- The Washington Times - Saturday, October 28, 2006

Mark Twain said once: “Rumors of my death have been greatly exaggerated.” If environmental factors in sexual orientation could talk, they might say the same thing.

For sure, social or family factors in influencing sexual attractions have been written off by numerous scholars and media. However, a new Danish study may prompt a fresh evaluation of the role of social factors in sexual orientation.

The study, in this month’s issue of Archives of Sexual Behavior, authored by Danish epidemiologist Morten Frisch and statistician Anders Hviid, reports the analysis of data from more than 2 million men and women. It is the first study to examine an entire group of homosexuals for environmental factors in their decisions to pair up homosexually. The research suggests a link between environmental factors such as geographic birthplace and family relationships and the probability of marrying a same-sex or opposite-sex partner.

The massive study also finds the number of brothers and sisters increases the probability of marrying heterosexually. This finding questions a recent, widely touted Canadian study of birth order that found the number of older brothers increased the probably of homosexuality in men.

Danish researchers found no evidence that having older brothers increased the likelihood of men marrying homosexually. On the contrary, they found that older siblings increased the probability of heterosexual marriage. The choice of homosexual versus heterosexual marriage serves as an obvious, though not perfect, assessment of sexual preferences.

Regarding the fraternal birth order effect, the authors said, “We found no indication that older brothers were particularly common in these homosexual men.”

The researchers found for each additional year one’s parents stay married, the probability of heterosexual marriage in the children increased 1.6 percent among sons and 1 percent among daughters. In contrast, the rate of homosexual unions decreased by 1.8 percent among sons and 1.4 percent among daughters for every year of intact parental marriage. Summing these effects over years of childhood and adolescence contributes to a noteworthy effect.

On homosexual marriages, the researchers found birthplace relates to the sexual orientation of marriage partner. Being born in urban settings increased the probability of homosexual marriage and decreased the probability of heterosexual marriage. Drs. Frisch and Hviid noted, “Our study may be the first to show that birthplace or some correlate thereof influences marital choices in adulthood.”

The authors also confirmed previous research suggesting children who experience parental divorce are less likely to marry heterosexually than children reared in intact families.

Drs. Frisch and Hviid reported, “For men, unknown paternal identity, parental divorce, short duration of cohabitation with both parents, and long duration of father-absent cohabitation with mother were all associated with increased rates of homosexual marriage.” For women, homosexual marriage rates were elevated among women whose parents were married briefly, and those who experienced long mother absences due either to abandonment or death during the teen years.

Taken together, the study’s findings suggest intact parents bearing multiple children and living in rural areas have an increased probability of heterosexual pairings in their children.

This study was not designed to examine all possible contributions to sexual orientation nor does it account for individual situations. We know, for instance, that homosexuals and straights come from all kinds of families and locations.

However, the Danish study raises the possibility family and social factors help shape adult sexual orientation, in combination with whatever biological factors may also operate. Also, by questioning the fraternal birth-order effect in male homosexuality, the study calls for additional studies to assess the theory based on high-quality data from other settings and by independent research teams.

In an interview, Dr. Frisch stressed, “Prenatal factors alone can not account for the variation in human sexual orientations — otherwise, all our urban/rural and family-dynamic findings should have shown no association.”

The study adds support to the theory that environmental and biological factors together influence sexual attractions and behaviors. Dr. Frisch concluded, “Whatever ingredients determine a person’s sexual preferences and marital choices, our population-based study shows that environmental factors are important.”

Thus, environmental influences on sexuality, rumored to be irrelevant, are actually alive and quite well.


Associate professor of psychology and fellow for psychology and public policy at the Center for Vision and Values at Grove City College, Pa. He hosts a blog at www.wthrockmorton.blogspot.com and can be contacted at [email protected]

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