Why is Incest Wrong?

There is a universal human aversion to incest. This is often described by psychologists as ‘moral dumbfounding’, because it is so visceral and has managed to persist despite common individuals being unable to provide rational justifications for it.

Family members tend to feel responsible for one another, so incest, even consensual, could be a form of exploitation. It is not considered ethically permissible to have intercourse in fiduciary relationships, like teachers are to students, or doctors are to patients. We usually construe family dynamics to work in a much similar way. Incest is also not conducive to the maximum satisfaction of preference, because people on the whole prefer not to have sex with their families.

From a rationalist perspective, incest does not give the proper respect to the unconditional worth of rational agents, being that incest treats people as means instead of ‘ends’, according to Kantian philosophy.2 An incestuous relationship is extremely difficult to maintain, mainly because the shared history between the individuals, along with the general power structure of family, make it quite impracticable to treat a family member as a genuinely autonomous end. Their relationship has already encoded them as something else, be it a dependent, a caregiver, an authority figure, or a co-dependent. And, furthermore, considering the maxim, if everyone were to partake, society would cease to continue. At least, not in any recognisable fashion of today.

In 1891, the Westermarck Effect was developed by Finnish sociologist Edvard Westermarck. He stated that all humans have an endogenous psychological mechanism that is triggered during the first few years of childhood, roughly from birth to age six. In his book, The History of Marriage, he wrote: ‘There is an innate aversion to sexual intercourse between persons living very closely together from early youth, and. . . as such persons are in most cases related, this feeling naturally displays

itself in custom and law as a prohibition of intercourse between near kin.’

Westermarck suggests that if you spend your first six years of life in close physical proximity with a certain someone (eating, sleeping, and playing together), your brain imprints that person as ‘family’. Hence, your brain permanently disables sexual attraction toward that specific person. It is innate because you do not have to be taught to feel this way. It happens automatically regardless of blood relation. In the Israeli Kibbutzim or Chinese Shim-pua marriages, it was observed that the children had little to no sexual attraction towards each other, with none of the 2,769 marriages within the Kibbutzim system occurring between individuals who had been in the same peer group from birth to age 6 and the Shim-pua marriages facing a 30 per cent lower fertility rate compared to arranged marriages between strangers, higher divorce rates, and higher rates of extramarital affairs.

In his book Reasons and Persons, Derek Parfit depicted a very famous brain-teaser of modern philosophy, known as the Non-Identity Problem. Normally, it is said that an act is wrong because it makes someone worse off. For example, if X punches Y, then Y is worse off than they were before they got punched. So, if a child is born from an incestuous union with a genetic disorder, is that child ‘worse off’? But if the child’s parents had not committed incest, that child would never have been born. A different child might have been born instead, but the inbred child would simply not exist. If we assume that a life with a disability is still worth living, which is generally assumed true, then the child has not been made worse off by the parents’ choice, because the only other option for that child was never existing at all. This is perhaps the strongest argument regarding the morality of both abortion and incest. It can be understood through a simple experiment, as directed below:

In a hypothetical scenario, you are requested to choose between two buttons. If you press Button A, which employs outbreeding, it results in a child with a 3 per cent risk of disability. If you press Button B, it exploits incest, and results in a child with a 25 per cent risk of disability.

Choosing Button B is definitely wrong, because you are intentionally choosing a higher

probability of unfitness. But this decision is often mixed up with eugenics. If someone believes a disabled child shouldn’t exist, that there is no way for someone with a disability to have a good life, and that disabled fetuses should be aborted, with laws to ensure the same, that would be eugenics. Parents, however, face a moral obligation to select the path that results in the least predictable suffering for their child. Hence, Button A is the only correct choice.

Critics at times argue that by banning incest, we might accidentally be preventing beneficial mutations or unique genetic combinations that could help the species in the long run. In ethics, if an action has a high risk of causing catastrophic harm, then the burden of proof lies with those willing to take the risk. First-degree incest faces a 25 per cent defect rate. This overwhelming proof only goes to show that a 700 per cent increase in lethal recessive traits is a very dangerous gamble, even for a common citizen. Due to this increase in lethality, the state has a compelling interest in public health that completely overrides the infinitesimal chance of a beneficial mutation.

‘Genetic Sexual Attraction’ (GSA) is a phenomenon that occurs when relatives who were separated at birth and meet as adults share a mutual sexual attraction toward one another. It is widely argued that since these individuals share DNA, they experience an exclusive, powerful affinity connection, one that non-relatives are incapable of understanding. They argue that suppressing this natural attraction is a form of psychological cruelty.

The problem here is that GSA only occurs when the growing up together is missing. This, therefore, proves that the attraction is a biological error. The human brain may misinterpret the familiarity of a shared gene as sexual chemistry because of the lack of the Westermarck Effect. Even then, the relationship remains problematic. Treating a sibling as a sexual object constitutes a categorical error. It violates Kant’s duty to respect the rational identity of the other. One cannot possibly honour the unconditional moral obligations of kinship, while also engaging in the sexual

instrumentalisation characteristic of romantic partnerships. Attempting to do this forces a contradiction onto the entire concept of the family itself.

In his work On Liberty, John Stuart Mill argued:

‘The only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others.’

Libertarians often use Mill to argue that if an incestuous couple is sterile, or uses protection, or refuses any form of intercourse, there is no ‘harm to others’, and therefore the state does not possess any paternal rights.

However, this line of reasoning does not count for something extremely vital. While a strict libertarian reading of Mill might permit sterile incest, a broader consequentialist view recognises that the mere creation of a high-risk genetic environment is a probabilistic harm. This can be explained through a very simple example: drunk driving is illegal as it creates an environment of harm, where there could potentially be a casualty. The state penalises this reckless behaviour regardless of casualties, and it is subsequently also responsible for prohibiting incest to protect the collective genetic commons. It is also quite literally impossible for humans to maintain celibacy, and additionally, the vulnerable individuals within a family hierarchy from the inherent power imbalances make true consent a statement out of the question.

In anthropology in the 1940s, incest being ‘wrong’ was quite a major debate. The answer isn’t obvious yet. Claude Levi-Strauss wrote The Elementary Structures of Kinship in 1949 wherein he proposed a model where the incest taboo actually created human society. His idea was that the ‘exchange of women’ between men of different families was necessary to create greater social ties outside the immediate family, and thus formed the kinship network, and thus formed society. If men could have intercourse with the women in their immediate family, then there would be no reason for them to create larger social networks. Kinship networks are what society is so often based on. Networks of interrelationships through family and marriage connect people within and between communities. So, essentially, humans who did not have an incest taboo never organised into meaningful societies.

From a biological viewpoint, it's rather easy to tell why incest is wrong: consanguinity. And, perhaps the effects of consanguinity were so obvious that it came to view rather quickly that incest, particularly on a large scale, gives subinferior results. Hence, at the end of the day, the costs of incest, be it biological, psychological, or social, far outweigh any perceived freedom of the act.