Dean Hamer wrote in the Preface to this 1994 book, "The aim of this book is to show that human sexuality can, and indeed must, be scientifically studied... the study must be based on carefully constructed observations and experiments, not on the hearsay, innuendo, and myths that characterize so much of the discourse on human sexuality and behavior. Second, it must produce specific and testable predictions, not just vague generalities that defy empirical examination. And lastly, it must ultimately be based on physical laws rather than on appeals to `nature's way' or `God's will' and the like. These are the principles that guided my search for the `gay gene' and led to the discovery that is the main topic of this book: the finding of a linkage between male homosexuality and DNA markers on the X chromosome... My purpose in writing this book is... to describe what we found using the tools of modern genetics, how biological findings can broaden rather than narrow our understanding of the diversity of human sexual expression, and what remains to be learned." (Pg. 14-15) [Later, he admits that Richard Lewontin's book Not in Our Genes "helped inspire me to launch the project in the first place." Pg. 130]
He states, "With the science approved and the funding assured, the only remaining hurdle was political... I knew the right wing would question our work because they think being gay is a `lifestyle' that people choose, not something genetic. The left wouldn't be happy, either, because they would worry about homosexuality being classified as a genetic defect that could be `cured,' instead of as a normal human variation." (Pg. 43)
He notes that "After only a few weeks of interviewing gay men, it was clear that few families were going to show any of the simple patterns of Mendelian inheritance... This was not all that surprising. If sexual orientation were strictly determined by a single gene, it probably would have been discovered already. Besides, it is well established that most behavioral characteristics do not follow Mendel's rules... [and] they involve both genetic and nongenetic components such as the environment---nature AND nurture." (Pg. 81)
He describes his research: "I tried the experiment again, this time using the DNA from the gay brothers in the four other families I'd collected by this time. Once again, all four pairs seemed to be concordant for the marker. Fearing that the marker was too common to tell me anything, I decided to try one more test, using the marker on the DNA from the four mothers from whom I'd been able to collect blood. Somewhat to my surprise, I found that three of them had different forms of the marker on their two X chromosomes, which indicated the marker was indeed working. The very next pair of gay brothers I tested came up discordant. They clearly had inherited different versions of the marker from their mother and therefore couldn't share the same `gay gene.'" (Pg. 121)
He states, "We had DNA available from only 15 of the mothers (and from one sister) of our gay brother pairs. How could we know whether the `motherless' matching brothers really had inherited the same Wq28 region[?]... In principle, it would have been better to have obtained DNA from every mother, but this was not possible because often the mother had died or did not know her sons were gay." (Pg. 140-141)
He more controversially says, "Most sissies will grow up to be homosexuals, and most gay men were sissies as children. Despite the provocative and politically incorrect nature of that statement, it fits the evidence. In fact, it may be the most consistent, well-documented and significant finding in the entire field of sexual-orientation research and perhaps in all of human psychology." (Pg. 166)
He wonders, "The gene has only one mission---to endure---and the only way it can continue to exist is if its host multiplies and passes on the genetic information to the next generation... That's why it would seem almost impossible for there to be a `gay gene.' After all, how could a gene that discourages reproduction survive more than a few generations? ... Even if half the male population had the gay version to start out with, the gene soon would die out because the men would have no offspring... the frequency of the gene would decline with every generation... It would appear something must be wrong with this simplistic theory of evolution or with our finding of a genetic link to homosexuality. But, in fact, there are several ways a `gay gene' could survive, even flourish in the population. What if, for example, a `gay gene' actually increased rather than decreased the number of offspring in some of the people who carried it? Or what if the gene existed in an unusually unstable part of the genome and was continually changing during the rough-and-tumble passage of generations? At this point, the only explanations of the evolution of `gay genes' are purely theoretical, but the various theories might help to explain how a gene for sexual orientation works in the real world." (Pg. 180-182)
This book will be of great interest to anyone researching homosexuality, and related issues.