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Partially. This being so, homosexual individuals cannot be “cured” of homosexuality or re-trained to be heterosexuals. Overwhelmingly, most biologists agree that sexual orientation in humans is inherited but have not settled on exactly how it is determined.
The gender of an individual is determined at the moment of fertilization. During the ordinary course of events, when a sperm cell containing X chromosomes penetrates and fertilizes an egg, the developed fetus will be female. If the sperm cell contains Y chromosomes, the fetus will be male. Since there is almost always a 50:50 mixture of X and Y chromosome sperm cells present at the moment of fertilization, there is a 50:50 chance for each gender in every pregnancy of an individual even if the gender of all previous offspring were the same.
On very rare occasions, certain inherited gene variations cause the development of genitalia with both male and female features. Biologists estimate these variations occur naturally in about 1% of the world’s human population, and are NOT the result of disease, evil spirits, cellular defects, or mistakes made by irresponsible parents. Whether an individual is born biologically male or female does not preclude he or she from having an opposite sexual orientation.
The sexual orientation any individual is born with can vary on a continuum between strong heterosexual tendencies and strong homosexual ones, with strong and weak bisexual ones in between. Studies of identical and fraternal twins prove that the genes one inherits are not solely responsible for these differences. Many identical twins, who have identical genes, do not have the same sexual orientation.
Master genes program the development of all human traits by timely activating the appropriate genes responsible for these traits. Biologists know other factors can sometimes alter the program through a process of epigenetics.
Some researchers now think that exposure to certain hormones shortly before birth helps determine sexuality. These hormones act on genes already programmed for sexual orientation, influencing the genetic combination active at birth. Different combinations produce different orientations.
Read Settled Science to learn how identical and fraternal twins occur and why identical quadruplets are so rare.
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