As I have mentioned in the previous article. This time I will discuss the relationship between a person’s fidelity and the hormone vasopressin. Before discussing this further, let’s first get to know what vasopressin is?
Vasopressin is a hormone that plays a key role in regulating a variety of biological functions, including regulating blood pressure and the balance of air in the body. However, in the context of social behavior and relationships, vasopressin is also involved in the formation of social and romantic bonds, especially in men. The gene that encodes the vasopressin receptor, known as the AVPR1A gene, has been the focus of scientific research into social behavior, including the tendency to be faithful or unfaithful in relationships.
Vasopressin is a neuropeptide that is significantly involved in the regulation of social behaviors, including pair bonding, aggression, and parental care, especially in mammalian species such as humans and primates. In animal studies, vasopressin has been shown to enhance bonding behavior in species such as prairie voles, which are known to be monogamous. Vasopressin acts through the vasopressin receptor 1a (AVPR1A), which is expressed in areas of the brain that regulate social behavior.
The gene has several genetic variations, and variations in these genes affect how the brain responds to vasopressin. One of the most studied variations is the length of the AVPR1A gene allele, which has been shown to impact social behavior, particularly in the context of romantic relationships. Several studies have shown that men with shorter variations of the AVPR1A gene tend to have less stable relationships and are more likely to experience commitment problems in relationships. A study by Walum et al. (2008) found that men with shorter alleles of the RS3 repeat in the AVPR1A gene were more likely to experience problems in their marital relationships, including lower levels of pair bonding and increased risk of infidelity.
Similarly, a study led by Hasse Walum at the Karolinska Institutet in Sweden, involving more than 500 couples, found that men with a short allele variation of the AVPR1A gene tended to have less close relationships with their partners and were more likely to be unmarried than men with the long allele. This gene is associated with an inability to form strong, stable emotional bonds.
The AVPR1A gene affects how vasopressin works in the brain, particularly in areas of the brain involved in regulating social relationships, empathy, and romantic behavior. Vasopressin affects areas such as the ventral pallidum, which is associated with feelings of satisfaction and happiness in social and partner bonds.
- The short allele of the AVPR1A gene reduces the sensitivity of the vasopressin receptor, resulting in a reduced ability to experience satisfaction from pair bonding. This makes individuals more likely to seek stimulation or satisfaction from other relationships, which can lead to infidelity.
- The long allele of the AVPR1A gene, in contrast, is associated with stronger pair-bonding behavior and a greater ability to maintain long-term commitment in relationships.
These genetic variations may explain why some individuals are biologically more predisposed to strong monogamous behavior, while others are more prone to infidelity or have difficulty maintaining stable relationships.
While there is evidence that variations in the AVPR1A gene can influence social behavior, it is important to note that human behavior, including infidelity, is not entirely determined by a single gene. Other factors, such as environment, past experiences, cultural values, and social influences, also greatly influence behavior in relationships. Even individuals with the short allele may remain faithful in their relationships, depending on other factors affecting their lives.
The question then arises, what is the reason someone might have a long or short variation in vasopressin, specifically the AVPR1A gene?
This has to do with genetic inheritance and natural variations in DNA inherited from parents. Like many other biological traits, the length or shortness of the AVPR1A gene allele is a result of genetic variation that occurs naturally in the human population.
Natural Genetic Variation
In DNA, genetic variations or polymorphisms naturally occur in many genes, including the AVPR1A gene. Polymorphisms are small differences in DNA sequences that occur among individuals in a population. One type of polymorphism is variable number tandem repeats (VNTRs), which are DNA sequences that repeat at multiple locations within a gene.
In the case of the AVPR1A gene, the length of the VNTR alleles within the gene can vary. Some individuals have long alleles (which may have more repeats in their DNA sequence) and some have short alleles (with fewer repeats). This variation is natural and occurs at the population level, so no individual is “choosing” or directly influencing whether they have long or short alleles.
Inheritance from Parents
Each individual inherits one copy of the gene from each parent. Whether a person has the long or short allele of the AVPR1A gene depends on the combination of alleles they get from their parents. If one or both parents have the short allele, their offspring are more likely to inherit the short allele, and vice versa.
The process of dividing genes from parents is random, so the resulting combination of genes in each offspring will vary. If a parent has the short allele, the offspring are more likely to also have the short allele, but there are many possible outcomes of genetic combinations.
Evolution and Natural Selection
Genetic variation, including the length or shortness of alleles in the AVPR1A gene, is also likely the result of a long evolutionary process. In evolution, selective pressures can drive the spread of certain alleles in a population if they confer a reproductive advantage in a particular environmental context.
In environments that favor monogamy or strong pair bonding, long alleles that favor such behavior may be favored and more frequently inherited. On the other hand, in environments where pair bonding is less important, short alleles that may be associated with a tendency to be less attached to a single partner may persist.
Interpopulation Differences
Variations in the length or shortness of the AVPR1A allele may also differ across human populations in different regions of the world, as a result of evolutionary differences and local selective pressures.
Human populations differ in many aspects of their genetics, including genes that regulate social behavior. Some groups may have a higher frequency of the long allele, while others may inherit the short allele more often, depending on their evolutionary history.
Random Effects and Mutations
Variations in length or shortness in the AVPR1A gene can also arise due to random genetic mutations. Mutations are changes that occur spontaneously in DNA and can be passed down from one generation to the next. If a mutation occurs in the AVPR1A gene, it can change the number of DNA repeats in an allele, resulting in a longer or shorter allele.
These mutations may occur for no particular reason and simply as part of random variation in the human genome. Some mutations may persist and be inherited if they do not affect survival or reproduction.
Unlike some other traits that can be influenced by the environment, the length or shortness of the AVPR1A gene is not directly influenced by external factors such as lifestyle, diet, or lifestyle. It is an innate genetic trait that is determined since a person is born.
References:
- Donaldson, Z. R., & Young, L. J. (2008). “Oxytocin, Vasopressin, and the Neurogenetics of Sociality.” Science, 322(5903), 900–904.
- Hammock, E. A. D., & Young, L. J. (2005). “Microsatellite Instability Generates Diversity in Brain and Sociobehavioral Traits.” Science, 308(5728), 1630–1634.
- Israel, S., et al. (2009). “Oxytocin, but not Vasopressin, Increases Both Parochial and Universal Altruism.” Psychological Science, 20(10), 1282–1287.
- Meyer-Lindenberg, A., et al. (2011). “Neurogenetic Mechanisms of Sociality: The Role of Oxytocin and Vasopressin.” Nature Reviews Neuroscience, 12(9), 513–524.
- Walum, H., et al. (2008). “Genetic Variation in the Vasopressin Receptor 1a Gene (AVPR1A) Associates with Pair-Bonding Behavior in Humans.” Proceedings of the National Academy of Sciences of the United States of America (PNAS), 105(37), 14153–14156.