Homosexuality: Inborn or Learned Behavior? (1)

Scientists have long debated whether homosexuals are born or bred. Ongoing research by neuroscientists at the Karolinska Institutet, one of Europe’s largest medical universities in Stockholm, Sweden, presents more evidence for the former being the case.

Homosexuality has gone from being once classed as a mental illness to being regarded as either a sin or an acceptable variation of human behavior. Whatever your view, research in this area points to a biological origin for homosexual behavior.

In the Swedish study, the scientists exposed heterosexual man and women as well as homosexual men to naturally-occurring chemicals containing male and female sex hormones. Both groups were asked to sniff male sweat which contains the male sex hormone testosterone. In addition, female urine was used as it contains an estrogen-like compound. The participants then underwent brain scans to determine brain activity as a result of sniffing these substances.

Interestingly when all subjects smelled substances such as lavender or other natural or chemical-based entities, their brains, irrespective of sexual orientation, showed a reaction in the part of the brain that handled smell.

However, when male sweat and female urine entered the picture, all that changed. A different physiological response was noted. After sniffing male and female sex hormones, the hypothalamus, a region of the brain responsible for many basic functions, including sexual response, differed significantly between gay and straight men.

When the testosterone-based male sweat was offered to all group members, the hypothalamus was activated in the brains of heterosexual women and homosexual men, indicating a pronounced sexual response. There was no response in heterosexual men. In short, straight men were not turned on by male sweat, but straight women and gay men were.

Conversely, the estrogen-based compound in female urine activated the hypothalamus of heterosexual man but not homosexual men. Thus the gay participants were not affected sexually by the smell of female sex hormone.

We will look at the implications for these findings in coming articles.


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