But geneticists have had only a handful of underpowered studies to address a complex, fraught, and often stigmatized area of human behavior. Now, the largest-ever study of the genetics of sexual orientation has revealed four genetic variants strongly associated with what the researchers call nonheterosexual behavior. Some geneticists are hailing the findings as a cautious but significant step in understanding the role of genes in sexuality. Others question the wisdom of asking the question in the first place. Andrea Ganna, a research fellow with the Broad Institute in Cambridge, Massachusetts, and Harvard Medical School in Boston, and colleagues examined data from hundreds of thousands of people who provided both DNA and behavioral information to two large genetic surveys, the UK Biobank study and the private genetics firm 23andMe.
Neuroscientist Simon LeVay made headlines with his pioneering work comparing the brain structures of gay and straight men. His article in Science led the way for numerous studies of sexual orientation as it relates to the biology of humans and nonhuman animals. In Gay, Straight, and the Reason Why: The Science of Sexual Orientation , LeVay provides a detailed overview of where that research stands now, drawing from work conducted by neuroscientists, endocrinologists, geneticists, and cognitive psychologists. LeVay, who is gay himself, addresses the broad range of human sexuality on two principal levels: traits found to differ according to gender, and the developmental mechanisms that potentially underlie those traits. Chapters on gender variation in childhood and adulthood focus mainly on behavior and personality.
Recently, scientists announced that they found some genes that might be associated with sexual orientation and a biological explanation for the reason gay men tend to have older brothers. But the field of sexual orientation research is far broader and more complicated than two studies—and Lisa Diamond , a psychologist and sexual orientation researcher at the University of Utah, knows that better than most. She spoke with Newsweek about what she and her colleagues in the field know—and what they don't—about how a person's sexual orientation might form.
In the Aug. In a large study of more than , men and women in the United States, United Kingdom and Sweden, researchers discovered four genetic variants that occur more often in people who indicated on questionnaires that they had had same-sex sexual partners. The other two influence sex partner choice for both men and women. Collectively, the DNA differences explained only 8 to 12 percent of the heritability of having same-sex partners.