In this blog post, we explore whether rape is an evolutionary adaptation for species reproduction or simply the result of sexual desire.
Since Darwin published “On the Origin of Species” at the age of 50 in 1859, the concept of evolution through natural selection has been widely accepted in the field of evolutionary biology. The concept of adaptation mentioned in this topic also originates from natural selection. Natural selection is the concept that individuals who adapt to the living conditions of the natural world are selected, while those who do not are eliminated. However, the term “adaptation” here has a slightly different meaning from the commonly known definition of “responding to or becoming suitable for certain conditions or environments.” In evolutionary terms, adaptation refers to genetic characteristics that enable organisms to survive and reproduce more effectively than other organisms by possessing specific traits. Take giraffes as an example. Among giraffes with short necks and those with long necks, those with longer necks survive because they can more easily eat leaves at higher positions. This trait of having a long neck can be considered an evolutionary adaptation. While there are few biologists who dispute that adaptation through natural selection is a crucial element of evolution, discussions continue regarding the scope to which this adaptation can be applied.
One such debate is whether rape can be understood as an adaptation. There are two main perspectives on this issue. The first perspective, held by adaptationists, argues that rape can be viewed as an adaptation. They claim that the act of rape allowed males who had difficulty finding mates to spread their genes through rape, and that this behavior, which increases the likelihood of reproduction, has emerged as a genetic trait.
The second view is held by anti-adaptationists, who argue that rape is an expression of excessive sexual desire manifested as violent behavior. They criticize the adaptationist view, arguing that rape is not an adaptation but merely a byproduct of sexual desire or learned cultural behavior, and that the possibility of reproduction alone cannot fully explain the cause of rape.
Before evaluating which argument is more valid, it would be helpful to examine the causes of rape. Fundamentally, the cause of rape can be said to be sexual desire. And sexual desire is fundamentally a desire aimed at preserving the species. Therefore, the fundamental cause of rape can be said to be the desire to preserve the species. This phenomenon can be easily observed in the natural world. The reproductive mechanisms of animals can be divided into polygamy, polyandry, and monogamy. In polygamous species, males other than the most dominant ones do not have the opportunity to mate. As Dawkins puts it, the selfish genes within males seek to reproduce the species. In animal cases, males overcome the denial of mating opportunities by giving food as gifts or disrupting other males through cross-dressing to mate with females. From this perspective, rape can be considered one of the primary behaviors for species reproduction.
The examples mentioned above are also evident in humans. While monogamy is the most common form of marriage in modern civilized societies, polygamy was prevalent in earlier societies. In such cases, many males would have had difficulty finding a mate. In this situation, forced sexual behavior may have been beneficial for species reproduction, and such traits could be considered adaptations. Such forced sexual behavior can also be observed in the form of kidnapping marriages, which have become customary. For example, in Kyrgyzstan, it is still common for men to kidnap brides. Additionally, this practice of forcibly abducting brides for marriage has existed in our own history, further supporting this argument. In other words, rape has been naturally selected as a behavior that aids reproduction.
Furthermore, the claim that rape is merely a byproduct of excessive sexual desire lacks validity, as rape is primarily committed by men against women, and the incidence of rape does not appear similarly across all social classes. Sexual desire clearly exists in both men and women. According to statistics, 98% of rape perpetrators are men, while only 2% are women, indicating a significant disparity. Therefore, it can be argued that other factors are at play beyond mere sexual desire. Additionally, statistics on rape perpetrators show that they are distributed as follows: 64.5% from lower socioeconomic backgrounds, 34.1% from middle socioeconomic backgrounds, and 1.3% from upper socioeconomic backgrounds. This indicates that rape occurs more frequently in situations where it is difficult to find a spouse through conventional means. This suggests that rape cannot be explained solely by excessive sexual desire.
As a counterargument to the claim that rape is a result of adaptation, it could be argued that the purpose of rape is not pregnancy but simply sexual desire. This counterargument is based on the fact that rape victims include not only women of childbearing age but also children, adolescents, and women past childbearing age, suggesting that the purpose of rape is not pregnancy. In other words, rape is simply a byproduct of excessive sexual desire.
A counterargument to this counterargument is that the fact that rape victims include not only women of childbearing age but also children, adolescents, and women past childbearing age can be understood from the perspective of the perpetrator, as humans do not clearly exhibit signs of being in the childbearing or ovulation phase externally. In the case of chimpanzees and other primates, it is easy to distinguish between fertile and non-fertile individuals because the female’s external reproductive organs swell significantly during the breeding season, but in humans, this distinction is not easy to make, so there is no need for a mechanism to identify fertile women. Rape may be committed not only against fertile women but also against a broader range of women to increase the probability of pregnancy. Additionally, since the desire for sex itself stems from the instinct for species reproduction, the claim that rape is an adaptation gains credibility because the two propositions—pregnancy and sexual desire—cannot be said to be unrelated.
Next, if rape is advantageous for species reproduction, one might argue that individuals with this trait would come to dominate the group. If rape is accepted as an adaptation that aids reproduction, these individuals would gain a competitive advantage, leading to natural selection, and eventually survive more survival competitions, ultimately coming to dominate the group. However, since it is difficult to observe an increase in rape in actual societies, it can be argued that the assumption that rape is advantageous for species reproduction is incorrect.
The following counterarguments can be made against this objection. First, the decrease in rape can be understood as a result of the disadvantages (legal sanctions) of rape outweighing its advantages (opportunities for species reproduction) in modern times. If we consider the distant future, we can expect that traits that do not engage in rape will gradually increase, but such natural selection occurs over many generations, so it is difficult to expect it to manifest immediately in the present. In fact, if we look at previous societies, we can easily find examples of men who were pushed out of reproductive competition due to polygamy. In Korea, polygamy was abolished only after the opening of the country to the outside world, and in the United States, it was abolished only 100 years ago. This means that historically, there have been a significant number of marginalized men, and for these marginalized men, rape may have served as a means of reproduction.
We have discussed whether rape is adaptive or not. Darwin explained in his book “The Descent of Man” that the power of sexual choice is always given to females. All behaviors such as males adorn themselves, build physical strength, or seek power can be understood as efforts to attract females and reproduce the species. However, just as there are males who are born but fail to compete, the same applies to humans. In such cases, humans who cannot find multiple mates may not be able to reproduce in that generation, but the act of rape would have clearly acted in favor of reproduction. Therefore, the trait of rape can be understood as an adaptation. However, the victims of rape include not only women of childbearing age but also those who are not. This raises the counterargument that the purpose of rape is not reproduction but sexual desire. However, this counterargument can be explained by the fact that in humans, the distinction between childbearing age and non-childbearing age is not clearly defined, making it difficult to identify women of childbearing age. Therefore, there was no need for a mechanism to identify women of childbearing age to form. The argument is that rape can occur against a broader range of women to increase the probability of pregnancy. Ultimately, rape is a desperate attempt by males to slightly increase the likelihood of pregnancy, which can be understood as an adaptation for species reproduction.
