THE GENETICS OF HOMOSEXUALITY
Submitted by SerendipUpdate on Fri, 01/18/2008 - 3:30pm.
Biology 103
Web Reports 1997
From SerendipTHE GENETICS OF HOMOSEXUALITY
Web Reports 1997
From Serendip
THE GENETICS OF HOMOSEXUALITY
Dara Newman
In trying to decide on a topic for this WWW project, it seemed logical to try and
focus on a current subject. Homosexuality and homosexual behavior has existed for
thousands and thousands of years, probably even before the times of homo-sapiens.
However, up until a few years ago, the issue was discussed mostly by people in the social
sciences. Psychologists, such as Freud, studied homosexuals extensively in hopes of
coming up with an explanation for their "abnormal" behavior. All of the explanations that
these people created linked homosexuality to experiences that homosexuals have while
growing up. Generally speaking, people in the world of psychology believed that
homosexuality could be explained by a person's environment. However, in the past four
or five years, the subject of homosexuality has been creeping into the world of biology.
Studies have been done recently that attempt to look at homosexuality in a scientific light in
hopes of coming up with a genetic explanation for sexual preference.
One of the first successful scientific studies that was done on homosexuality was reported on in 1993. The purpose of this study was to look at families in which there was an abnormally high occurrence of homosexuality. By extensively studying the family histories of these families, researchers hoped to find some clues pointing towards the genetic factors that affect homosexuality. That is exactly what happened. By looking at the family trees of gay males (For some reason, this study only focused on male homosexuality, but made the claim that their findings would be similar to the ones that would be found by looking at female homosexuality. As this paper will discuss later, this assumption that male and female homosexuality can easily be compared may be entirely inaccurate.) it seemed that the majority of homosexual occurrences were on the maternal side of the tree. From this information, researchers concluded that if in fact there was a "homosexual gene", it appeared to be passed down from mother to son. This means that heterosexual females are carriers of this gene, and when it is passed down to a male child, there is a chance that the child will be a homosexual. While this study did not come up with any hard core facts about the genetics of homosexuality, it showed that a connection very well could exist. Since this study did determine that the gene influencing homosexuality was carried by the mother, researchers participating in further studies knew that they could limit their search to the X chromosome, and that is exactly what they did (5).
One of the most influential studies on the genetics of homosexuality was done by Dean Hamer and his co-workers at the National Cancer Institute in Washington DC (1993). Hamer's research involved studying thirty-two pairs of brothers who were either "exclusively or mostly" homosexual. None of the sets of brothers were related. Of the thirty-two pairs, Hamer and his colleagues found that two-thirds of them (twenty-two of the sets of brothers) shared the same type of genetic material. This strongly supports the hypothesis that there is an existing gene that influences homosexuality (4). Hamer then looked closely at the DNA of these gay brothers to try and find the region of the X chromosome (since the earlier research suggested that the gene was passed down maternally) that most of the homosexual brothers shared. He discovered that homosexual brothers have a much higher likelihood of inheriting the same genetic sequence on the region of the X chromosome identified by Xq28, than heterosexual brothers of the same gay men. Keep in mind though, that this is just a region of the X chromosome, not a specific gene. Although researchers are hopeful, a single gene has not yet been identified (7). Hamer's study also acknowledges the fact that while it does suggest that there is a gene that influences homosexuality, it has not yet been determined how greatly the gene influences whether or not a person will be homosexual (4). In addition, Hamer attempted to locate a similar gene in female homosexuals, but was unsuccessful (7). The results that Hamer's study did find though, cannot yet be accepted as absolute truth. Another study took place in 1993 by Macke et al. This study examined the same gene locus as the Hamer study, but found that it had no influence on homosexuality (8). As you can see, the results on this topic are still extremely varied and reasonably new, so it is difficult to come to any lasting conclusion.
Other studies have been conducted that look at twin brothers rather than brothers of different ages. Bailey and Pillard (1991) did a study of twins that determined a Ò52% concordance of homosexuality in monozygotic twins, 22% for dizygotic twins, and 11% for adoptive brothers of homosexual men (8). These results, like Hamer's, provide further support for the claim that homosexuality is genetically linked. Studies very similar to the Bailey and Pillard study have been done both with female homosexual siblings and siblings of both sexes. The results for both of these studies were only off from Bailey and PillardÕs by a few percentage points. Putting all of these results together, it seems like genetics are at least 50% accountable for determining a personÕs sexual orientation (8).
Looking at the results of many of the other studies I have discussed, it seems a little strange to me that the student of homosexual siblings who were both male and female came up with similar result as the studies that looked exclusively at male homosexuality. Hamer's study, along with others, have tried to located a gene that influences female homosexuality, but they have been unsuccessful. More importantly, the region of the X chromosome that very possibly could influence male homosexuality does not influence females in the same way. Female heterosexuals merely pass the gene sequence on to their sons. Knowing this, it seems odd to me that there would be such a high percentage of male and female homosexual siblings. Perhaps this suggests that if genetics are responsible for homosexuality, we have a long way to go before we completely understand the gene loci that determine sexuality.
Aside from the scientists who are researching the topic of homosexuality and genetics, there are many other people who have concerns and vested interests in the topic. The information that is being discovered has been used by people in both positive and negative ways. On the one hand, there are members of the gay community who are very excited to find that the life-style they live is not entirely a choice that they made, as homophobic people often like to believe. Some homosexuals feel that if the world realizes that homosexuality is something people are born with, just like the color of your skin or your eyes, then people will begin to be more accepting of the homosexual life-style (5). However, on the other hand, there is also a group a people who believe that if homosexuality is in fact genetically linked, then there should be a way to genetically alter homosexuals in order to make them "normal" (3).
Before I started researching this topic on the world-wide-web, I did not realize what a new and controversial issue the genetics of homosexuality was. From tid-bits of news that I had picked up along the way, I thought that scientists had located, without a doubt, a gene that plays a role in influencing sexual orientation. From the research that I have discussed above, that is obviously not the case. I am eager to follow this subject more in the future and see what biology will discover next.
References
1) Genetics and Homosexuality, from the Gene Letter
2) Homosexuality: Genetics and the Bible, by Tom Terry, Cutting Edge Magazine
3) Statement on NIH Genetic Study on Homosexuality, from the National Gay and Lesbian Task Force
4) New study says genetics influences homosexuality, from St. Louis Post-Dispatch, 1995
5) Homosexuality and Genetics, one person's views
6) A commentary on "Research on Sex Orientation Doesn't Fit the Mold"
7) Genetics Press Cuttings, from The Knitting Circle, South Bank University, London
8) The Hypothetical Genetics of Sexual Orientation, by Keith Bell, a Boston University undergraduate
9) Is there a genetic basis for sexual orientation?, from Ontario Consultants on Religious Tolerance
10) Lesbianism/homosexuality - a human surival trait, a commentary on the Queer Resources Directory
11) Homosexuality: Its in Your Genes, an article posted on QRD
12) Genetics and sexuality, a news report
Comments made prior to 2007
I am iranian gay in a gay family, my dad was gay and my brothers and the sons of my brothers all are gay, o know something about the homosexuality factors that is can be proven, i have some ideas so i ll be glade if i receive a comment from a scientist working in this area, by the was i am also aducated person and can help more in this matter ... Kamyar, 28 December 2007
Science
I have read about that study. These studies really don't make a difference in whether or not people should feel homosexuality is right or wrong. Even if the results had indicated that there was an 80% of genetics playing a role in homosexual traits, if something is right... every scientific fact would be pointing to it's correctness. If something is wrong (looking even from an unreligious standpoint) there's evidence to prove that it's a "crime against nature." No one needs to tell anyone what they REALLY need to feel. But unless your to deeply rutted into what you think if you dig deep down you should know it's wrong.
You "should" know that it's
You "should" know that it's wrong? Wow, I've never witnessed such an oblivious case of trying to force your beliefs on other people.
Where are you coming up with such a strong moral claim, if not from the Bible?
It's tough to call something that is caused genetically immoral. Don't confuse this with a psychopath being predisposed to audacious crimes (murder, rape, theft). Homosexuality is a victimless crime.
A Thought
Okay, one major thing to point out: monozygotic twins have completely identical DNA, correct? If so, and if homosexuality is indeed genetic, shouldn't there be a 100% rate of matching sexual orientation? And since there is only a 58% match according to this article, doesn't that immediately disprove the idea? Just a thought.
ummm.. that's where the part
ummm.. that's where the part about genes being 50% of the reason for homosexuality comes in. Genes are just a factor that influence it as this article states. It then makes 1 0 0 % perfect sense that 58% of monozygotic twins show a match in sexual orientation. Genes are only half of it, but they are definitely a part of it.
"Okay, one major thing to
"Okay, one major thing to point out: monozygotic twins have completely identical DNA, correct?" incorrect
http://www.sciam.com/article.cfm?id=identical-twins-genes-are-not-identical
Homosexuality was the "norm" in the past
I think for me, the question is not whether there is a specific homosexual gene (though i would like to know if there was one) but the fact that in the past, specifically during the times of the greeks, homosexuality was the norm. It wasn't seen the way it was today. In fact sexual orientation was not even a concern for men at that time. In fact, sex with boys was even seen as the purest form of love. That said, my main concern with homosexuality today is how did it evolve from something that was so tangibly prevalent to something so deviant and taboo?
Homosexual gene
" my main concern with homosexuality today is how did it evolve from something that was so tangibly prevalent to something so deviant and taboo?"
In short, today's Bible is responsible for homosexuality being considered deviant behavior.
The Bible's history is availabe at http://www.allaboutthejourney.org/history-of-the-bible.htm where it says ..."In 397 AD, in an effort to protect the scriptures from various heresies and offshoot religious movements, the current 27 books of the New Testament were formally and finally confirmed and "canonized" in the Synod of Carthage."
homosexual gene
As a response to your comment I have the following. Most people today look at the Bible just as a book, they question its integrity and suggest it is fallible. But they do not answer the very compelling question in that the Bible talks about, and gives us a picture of "God". That is were the rub is . First, if God exists, and he is the god of the Bible, then He has all the authority, power and right to say to us "Where were you when I laid the foundations of the earth?..." as found in Job 38:2 The context here is Job complaining over the teatment he believes God has given him. ( please read the background on your own). Secondly,the God of the Bible states in Genesis 1:18-25 wherein He creates man, then woman as a "helpmeet" for him because "it is not good for him to be alone". Thirdly, this idllyic relationship was destroyed when Adam and Eve "sinned" or disobeyed God's one command (Genesis 3:1-7). Were there weeds and hard work before that? NO! Was there pain and suffering before that? NO! Was there various forms of negative and destructive relationships before that? NO!Only after that event has the world seen itself struggle, with wars, famine, social injustice, strained and broken relationships, and human pride and selfishness.
Has homosexuality existed in all societies throughout history? Yes. But, the answer we need to ask ourselves is why? And does this make it right? Of course the answer will depend on your belief/value system and your own pride.
Now the final thought: if God does exist as described in the Bible and we refuse His redemption process as exemplified in the person of Jesus Christ ("beleive in the LORD JESUS CHRIST and thought shall be saved!" because ALL have sinned and come short of the Glory of God!") then we have either accept Him and His son Jesus Christ and the only means by "which we are saved" or we can reject it...stating it is not right and God does not really exist. But if He does exist and the Bible is correct we must REPENT and turn form our ways and worship HIM and HIM only!. Not ourselves, not our own desires, not our own wants because they are and have been perverted since the fall of man I mentioned above. The choice is yours! Does this answer your question?
Straight-ness
How can homosexuality be genetic, when almost everyone is born to straight parents??? This entire argument is pointless.
questions
In fact, I'll keep it non-threatening by asking questions to make my point.
Point 1.
Do left-handed parents only and always have left-handed kids?
Point 2.
If I play the role of Brutus in a high school play which leads to drama courses in college, playing Brutus which then leads to a local theater production where I play Brutus again. Does that mean that I am indeed Brutus? Am I murderer?
The idea that homosexuality
The idea that homosexuality is purely genetic is not without its flaws. Although there is very compelling evidence to show that homosexuality is indeed genetic, there are other factors such as, prenatal hormonal environment, which will also have an influence on sexual preference.
Make an attempt to understand the subject matter before you dismiss it as pointless.
No one is saying it's
No one is saying it's HEREDITARY, as in, passed on between generations, necessarily. We are simply arguing that it is BIOLOGICAL, as in genetically inherent.
A genetic component of homosexuality
Scientists have identified genetics as a cause of homosexuality. This has been accomplished through a type of study on people who identify as homosexual (and non-homosexual as a control group) and a region of the genome to identify whether there is a genetic component to homosexuality. Another type of study, "twin studies," uses pairs of non-twin siblings, dizygotic twins, and monozygotic twins, who share between half and all of their genetic information (non-twin siblings-50%, dizygotic twins-50%, monozygotic-100%). One sibling (or twin) is compared to the other one of the pair in terms of their sexuality, and the co-occurrence is measured across the three types of pairs. A higher co-occurrence of homosexuality among monozygotic twins, who share the same genetic information (compared to dizygotic twins and non-twin siblings who share only half), provides evidence of a genetic link to homosexuality.
Both of these types of studies, as well as others, have shown with statistical significance that there is evidence of a genetic component to homosexuality. I have provided links to webpages that reference studies on the topic of a genetic link to homosexuality. Here are a few that seem to support the idea of a genetic influence on homosexuality:
http://serendip.brynmawr.edu/exchange/node/1925
http://www.dailyprincetonian.com/archives/2006/10/12/news/16168.shtml
http://www.webmd.com/sex-relationships/news/20050128/is-there-gay-gene
Evidence or Proof
Would you please clarify; are you saying genetics is a cause of homosexuality or that there is evidence to suggest genetic is a cause of homosexuality?
Thank you!
Would you choose to be gay?
I sincerely agree with the research. People who are truely homosexual (not just bi or curious or whatnot), but are truely and innately gay DO NOT have a choice. They are born to be gay, just like someone who is heterosexual is born to be that way. Now, if we DO propose that it is due to environmental factors, then why are some brothers or sisters who live in the same household, and grow up with the same influences, opposite in their sexual orientation? As far as the twins argument goes, genes do not play the entire roll when it comes do determining who we are. The human design is so complex that any change in its design can result in dramatic changes. To say that being homosexual is wrong would be like saying someone born with down syndrome is wrong. If you are going to say that homosexuality is a choice, than you must say that heterosexuality is a choice as well, and that we are all born neutral, and deside "I want to be gay or I want to be straight," which is ridiculus. Imagine if someone ridiculed you for being straight, you would think to yourself, "I can't help it," so why should it be any different for someone who is gay?
hi friend
thanx for your comment
iam gay and i didnot chose to be gay ,it is not a choice
iam living in an islamic country and the punishment of homosexuality is DEATH,so am i a fool to chose to be gay????
thanx
This is absolutely true for me
I completely agree. Being truly homosexual is not a choice. I believe genetics play the largest part by far in determining an individual's sexuality. I know this as i have always been attracted to boys and men all the way through my life growing up (i am now 23). When i was very young, even though i couldn't interpret my feelings at the time, i recall having sexual desires for boys my age as early as when i was 4 years old.
To me this is all the evidence i need to believe the environment i grew up in was irrelevant in determining my sexuality considering i started having these feelings so early. The only choice to make is whether or not to embrace or suppress your inherant sexual desires
Homosexual gene and evolution?
The idea of a "homosexual gene" is difficult to reconcile with the theory of evolution. Two points: 1 Carriers of such a gene would be much less likely to seek heterosexual partners and procreate, causing such a gene to be eliminated from the pool; 2 What possible evolutionary advantage would such a gene bring to the carrier?
In fact, a "homosexual gene" is in flat condradiction with the basic idea of genes battling incessantly to perpetuate themselves; it would be self-sabotaging.
I think you guys are all
I think you guys are all foolish for even believing or thinking about believing that there is a gene that causes homosexuality, it is a choice and lifestyle that people choose the bible says that God has not made man bent toward the unatural relationship but towards the natural and homosexuality is not natural.
Homosexuality is not natural?
Dear Anonymous, I am currently writing a paper on homosexuality and it's significance in anthropology, sociology and psychology. I am curious to understand where you come to the conclusion that homosexuality is not natural? Is this something that you were taught or something that you blindly assume? I know that sounds harsh but it is not intended to be, obviously you are reading this with some sort of open mindedness or curiosity. Homosexuality is prevalent throughout nature. Petter Boeckman had an exhibit in Norway displaying homosexuality in the animal kingdom. If you need examples of this there are many articles I am uncovering that might help your understanding that homosexuality is definitively NOT against nature:
http://www.news-medical.net/?id=20718
http://en.wikipedia.org/wiki/List_of_animals_displaying_homosexual_behavior
You can check those out. I have been reading a lot of the comments here and it seems that some people are missing a basic understanding of genetics and the roles of genotypes and phenotypes. I don't claim to be an expert but I do understand enough to say that 58% is a pretty good indicator that homosexuality is affected by genetics. In nature many of the animals that practice homosexuality still produce offspring. There are many reasons why homosexuality could be seen as a positive. A couple hypothesis are that homosexuals in a species help more with rearing the offspring than the heterosexual males, this is seen with a lot of primates and heard animals (as stated in the above articles). Another hypothesis is that in heard animals homosexuality helps with a peaceful means of population control. Just because someone is a carrier of a gene that has a potential of building a person this way or that way doesn't make it 100% so. In science nothing is 100% true, any study that will show you otherwise is not scientific. There is always a potential of fallibility.
The big question raised in my mind is that if more people were educated to know that homosexuality is not against nature and is about as natural as breathing, what would the next argument be? I would think that if the people that are saying this are implying that God created nature and God's will is infallible then it would be a contradiction to say that god is against homosexuality at all.
Spoken like a know it all
Spoken like a know it all straight guy. How can anyone who isn't gay really truely understand?
And what about the human rights element?
iam depressed
everyone there listen:
i am a homosexual who is living in an islamic country.i didnot chose to be gay,
if you just think for one second you will realize how redicolous it is to chose to be gay in an islamic country,because the punishment of homosexuality in islam is just DEATH.
from the very first day of my puberty i realized that i have homosexual desires
i was truly terrified,because i didnot want to be like this.
year after year i understood that its something inside me and i dont have any control over it.you know can imagine how hard it is that you are a gay and you cant change it.
now iam 25 years old man,who is a medical student and have many achievements in my life(imnot saying it as a compliment),but has a very sad aspect of life,which is iam still a virgin ,because iam gay.and if i find a partner ,and i be arrested ,i will be killed.
i have no desire for sex with women.and let me tell you another fact:
my twin brother is homosexual too.and we were both afraid to tell this truth to each other.
you cruel people who think that homosexuality is a choice,is better to go and discuss with gay people.you will find out that we all were born that way.
again its soooooooooooooooooo rediculous to think that i chose to be gay in an islamic country
Mixed evidence on genetics and homosexuality
There is a mixed record on whether or not homosexuality is genetic or not. The consensus seems to be that genetics does play a role in influencing homosexuality, but it seems that genes might pre-CONDITION people to homosexuality, but not pre-DETERMINE homosexuality, and that homosexuality is no more determined by genes, than is interest in playing guitar or interest in reading.
-Ted
Re: Gene of homosexuality passed from mother to Child
I would like to have concrete evidence that actually does prove that the mother actually does pass down the "gay gene". I may have had several cousins that are gay, but that is neither here nor there, I would just like the facts,one more thing I think that most people that are gay really did not choose to be gay, and alot of different religions they would be an outcast.
If homosexuality is normal
If homosexuality is normal then why are homosexual men and women unable to have children on their own?
Why is the anotomy of the homosexual men the same as a straight man.
If something is normal then everything else is normal.
Why is it that in africa and Asia homosexuality is not common as it is here.
Fraternal Birth Order and the Genetics of Homosexuality
I wrote a blog post "Fraternal Birth Order Threatens Research into the Genetics of Homosexuality": http://blog.tanyakhovanova.com/?p=40. Here I present one paragraph from this post:
Let us create a theoretical model where homosexuals would be born randomly with a fixed probability if they are the first sons of a woman, and increasing probability for subsequent sons. In this model there would be two interesting consequences:
* Mothers of homosexual men would be more fertile on average than mothers of men in general. Remember, this random consequence can be misinterpreted as a genetic correlation between homosexuality and fertility.
* If a homosexual person has a brother, then the probability that this brother is homosexual might be very different from the probability that a random person is homosexual. Again, this might create the suggestion that there is a genetic component, when it is not there.
Ask Any Homosexual
A great experiment would be to ask any amount of homosexuals if they feel as if they chose their orientation or if they feel as if a genetic predisposition played a role in their sexuality.
I'd bet dollars to donuts that 100% of participants say that homosexuality is not something that can be chosen.
I am a young (25), successful and attractive woman and I haven't had/wanted/or even thought about for that matter, any sort of sexual contact with a man in eight years. Being gay is not an easy lifestyle and no one would choose this. Reading posts about the bible and God's will are actually entertaining to me at this point. Hopefully, someday everyone will get it.
CRAZY TALK
I don't know if it is ignorance, religious practices, or selfishness that causes some to believe that homosexuality is a choice. Especially after knowing and reading previous accounts of the hardships associated with being gay. I have a little sister, who I love dearly, and am sad that she has to endure such criticism from people who don't even know her. She has been clearly gay from puberty on. She is a smart, creative beautiful woman who is also a doctor. Those of you are so ignorant to suggest that anyone would live a homosexual lifestyle have already made up your stubborn minds and clearly have issues yourselves. And let me tell you all something, you can't change the fact that homosexuality exists, so you may as well go with the flow. These days, thinking that homosexuality is a choice makes you appear uneducated. I am talking about people who are truly homosexual, not just looking for some attention or satisfying their curiosity.
Everyone has choices and my worldview
I would like to pre-face this with: I am a Bible-believing person and a chemist. The comments that I am about to make are sure to draw ire and ridicule from both side of this discussion, so ... here goes.
I am, I believe different from many "true" followers of Christ in that I do think genetics plays a part in homosexuality. That comes as a great shock to many I am around, so I rarely discuss it, but I do when I see fit. However, I also, believe that God's word is infallible, so how can I reconcile these differences. Genes are said to be the root cause of many things in our society. Some families have strong predisposition to drink alcohol or engage in risky behaviors. Some families' genes predispostion them for heart disease, etc. My family is one that has an extremely high rate of diabetes, type 1 and 2, and as a precaution I have chosen to be more careful in my diet and exercise. This is something I find very difficult. But, the choices are mine to make. As far as homosexuality goes, I think myself and some others may feel like the choice isn't in what or who you are, but how you chose to live your life. For a Bible believing person, who feels that they are gay or is gay, however you want to say it, that person either chooses to live within God's law or not. The alcoholic has the same choice, the adulter too. It isn't who we are that is the problem sometimes, because God say that we are all sinful and fall short of his glory. To NOT participate in behaviors contrary to His word take stregth that we do not have on our own. It take a relationship with Him through Jesus.
Thanks for letting me post. I appreciate you reading even though I know I am probably making many of you angry. Please know though that I keep homosexuals in my thought often. I feel they do need the true love of Christ, not some man's made up version of Him. Thanks again!
Having a hard time understanding...
I've been reading on this for a while now. Some say they have definitive proof through research that homosexuality is purely genetic. There are others who claim the opposite with similar experiments. There are those who take the middle ground and say there is a genetic element but environment/experiences/relationships play a large factor also.
I am sick to death of hearing all of these people who have "decided" that research shows one or the other when there is CLEARLY contradictory evidence on BOTH sides in MANY countries through MULTIPLE tests and surveys and experiments.
Would you open your minds please and stop acting like children? There is too much contradictory evidence to know for sure! STOP picking the side that works best for you just because you want an excuse to feel the way you do. STOP IT. You are not helping your cause by looking like a fool.
In the long run, it will be nice to know. BUT WE DON'T KNOW YET. I for one have seen evidence on both sides of the argument and then seen it flipped completely around. If you are all gonna pick sides on scientific evidence that has yet to securely hold it's conclusion, we may as well bring religion back into the conversation and argue over whether God exists or not. Hell, lets argue over the gender and sexual orientation of the higher power. The arguments will be the same. "GOD IS. I've seen evidence." and "GOD IS NOT. I have seen evidence."
For what it's worth, I believe most of us are born with a predisposition to swing one way or the other on that orientation chart. I believe that predisposition solidifies more firmly as we age but I believe that trauma can offset the balance (as evidenced by research on abused children). BUT THAT DOESN'T ENCOMPASS EVERYONE. There is still so much we don't know.
It doesn't matter
whether a person is homosexual because of genetics, environment and learned behaviors, or choice is irrelevent. if homosexuality is what makes an individual happy then the rest of us should accept that with no questions asked. we should each live our lives for what we feel is right and let others do the same.
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