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The Chemistry Between Us: Review and Summary

Book Reviews

The Chemistry Between Us: Love, Sex, and the Science of Attraction is unbelievably fascinating!

I have never used so many of my post-it page markers in one single book; I felt like I was marking every page, and sometimes twice or thrice! Halfway through the library version, I had to order my own copy, so that I could keep this book (and all my notations) on the shelf for future reference.

The authors’ writing styles are cohesive and so layman-friendly that they make intricate scientific ideas accessible to the casual reader. Science was never my strong subject in school, yet this book has completely captivated my attention and taught me so much about how our brains work. Absolutely, completely, and HIGHLY recommended.

This is another situation where I can only touch on some of the most fascinating points from (a wealth of fascinating points in) each chapter, and even then, this post has become a tome in its own right. Even though I will share here many of the ideas the authors put forward, the presentation of information and the arguments for their conclusions are far more compelling in the full form. If you want to be repeatedly blown away by insights into the workings of our brains and sexuality, pick up a copy and get reading! You won’t regret it.

And, if you’re ready for my attempt at distilling some of my biggest takeaways into something slightly shorter than book length (heh), grab a cup of cocoa (or coffee, or tea, or whatever) and let’s get started!


sexy couple lounging together

Photo by Vidar Nordli-Mathisen on Unsplash

The Chemistry Between Us


While some of it may be socially guided, intensified, or shaped, there is definitely a biological component to gender identity that exists in our brains and cannot be overridden by social programming.

Take for example, the case of the machihembra of Las Salinas, in the Dominican Republic. These children were visibly female at birth and raised as females (with female socializing, dress, etc), but upon the onset of puberty (due to a genetic mutation traced back to a common ancestor), they grew penises. Upon testing, it was found that they were, indeed, biologically male. All but one of the machihembra who were studied transitioned into the life of a male, despite having been raised to think of themselves as female, and living all of their daily lives in the role of females.

Similarly, there is a case discussed of Bruce/Brenda Reimer, whose infant penis was destroyed in a botched surgery, and who, it was decided, would be reared as a female child, with gender reassignment surgery and estrogen therapy. Despite having been socialized to be female, he hated dresses and preferred his twin brother’s toys. As an adult, he changed his name to David and began the transition back to maleness, physically and socially. Sadly, David could not find peace with his journey, and ultimately (on his third attempt) committed suicide.

While some part of our gender identity seems to be hardwired into the brain from birth, just how masculine or feminine we feel individually seems largely to do with how much testosterone we received in utero.

Charles H. Phoenix conducted a study at the University of Kansas, where pregnant guinea pigs were injected with testosterone. When born, the pups had “ambiguous genitalia”. And when stimulated for sex, these pups did not react as other female guinea pigs would react; they barely displayed the female response (lordosis). Moreover, they did a lot of mounting of other females – about as much as males would.

“The hormone hadn’t just changed the daughters’ bodies, it had changed their behavior, too. This means it changed their brains. Phoenix tried giving testosterone to normal adult females, but it didn’t have the same effect. Whatever was going on was happening in utero, during fetal development, to organize the brain in gender-specific ways.” (P17)

Another study goes a little deeper and blew my mind even more. Researcher Robert Goy conducted a similar experiment with Rhesus monkeys (with similar results), but then began to question whether the behavior of the subjects was affected by their perceived gender and socialization.

“To answer the question, Goy tried giving testosterone to pregnant monkeys at two different times. One group got the hormone early in the pregnancy, the other group got it late. The mothers who received doses early in pregnancy gave birth to females like the ones in the first experiment, with masculine genitals. But, despite having masculinized body parts, they played like their normal sisters and took on female roles. The babies of mothers given testosterone late in pregnancy looked just like typical female monkeys with all the proper female body parts. Clearly, the late testosterone boost missed the window to influence physical development. Amazingly, though, these females played like young males–with more roughhousing and aggressiveness–but because they looked like females, their malelike behavior could not have been caused by monkey social pressure. There were clearly two windows of development that could be affected by androgens. One opened early in pregnancy and controlled the formation of genitals. The other opened later and organized the brain according to gender, masculinizing and defeminizing it in males. Without the testosterone surge, the brain would remain feminized–its default setting.” (P20, emphasis mine)

While most of these studies have been (unsurprisingly) performed on animals, they are nonetheless illuminating. Clearly, there is a chemical and biological reason that some beings experience a disconnect between their physical genitalia and their gender identity.

And, lest we be less-than-content with studies of monkeys and guinea pigs, the authors delve into the human side of things as well. Dick Swaab studies brains, and he has found the transgender brain:

“After years of searching, his lab discovered differences in a structure called the bed nucleus of the stria terminalis (BNST). In lab animals, the BNST shares circuits with the amygdala and the MPOA of the hypothalamus. The BNST is also loaded with hormone receptors. It is sexually dimorphic like the rat, sheep, and human SDNs, and it is a key player in masculine sexual behavior. When Swaab’s lab looked at the BNSTs of male and female heterosexuals and homosexuals, and at those of male-to-female transsexuals, it found that the transgender BNST was the same size of the BNST of women. This was true whether or not the transgendered people had their testicles removed. (P30, emphasis mine)

The book goes on to cite other evidence of structural differences found between cisgendered and transgendered brains. What’s beautiful about this to me is that, if more people understood this, perhaps it could engender a greater sense of respect for a person’s chosen identity (gender or otherwise). Each of us are uniquely and precisely who we are, because our brain structure–decided long ago–dictates it. And while much of life is elective, many things (perhaps more than we can possibly realize) are simply wired into our very nature.

“But if we accept that we are our brains, then a 46,XY human being with complete androgen insensitivity is a woman. If a person with a penis, a beard, and big muscles is unshakable in his belief that he is supposed to be a female, wants to act as a female, and is attracted to men, that person is a heterosexual female, not a gay man. A man who’s attracted to other men but behaves and feels like a man is indeed a man; he just happens to have the brain of a homosexual. What the organizational hypothesis and work like Swaab’s and Roselli’s teach us is that genitals, and even chromosomes, can be irrelevant to gender behavior. (P32, emphasis mine)

We have to stop seeing the world through the lens of our own experiences, even if that’s the most natural way we see things. We have to allow every human being to have their own personal identity, born from a unique recipe of neuro-chemicals and experiences we could never know or fully understand, and to trust them in their choosing of their own path.


“…when Larry began his scientific career, he started with lizards. He found that if he gave female lizards estrogen, they would always give in to a male’s courting and mate. If he gave a male lizard testosterone, the male would become so sexually motivated, the animal would try to have sex with Larry’s finger.” (P38)

As much as we want to believe that we are the logical overlords of our animal urges, our hormones have a lot more to do with our mating habits than we would like to admit. When estrogen is more active in women’s systems, studies show that they are more attracted to “the bad boy,” as compared to the “nice guy” they might rationally select at other times of the month. They are also more likely to make riskier decisions overall–be it regarding men, real estate, etc–during this time frame. “Ovulation lowers a woman’s resistance to risk taking, just as an increase in testosterone lowers such resistance in men.” (P47) This may be partially because a larger portion of estrogen connecting to estrogen receptors (as happens with ovulation) actually dampens the female’s stress response, allowing her to overlook things that may otherwise cause anxiety, and focus on the enjoyment of sex. (Let’s hear it for evolution…?)

And it’s not just the female who is subjected to the whims of sex hormones. Researchers have shown that implanting testosterone into the brain’s MPOA will restore sexual desire (and erections/ejaculations) to castrated animals. Outside the severity of castration, many common life experiences can reduce testosterone in men:

  • smelling his own infant(!) – this one acts quickly… testosterone dips within 20 minutes.
  • losing a sports match
  • watching the team he roots for lose a sports match
  • driving an old, clunker family car
  • being married for a long time
  • getting fired from a job
  • aging

There’s a lot in life, it seems, that can bring down a man’s testosterone. Luckily, other things can raise it:

“Winning does it, whether the competition involves sports, a battle, a chess game, or a political campaign. This effect can self-perpetuate: a win imbues a man with confidence, further enhancing his chances of winning again. Driving a Ferrari will do it. When male mice catch the scent of an estrous female, their testosterone rises…” (P49)

Heavy resistance training has also been shown to increase testosterone levels in men.

My favorite quirky takeaway from this chapter is how much estrus affects male attraction to females:

“Miller and his colleagues used New Mexico clubs as real world labs to conduct a study they titled “Ovulatory Cycle Effects on Tip Earnings by Lap-Dancers: Economic Evidence for Human Estrus?” Based on the financial outcomes, it seems clear there’s no need for the question mark. When the strippers Miller chronicled were in estrus, they made about $354 per five-hour shift. Anestrous women made about $264–a difference of $90. Menstruation cut dancer’s earnings in half. The difference can’t be attributed to one woman’s attractiveness over another’s, or to fashion choices, because the research took place over two months. The estrous and anestrous women are the same women, documented at different points in time. Dancers who were on the birth control pill–which essentially eliminates estrus–made about $193 per shift, also far less than ovulating women. By linking dancer preference to money, rather than to customers’ statements, Miller was able to show this preference was real and unconscious.” (P53)


“Dante may have condemned people who betray their reason in favor of lust to the first circle of hell, but he didn’t know that nature–or God, if you prefer–designed this betrayal into our brains. Dopamine mutes the prefrontal cortex, disinhibiting sexual desire and giving us tunnel vision for cues that could lead to satisfying that desire.” (P75)

Our brains are wired to pursue pleasure, and as many popular scandals have shown, our logical rationalizations are not always enough to keep us out of trouble. When scientists wired rodent brains to provide a pleasurable stimulus at the press of a lever, and left them to their own devices, the rats would constantly press the lever–ignoring food, sleep, and water–until they died. Given full power over their reward systems, they literally “pleasured themselves to death.” (P67)

What’s more, the consummatory reward of orgasm is powerful enough to actually rewire our brains. With enough association of cues and reward, you can alter the synaptic connection (like Pavlov’s dog). This is how we develop “a type” when dating, or, with more specific circumstances, a fetish.

A study by Jim Pfaus (which may have caused my most audible “holy shit” reaction of this whole book) tested this fetish hypothesis. Rats have an innate and intense aversion to the smell of death, and will go to any means (including crossing electrified grids) to get away from the smell. Pfaus exposed virgin male rats to an estrous female who had been painted with the smell of death. Multiple attempts were needed before they were willing to mount, despite the seductive mating behaviors exhibited by the female. Here’s where it gets crazy. Pfaus later placed the (naturally polygamous) male rats among other, naturally and artificially scented estrous females, and the males preferred the death-scented females. In fact, some rats refused to mate with any female who smelled of anything other than death. Pfaus had instilled a death-smell fetish in the virgin rats.

Pfaus also did further studies, placing rats in tiny rat jackets for their first copulation (thereby establishing a jacket fetish), and found that some of those rats, when bereft of their jackets, would refuse mating entirely. Even those who did proceed with the mating process weren’t free from the influence of the fetish — many couldn’t get an erection without their jacket, and even for those who could, the sex act took much longer and “the female really had to work for it.” (P84)

How powerful are the sexual associations we create in our brains!


This chapter is filled with compelling examples and evidence for the argument that a mother’s nurturing during infancy is absolutely critical, if the child is to grow up without hindrances to their ability to develop empathy, connect to other people, and form trusting and loving bonds.

Yet, interestingly, a mother’s level of nurturing may depend on certain chemical cues that she receives. These chemical changes in the mother’s system encourage her to nurture, even if she would not normally be predisposed to do so. This was shown in an experiment where researchers injected blood from a pregnant rat into a virgin rat (by nature, virgin rats avoid or antagonize rat pups). After the blood transfusion, the virgin rats nurtured pups, just like the pregnant mothers.

However, there are certain “missable” triggers that set off these nurturing chemicals. Breastfeeding seems to be one, and vaginal birth is another (as cesarean section “prevents nerve signaling from the vaginocervical area from reaching the brain, muting the oxytocin release from the PVN [paraventricular nucleus].” (P102))

Indeed, in studies of ewes, giving birth under “an anesthesia that blocks the signals from their cervixes to their brains” (P103) results in muted oxytocin in the mother’s brain, a reduction of maternal behaviors, and, in some cases, rejection of the lamb entirely. None of this is to say that a mother can’t be nurturing WITHOUT these chemical triggers, but having them certainly helps.

Unfortunately, when babies aren’t properly nurtured by their parents, they develop a shut down or “silenced oxytocin response”, which “may result in a blunted ability to calm down when experiencing stress, in less empathy towards others, and in an autistic-like social blindness.” (P113) Much of the chapter is devoted to the story of a Romanian orphan who, deprived of physical affection as an infant and young child, exhibits a significant and somewhat debilitating social disconnect, despite being adopted by loving parents, and provided affection, as well as therapy, special schools, etc, during her later childhood and teenage years. And this orphan is only one of many examples that scientific studies afford, showing how latter intervention cannot fully repair the system, once established (or, more accurately, NOT established) during those infant years. Similar studies have been repeated among many species:

“Rhesus monkeys raised without their mothers also experience a sharp decline in oxytocin levels, are more aggressive, and are very impulsive, showing little self-control when it comes to seeking pleasurable experiences.” (P120)

Here’s a deeper dive on the famous Harlow Monkey study, which deals with similar concepts, if you’re interested:

As everything I read in this chapter corroborates my own personal, anecdotal experiences, I am now so thoroughly convinced of this correlation that, “How nurturing was your mother?” will likely become a future getting-to-know-you dating question, with deal-breaker status.

I’m kidding.



Studies have shown that the same chemicals that encourage maternal behavior towards one’s young (oxytocin and dopamine) are also necessary for the bonding to a romantic partner, and are both released during sex. There’s also some association shown between the amount of receptors for these chemicals and the extent of pair bonding exhibited.

There is, however, an additional chemical required to establish the bond of “love” – opioids. In studies where opioid receptors were blocked in female prairie voles (a normally pair-bonded species), the females would engage in sex, but fail to bond with their partner. (By the way, if you’re starting to make a serious wow-factor connection between last chapter’s insight about receptor-development in infancy, and the ability to bond with a partner emotionally when sex occurs… I’m right there with you.)

Oxytocin contributes to relationships in many other significant ways. It encouraged study participants to fixate on the eyes of portrait photographs (the windows to the soul), even when they were instructed to look at the mouths. It helped subjects recall, with more accuracy, faces they had previously seen. It reduces the stress response. It encourages more positive behaviors between couples during arguments or difficult discussions. High levels of early oxytocin can even predict relationship success. It improves empathy and the ability to read emotions by up to fifty percent.

Oh, and did I mention oxytocin is a byproduct of sex? 😉

And, on the subject of creating oxytocin, one of the authors even weighs in on the age old debate of whether or not size matters:

“Larry believes the human penis has evolved as a tool to stimulate the vagina and cervix so oxytocin is released into a woman’s brain. The bigger the penis, the more effective it is at triggering an oxytocin surge during intercourse. Surges of oxytocin help ease any apprehension or anxiety a woman may have, making her open to her lover’s emotional and social cues.” (P150)

Intriguingly, the authors also specify:

“A study conducted by Stuart Brody, of the University of the West of Scotland, has indicated that, as fun as they are, neither oral sex, nor masturbation, nor any other form of sexual activity gives women the feeling of overall relationship satisfaction, including “feeling close to one’s partner,” than penile-vaginal sex creates.” (P150)

How does one get signed up for THOSE studies? ;P


Despite how we may want to move forward from the antiquated view of women as property belonging to their husbands or male partners, it seems there are some genetically-encoded reasons for the persistence of this association. There may also be a biological component to how monagamous a person is programmed to be. Enter the neurochemical vasopressin.

Vasopressin has been shown, when injected into the brains of hamsters, to put them into a “frenzy of turf grabbing, using the scent glands on their hindquarters to mark out territory,” in an unusually zealous way. (P160)

Vasopressin has also been shown to play a significant role in male bonding to a female sexual partner, in other words, in male monogamy:

“…the scientists had proved that brain vasopressin, which is released in males’ brains during mating, not only was involved in their postmating behaviors, but the male prarie voles wouldn’t do the behaviors without it. If vasopressin was blocked, they didn’t form a partner preference even if they mated. Without vasopressin, males have a very poor social memory. And while they would mate if vasopressin was blocked, they wouldn’t act aggressively toward other males afterward.” (P162)

To further isolate whether the vasopressin sensitivity was at the root of partner bonding, Larry Young took the vasopressin-receptor gene from a generally more monagamous species (prarie voles) and placed it into the embryos of a polygamous species (mice). The result?

“When those male mice–which are firmly polygamous–grew up and were injected with vasopressin, they acted a lot more like prarie vole males when they encountered female mice than their normal brothers did. They did much more sniffing and grooming of the females.” (P164)

Delving further into the connection between a mother’s nurturing and a child’s receptiveness to neurochemicals (established in THE MOMMY CIRCUIT), this chapter states that “Male pups of [more nurturing] mothers were more sensitive to vasopressin,” (P183) and “it isn’t the amount of the chemical but the specific brain regions that are sensitive to it that counts.” (P163)

Again, these are not human mating studies (imagine trying to get approval for that!), and scientists are hesitant to proclaim a true causal connection, as human behaviors are complicated. But these experiments clearly demonstrate a link between vasopressin sensitivity and partner bonding behavior.

A team did carry out some observational studies on this subject in humans, based on genetic information, reported data, and surveys, and “it found a “significant” association between one variant of RS3 and male personality, behavior, and quality of relationships.” (P182) To summarize the findings, those with a particular variant of RS3–the 334 AVRP1A RS3 allele–were not as good at relationships, and their partners did not rank them highly in “relationship cohesiveness, satisfaction, and affection.” (P183)

And at the risk of sounding like an embittered woman myself, I feel compelled to note that when women lament the inability to find a good man to monagamously settle down with (side note: whether or not monogamy is a desirable goal is an argument for another day), they might not be exaggerating their frustrations:

“The particular version of the gene that was liked to all these traits is one of the most common in the human population.” (P183)

The prevalence of this genetic variation makes me think of the introductory scene of the (excellent) movie Idiocracy:

Do we have an abundance of allele 334s because the allele 334s of our past were out, wildly spreading their seed, and making more allele 334 babies? Is this part of the reasons for the rise of alternatives to the monogamous marriage (polyamory, open and “monogamish” relationships, etc) in today’s society?


You may already be aware of the fact that there is a strong parallel between the addiction experienced by drug users and the experience of romantic love and sex.

“…the brain processes activated during sexual bliss, and during the development of fetishes and partner preferences, have tremendous overlap with the brain circuitry that makes drug use feel so good. They both rely on most of the same structures, the same neurochemicals, and create the same changes in the brain. (P186)

In the beginning, we are drawn to our lovers (or our drug of choice) because of positive factors. They flood our brains with chemicals that make us feel good, and we want more and more of that feeling. Eventually, the motivation transitions from seeking a positive hit to avoiding a negative one.

Interestingly, the brain also seems designed to focus on one primary obsession:

“Studies in humans and animals have shown that drug addiction can place the nucleus accumbens into a kind of deep freeze, blunting neuroplasticity. The reward system loses much of it’s ability to react to new, potentially lovely stimuli like, for example, one’s first taste of truffles, one’s new baby, or a new lover. In the Wang lab’s experiments, pair-bonding took most of the fun out of drugs, and drugs took most of the fun out of bonding. (P197, emphasis mine)

This reminds me of the Rat Park study (that link leads to a great, long-form cartoon that explains the study and its findings), that showed that addiction is highly correlated to social isolation, and that, when given the choice, even previously addicted rats would opt out of additional drug hits when surrounded by a comfortable environment and social support.

Given the similar patterns of love and drug addiction, it is no surprise that the sudden loss of either will lead to the experience of withdrawal. In a study performed by Oliver Bosch, voles that were forcibly removed from their pair-bonded female (I’m going to call them “divorced voles”) showed striking differences in response to stress than those removed from a brother vole, or those not removed from either a brother vole or a pair-bonded female. When placed in water, rodents will paddle like crazy to avoid drowning (even though they will simply float if they don’t bother). Of the four circumstances mentioned above, only the divorced voles “gave up” and floated instead of paddling for their lives. In another similar test (tail suspension), only the divorced voles hung like a limp noodle, while the other three types of voles ran their limbs, seeking escape. Lastly, in a maze that tested the voles’ anxiety, by pitching their desire to explore against their apprehension of exposure, the divorced voles explored significantly less than the others. This is called passive-stress coping.

“The males separated from their mates had much higher levels of corticosterone, a stress chemical, in their blood than did any of the other groups, including voles separated from their brothers.” (P201)

It should be noted that while females also experience this stress of separation from their pair-bonded male, they ALSO experience similar anxiety when separated from a female sister, unlike the males who did not show separation anxiety when removed from their brothers.

Bosch also found that if he blocked CRF receptors in the voles brains, the divorced voles no longer behaved as depressed as those who experienced the full chemical force of the separation. The CRF is part of the fight or flight system. In most situations, the CRF triggers the HPA axis, to give you the energy boost needed to escape the danger, and then when the coast is clear, the opioid-producing VTA will kick in, to calm you back down. But addiction can damage the natural feedback system, leaving the addict in a constant state of CRF and HPA axis activation, when the object of stimulation is unavailable. And just as with drug addiction, it seems love addiction can also leave the “addict” in a chemically panicked and depressive state, when the object of love is removed.

There does seem to be potential in manipulating these CRF receptors, to potentially provide transitional remedies for addicts:

“When alcoholic rats denied booze are given the same CRF-blocking drug Bosch used in the voles, they stop drinking excessively even if given access to alcohol, and they don’t show the same passive-stress coping.” (P202)

One experiment exploring this addiction provided a result that I personally think helps explain the seemingly counterproductive act of “Facebook stalking” one’s ex. When subjects who had been in relationships long enough to fall in love were placed “in fMRI machines and subjected to varying degrees of pain caused by heat” (P204), being shown pictures of their lovers “reduced pain by activating the reward system, including the accumbens, amygdala, and prefrontal cortex, just like drugs of abuse do.” (P205, emphasis mine) So even though checking up on someone you’ve lost may lead to unwanted discoveries about their new life, it may also temporarily trigger a cascade of pain-relieving responses in the brain. And given that, in another fMRI study, “The exact same areas of the brain became activated when subjects relived their heartbreak as when they experienced the highest degree of physical pain–the level that was only a couple of notches below “unbearable.”” (P36, How to Fix a Broken Heart, emphasis mine), it can be assumed that the heartbroken might be pretty severely jonesing for a hit of pain relief, regardless of the consequences.

Interestingly, just as we’ve seen with the maternal nurturing experience and it’s subsequent effects on empathy and bonding, it seems some individuals are more prone than others to both drug and romantic addictions:

“When scientists examined over two hundred people for variation in the mu-opioid receptor gene, they found that those carrying a certain polymorphism were more likely to become romantically entangled, and receive more pleasure from doing so, than those carrying another polymorphism. This version of the gene has also been associated with increased drug highs and a heightened stress response compared to other polymorphisms.” (P209, emphasis mine)

So if you’re someone who falls harder for your beloved than others around you do, and suffers romantic losses more intensely than others seem to think you should — rejoice! There’s an explanation, and when others act as if they don’t understand the depth of your experience… they probably don’t. It’s just not in their chemical make-up to experience what you experience, and you shouldn’t hold yourself to their standards.


There definitely seems to be a genetically programmed component, which biases certain individuals (of our species and others) towards infidelity.

In a study of captive finches, the likelihood to stray sexually–in both males and females–came from the genetics of their fathers. In humans, those who carry one or more versions of the D4 receptor gene, with seven or more repeats (7R+), experience differences in dopamine and receptor distribution, reward circuitry, and the prefrontal cortex (PFC, i.e. self control). These people tend to “seek adventure, novelty, sensation” and “have higher rates of attention-deficit disorder/hyperactivity disorder, drug addiction, and alcoholism. They are prone to risking money, as in gambling or making chancy investments.” (P229)

There also seems to be an “Idiocracy” pattern, similar to what I suggested above with the 334 AVRP1A RS3 allele, that these 7R+ genes show up more frequently in cultures where sexual polygamy is commonly accepted.

“The true answer to the question of whether humans are designed to be sexually monogamous seems to be, It depends. Some are. Others maybe not so much.” (P237, emphasis mine)

Probably coming as a news-flash to no couples married more than a handful of years, there is also a natural tendency, within long-term monogamous relationships, to lose interest in sex with the partner over time, whereas a novel partner sparks new interest. It is, as the authors say, a trick, that nature has played on us, perhaps in an effort to create a situation in which parents will be focused on, and committed to, the rearing of children.

“Many factors affect sexual frequency and motivation, including children, work, bills, and how fit and healthy you are, but there’s little doubt that the falloff is neurochemically based. Married men have significantly lower testosterone than single men, just like the marmosets. They have higher estrogen and lower stress hormones. They are bonded and settled. They give back rubs that are just back rubs. Living with somebody for a long time diminishes our interest in having sex with that person. It’s sad, but true.” (P223)

That being said,

“Also, many people express even more overall satisfaction with marriages that are decades old than they do with marriages younger than a presidential term, regardless of sexual frequency. Social monogamy even seems to be good for our health… Married men live longer, and are healthier for longer, than single men. The same holds for married women.” (P237)

So while sex is an important part of the human experience, it isn’t the full story of what provides relational (and life) satisfaction. And our genetics are never fully to blame for our actions, as we have that lovely part of our brains–the prefrontal cortex–which allows for rational thought and self-discipline. But it seems there is evidence for genetic predispositions towards certain behaviors.


In this final chapter, the authors discuss the potentially beneficial uses for neurochemical supplements/therapy, as well as the unfortunate opportunities for manipulation and control. They also pose questions about how we might improve our brain chemistry.

For one, we know that cesarean section births bypass the vaginocervical canal, resulting in a greatly diminished release of oxytocin in the mother’s brain, which could then potentially affect the mother-infant bond, which could then go on to affect the child’s future bonding opportunities. (Of course, some cesarean section births are medically necessary! But not all are.) Hospitals also often take the babies immediately away from mothers after birth, rather than allowing the skin-to-skin bonding time that can help facilitate their connection. This removal may increase “the respective risks of postpartum depression and negative childhood behavior.” (P248)

It is also noted that this understanding of chemistry and it’s effects on our brains should encourage us to consider our physical environments:

“Pollutants known as endocrine-disrupting chemicals (EDCs)–found in certain plastics, weed killers, even drugs–may be doing more to change our social brains than any other factor, playing the same role in the sexual organization of our brains as estrogen and testosterone used in the experiments conducted by Charles Phoenix and his successors. Among the most famous and widespread are BPA (found in can epoxy linings and heat-sensitive store receipts); phthalates (found, well, everywhere, but especially in softened, pliable plastics); atrazine (the nation’s most popular herbicide, used on the majority of the US corn crop); and estrogens from drugs such as birth control pills. But there are dozens more. Experiment after experiment has proven that, even at low doses, exposure to EDCs in utero or in very early life can permanently alter the gender-typical behavior of lab animals, usually feminizing males.” (P254)

Lastly, they argue that knowing that these chemicals are behind the experience of love doesn’t have to change the stories we tell ourselves about love, or the depth of our experience in love and relationships. While we can prove links and associations with science, there is far more to the human experience than can be found in a test tube.


My biggest takeaway from this book is that we just have NO idea how another person’s brain is firing… what it is telling them to do or be, or how, or why. We don’t understand how the chemistry of their brain works, or how uniquely configured it is, from their own set of circumstances which are (and will always be) different from our own.

More than anything, we need to respect and love each other — for exactly who we all are — knowing that our brain chemistry can never truly explain or understand their brain chemistry, and the best thing we can do as human beings is live and let live, without judgment, without criticism, without trying to shape, change, or bend someone to our framing of “what should be.”


Non Fiction Bingo 2018 Progress

This was definitely my favorite read of #nonficbingo2018 thus far! 😀

nonfiction bingo 2018 the chemistry between us


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