#21. A Summary of ‘The Chemistry Between Us: Love, Sex, and the Science of Attraction’ by Larry Young and Brian Alexander

'The Chemistry Between Us: Love, Sex, and the Science of Attraction' by Larry Young and Brian Alexander

‘The Chemistry Between Us: Love, Sex and the Science of Attraction’ by Larry Young, and Brian Alexander (Current Hardcover; September 13, 2012)

Table of Contents:

i. Introduction/Synopsis


Section 1: Gender Identity

1. Pseudohermaphroditism: The Curious Case of Machihembras in Las Salinas, Dominican Republic

2. Bruce, Brenda and David Reimer: The John/Joan Case

Section 2: Sex and Sexual Orientation

3. Sexual Desire and Human Estrus

4. Sexual Orientation: The Mystery of Homosexuality and Transgendered Individuals

5. The Mystery of Fetishes


6. The Maternal Instinct

7. Women in Love

8. Men in Love


9. Love as an Addiction

10. Infidelity: Cheating and Adultery

11. Conclusion

 i. Introduction/Synopsis

Love and sex play a central role in the human drama. But when we talk about the emotions and decisions that we make in connection with them, we tend to remain strictly at the macro level, referring to people, and relationships, and our freely made choices. However, in their new book The Chemistry Between Us: Love, Sex and the Science of Attraction social neuroscientist Larry Young and journalist Brian Alexander contend that our biology and chemistry play a much bigger role in love and sex than most of us ever acknowledge (since Larry Young is the scientist behind the book [and responsible for the ideas therein], I will refer to him as the main author throughout). Young explores everything from gender identity (and sexual orientation), to romantic relationships (and parenting), to monogamy (and infidelity), taking us inside our bodies to investigate the genes and hormones that influence our approach to love, sex and relationships. While the focus here is on us humans, the evidence comes not only from our own species but from a host of other animals that exhibit similar biology and behavior.

Young begins by way of smashing the notions that gender identity is constructed by culture, and that sexual orientation is a matter of choice. The foundations of these phenomena, the author argues, are laid down in utero by the specific hormones that wash over the fetus as it develops. Interestingly, we learn that the genes and hormones that are responsible for genital development are active at a different time than those that are responsible for gender-specific behavior, thus explaining how the two can become separated from each other.

While the foundations of gender and sexual orientation may be laid down in utero, it is also the case that they are capable of being influenced to a degree by learning and culture, thus explaining cross-cultural differences in the manifestation of gender, as well as such phenomenon as fetishes.

When it comes to a woman’s gender identity, Young explores the hormones that explain maternal behavior, and why women differ in regard to just how maternal they are–as well as what effect this has on their children. Interestingly, we also learn that a woman’s love for a man appears to have been built on the same brain mechanisms responsible for her maternal behavior. This fact helps explain a number of baffling phenomena (including, incredibly, the size of women’s breasts, and men’s penises!).

While men are capable of experiencing romantic love just as strongly as women (if not more so), we learn that a man’s love is built on an entirely different biological mechanism. Specifically, a man’s love is built on the ancient mechanism responsible for territoriality. This helps explain such phenomenon as male possessiveness and jealousy; but it also helps explain why men are more paternal than the males of most other species.

While love may have a different biological basis in men and women, it takes on a strikingly similar form in both. In short, it is an addiction–not at all unlike a drug addiction. Indeed, like a drug addiction, a romantic relationship starts out as a high, then morphs into an experience whereby the lover cannot stand to be away from their love, and experiences deep stress when this occurs. Even the brain chemistry of using drugs, and the way the brain changes as a drug user becomes addicted, is the same as occurs in the progression of a romantic relationship.

While men and women in love may be addicted to one another, this does not mean they are incapable of cheating on one another. And, indeed, the prevalence of adultery in all times and places (despite the near ubiquity of social mores opposed to the practice) indicate that it is a deep part of our biology. Young explores this biology, and also why some people are more disposed to the practice than others.

What follows is a full executive summary of The Chemistry Between Us: Loves, Sex, and the Science of Attraction by Larry Young and Brian Alexander.


Section 1: Gender Identity

Beginning with the rise of behaviorism in the 1920’s, and lasting for much of the next 50 years, the social sciences were dominated by the view that human nature is essentially a tabula rasa. That is, a baby is born as a blank slate, without any preformed instincts or inclinations, and is just waiting to be imprinted by the stamp of learning and culture. This included, of course, the baby’s gender identity. As Young explains, it was believed that “gender behavior was imposed by parents, society, and culture. It was a position of nurture over nature” (loc. 168). By the 1970’s, though, cracks were beginning to form in this theory.

1. Pseudohermaphroditism: The Curious Case of Machihembras in Las Salinas, Dominican Republic

One of the earliest cracks in the theory that gender identity is constructed by culture took shape in the 1960’s and 1970’s when scientists began studying the curious case of people in Las Salinas, Dominican Republic, whom the locals referred to as machihembras (literally ‘first woman, then man’ [loc. 184]). As the name suggests, machihembras were born looking, to all eyes, like girls, with “female-appearing genitals, complete with labia and clitorises” (loc. 177). Once they reached puberty, however, machihembras became masculinised. Specifically, “their labia turned into scrotums filled with testicles. Their voices deepened and they grew muscles—a picture of one machihembra, around nineteen years old, shows the carved physique of a strutting middleweight boxer” (loc. 184).

As it turns out, machihembras are pseudohermaphrodites. What this means is that they are actually boys all along (biologically, anyway, in that they are XY chromosomally), even though they may appear to be girls for the first part of their life (loc. 240). Normally what happens is that XY fetuses produce the hormones testosterone, and dihydrotestosterone (DHT), which activate cells to form “the prostate, penis and scrotum” (loc. 249). In machihembras, though, there is a glitch in the gene that is responsible for triggering the release of these hormones during development. As a result, the organs in question fail to fully form (loc. 249). (The male organs are actually there all along, but remain underdeveloped to the point where the individual appears to be female [237].)

Now, when XY’s reach puberty another rush of male hormones is triggered (loc. 252). In the machihembras, this extra kick of hormones was enough to trigger the development of the sexual organs that had failed to take place in utero: “Voila!—girls appeared to turn into boys” (loc. 252).

Given that the machihembras appeared to be females all the way up to puberty, they were naturally raised as girls (loc. 177). As Young explains, “they wore bows in their hair and dresses—if they had any. They did the domestic chores girls in Las Salinas were expected to do while the boys roughhoused together and had fun exploring away from home” (loc. 180).

If gender identity really is a matter of nurture, then, we would expect that by the time the machihembras had reached puberty that they would have formed a strong sense of identity as a female. Indeed, a sense of female identity strong enough that it would not be easily wiped away by a shift in physiology (even if this shift in biology was a major one). This being the case, we would expect that the machihembras would continue to hang on to at least some aspects of their female identity well beyond the time when they had become masculine in physiology; or, at the very least, that they would experience a very real conflict in their gender identity.

Now, it cannot be said that the metamorphosis that machihembras experienced was in any sense an easy transition. This is particularly the case given the social stigma that they endured: “imagine the taunts an adolescent schoolboy might suffer if his fellows knew he’d once been a girl” (loc. 188). As difficult as this transition was, though, issues of conflict in gender identity were not a part it. Instead, the shift in physiology in machihembras signaled an immediate and seamless shift in their behavior and gender identity. Indeed, as Young explains, once the transition occurred, the machihembras “walked with a macho bearing, joined the village boys in male play, and eventually started chasing girls. Most married. Some fathered children… More importantly, they accepted themselves as male” (loc. 191). This makes it look like gender identity in the machihembras was being governed by their hormones (and specifically the hormone rush that they experienced when they hit puberty), rather than their upbringing.

Given that this is the case, the case of the machihembras is tantalizing evidence in favor of the view that gender identity is more a matter of biology than upbringing and environment. Nevertheless, one could argue that the machihembras’ new physiology triggered others to treat them as males, which behavior triggered the machihembras themselves to both act and identify as males (loc. 284). However, other evidence indicates that this is almost certainly not what was going on here. Some of the most telling evidence comes from an episode known as the John/Joan case that unfolded simultaneously alongside the investigation into the machihembras (loc. 224).

2. Bruce, Brenda and David Reimer: The John/Joan Case

The case begins with the birth of twin boys in Canada in 1965, Bruce and Brian Reimer. Both boys were circumcised following birth; however, something went wrong during Bruce’s procedure, and Bruce’s doctor accidentally mutilated Bruce’s penis to the point where it could not be repaired (loc. 215).

*For prospective buyers: To get a good indication of how this (and other) articles look before purchasing, I’ve made several of my past articles available for free. Each of my articles follows the same form and is similar in length (15-20 pages). The free articles are available here: Free Articles

4 thoughts on “#21. A Summary of ‘The Chemistry Between Us: Love, Sex, and the Science of Attraction’ by Larry Young and Brian Alexander

  1. I am impressed by this article,although I had already read similar information about love etc., but the present article is more recent, provides much more information , in a short time, is logical, full of rationality, and is a very quick way of learning latest reasonable scientific logical view of life and world from great scholars, What else do we want? I have read many of these articles from this website. I wish to thank the authors for providing us this material .

  2. can you give a little bit of insight into the citations and where I can find your referenced material in the actual book?

    • Hi Amy. The citations in my articles (loc. ) refer to location. This is how ebooks are paginated. If you have the print copy of the book I don’t know that there’s a convenient way to translate.


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