FOR YEARS researchers and doctors have sought an elusive gene, or some biological determinant for being LGBT.
As recently as last year, one of the long standing hypothesis regarding determining sexuality was still centered on the functional connectivity between the thalamus and hypothalamus in the brain. The argument being that the connection between these two important nodes for sexual behavior was believed to be stronger in “heteronormative” people.
Not so fast says the study published in Science magazine, “Twin studies and other analyses of inheritance of sexual orientation in humans has indicated that same-sex sexual behavior has a genetic component. Previous searches for the specific genes involved have been underpowered and thus unable to detect genetic signals. Ganna et al. perform a genome-wide association study on 493,001 participants from the United States, the United Kingdom, and Sweden to study genes associated with sexual orientation (see the Perspective by Mills). They find multiple loci implicated in same-sex sexual behavior indicating that, like other behavioral traits, non-heterosexual behavior is polygenic.”
The study concluded: “Same-sex sexual behavior is influenced by not one or a few genes but many. Overlap with genetic influences on other traits provides insights into the underlying biology of same-sex sexual behavior, and analysis of different aspects of sexual preference underscore its complexity and call into question the validity of bipolar continuum measures such as the Kinsey scale. Nevertheless, many uncertainties remain to be explored, including how sociocultural influences on sexual preference might interact with genetic influences. To help communicate our study to the broader public, we organized workshops in which representatives of the public, activists, and researchers discussed the rationale, results, and implications of our study.”
Or as CNN concluded in its coverage, “the study showed that sexual orientation “is not a single dimension and same-sex attraction is not inversely related to opposite-sex attraction, arguing for a more nuanced social understanding of sexual orientation that also includes bisexuality and asexuality.”
Associate Professor Greg Neely at the University of Sydney told Science Media Centre that “a major weakness of this study is that it is primarily based on data from 40- to 70-year-old people across the UK.” And same-sex attraction might be underrepresented “based on societal pressure from a previous era,” he said..
In the end, genes cannot be used to predict who will be gay or straight. sexual orientation “is influenced by genes but not determined by genes,” said Brendan Zietsch, senior author of the study and a genetic researcher at the University of Queensland. “Non-genetic influences are also important, but we know little about these and our study does not shed light on them.”
The New York Times reported: “There might be thousands of genes influencing same-sex sexual behavior, each playing a small role, scientists believe. The new study found that all genetic effects likely account for about 32 percent of whether someone will have same-sex sex. Using a big-data technique called genome-wide association, the researchers estimated that common genetic variants — single-letter differences in DNA sequences — account for between 8 percent and 25 percent of same-sex sexual behavior. The rest of the 32 percent might involve genetic effects they could not measure, they said.”