A supporter of same-sex marriage holds American and gay pride flags in San FranciscoNational Journal

Even as the number of Americans who support same-sex marriage reaches an all-time high, the ratio of Americans who believe that sexual orientation is innate to those who believe it is environmentally determined has remained relatively unchanged since the year 2000.

Gallup Poll conducted earlier this month showed that 37 percent of Americans believe that being gay or lesbian is "due to factors such as upbringing and environment"; 42 percent think that people are born with their sexual orientation.

There is no consensus on the issue in today's scientific community. "Many think that nature and nurture both play complex roles," the American Psychological Association writes. "Most people experience little or no sense of choice about their sexual orientation."

There is evidence of physical differences between homosexual and heterosexual brains: A research project at the Karolinska Institute in Stockholm found that "the brains of gay men and women in some aspects are similar to the brains of those of the opposite sex." But those differences probably did not arise from environmental or genetic circumstances alone. Another study from the same institute examined differences between identical and fraternal twins in Sweden. It found that both genetic effects and the non-shared environment — that is, environmental differences in each twin's upbringing — had moderate effects on determining sexual orientation.

But perhaps the question of nature versus nurture is not the question we — or Gallup — should be asking. "It's not worthy of debate, necessarily," said Ellen Kahn, director of the Human Rights Campaign's Children, Youth & Families Program. "What your beliefs are is less relevant because we're familiar, more and more, with gay and lesbian people. Why doesn't matter as much." This view is borne out by the data: Even as beliefs on the origins of sexual orientation remain the same, acceptance is steeply increasing every year.

The more pernicious question, Kahn said, has to do with malleability of sexual orientation. "We have to continue to point to volumes of scientific evidence that you cannot change your sexual orientation; the only thing you can do is choose to acknowledge it and share it." A comprehensive 2009 APA review of journal literature on sexual-orientation change efforts found that attempts to alter a person's orientation are "unlikely to be successful and involve some risk of harm."

Perhaps, then, we should stop considering the nature-versus-nurture question altogether. Jamie Tabberer wrote in The Independent earlier this year, "For me, a resolution will come when people stop asking about it — because acceptance shouldn't depend on the answer."

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