When Sisters Love Brothers: A Taboo That Must Not Be Broken!

In most human civilizations, incest is taboo. The debate over the origin of this prohibition has been a long - standing war of ideas. On one side are S. Freud and his followers, who see incestuous impulses as natural subconscious desires and the taboo as a cultural restraint. This is linked to the Oedipus complex. On the other side are E. Westermarck and his followers, who view the incest taboo as an ancient instinct, not a cultural construct.



If we start counting from Westermarck's 1891 publication of *The History of Human Marriage*, the debate over incest taboos has lasted over a century. In the first half of the 20th century, the view of incest taboos as cultural inventions was widely accepted. The Oedipus complex theory held significant influence. In contrast, Westermarck's hypothesis was largely ignored.



But since the second half of the 20th century, Westermarck's views have gained more support and evidence. The incest taboo is seen as an instinctive psychological response closely tied to kin recognition mechanisms. In comparison, Freud's Oedipus complex remains a literary metaphor, unverified.



**Animals Protest: We Are Not Incestuous!**



Many scholars, including the renowned French anthropologist Claude Levi-Strauss and Freud, have assumed that animals have incestuous instincts. They think animals mate indiscriminately, leading to the rarity of incest in human societies being seen as a result of cultural repression. However, this view is more imagination than fact. Occasional incest in animals often leads to genetic degradation in offspring, with most such offspring dying young.



Zoological studies consistently show that incest is rare in the animal world, and many animals avoid mating with relatives. For example, from 2006 to 2007, Chinese biologists observed the mating behaviors of short-tailed macaques in Huangshan. In 360 matings, only seven were between close relatives, with no mother-son incest.



In a 1996 paper, A. E. Pusey, an evolutionary psychologist and anthropologist at Duke University, outlined strategies animals use to avoid inbreeding:



1. **Dispersal**: Many mammals leave their family upon reaching sexual maturity. Even if other factors like mate competition also lead to this, evidence suggests it helps avoid inbreeding. White-footed mice reduce migration when their opposite-sex parent is removed.

2. **Infidelity**: For non-migratory animals, infidelity is a way to resist inbreeding. Male and female pilot whales stay in their territory, but all offspring are sired by males from other areas.

3. **Kin Recognition**: In laboratory experiments, animals choosing mates tend to avoid siblings or same - nest individuals.

4. **Delayed Maturity**: When a lioness's father is replaced by a young male, she reaches sexual maturity earlier. Similarly, white-footed mice mature faster when their opposite - sex parent is removed. In single-parent families without fathers, girls also reach puberty earlier, though the exact reasons are unclear.



In 2005, Pusey reviewed incest - avoidance behaviors in primates and found that in our closest primate relatives, incest between direct relatives is almost non - existent. She concluded that kin - recognition mechanisms to avoid inbreeding existed in animals before humans evolved.



**The Powerlessness of Civilization: The Tragedy of Childhood Sweethearts**



According to Westermarck, children who grow up together develop sexual aversion, leading to incest - taboo behaviors. Even without kinship, shared upbringing serves as a kinship cue, preventing marriage between childhood sweethearts. Forced marriages between such individuals may result in unhappiness due to sexual aversion, as shown in Stanford anthropologist A. P. Wolf and J. Shepher's classic studies.



Anthropologists often study incest taboos through social marriage phenomena. Wolf and others investigated childhood marriage in Taiwan under Japanese rule from the 1960s to 1990s, surveying 14,000 people. In this system, girls were sent to their future husband's home before age four, living with their small husband and marrying at around 17. Other marriage customs involved betrothal in adulthood, with couples living in either the husband's or wife's home.



Wolf found that child brides had 25% lower fertility, were more likely to be unfaithful, and had a divorce rate three times higher than average. The age at which girls were adopted was a key factor in marital happiness. Those adopted after age three had normal marital outcomes. In contrast, the age at which boys and girls met in the child - bride system had no impact on the boys' future marriages.



Child brides' health wasn't worse than average, and some who later married other men had as many children as average women. This ruled out alternative explanations for their unhappy marriages, such as poor health or stress in adoptive families.



As Wolf noted, Westermarck's critics argue that incest taboos prevent people from acting on desires. However, in reality, the incest taboo is an unavoidable psychological expression, regardless of social acceptance.



In the same period, Shepher studied Israeli kibbutzim, where children were collectively cared for by trained nurses for about 22 hours a day until adolescence. Observing 65 kibbutz members, he found no sexual relationships or marriages within the same kibbutz. This avoidance was voluntary, with no formal or informal sexual - behavior sanctions from supervisors, parents, or peers.



Surveying 2,769 married couples across 211 kibbutzim, Shepher found almost none from the same peer group in the same kibbutz before age six. Among 13 couples who had lived in the same kibbutz, eight met after age six, and the other five before age six but for no more than two years.



Like Wolf's findings, Shepher's research strongly supported Westermarck's hypothesis. Whether in the culturally neutral kibbutzim or the culturally encouraged child - marriage system, shared childhood led to a lack of sexual attraction in adulthood.