A new theory of sexual attraction: genetic similarity
What if romantic attraction was purely genetic and not just about finding each other physically attractive? That is, while you may find someone physically attractive it does not mean, even if you get into a sexual, romantic relationship, that you will be ‘’sexually attracted’’ to them.
By sexually attracted this article means, ‘’infatuated,’’ ‘’in-love,’’ ‘’attracted,’’ and is not to be confused with finding someone sexy due to their physical attractiveness (see Helen Fisher’s work). You can find someone physically attractive and be engaged in sexual relations without being ‘’sexually attracted.’’ Being ‘’sexually attracted’’ is generally the first, default stage of a relationship, and generally lasts for the first year, but more commonly lasts for only 6-8 months – this short duration of infatuation is to stop your brain from frying from the upsurge in the levels of neurotransmitters, dopamine and norepinephrine. Infatuation also subsides for a very practical reason, obsessiveness for your lover inhibits the ability of a couple to successfully rear a child. The phase of a relationship after passionate love is the attachment stage, which is also known as 'companionate love.' In this stage the couple are bonded by a glue of vasopressin and oxytocin, as their lives become entwined.
It is the argument of this article that the eliciting and secreting of certain hormones and chemicals in the sexual attraction/romantic love phase is for purely genetic and biological reasons, and this genetic cause for sexual attraction is an evolutionary mechanism to ensure genetic continuity: the replication of similar genes. To understand this argument is to understand one simple rule of thumb: genes are selfish and are only interested in their own survival and replication, either through promulgation or through altruism, and as such biological reproduction is adaptive – firstly by helping an organism reproduce and secondly for the preservation of its genes. In essence, the phenotype - a complete organism that develops using information carried in the genotype and environment - is a vehicle for the perpetuation and preservation of the genotype - an organisms set of genetic information - through survival and reproduction. To such an extent that the evolutionary process can essentially be boiled down to this: the self-replication of an entity. When we view sexual reproduction through the lens of genetics, it becomes apparent that the ultimate interest is not individual survival (or its subsidiaries and proximate interests: liberty, wealth and resources) but the reproduction of genetic information that survives long after the death of an individual organism. The more similar the two genetic codes, the better , theoretically, the copy of self-replication.
In this sense, then, sexual attraction (infatuation) is a biologically adaptive phenomenon to ensure greater inclusive fitness and maximization on behalf of the family, and greater genetic fitness of the child – that is, while children are assemblages of two different genotypes, and while copies can be, so to speak, ‘’perfect’’ or ‘’less than perfect,’’ due to random mutations or selections, the chances of a more perfect copy, or at least more ideal copy, is maximised when parents share similar genes and heritable traits. That is, the traits and attributes valued by the parents will more than likely be assembled to a greater degree in the child than if the parents were dissimilar.
When we are ‘’sexually attracted’’ to someone, the second brain system (the first system is lust and the third is attachment) concerned with reproduction is activated (to make mating more efficient) and subsequently, once activated, increases the levels of neurotransmitters: dopamine and norepinephrine (see the work of Helen Fisher) and concomitantly decreases the level of serotonin, leading to obsessive nature of romantic love; there is also a subsequent increasing of testosterone in the female (women become hornier) and a subsequent increasing of oestrogen in the male (men become more sensitive and emotional). The couple consequently suffer from an emotional state characterised by separation anxiety, pining and constant intrusive thinking of their love object. The activation, then, of this brain circuit leads to a specific goal-directed behaviour: sexual and emotional union with the beloved. The ventral tegmental area of the brain is awash with dopamine. Love in this stage has subsequently been described as an addiction, similar in effects to cocaine and cocaine withdrawal - thus explaining the increased energy and motivation of the couple. As such, this brain system evolved so that their is only room for on one: monogamy – as attention is directed to a singular ‘’special’’ partner. Sexual attraction, then, is basically the activation of a specific neural circuit: Sex and love, then, quite literally is in the brain.
But nature has tricked infatuated couples: this infatuation, this height of sexual attraction lasts only one year – (six to eight months is more common). At most, this sexual chemistry lasts between one to two years. After a year (or 6-8 months, it depends) the level of nerve growth factors and the level of bodily hormones decrease and return to their normal rate, assuming the same baseline rate of a singleton or a long term-relationship – the normal baseline rate for that particular individual depending on their personality profile.
This sexual attraction phase or ‘’falling-in-love’’ is important for two reasons: firstly, it is the chemical that cements the biological bond of the couple in the brain; it is nature’s way of creating the chemical glue which will pair bond a couple and makes mating efficient. Secondly, it is the chemical that creates attachment afterwards to enable a long term relationship – the chemical factors that create the phenomenological experience of love. As a caveat, it has to be mentioned that, of course, there are variables in every individual case. Whether long term love will occur is couple and personality dependent, and there is also couple and personality compatibility to figure. This chemically induced infatuation with a partner is nature’s way of developing and establishing a neural pathway between the partners, filled with memories of euphoria and exhilaration. This is necessary because the couple are not genetically related to the extent of family members or kin. I would add that it is also nature’s way of suggesting you are, in a broad sense, genetically compatible, urging the couple to procreate despite differences which may later derail the relationship. It is also nature’s way of ensuring the continuation of the species and urging reproduction (especially before contraception), literally forcing it to happen through an emotional reward mechanism compelling lovers to mate. Almost instantly, feelings of love and dependency are developed, and the couple are, for better or for worse, bonded. Love is a biological, neural process.
As an aside, I just want to emphasise the miraculous nature of this romantic attraction. That we find a person aesthetically pleasing or good-looking is not surprising at all, but the idea that we become infatuated, ‘’in-love’’ with someone for 6-8 months (maybe even a year) is. Not only that, but that two people, independently but simultaneously, after a romantic encounter or exchange, both undergo hormonal and neurotransmitter changes ensuring reproductive success (before contraception), developing similar feelings of euphoria and dependency, is. Studies have shown that love-styles are not genetic (which is surprising) but environmental, meaning that it is whom we come into contact with which evokes the rapidity (or not) of falling-in-love. Essentially, it is as if both bodies have a switch (presumably activated by similarity in DNA) which ‘’infatuates’’ both bodies to direct their undivided attention towards one another. This switch is not conscious, it cannot be activated by any romantic encounter; it can only be switched on it seems by mutually compatible DNA and genetics. If this is the case, it is not at all random, nor based purely on a certain level of physical attractiveness. But why does this happen? What is nature trying to achieve? Why did this mechanism evolve? And how do genetically viable matches come into contact with each other?
Perhaps the best way to explain this comes from abnormal situations which shed a light on the normal working of mechanisms. Just as adopted twins reared apart (an aberration in nature) exposed the degree of genetic influence in I.Q and personality traits (to name but a few choice similarities), the mechanism that has exposed the underlying genetic basis of sexual attraction is the abnormal but significant occurrence of Genetic Sexual Attraction (GSA). GSA is a phenomenon resulting from when adult adoptees meet their opposite sex biological relatives for first time in adulthood. With no prior exposure, with no Westermarck effect (family proximity desensitising sexual attraction), they immediately, almost simultaneously, fall madly in-love with one another, and begin sexual relations. In these cases, the attraction and emotional craving for their beloved ameliorates the consanguinity between the two and they see themselves as lovers, which is understandable considering that activation of the brain system and the emotional reward mechanism described above. It does not matter to the couple that they are committing incest and flagrantly dismissing cultural and societal taboos, such is the level of attraction and obsession in these cases: the heart really does rule the head.
GSA is so prevalent that is estimated that 50% of biological adopted adoptee reunions in adulthood are affected by this phenomenon. While others have posited an environmental reason for this attraction: the ‘’missing’’ parental/child bond in childhood, I argue that based on similarity the attraction is genetic. It seems only convenient to ascribe an environmental cause to this attraction: to explain it away and to environmentalise it. But this explanation fails to take into account that the lovers affected by this phenomenon do not see the other person as a family member – they’ve never related to them as a relative - but relate to them as an attractive stranger to whom they’ve developed an overwhelming attraction for. As if struck by 'love at first sight.' Time is not also a prerequisite for these feelings to form: GSA couples 'fall' for their partners within a week or first meeting.
In these cases, physical attractiveness doesn't even really matter so much. Even if the younger child is significantly more attractive than the parent, they still seem to ‘’fall’’ for each other. An environmental explanation also fails to explain why reunited brothers and sisters ‘’fall’’ for each other, nor does it explain the attraction between half-brothers and half-sisters. In many of the cases, the adoptees have had adopted brothers and sister and/or adopted parents, so they’ve environmentally already experienced the bonding between those in close proximity. An adopted mother still acts maternally to their adopted child. However, if attraction is based on genetic similarity, it makes perfect sense. We know, for instance, that genetic similarity accounts for friendship and best friends (see work of Philippe Rushton). In cases in which twins are reared apart in different environments and cultures, thousands of miles apart, upon initially meeting the identical twins very quickly become best friends or, it should be said, significantly closer than best friends. Similarly, twins reared apart (not lovers) experience feelings of platonic love for their other twin upon one or two meetings. Time is not a prerequisite to form a close emotional bond or to recognise and detect similarity. In the documentary, Twinsters, for instance, the two reared apart Asian twins immediately feel an unconditional love for each other, and these feelings were developed by talking over Skype. Neurochemically, they form an acute attachment, and mentioned how this relationship feels different from relationships with their adopted family. Perhaps the most telling statement is when the twin, Sam, says ‘’it’s crazy how you can love someone unconditionally you’ve never met. I don’t love my [adopted] brothers any less, or my [adopted] parents any less, but there is definitely an unexplainable connection that I have with her [her twin sister, Anais]’’ After meeting for the first time physically in London, they immediately develop a close bond, leading to overwhelming feelings of love and closeness. They hold hands; they sleep next to one another; they talk incessantly; they continually touch one another. They have an insatiable desire to be close to one another. They want to feel their twin's love and to demonstrate their own love. The attraction is mutual. Sam continues to say ‘’ when we’re running around with each other I feel completely fearless and I guess I’m scared of losing that.’’ As Sam is saying that, there is a juxtaposed clip of Anais crying while being hugged by Sam. In an acute sense, attraction is a reciprocity of similar genetic coding and neural circuits.
It is illustrative to think that not a single other person in the world could evoke such an emotional response in either of the twin other than their twin. By the end of the meeting in London they are crying: happy that they have found one another but desperately sad to be leaving one another. They vow never to forgo this bond and to be geographically closer to one another. There is no hesitation (finances excepting) to fly from continent to continent to see one another. In the documentary Twin Sisters: a world apart the attraction between the two reared apart sisters is instant, despite not sharing a common language. Despite being only just self-aware (in the documentary they are six years old but turn seven), they think about each other constantly and send letters telling each other that they love one another. They are best friends. Upon leaving, both sets of twins in both documentaries, experience immediate withdrawal and intensely miss one another. In Twinsters Sam comments ‘’It’s very weird settling back into life now. I have a [identical twin] sister and I really miss her, and I really want her to come and visit and I can’t wait for her to get a job and I wish so bad she could get a visa and come and work in the States.’’ The documentary then cuts to Anais who comments: ‘’ I feel like I’ve known her my whole life, so it’s like, yeah, she’s the brightest, the smartest, like the most handsome girl [laughs] but no, it’s really great, and it’s nice. It’s . . . I don’t know how to describe it’’ In the next clip Anais expands upon this: ‘’I really wanna be closer to her now, I think. We can’t go back on each other’s life completely now that we’ve met and shared a lot of things. I just want to keep sharing my things of my life, of my everyday life, with her. So yeah, being apart is a bit difficult. So I really miss her already.’’ Texts abound with expressions of love ‘’Anais! I love you! Likewise, the young twins in Twin Sisters, for instance, immediately sob when upon departing one another, after they shout 'I love you' in their own foreign language. Ultimately, platonic or intimate, attraction is an emotional affair regulated by biological similarity. The important facet is to recognize the mutual feelings of kinship and closeness. Quite literally, when similarity occurs, the feeling is spontaneously mutual.
To emphasise the non-environmental nature of sexual attraction, I just want to give an anecdotal example of a relationship without sexual attraction. That is, so to speak, a relationship not ordained by nature, despite mutual ‘liking’ and physical attractiveness. I have, for instance, recently been in a relationship with an Indian doctor. When she wore her contacts and straightened her hair she was extremely physically attractive. I would not hesitate to give her a 9out of 10, on the scale of physical attractiveness (thankfully she took off her glasses in bed). In fact, on our first date, I thought she was perhaps the most aesthetically attractive girl I had ever seen – certainly the most attractive girl I have dated. But even then on the first date I recognised the lack of similarity and expected nothing to ‘’spark’’ between us, even knowing there was mutual physical attraction - she laughed at my jokes, punched me on the arm, and made comments on how ‘’she could get used to dating a nerd’’ (I told her I played chess). At the end of the first date we hugged, but in subsequent dates she mentioned she was willing to kiss me on the first date. She sent me a text immediately afterwards facilitating a second date.
We dated for five months. I was not remotely close to ‘’falling in-love.’’ I had no strong feelings for her other than feelings of ‘’companionate love’’ (the stage after ‘’infatuation),’’ but will admit that I got attached and ‘’semi-emotionally invested.’’ I liked her. She was my special companion, and she was the only girl I was having sex with. Without nature’s ‘’chemistry,’’ however, it was essentially a bond of friendship (with diminishing returns) with a girl I had no qualms with having sex with. We got on really well and had a lot of fun. At first it was exciting in its newness. We bantered well and laughed a lot, and of course it helped that I found her physically attractive, and her to me. But it baffled me why I never truly developed romantic feelings for her – as described above. I wasn’t infatuated in the slightest. I had no separation anxiety. I didn't 'miss her,' even though I wanted to see her. The first time I had sex with her (she dragged me into a hotel after declaring 'she wanted me') it felt like I was going through the motions – as if I was watching myself have sex and ‘’patting’’ myself on the back for having sex with a ‘’hot’’ girl. I was also slightly bemused that she was ‘’way more into me than I was into her,’’ to the extent that she offered herself to me willingly and freely.
Admittedly, I’ve felt like this way before, but only after having sex with the same girl for 18 months when the chemicals of sexual attraction had dissipated. I fell ‘’in-love’’ with my last girlfriend almost instantly, and it took a year to shake off my feelings for her after we broke up. There was depression and withdrawal in the brain. It was pretty traumatic emotionally. Unlike that relationship, it only took a month or so in regards to this breakup to ‘get over it.’ Even if the sexual chemistry wasn't there I still liked this girl, so the romantic rejection still hurt. But Neurochemically, the breakup was traumatic or as painful, I ultimately didn't have the intensity of feeling for this most recent girl. The ‘’chemistry’’ or ‘’spark’’ was not there, despite this girl far outranking the previous girl in looks. If I didn’t want to answer her phone calls I readily ignored them - (and I did). If my previous girlfriend phoned, quite simply, I answered. If my previous girlfriend cried hysterically, I would endeavour to rectify the situation. I can only conclude, the, that with the new girl the genetic similarity just wasn’t there. I’m an INTP (possibly INFP w/ 5w4?) and she was an ESFJ. Personality wise we are total opposites (if we accept that MBTI has a biological basis – some studies suggest that MBTI is 50% heritable and genetic in origin, while others dismiss MBTI as pseudoscience). This is not me typing her personality: she took the test as it was mandatory in her medical practice. She was adamant that ESFJ explained her. I wish the genetic similarity was there, because this girl was much smarter, attractive and conscientious than the girl I was infatuated with.
Essentially, romantic attraction has evolved to help the species procreate, but more than that, romantic attraction, based on genetic similarity, I would argue, evolved as to increase the inclusive fitness of the child, to improve fecundity (more attracted to those more similar – in personality and appearance) and to improve the relationship between baby and parents (as we select partners with similar attributes and values, ensuring that our child has the same attributes and values as us). This evolutionary mechanism, then, evolved as nature’s blessing for the match and to instigate reproduction. As strange as this sounds, while we can theoretically breed with any opposite sex human, I would speculate that the mechanism of ‘’falling-in-love’’ is analogous to a certain breed of dog dating the same breed of dog; that is, dating others without the romantic attraction phase is analogous to two different types of dog breeding: creating a half-breed rather than a pure breed. The genetic coding of the two, then, are dissimilar – and the likelihood of a successful genetic replication is lessened – but not impossible. But obviously, in the case of dissimilar dog breeds mating the genetic coding of either dog will not be replicated, and in a genetic sense, while adaptive for the phenotype, it is maladaptive to the genotype – and hence no genetic mechanism of romantic attraction urging procreation.
This would also explain why a female (and a male, for that matter), is less likely to become infatuated as she ages. While infatuation, it seems, does have a correlation with psychological maturity (girls in their early twenties seem to be perpetually infatuated), it figures less than it does with nature urging procreation. The reason we are more sexually attractive when we’re younger is nature’s urge to procreation, not simply because we’re younger and immature. Specifically, there is a significant correlation between a female’s physical appearance and the rate of her fertility: natural beauty and fertility significantly reduces at 35. This fact may be overshadowed in contemporary society due to the advances in makeup. Women may believe that they have more sexual value than they actually do.
The same applies to a male, but it is less important because a female chooses her reproductive partner – not the other way around. The obvious conclusion to draw from this is: the more relatively naturally physically attractive you are - i.e. when you are between the ages of 18-25 - the more fertile and hence better genetic replications (less genetic mutations) you are able to produce – the more nature will urge you to procreate and produce better genetic stock. Obviously, if you have lower genetic stock (lower I.Q and lower psychometric personality profile etc..) and you get pregnant at sixteen, you’ll still have lower genetic stock regardless of when you procreate – and to be pregnant at such a tender age is indicative of poor genetic coding, and your offspring will inherit mutations of poor genetic coding. The evidence suggests that the children of older parents are more likely to develop autism, or down’s syndrome, (to name but a few) and generally be dumber and less attractive. It would be erroneous just to assume that once you reach a certain age this happens, rather than the idea that it’s on a continuum with every month the quality of the fertility decreasing (if only incrementally). Of course, whether someone will be smart or dumb depends on their parent’s genetic material – so they will relatively, on average, be less well - endowed than they could be, genetically (though exceptions do happen), if fertility is deferred or delayed.
Arranged marriages, then, based on random sampling are not wrong because they’re arranged (some are very successful and a minority of spouses genuinely love each other – but these are exceptions to the rule, and the successful are based on similarity) but because it is not based on these factors: genetic similarity, fecundity and inclusive fitness – (though as a practice it ensured the continuity of the species and restricted one female to one male, it is essentially maladaptive compared to genetic similarity). As such, as traits are heritable, the benefit of passionate love matches is that it maximises the role of child and parent in being similar. If both parents are opposite personalities, and the child takes on the attributes of one parent more than the other, the relationship between the child and the parent of whom attributes the child hasn’t inherited will suffer – increasing the likelihood of a poorer than normal and counter-productive bond. Though, it must be admitted, there will be a bond there.
This is important as the child depends, as mentioned before, on the parents love to survive. A mother, for instance, suffering from postpartum depression, is not an adequate caregiver for the child – especially if the mum is single or without extended family. Postpartum depression directly threatens the new-born’s existence. Neurochemically, the baby is being rejected. I would argue, however, that the evolutionary mechanism of ‘’falling-in-love’’ with your child (the same brain system is activated) is because the brain has evolved a mechanism in response to similarity – ergo, considering your child is the most genetically similar to you (identical twins excepting) the brain, in response, activates the emotional reward mechanism similarly seen in ‘’infatuated’’ couples. Ergo, GSA then occurs between two biologically similar relatives.
However, as an evolutionary mechanism, the eliciting of chemicals and hormones to facilitate the sexual union between two people must occur when any similarity is detected, not just the rate of similarity detected in a relative. The simple reasons why this happens is because it confers fitness benefits – as mentioned previously: the replication of genes.
The empirically true measure of this is in assortative marrying where ‘’like’’ marries ‘’like.’’ Quite simply, we ‘’like’’ those who are most similar to us. In a free society, where we are free to marry who we like, we are only (in most cases) going to marry those who evoke pleasing brain signals within us – (try marrying or sleeping with those whom appal or repulse us). That is, those whom we find attractive (the first level of dating), those whom we are ‘’sexually attracted’’ to (the second level of dating) and those whom we are compatible with (the third level of dating). If the match doesn’t fit or no longer fits after duration, according to one or more of the partners, a breakup inevitably occurs – (of course there are exceptions and desperations, and dependent on particular brain chemistry, expectations and personality). Essentially, to de-personalise this, if the brain does not signal infatuation or love, dopamine or oxytocin, then not enough has occurred within the brain to keep the relationship going. But what signals dopamine or oxytocin – or not - in the other is our genetic makeup, and likewise to us – dating and attraction is essentially beyond our control.
But to suggest that incompatible genetic personalities would ‘light up’ the brain is illogical, to the extent that it is illogical to suggest that people whom we find unattractive will evoke pleasing brain signals. The upside to this, then, is to realise that nature has made it so that who we find attractive are likely (if based or heritability - and not delusion) to find us, equally – to some extent – attractive. This is a bit of a truism, though, as we only generally fancy those similar to ourselves – but not always – as sometimes we date those (in my case) who we find physically attractive and yet know that the ‘’chemistry’’ is not really there, or will never be there. Women, then, as part of nature’s biological breeding cycle, are much more sensitive to this, and therefore initiate significantly large proportion of breakups – and because they’re more emotional and immature. In the animal kingdom, for instance, Prairie Voles, the most monogamous of creatures (they bond for life), leave their mate if the oxytocin receptors are disabled. It is neurochemistry, then, a mechanism beyond our control, and not free-will, which binds us.
In the case of those affected by the phenomenon of GSA, then, both brains immediately light up at the thought of (heritable) similarity. It is the neurochemistry which binds them. Both brains simultaneously activate the emotional reward mechanism of the second brain circuit system of ‘’attraction,’’ and consequently there is an intense craving for one another. If we could perform an fMRI scan, the brains of those GSA would be no different than those whom have fallen madly in-love - the same areas in the brain would ‘’light up’’ in a fMRI scan. It does not matter to the brain that they are committing incest – as the brain perceives this new lover as a lover, and not family. To clarify: incest does not occur in families because it is horrific and abhorrent to the brain. The Westermarck effect makes it truly repulsive. The brain cannot signal attraction because it perceives the family members as family.
To emphasize the genetic nature of GSA, it will be relevant to delve into the nature between physical similarities and psychological traits in identical twins. In identical twins, despite some identical twins being less physically similar, this does not impact difference in psychological traits between identical twins. Moreover, two people whom are physically alike (lookalikes) but share no genetic similarity (unrelated lookalikes), are treated differently by others and show negligible similarity – we evoke responses from others based on our personality and appearance, which is to say genetic data: ‘’reactive gene-environment correlation.’’ If we extrapolate this information towards GSA, it explains why an adoptee will find their biological relative sexually attractive (though they must be less physically attractive on average than their child’s same-age peers). That is, it has more to do with genetic similarity than physical attractiveness.
Considering none of us plan to marry a relative, the best matches are those with similar, heritable traits. As genes seek expression through culture, the best way to ascertain similarity is through similar attitudes and interest. The most heritable items are similarity in values and opinions (0.57), followed by similarity in I.Q (0.37). Crucially, then, it does essentially boil down to similar interests and values/opinions. A good way to ascertain genetic similarity, is to have a similar interest in music and a similar value system. Similarity in music genre is quite a high heritability (0.47), and therefore a legitimate similarity which can predict genetic or personality similarity. In my case, if you’re conservative (more specifically, Identitarian – but allowances can be made) and into classical music and/or serious literature, as long as we find each other physically attractive, we are good to go. The similarities cannot be too broad, for instance. ‘Liking’ food or ‘going to the gym’ is too broad of a similarity – it must be more specific. The reason I am emphasising this point is this: stop wasting your time on dating sites if you’re dating people whom are not genetically similar on heritable traits – it’s not about casting a wide net, it’s about casting a very specific net – or you’ll catch fish you don’t want to catch (this can take months to realise). It may be a better reproductive strategy to 1) date friends of friends 2) join a club or profession based on heritability. 40% of marriages are couples who met at work or university, or similar institutions. I would suggest the other majority of couples met through clubs or friends. Internet dating is a good tool, but only date if similarity and physical attractiveness – not just physical attractiveness alone. But the takeaway lesson from this is this: nature has made it that you appear attractive to others you find attractive. Those with a similar genetic profile appear mutually attractive to one another. Genetic similarity will likely manifest itself in a similar level of physical attractiveness; similar personality profile and similar choices in life, especially in regards to jobs, education and interests – as a result of reactive gene-environment correlation. As such, all we really need to do, is to live our lives true to our own genetic profile.
The key, then, is recognizing whom you are attracted to because of similarity and not because they're objectively physically attractive. In some respects, nature has made it easy for us. To attract a mate, one has to literally be the best version of himself and just go about his life as the best way of living it. I would also suggest assortatively mating on personality type.