Technology » Science

New Study Reconfirms Older Brothers a Factor for Gay Men

by Kilian Melloy
Thursday Mar 19, 2020
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Since the idea that birth order and a mother's production of multiple male children was first investigated in 1996, study after study has yielded data that reconfirm the hypothesis that men with older brothers are more likely to be gay. Moreover, the more older brothers they have, the greater the chances are that they will not be heterosexual.

That theory was reaffirmed yet again in a new study carried out by scientists from Germany and Canada, reports the New York Post.

In a paper titled "A method yielding comparable estimates of the fraternal birth order and female fecundity effects in male homosexuality," by Ray Blanchard, Jurian Krupp, Doug P. VanderLaan, Paul L. Vasey, and Kenneth J. Zucker, the researchers reviewed ten previous studies, which involved 5,390 men, both gay and straight.

The study restated the "maternal immune hypothesis," summarizing it as positing a "progressive immunization of some mothers to male-specific antigens and the consequent effects of anti-male antibodies on sexual differentiation in the brain in male fetuses."

In other words, carrying male fetuses triggers a mother's immune response in ways that increase the probability that a male fetus' brain development will proceed in such a way that the child will experience sexual and romantic attraction toward other males.

Each successive pregnancy with a male child increases the odds by a third that the next male child will be gay, the study suggested.

The study found no similar pattern for lesbians, however.

This is only the latest in a long series of studies that present the same results time and again. Those results scientifically demolish arguments that gay people "choose" not to be heterosexual, and disprove claims that quack practice known as "conversion therapy" - which suggests that gay people can be "cured" and "turned straight" through talk therapy and prayer - has any basis in reality.

As reported at EDGE in 2013, a Canadian study from that year verified what earlier studies had indicated. Reported EDGE at that time:

A study of 1,000 men, including some who were adopted or brought up with stepsiblings, revealed that having many brothers raised a man's odds of being gay. This correlation only occurred among blood brothers, however. Stepbrothers did not have an effect, but biological brothers who were brought up separately did. No similar link has been found between having many older sisters and becoming a lesbian.

Each older brother raised by one-third the odds that a man will be gay. If a firstborn son has a 3 percent chance of being gay, the figure for the second son will be 4 percent. By the fourth son, the odds of the so-called "fraternal birth order effect" will have doubled.

That same study found that external factors seemed to play no part in the statistical outcome; boys with older brothers who were raised in different families than their older siblings were gay at the same rate as those who were raised by the same parents in the same households. In other words, nature - and not nurture - seemed to be the driving force.

Similarly, an EDGE article from 2009 reported on a Canadian study that:

...involved one thousand male Canadians, the article reported, and appeared in the journal Proceedings of the National Academy of Sciences. The study showed that even if gay men were reared separately from their siblings, the number of older brothers they had still seemingly had an effect on how likely they were to be gay.

That result supports the theory that homosexuality has a biological basis, rather than a sociological or psychological basis. In other words, the study suggests that being gay is neither a mental illness nor a choice.

Despite the consistency of the results from so many studies, anti-LGBTQ social conservatives continue to insist that sexual minorities "choose" their sexualities. Some have gone so far as to suggest that societies honoring such "choices" offend sky gods who respond by unleashing natural disasters on the world in the form of wildfires or pandemics; indeed, those same unfounded claims have resurfaced as the current COVID-19 (coronavirus) pandemic has spread around the world, triggering governmental efforts to limit viral spread by imposing "social distancing" policies and crashing the stock market.

Reputable scientists, meantime, have pressed for those very same proactive policies, showing with statistics and graphs how social distancing and other techniques can "blunt the curve" of the epidemic's growth, hopefully avoiding a situation in which hospitals are hit with an overwhelming number of coronavirus cases all at once.

Meantime, scientists in Japan have shown some promise with a treatment that might address COVID-19 and lessen the pandemic's impact.

Kilian Melloy serves as EDGE Media Network's Assistant Arts Editor. He also reviews theater for WBUR. His professional memberships include the National Lesbian & Gay Journalists Association, the Boston Online Film Critics Association, The Gay and Lesbian Entertainment Critics Association, and the Boston Theater Critics Association's Elliot Norton Awards Committee.


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