I’ve had several requests to share some information about homosexuality, so I’ve decided to make a blog. The following information is taken from my medical school courses as well as an undergraduate anatomy and physiology course. My undergrad professor would often go off-topic and share interesting facts with us that didn’t necessarily appear on the exam. When we studied human development and embryology/endocrinology, she referred to a study where researchers modified the levels of testosterone/estrogen of premature lab rats. They found in cases of increased estrogen, male rats demonstrated female behavior. In cases of increased testosterone, female rats demonstrated male behavior.
However, I didn’t start producing this series until my first year of medical school, in 2009, so I never thought to ask my professor for the name of the study. I have her contact information and I am still meaning to get in touch with her about that. In the meantime, I have found information about a Dr. Marc Breedlove, who has done experiments of the nature I just described and he very well could be the researcher my professor was referring to.
Dr. Marc Breedlove is featured in the “60 Minutes” story called “Gay or Straight”. Breedlove’s research is discussed in the third video, but I highly recommend you watch the whole thing:
Here is a research article by Dr. Breedlove on pubmed: “Sex Differences and Laterality in Astrocyte Number and Complexity in the Adult Rat Medial Amygdala”
I also found a pretty good website with a lot of journal citations. I don’t have time to look up these journals myself, but take a look at the references of this link and you might find some useful information: Website
The subject of homosexuality is not a major focus of my series at this time, but eventually I will discuss homosexuality within the morality miniseries that I am currently working on. I am posting a rough outline of the episode that I originally wrote in 2009, but there has obviously been a lot of research since then and my original script could use some updating. As of now my script contains a lot of good information on sexual development, specifically the role of hormones and enzymes on gender differentiation. The following is my working script as well as a few notes at the end:
Discovering Religion: Homosexuality
I would like to introduce you to a baby girl, whom I will call Jennifer. When Jennifer was born she had what only could be described as typical sexual characteristics of a healthy baby girl, consisting of a vagina, labia, and a slightly enlarged clitoris. Jennifer lived a normal life until the age of 13 when she found that all her girlfriends were developing breasts and experiencing menarche, but she was not. Instead, Jennifer began to develop a more masculine body and a deeper voice. Soon Jennifer’s clitoris became very enlarged and started resembling a penis!
Jennifer’s parents became alarmed and immediately took her to the doctor. Upon closer examination, Jennifer’s physician discovered her vagina ended in a blind pouch without a uterus, ovaries, or fallopian tubes. Instead, Jennifer had undescended testes located in her peritoneal cavity, along with an epididymis, vas deferens, and seminal vesicles. The doctor found Jennifer expressed the XY genotype, which is the genetic definition of the male sex. Jennifer was raised as a girl, she thought and felt like a girl, but when she reached the age of puberty she suddenly found she was, in fact, a boy. Jennifer’s story is not uncommon within the medical community, in fact, it is a condition known as male peudohermaphoditism. How could such abnormal developments occur in what was believed to be a healthy baby girl? To discover the answer to this question, let’s examine the basic physiology of human sexual development.
Humans have 46 chromosomes, of which 44 are autosomes and 2 are sex chromosomes. A male is genetically defined as 46 XY and a female is defined as 46 XX. During the production of gametes (sperm and egg) the genetic information within our chromosomes divides in half, providing the offspring with 23 chromosomes from the mother and 23 from the father. Because a man has two different sex chromosomes, each sperm that is produced is either 23X or 23Y. However, a woman has only one type of sex chromosome, so all her eggs will be 23X. During fertilization the genetic information will be reunited into a complete genome that is either 46 XY male, or 46 XX female. However, it is not only our genetics that define the male and female gender; hormones play a crucial role in determining one’s anatomical sexual characteristics.
In order for a 46 XY male to develop proper anatomical sexual characteristics he must produce two important hormones.
2. Anti-mullerian hormone
Leydig cells in the fetal testes secrete testosterone needed to develop the Wolffian Duct, which becomes the internal male genitalia. Sertoli cells secrete Anti-Mullerian hormone which causes the Mullerian Duct to shrink and disappear, this is a good thing because the Mullerian Duct is the fetal structure from which internal female genitalia is derived. In addition to these 2 hormones, the enzyme 5-alpha reductase is responsible for converting testosterone into dihydrotestosterone, or DHT for short. DHT is required for the development of external male genitalia, such as the penis and scrotum, as well as the growth of typical male body hair found on the face and chest. As a side note, increasing levels of DHT throughout a man’s lifetime can lead to male pattern baldness.
In contrast, a 46XX female requires a complete absence of both testosterone and Anti-Mullerian hormone in order for her sexual characteristics to properly develop. A lack of testosterone prevents the Wolffian duct from developing into the internal male genitalia, and the lack of Anti-Mullerian hormone allows the Mullerian duct to develop into the internal female genitalia.
Therefore, to answer the question posed in the case of Jennifer, who expressed the 46 XY genotype but lacked external male genitalia, we see there was a deficiency in DHT due to a problem with the enzyme 5-alpha reductase. For a brief moment, let’s explore the other problems that might occur during sexual differentiation.
If 46 XY male fails to produce:
1. Testosterone = He has no genitals of either sex.
2. Anti-Mullarian Hormone = He has both a male and female genitals.
3. Both hormones = He has both internal and external female genitals.
If a 46 XX female produces:
1. Testosterone = She has both a male and female genitals.
2. Anti-Mullarian Hormone = She has no genitals of either sex.
3. Both hormones = She has both internal and external male genitals.
As we can see, hormones and enzymes play an absolutely essential role in the development of our sexual characteristics. As the fetus develops inside the womb, if certain hormones are not produced at the required levels, or if the fetus experiences over-exposure to inappropriate hormones, there will be an abnormal course of development or sexual assignment as defined by one’s genetic sex, or genotype.
Now I would like to introduce you to another child, who I will call him Jim. When Jim was born he had what only could be described as typical sexual characteristics of a healthy baby boy, consisting of a penis, scrotum, and testes. Jim lived a normal life until the age of 13, when his male friends began showing signs of attraction toward the girls of their class. However, Jim did not share the same attraction. Instead, he found himself becoming attracted to his male friends, a feeling Jim first noticed from the time he was about eight years old.
Jim’s attraction to the boys of his class was not due to any outside factors that might be influencing him on how to think or feel, nor did Jim make a conscious decision as to which gender he felt sexual attraction. Jim just simply knew he was gay. How could such feelings of attraction for the same sex develop in a boy that appears to be physically and mentally healthy?
Medical science has discovered much about the development of homosexuality though intensive research in the fields of embryology, endocrinology, anatomy, and physiology. There have been studies on the effects of low level hormones on fetal development, which have resulted in unexpected discoveries about origin of homosexual behavior (citation). Indeed, much of what we understand about the origins of homosexuality can be traced back to brain chemistry and the influence of hormones of in the womb.
Women have a cyclic release follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary of their brains, which is responsible for fluctuations in the release of estrogen and the cyclical nature of the menstrual period. The normal menstrual cycle has four phases: menstrual, follicular, ovulatory, and luteal. Following the onset of menstruation, FSH stimulates the dominant follicle to form in one of the ovaries. FSH also stimulates estrogen production from the ovaries. As the follicular phase advances, there is a progressive rise in serum estradiol. High levels of estrogen in the late follicular phase has a positive feedback effect on the LH production, causing a very high LH level, known as the “LH surge”, resulting in rupture of the dominant follicle, leading to ovulation.
However, men have a more constant release of LH and FSH from the pituitary, which corresponds to the constant production of testosterone by the male body. Men do not experience a cyclic production of testosterone and therefore sperm is constantly being produced in the testes. In a study by Dr. Marc Breedlove on the fetal development of lab animals, it was found that premature lab rats exposed to abnormal levels of hormones experienced changes in brain chemistry that could manifest in their adult life. Male lab rats given a shot of estrogen after their birth expressed a more cyclic release of hormones in their brains, similar to the brain chemistry of females. Although there was no congenital deformity as a result of this hormone imbalance, as in the case pseudohermaphroditism, the chemical changes in the brain were very pronounced. Male rats exposed to increased levels of estrogen expressed greater female tendencies in behavior and female rats exposed to increased levels of testosterone expressed greater male tendencies. (refer to the third “60 Minutes” video, above)
The hormonal imbalance leading to homosexual male offspring has come to be known as the “Big Brother Effect” . This phenomenon occurs only in males that are born to mothers who’ve previously given birth to other male children. In a study titled, Biological versus nonbiological older brothers and men’s sexual orientation lead by Anthony Bogaert of Brock University, Ontario, a group of 944 males was examined for their number of blood-related male and female siblings. It is estimated that homosexually naturally occurs in 4% in the general population. However, this rate exponentially increases in male offspring with the more older brother they have.
Discover Magazine states:
“So a man with 1 older brother has around a 5.3 percent probability of being homosexual. For the youngest of 3 brothers, that figure rises to 7 percent. Hypothetically, a man with 9 older biological brothers, according to Bogaert’s estimates, has about a 50 percent chance of being gay. Notably, Bogaert’s estimate breaks down at 12 brothers, when the probability exceeds 100 percent.”
Although the exact cause is still unknown, it appears the mother’s immune system keeps track of how many male children she has carried, and each successive male fetus is subjected to increasing levels of antibodies. These antibodies appear to elevate the level of estrogen the male children are exposed to during gestation, thus leading to the development of Homosexuality as described in the study by Dr. Breedlove.
As a footnote, Dr. Bogaert’s proposed mechanism by which homosexuality occurs through immunological “memory” is similar to a condition known as erythroblastosis fetalis which occurs as the result of Rh incompatibility. An Rh-negative mother produces antibodies when exposed to Rh-positive fetal blood. Upon a second pregnancy with an Rh-positive child the mother’s antibodies will cross the placenta and attack her baby’s red blood cells, producing a type two hypersensitive reaction. However, not all antibodies produced by the mother are dangerous to her child. In fact, a newborn’s immune system is not yet fully developed and if it were not for the IgG immunoglobins that cross the placenta from the mother’s blood, newborns would be in serious risk of infection until their own immune systems can take over.
Although the Big Brother Effect appears to be a curious phenomena, it can be viewed in terms of an evolutionary advantage. It is suggested that homosexual males belonging to groups of hominids in early hunter-gather societies provided key support as well served as group population control. Early hominids lived in small groups, known as “Band Societies”, that were scattered from one another in territorial hunting grounds. Homo erectus and Homo heidelbergensis lived in kin groups of 20-30 individuals. Although Homo heidelbergensis, living from 600,000 BC, is known to have hunted with spears, anthropological evidence suggests the much older species of Homo erectus, dating back 1.8 million years, were scavengers. In fact, the stone axes Homo erectus was famous for producing were not well-equipped for hunting prey.
The development of agriculture and animal domestication were many hundreds of thousands of years away. Indeed, hunting technology in the way stone axes pioneered by Homo erectus remained stagnant for over a million years. Such limited technology suggests many of these early hominid groups heavily relied on scavenging meat from dead animals, essentially eating whatever they could find. Because resources were so limited a group could not grow beyond it’s means.
These groups were small for a reason — they physically could not support any more than 30 members. Imagine a band of hunter-gatherers that consisted of 70-100 individuals could not walk days upon end scavenging for food only to find enough to support a handful of individuals. Therefore, once a group started exceeding its maximum capacity it would fracture, allowing its members to go their own way — covering more ground with fewer mouths to feed.
If anyone was likely to leave the group it would be a heterosexual male with his wives or heterosexual females that were exchanged as mating partners to males belonging to other groups. Therefore, the homosexual males were more likely to remain within the family group, thus reinforcing group stability. Furthermore, homosexual males would not be likely to reproduce and therefore they would not add to the growing number mouths to feed, effectively serving as population control within a group that can only support 20-30 individuals in the first place.
Anthropological studies have also shown that homosexuality is advantageous within a group dynamic. In fact, one study in Samoa found gay men devote more time to their nieces and nephews, suggesting it might be an example of kin selection — promoting your own genes in the bodies of others.
***Next I will discuss the gay gene and finger length. The following website talks about finger length in relation to homosexuality, among many other factors such as cognitive development, musical ability, the development of certain cancers, and so on: Finger Length
I still have a lot more research to do, but I hope you’ve enjoyed what I’ve written so far. I also plan to discuss gay marriage in addition to the persecution of homosexuals, such as in the cases of Alan Turing and Oscar Wilde. If you have any questions or comments feel free to post them here or via PM on youtube.
Thanks a lot!