The main argument: 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 adultery), 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.
As we might well expect from a book co-written by a scientist and a journalist, the work delves deep into the technicalities of the science that is discussed, while at the same time mixing in a large measure of anecdotes and humor. The result is a book that is scientifically sound, while at the same time being highly readable and entertaining. On the negative side, while the authors do touch on the evolutionary reasons behind the phenomenon and biological mechanisms that are discussed, a more thorough exploration of this would have added greatly to our understanding of the subject matter. A full summary of the book is be available here: An Executive Summary of Larry Young and Brian Alexander's 'The Chemistry Between Us: Love, Sex, and the Science of Attraction'