You Fall in Love with Someone Genetically Similar to You

Posted on February 13, 2022 by Victor Karandashev

This article explains the surprising findings of studies which show that you are more likely to fall in love with someone who has genetic similarities to you.

The Irresistible Attraction of Genetic Similarity

What is more attractive to a loving person: similarities or differences? What draws people to each other? Do they like those who resemble themselves, or do opposites attract? It is commonly known that “birds of a feather flock together.” Multiple studies have also provided evidence to support this similarity effect (see for review, Karandashev, 2019).

Studies have demonstrated that men and women tend to initiate relationships with those who resemble them in such characteristics as socio-economic status, income, ethnicity, religion, cultural identity, age, and even body type (Karandashev, 2022).

Generally, when it comes to race, ethnicity, or even size and shape, people tend to fall in love with those like themselves. Spouses tend to have a higher level of genetic similarity than two random strangers.

Are We Genetically Predisposed to Fall in Love?

The quality of our relationship is influenced by more than just our shared experiences with a partner. In evolutionary terms, establishing interconnectedness necessitates the display of similarities between organisms. In humans, we tend to select our mating partners according to the principle of optimal genetic similarity. Because sexually dimorphic animals like humans cannot produce healthy offspring with anyone, intersexual attraction aids them in the proper selection of a mate. It’s possible that biological evolution has created a psychological mechanism that unconsciously attracts us to mates who are similar to us while excluding those who are significantly different (Lampert 1997).

We tend to fall in love with others who are genetically similar to us and look alike. We are drawn to each other subliminally because of our genetic resemblance (Robinson et al., 2017).

On the other hand, this evolutionary mechanism of optimal genetic similarity prevents incest in human societies and other species, reinforcing incest taboos (Lampert 1997).

Genetic Studies of Marital Similarity

Genetic similarities with the partner appear to be important for their short-term sexual attraction and long-term loving relationships. For example, the thousands of cases of DNA paternity tests provided evidence that men and women, when they were in sexual relations, were genetically more similar to each other than random couples (Rushton, 1988).

These findings suggest that partners are likely to recognize their genetic similarity. They experience sexual attraction without even realizing it.

Another genetic study using genome-wide SNPs in a sample of married couples in the US is also in support of this similarity explanation (Domingue et al., 2014).

Researchers discovered that spouses have significantly more genetic similarities than any two randomly chosen individuals. Surely, compared to siblings, who have around 40–60% genetic similarity, marital partners share considerably less genetic similarity. Thus, spouses tend to share a greater degree of genetic similarity than other members of the population. The contribution of a genetic factor is statistically significant. Yet it is a relatively modest one.

How Our Genes Make Us Fall in Love

The GG genotype is the set of specific genes within the oxytocin gene receptor that affects our feelings of love. The studies of the GG genotype show how genetics affect a person’s feelings toward another and a relationship between partners. Our genes determine what hormones we are predisposed to and, therefore, what personal traits we exhibit in relationships. When our hormone levels are out of balance, we may have difficulties in our ability to create interpersonal relationships and bonds. For instance, low levels of testosterone and estrogen can cause low sexual drive. Consequently, this may cause low relationship satisfaction.

Several studies have demonstrated that individuals who have the GG genotype have greater sociability, empathy, and emotional stability. It has been shown that these psychological resources are associated with happier close relationships (see for review, Monin et al., 2019).

The quality of our marriage is influenced by more than just our shared experiences. A recent study of the GG genotype, which included 178 American couples, discovered its genetic impact on marital relationships (Monin et al., 2019). Researchers revealed that when at least one person in a couple has the GG genotype, he or she is less anxious in psychological attachment to the partner, and both partners benefit by feeling significantly higher marital satisfaction than other couples with different genotypes. Even though the percentage of this genetic impact on marital satisfaction is small (about 4%), it is statistically significant compared to other factors.

How Environmental, Social, and Cultural Factors Make Us Fall in Love

Environmental, social, and cultural factors also play a substantial role in explaining why we fall in love (see more elsewhere). Similarities in social class, political orientation, ethnicity, religion, education, interests, and characters of partners play substantial roles, which are frequently more important than genetic similarities.

Genetic Diversity and Genetic Sexual Attraction

Posted on January 26, 2022 by Victor Karandashev

Despite the importance of similarity in genetic sexual attraction, genetic diversity is equally important in love. It appears that both similarities and differences between love partners play important roles.

Evolutionary Value of Genetic Diversity

Genetic sexual attraction plays an important role in triggering love between men and women. However, sexual attraction for sexual reproduction also strives to avoid the negative effect of excessive genetic similarity between loving partners. Inbreeding has a deleterious biological effect on the offspring in terms of health quality, the likelihood of diseases, disabilities, and mortality (see for review, Ceballos et all, 2021; Hasselgren & Norén, 2019).

Therefore, human evolution and population growth throughout history have promoted people to exclude mates with extreme genetic similarity from the pool of possible mating partners. Such mating increases the likelihood of harmful recessive genes and reduces offspring fitness (Ceballos et all, 2021).

Cultural Evolution Encourages Diversity in Genetic Sexual Attraction

Even though consanguineous marriages—mating relations with blood relatives—have been widespread throughout history, cultural norms of incest taboos have evolved in many societies to safeguard against this harmful effect of inbreeding. People likely became aware of the harmful effect of sexual relations between close relatives on the quality of their offspring. Incest, or sex between family members, became a cultural taboo in many societies. Evolving social norms and psychological experiences of love began to respect the principles of biological evolution. They were adjusted accordingly, encouraging the extended reproduction of offspring.

A Controversy over Genetic Sexual Attraction among Family Members

Although people perceive potential mates who resemble their kin as more sexually appealing, incest avoidance evolves from the development of taboos. When awareness of the kin relationship between self and other is bypassed, relatives often look sexually appealing to a person. So, by only consciously acknowledging incest taboos, people suppress their sexual attraction to kin (Fraley & Marks, 2010).

The Benefits of Diversity in Genetic Sexual Attraction Encourage Cultural Taboos against Incest

The difference between partners in their genetics leads to healthier offspring. Therefore, natural selection—and cultural norms accordingly—developed protective psychological mechanisms to decrease the sexual drive for similarity and allow only a suitable measure of variance between partners in love relationships. This evolutionary mechanism might be at the origin of the strong incest taboo among many populations of species and human societies (Lampert 1997, p.14).

Societies in history and modern times have respected the incest taboo, prohibiting sexual relations between females and males who are in kinship relationships. Many human societies have cultural norms prohibiting sexual relations among kin (Lampert, 1997; Murdock, 1949; Westermarck, 1891/1921).

References

Ceballos, F. C., Gürün, K., Altınışık, N. E., Gemici, H. C., Karamurat, C., Koptekin, D., … & Somel, M. (2021). Human inbreeding has decreased in time through the Holocene. Current Biology, 31(17), 3925-3934.

Hasselgren, M., & Norén, K. (2019). Inbreeding in natural mammal populations: historical perspectives and future challenges. Mammal Review, 49(4), 369-383.

Fraley, R. C., & Marks, M. J. (2010). Westermarck, Freud, and the incest taboo: Does familial resemblance activate sexual attraction?. Personality and Social Psychology Bulletin, 36(9), 1202-1212.

Lampert, A. (1997). The evolution of love. Praeger.

Murdock, G.P. (1949). Social structure. Macmillan.

Westermarck, E. (1921). The history of human marriage (5th ed.). London, UK: Allerton. (Original work published 1891).

Genetic Secrets of Love Attraction

Posted on January 25, 2022 by Victor Karandashev

From a biological evolutionary perspective, the genetic similarity must be important for sexual attraction. Intersexual attraction helps sexually dimorphic animals, such as birds and mammals, select a proper mate because they cannot reproduce offspring with anyone. They can do this only with those with whom mating success is possible and higher than with others (Karp et al., 2017; McPherson & Chenoweth, 2012; Owens & Hartley, 1998; Rigby & Kulathinal, 2015).

Do People Fall in Love with Genetically Similar Others?

For a weird example, a human individual can be attracted by a sexual relationship with a horse, cow, goat, or gorilla. They can even be a nice couple. They may attain sexual pleasure. Nevertheless, such relationships, from an evolutionary point of view, are wasteful expenditures of energy because they are destined to be childless. They are genetically too distant to produce offspring.

However, humans and chimpanzees are more similar in this regard—they have a genetic distance of less than 2%. Therefore, reproductive success in that case could be possible (Lampert 1997).

Therefore, we can expect that genetic factors and corresponding similarities in the physical appearance and chemistry of human individuals can determine their sexual and love attraction. The chemistry of love, which makes some partners more compatible with each other than others, can be real, not metaphorical.

Do we have a genetic predisposition to fall in love with someone?

Optimal Genetic Similarity

In biology, the principle of optimal genetic similarity is important for the evolutionary selection of partners among animals (Lampert 1997). Individuals tend to be attracted to others who are genetically similar to them. However, they prefer to keep their distance from those who are genetically very dissimilar from them. Both factors play their roles in the selection of mating partners with optimal genetic similarity to them.

This principle of genetic similarity may also work among humans. An individual tends to fall in love with a person who, to some extent, is genetically and physically similar. Biological evolution has developed a psychological mechanism that unconsciously attracts individuals to mates who are similar and excludes those who are significantly different.

Why Are Genetically Similar People Sexually Attractive to Us?

Here is one piece of evidence that such an unconscious attraction is possible (Rushton, 1988). Rushton examined the thousands of court cases in which courts investigated the validity of fatherhood. Genetic testing was used to identify whether a man with whom a woman had sex was actually the father of her baby. Examining those cases, Rushton (1988) was interested in knowing how men and women, at the beginning of their sexual relationship—at the time of conceiving a baby—were genetically similar to each other. The data showed that they were genetically more similar to each other than a random couple. These results indicated that it was likely that potential mates unconsciously recognized their genetic similarity with a partner and, therefore, felt sexual attraction (Rushton, 1988).

Another study used genome-wide SNPs and also supported this genetic similarity explanation of sexual attraction. In a sample of American Whites (non-Hispanic), researchers found that married partners are genetically similar to each other—more than random pairs of individuals (Domingue, Fletcher, Conley, & Boardman, 2014).

The Words of Tentative Limitations

It shall be acknowledged, however, that these findings are descriptive and can be considered tentatively true for a causational explanation. The genetic similarity between partners can be due not only to their genetic assortative mating but also to their shared ancestry (Abdellaoui, Verweij, & Zietsch, 2014). The genetic similarities in couples can be due to genetic population stratification that evolved in a society due to geographical proximity, social homogamy, and ethnic homogamy.

Are Close Relatives More Likely to Fall in Love?

According to the findings presented above, genetically similar relatives in nuclear and extended families perceive each other as physically similar and attractive. Does the genetic similarity of close relatives make them more likely to be attractive and love each other? For example, they can perceive each other as more sexually appealing. Then, the psychoanalytic myths of a boy’s unconscious sexual attraction to his mother (the Oedipus complex) and a girl’s attraction to her father (Electra complex) can be partially true due to their genetic similarity, although the effect of imprinting can also play a role.

Many cases of consanguinity in sexual relationships and marriages have been documented throughout history. In these cases, blood relatives find each other attractive (see Karandashev, 2017, 2022 in press for a review). Consanguineous marriages are still widespread and preferred in many societies in West Asia, the Middle East, and North Africa (e.g., El-Hazmi et al., 1995; Hamamy, 2012). Surprisingly, these cultural traditions have been persistent.

However, the negative impact of incest (sexual intercourse with a child, sibling, grandchild, or parent) on offspring is well documented. Therefore, to safeguard against this harmful effect of incest, cultural norms and incest taboos have evolved in many cultures.

The Diversity of Love

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