In this blog post, I will examine the arguments that seek to interpret rape from the perspective of evolution and natural selection, along with their supporting evidence, and summarize the content by focusing on the underlying logic.
Recently, social controversy surrounding sex crimes has been unceasing. Issues such as the chemical castration of sex offenders and sex crime cases occurring across all sectors of society continue to be the subject of public attention and debate.
Among sexual crimes, rape is a serious offense classified as a major violent crime alongside murder, arson, and robbery. It has long been discussed as a social problem not only because it leaves victims with severe psychological trauma that can last a lifetime but also because it occurs regardless of social status.
In this article, I intend to discuss the phenomenon of rape itself. However, I would like to make one point clear from the outset: this article is not intended to debate the morality of rape. I, too, agree that rape is a morally reprehensible felony that deserves severe punishment.
What I wish to discuss here is the nature of the phenomenon of rape. I believe that rape is an adaptation that emerged during the course of evolution. The reason for this is that the act of rape is most directly related to human reproduction.
Before discussing whether rape is an adaptation, we must first clearly examine what an adaptation is. Generally, an adaptation refers to the process by which an organism’s traits change in a way that gives it an advantage in surviving and reproducing within a given environment. The giraffe’s long neck is often cited as a classic example of an adaptation. Over a long period of time, countless organisms have adapted in various ways to better survive in their respective environments.
So, through what process do these adaptations occur? By what mechanism did the giraffe’s neck become so long?
In modern biology, evolution through natural selection is the most widely accepted explanation. Let’s assume that, in the distant past, both short-necked and long-necked giraffes coexisted. In this scenario, the long-necked giraffes could more easily reach leaves high up in the trees. Consequently, the long-necked giraffes secured relatively more food and gained an advantage in survival and reproduction. Conversely, short-necked giraffes would have had a lower chance of survival and fewer opportunities to reproduce. As this process repeated over a long period of time, the trait of a long neck was gradually passed on to subsequent generations more frequently, and as a result, the average neck length of giraffes increased. According to this principle, giraffes adapted to become better suited to their given environment.
So, how can rape be defined? Generally, rape refers to the crime of forcing sexual acts upon another person without their consent. The act of rape involves sexual intercourse, and since sexual intercourse is biologically related to reproduction, it is sometimes discussed from an evolutionary perspective. Of course, rape is a crime that can occur to both men and women, but in this article, I will focus on rape committed by men against women, as this is the context in which discussions regarding adaptation have primarily taken place.
Consequently, I believe that rape is a form of adaptation. The core of natural selection is the process by which individuals with traits that are more advantageous in a given environment produce more offspring, and those traits are passed on to the next generation. As this process repeats, the population as a whole gradually changes in a direction better suited to the environment.
I believe rape is a behavior related to the most fundamental principle of producing more offspring. The most direct way to produce more offspring in a given environment is to have sexual relations with multiple women, thereby increasing the likelihood of pregnancy. I argue that rape is a behavior in which an individual attempts to pass on their genes through forced sexual intercourse without the other party’s consent, and is therefore a form of adaptation driven by natural selection.
However, there are also researchers who argue that rape is not an adaptation. They explain that rape itself is not an adaptation, but rather a byproduct of other adaptations. In other words, it is not rape that has adapted, but rather increased sexual desire, and rape is a side effect produced by that increased sexual desire. In the following sections, I will examine these arguments one by one.
However, there are also those who argue that rape is not an adaptation. They contend that rape is not an adaptation in itself, but rather a byproduct that accompanies other adaptations. Their core argument is that it is not rape itself but increased sexual desire that is the result of adaptation, and that rape is a side effect produced by that desire. Let us examine the evidence they present one by one.
First, they cite the existence of rape targeting women who cannot become pregnant, such as children or the elderly. They argue that since rape of women outside their fertile period cannot achieve the goal of reproduction, it is more reasonable to interpret it as a byproduct of increased sexual desire rather than viewing rape itself as an adaptation.
However, I would like to question this concept of “increased sexual desire.” My view on the claim that rape is a byproduct of increased sexual desire is as follows: While increased sexual desire may be a cause of rape, it is difficult to view it in itself as an adaptation directly selected through natural selection. Rather, I believe it is more appropriate to regard the act of rape itself as a direct adaptation and to understand increased sexual desire as a byproduct that arises in that process.
The key point here is not whether increased sexual desire causes rape, but whether increased sexual desire itself can be a factor in adaptation.
To understand this, we need to revisit the concept of adaptation. What are the criteria for determining whether a factor is an adaptation or not? To answer this, we must first clearly understand the principles underlying adaptation. The most fundamental principle of adaptation is natural selection. Natural selection is the process by which traits advantageous for survival and reproduction are passed on to the next generation in greater numbers. Therefore, the objects of adaptation can be viewed as traits that are directly influenced by natural selection.
For example, in the case of the giraffe, we say that its long neck is the result of adaptation, but we do not refer to the desire to eat leaves from high places as an adaptation. Traits that directly influence survival and reproduction—such as a long neck, fast legs, or sharp teeth—are cited as examples of adaptation.
From this perspective, the act of rape, as explained earlier, is directly related to passing on one’s genes more widely; in contrast, increased sexual desire is not so much a trait that directly affects survival or reproduction as it is an internal factor that triggers such behavior. Therefore, I view the element of adaptation not as internal sexual desire, but as the externally manifested behavior of rape. In other words, I believe that rape is not a byproduct of increased sexual desire; rather, increased sexual desire is a secondary phenomenon that occurs alongside the behavior of rape. Furthermore, I interpret that various forms of rape have emerged because this sexual desire is directed not only at women of childbearing age but also at same-sex partners and others.
Another counterargument could be raised against this claim: Is it appropriate to limit the definition of adaptation solely to direct, externally observable traits? In response, I believe that objective criteria are necessary to clearly distinguish what constitutes an adaptation. There are broadly two possible criteria for determining adaptation. The first is to view only those traits that are the direct targets of natural selection as adaptations, as I propose. The second is to include all psychological factors—such as appetite, sexual desire, and morality—that indirectly influence natural selection within the definition of adaptation.
However, applying the second criterion raises the problem that nearly all human psychological traits and behaviors would be interpreted as adaptations. Therefore, the author believes that the scope of adaptation must be defined more strictly in order to clearly distinguish between adaptive and non-adaptive elements. For this reason, I argue that the first definition—which views only traits that are the direct targets of natural selection as adaptations—is more appropriate, and from that perspective, rape can also be understood as an adaptation.
Another counterargument is: if rape is an adaptation, why is the proportion of people who actually commit rape so low in the general population? The argument goes that if rape were an adaptation formed through natural selection, shouldn’t more people exhibit this behavior?
However, I believe this phenomenon can be explained by the influence of education and the sociocultural environment. Even assuming that an adaptation related to rape was formed, it likely emerged in an environment where social norms, laws, and moral systems had not yet fully developed. As human society subsequently evolved, morality and laws were established, and people learned through education that rape is a clear crime and an unacceptable act. Furthermore, with the implementation of severe legal penalties, such behavior has been strongly suppressed by society. Therefore, I believe that the mere fact that rape rates are low in modern society does not immediately rule out the possibility of such an adaptation.
In conclusion, I argue that the act of rape is a direct result of natural selection in that it serves to produce more offspring, and is therefore an adaptation. Furthermore, I view increased sexual desire not as an externally manifest adaptation, but rather as a byproduct of the adaptation process of rape. Additionally, I believe that in modern society, such behavior is strongly suppressed through the establishment of social norms, education, and legal sanctions.
Finally, I would like to emphasize once again that this article is not intended to morally justify or defend rape. Rape is a serious crime that causes severe physical and psychological harm to the victim, and it is an act that cannot be tolerated under any circumstances. The purpose of this article is to examine whether the phenomenon of rape can be interpreted as an adaptation from the perspective of evolution and natural selection, and to discuss that possibility.
