Genetics of cheating
For the past couple of years, in celebration of Valentine’s Day, Merogenomics has posted articles dedicated to the genetics that concern romantic relationships. We started the trend with the genetics of sexuality, then last year we moved to the genetics of love, and we wanted to play a “dirty” joke by completing the trinity of relational aspects with a topic dedicated to… the genetics of cheating!
Can your genes really contribute to a likelihood of infidelity?
Let’s find out what the science hints about on this topic!
But before we move on to this subject, which to a degree is a satirical statement on relationships in general, let us define cheating, and point out how potentially damaging such actions can be to the victims of infidelity. Cheating can have very serious consequences to the well being of others.
For the purpose of this article, cheating, or infidelity, is defined as intercourse with someone other than one’s spouse or committed partner. As such, infidelity is a form of personal betrayal, defined as intentional actions or omissions by a trusted person that result in another person/partner feeling profoundly harmed. Betrayal can also include dishonesty and unwanted disclosures of confidential information. Most of the time, betrayals are unexpected and come as a surprising shock. Consequently, betrayals can have a catastrophic effect on the victim including the subsequent development of psychopathological problems. This can lead to OCD symptoms such as feelings of mental pollution or dirtiness and compulsive washing, and even PTSD-like symptoms such as emotional numbing, avoidance, involuntary re-experiencing or intrusive images, avoidance of reminders, self-doubt, anger, and a foreshortened future. This is not a good list of adjectives to ascribe to anyone, and yet it can happen unexpectedly to any unsuspecting victim. Those perpetrating the betrayal doubtfully think of such consequences of their actions when they chase their immediate psychophysical reward. But they are very real and can be very damaging. If you identify with any of these symptoms, perhaps do not continue reading this article.
The point to make here is that any discussion of hypothetical genetic contributions to a cheating behaviour does not to absolve the perpetrators of the seriousness of their actions towards their victims. These days, genetic influences are being ascribed to nearly every behaviour and this topic is only investigated here for those who are curious and will not be triggered by the topic. Please proceed accordingly.
How do you study the genetics of infidelity?
This is not a trivial process. You cannot easily set up an experiment for this. You need to rely on a high-quality assessment of a particular trait that is being studied, and when it comes to infidelity, there is no choice but to depend on the self-reported (qualitative) information of a large number of individuals. To estimate heritability (or the genetic contribution to a particular behaviour), the classic approach is to use twin studies. Identical twins are expected to be 100% genetically identical, and thus a comparison of their behaviour in relation to the environment in which they grew up allows us to make estimates of the genetic portion or contribution to a particular trait.
To get to the specific genes that might be driving these traits/behaviours, the genetics of all individuals in the study are compared to one another. These are association studies, a topic frequently brought up in past posts (often referred to as GWAS for genome-wide association studies). Such studies are exceedingly popular and allow links to almost any trait of specific genetics in investigational studies. However, confirming such studies to prove that an association is a real phenomenon becomes a very different story. There are many pitfalls that can lead to aberrant associations that have nothing to do with reality, such as: how the population was selected for the experiment; whether appropriate statistical methods are selected: whether the study was empowered enough with appropriate amounts of collected data; and even whether the genetic information was captured appropriately. Many (but not all) non-clinical DNA tests that are directly available to the consumer (meaning no doctor is required for the test to be purchased) are based on nothing more than such GWAS studies and therefore may suffer from reporting results that have nothing to do with reality precisely because the accuracy of GWAS finding might have never been verified. Thus, when you are selecting a DNA test for purchase, do your due diligence! If you are interested in clinical DNA testing for investigating health-related information, that is definitely where Merogenomics can help.
Maybe, keep all of this in mind before you run off to investigate your (or your partner’s) genomes for a cheating propensity.
First, let’s look at the issue of heritability.
In a first of its kind, one study among 1600 women twins, suggested that infidelity is 41% heritable (with the remainder of influences on such behaviour being affected by the environmental factors). Interestingly, the same study also indicated that this was strongly correlated with the number of sexual partners (38% heritable). The authors could not pinpoint any specific genes linked to this behaviour though, apart from a vague association to certain regions encompassing large genetic landscapes. By the way, 22% of the twins reported to be unfaithful, and their number of partners was double that of faithful versus unfaithful females (approximately 4 versus 8). The author stated, “the logical conclusion is that these behaviors persist because they have been evolutionarily advantageous for women,” and if they are still heritable, then the selective pressure of the environment to retain these genetics in our population are still in play.
You must be wondering what those are!
The authors had to venture with their theories. For a woman, it is obviously very valuable to secure a long-term mating partner in order to help raise and protect the children. But once such relationship is established, from a genetic point of view, there is no advantage of being monogamous unless that partner is the most genetically fit male available, which the authors venture (and most women would probably concur) is “an unlikely position”. To put it bluntly, unless the risks associated with infidelity are greater than the risks of crappy genetics for your offspring, evolutionarily-speaking, go seek the best seed in the flock to ensure the best survival advantage for your children. If this evolutionary theory is true, clearly this influence was prior to the advent of DNA testing! Right now, as we illustrated in our last post, parental infidelity can easily be discovered with just a little bit of spit.
But why are not all women cheaters then? Because, the authors posit, you need to strike the correct balance in a society in order to keep the adulterous behaviour off the radar of the unsuspecting partners/fathers.
In other words, women are so clever, they even drive the evolution of our genetics without anyone being the wiser. Sorry guys. No point competing for that prize, even though supposedly the thought has been otherwise all this time.
Before you espouse any indignity towards women based on the above findings, consider comparing them with one survey from the US where, around 20—25% of men and 10—15% of women admitted to extramarital sex at sometime during their marriages (although not all of these may necessarily constitute acts of infidelity). These are also lifetime figures.
So what about men?
Another study of the heritability of extramarital sex behaviour in over 7000 twins of both genders concluded that genetic heritability accounts for 62% of such behaviour in men and 40% in women.
And what could be men’s apparent evolutionary advantage? Men who have secured a long-term mating partner will ensuring that their children from such a primary relationship will be well cared for, whilst spreading their semen about elsewhere could increase their reproductive fitness by increasing the overall chances of other bastard children from other women surviving to propagate their oh so important genetic material. Not to mention that unlike women, men have a very low minimal investment to reproduce. In other words, one copulation of probably very short duration, et voila, here is a reproduction of your genetic material!
All these theories sound like evolution is hinting at orgies, but that is not a very Valentine’s day thought. But at least at any given time, most people are not involved in infidelity, with only approximately 2% of those surveyed engaging in such acts in past year. Not sure if that is a comforting thought either, to find out whether you were cheated on in the past year or five years ago. Still not Valentine’s material.
Let’s turn it around – we’ll start with the information from the above mentioned theory of evolutionary advantages for why women cheat on their partners which shows no direct evidence that offspring of short-term mating are fitter than children from a long-term mating partner. Apparently, studies in other animals do not show such evidence either.
To reiterate, we still do not fully know what could be the genuine advantage of such behaviour in women. In other words, science concludes women are mysterious. Or phrasing it differently, women know, science doesn’t.
What genes might play role in cheating?
The literature seems sparse on this and appears relatively new. This is likely an area of further future exploration.
The first study to identify a candidate looked at a gene responsible for the production of a dopamine receptor, DRD4, a gene that has previously been associated with sensation-seeking behaviour. What is interesting about that gene is that part of it has a tandem repeat, meaning a small fragment of DNA that can be repeated numerous times in a row. How many of these repeats are present inside the gene can vary from person to person, with potentially dramatic impact on individual’s behaviour as a consequence. In the case of the DRD4 gene, typically there are 2 to 11 such repeats in different people. Those who have at least 7 such repeats (7R+) show reduced receptor binding for dopamine neurotransmitter and are more predisposed to sensation-seeking, disinhibition, impulsivity, and sexual behavior. The authors of that study showed that individuals with 7R+ are more likely to engage in promiscuous sexual behavior and demonstrate more than 50% increase of sexual infidelity compared to those individuals with a shorter number of repeats in the DRD4 gene.
The same study mentioned that estimated heritability of extramarital sex in men and women has also linked this behaviour in women only to the AVPR1A gene, responsible for the construction of the arginine vasopressin receptor. Arginine vasopressin is a hormone that has previously been linked to differences in social behaviour, including variations in pair-bonding quality in couples. As such, we discussed vasopressin extensively in our past article on the genetics of love.
Honey, it’s not you, it’s my genes! Or how to overcome your cheating ways
What if you got stuck with the genetic lottery that makes you more prone to cheating, but it is not a genetic destiny you actually desire? Is there anything that can be done? Perhaps there is more to it than just your will in being a kind and descent person so as to not ravage another’s emotional stability by engaging in cheating. Or are you doomed to failure in creating long-lasting bonds due to the desire to seek pleasure elsewhere?
First, to quote from one of the above-mentioned references, let’s say that “the behavioral outcomes examined are probabilistic and by no means deterministic.” This means that the above-mentioned genetics might increase the probability of certain risky behaviour, but does not guarantee such behaviour. However, there might be something to the adage of, “once a cheater, always a cheater”. Not long ago, a first-of-its-kind study came out assessing the propensity of being a serial cheater. This study showed that those who reported engaging in sex on the side while being in their first relationship were three times more likely to do so again in their next relationship compared to those who did not report engaging in infidelity in their first relationship.
Perhaps as you go on your Valentine’s date, seemingly jokingly ask if your date has ever cheated. Then you will know maybe if you will not need to follow up with another date. Future betrayal problem solved! Alternatively, you could always ask how many tandem repeats do they think they have in the DRD4 gene.
Joking aside, scientific literature does also offer some hints towards nurturing fidelity. Gentlemen, you know how you get instantly scolded by your partner if you even dare to venture a passing glance at another woman? There seems to be some merit to that! One study showed that individuals who disengaged attention from attractive alternatives 100 milliseconds faster (that’s 0.1 second! Seriously?) were 50% less likely to engage in infidelity!
Once again, women have already figured it all out! They know if you look 0.1 seconds too long, it could spell trouble! So, if you glance, it better be below that threshold of detection buddy! Good luck!
And if you get caught, here is a line for you: “Honey, I couldn’t help but notice that she is at least 2 points lower in attractiveness than you, and it made me think once again, what a lucky man I am to have you!” Why?
The same study also showed that those who rated an alternative at least 2 points lower in attractiveness were also 50% less likely to engage in infidelity compared to those who ranked that attractiveness higher. Basically, if you can engage in purposeful devaluating of attractiveness of others, and if you are a man, in the purposeful enhancement of attractiveness of your partner, you are more likely to remain faithful. For whatever reason, according to same study, enhancing partner attractiveness by women does not do the trick. Again, whatever it is, they already figured it out. Just science hasn’t.
Now, on the very serious note of those who have been victims of betrayal (including infidelity) and who experience any of the negative symptoms described above (at the start of the article), you might want to consider undergoing assessment and psychological therapy for any PTSD-like symptoms produced by such potentially catastrophic betrayals. Such treatments appear to be quite effective, so it might be the solution to any continual suffering.
Genetics or not, we wish you all a loyal and romantic Valentine’s! You deserve nothing less.