Therefore, it is also necessary to consider that it is difficult to categorize morality itself simply as either innate or acquired.
The claim that rape is an adaptation does not in any way imply that rape is justified. In fact, researchers who have presented this perspective—including Thornhill and Palmer—have clearly stated that rape is a serious crime that must be prevented and punished. Studying evolutionary origins is merely an academic attempt to understand the causes of behavior; it does not imply an acknowledgment of the legitimacy of that behavior.
Ultimately, one of the key characteristics that distinguishes humans from other animals is the ability to regulate one’s instincts and follow social norms. Humans respect and care for others within their communities and take responsibility for their actions. No matter how likely it may be that a certain behavior has an evolutionary background, in modern society, respecting the law, ethics, and the rights of others is of the utmost importance. Therefore, the crime of rape cannot be justified by any theory, and humans can be said to be distinguished from other animals in that they are beings capable of making responsible choices rather than acting solely on instinct.
