GENETIC COMPONENETS OF HUMAN BEHAVIORS AND SEXUALITY Part II
WHY ARE SOME PEOPLE ATTRACTED TO THE SAME SEX?
The genetic components of human sexuality and sexual orientation are scientifically not very clearly understood. The biology and evolutionary imperative of sex is to procreate and assure the survival of the species. For this reason, homosexuality does not make biological sense. Therefore homosexuality is considered by many to be a biological anomaly. But why then is homosexuality so widespread, across all species?Almost 10% of world population is homosexual and 400 different animal species in the animal kingdom, demonstrate homosexual behaviors.
The scientific world has confusing array of data from the animal as well as humans studies about homosexuality. No single and specific genetic abnormality or a “ gay gene” could found anywhereand in XX or XY chromosomes. But many nonspecific changes have been found in different genes.
In one study, the brain region called diencephalon has been found to different in size in heterosexuals than in homosexuals. Could this lead to homosexuality is not clear.
Animal studies have found a gene called “FucM” that directs sexual orientation. When this gene is deleted in female mouse, it only become attracted to only female mice.
Another study has shown a different gene in the brain cells that directs odor detection. Disruption of this gene makes a female mouse act like a male mouse.
Based on available scientific data, it is very unlikely that our sexual orientation and sexual pleasure is induced and depends on a single gene but many factors. It is very possible that besides genetic factors, epigenetic factors, hormonal factors, environmental factors, especially during the prenatal life in mother’s womb, play a combined influence in our sexual orientation?
Epigenetics influence gene expression, are chemical additions to DNA molecules without causing any structural changes in the DNA. May be this is why it is very difficult to find a single “gay gene”.
Several studies have shown differences in DNA methylation marks in homosexual individuals as well as animals that exhibit homosexual behaviors.
In another study, a neuroscientist has shown that when female rats are injected with a drug that inhibits DNA methylation, they sexually behave like male rats.
There is a critical period during the intrauterine fetal development when male or female hormones shape the brain development and wirings into male or female forms. At this critical stage, there has to be proper communication between brain development and the development of external sexual organs. This critical period is also influenced by many other factors such as mother’s health, nutritional status, mental status, substance abuse and external and internal environmental factors. If any discrepancy occurs at this period, aberrant sexual behaviors could develop. The brain is in charge of our sexual identity.
For example there is a congenital genetic abnormality called Androgen Insensitivity Syndrome (AIS)where there is a lack of proper receptor for androgen hormone testosterone (male hormone) in the brain cells. Even though these people have XY (male) chromosomes and produce testosterone, the brain does not get the proper message and these people develop external female sex organs. In reality, they are genetically male.
Similarly, sometimes females could have Congenital Adrenal Hyperplasia (CAH) that produces very high level of male hormone testosterone in fetal life. This high level of testosterone affects their brain and increases the odds of this individual becoming a lesbian.
To summarize, both hetero and homosexual behaviors are biological and programmed into our brainbefore birth, regardless of external sexual organs. As I See It, sexual identity and choice is not under our control. Everyone should show an understanding and empathy towards fellow human beings.
