View Full Version : Identical Twins and Homosexuality


Orleander
12-16-09, 10:49 AM
Since you are born gay, if you are gay does that mean your identical twin would be gay as well?

Nasor
12-16-09, 11:52 AM
Since you are born gay, if you are gay does that mean your identical twin would be gay as well?
If one twin is gay, the other has about a 50% chance of being gay - so it's far from certain, but the odds are a lot higher than average. This seems to indicate that there's a substantial genetic component, but that genes aren't a single deciding factor.

GeoffP
12-16-09, 12:09 PM
I was surprised how rare the penetrance was in the other identical sib. So on guess homosexuality is 50-70% environmental or residual variance. Strange. Then again, they're coding what could be expressed quantitatively as a binary, so maybe odd ratios aren't so unexpected.

Orleander
12-16-09, 06:08 PM
could it be because of something happening during the pregnancy and it not being genetic?

Idle Mind
12-16-09, 10:28 PM
Just because it happens during pregnancy, doesn't mean it's not genetic. Genes as well as environment dictate how an organism develops. There are genes that are only active during embryonic phases, for example.

Hercules Rockefeller
12-16-09, 11:33 PM
Since you are born gay, if you are gay does that mean your identical twin would be gay as well?

There is likely to be a genetic component to homosexuality. Scientific studies of homosexuality running in families agree with this. However, this does not mean that the trait is determined solely by genes. Like nearly every trait, there is almost certainly a mixture of nature and nurture (genes and environment) at play.

So, when it comes to monozygotic twins, homosexuality is like other complex personality traits – they may or may not be shared with the chances being almost impossible to determine beforehand.



If one twin is gay, the other has about a 50% chance of being gay....

Really? Who says this?

Repo Man
12-16-09, 11:43 PM
Really? Who says this?


Later that same year, Boston University psychiatrist Richard Pillard and Northwestern University psychologist J. Michael Bailey announced the results of their study of male twins. They found that, in identical twins, if one twin was gay, the other had about a 50 percent chance of also being gay. For fraternal twins, the rate was about 20 percent. Because identical twins share their entire genetic makeup while fraternal twins share about half, genes were believed to explain the difference. Most reputable studies find the rate of homosexuality in the general population to be 2 to 4 percent, rather than the popular "1 in 10" estimate.
http://www.bri.ucla.edu/bri_weekly/news_050812.asp

Fraternal birth order's influence on homosexuality wasn't known at that time as far as I'm aware, so that may have altered the interpretation of these findings.

S.A.M.
12-16-09, 11:49 PM
could it be because of something happening during the pregnancy and it not being genetic?

Hormonal changes in womb environment have been postulated as a factor. Perhaps a comparison between identical and fraternal twins may be useful.

One cannot underestimate the psychological effects of twins on each other. People expect identical twins to be similar.

Hercules Rockefeller
12-17-09, 12:05 AM
http://www.bri.ucla.edu/bri_weekly/news_050812.asp

Fraternal birth order's influence on homosexuality wasn't known at that time as far as I'm aware, so that may have altered the interpretation of these findings.


Interesting. Thanks for that! Here’s the study in question:

http://www.ncbi.nlm.nih.gov/pubmed/1845227 (http://www.ncbi.nlm.nih.gov/pubmed/1845227)

Asguard
12-17-09, 12:59 AM
orleander, there is a 50% chance that if you are schizophrenic then your identical twin will be too which means there is a genetic componant there as well (i cant rember the full list of percentages but it was an interesting list) however it shows its not CERTAIN that you will be and that there are enviromental factors as well (hense its not 100%)

Ahem
12-17-09, 09:13 AM
Since you are born gay, if you are gay does that mean your identical twin would be gay as well?
No. My nephews are identical twins. Barry is gay. Brian is not.

edenocp
12-17-09, 02:57 PM
In the study, none of the identical twins raised separately were both gay. Not 50%

Grim_Reaper
12-17-09, 08:16 PM
So 1 in 3 are born gay so that means if you have triplets one of them are gay?

Idle Mind
12-17-09, 10:06 PM
So 1 in 3 are born gay so that means if you have triplets one of them are gay?
No, that's not a reasonable assumption.

Nisus
12-17-09, 10:20 PM
Since you are born gay, if you are gay does that mean your identical twin would be gay as well?

yea if they are siamese twins.

baftan
12-17-09, 10:48 PM
yea if they are siamese twins.

This is clever...

Orleander
12-18-09, 03:37 PM
well, if its genetic, is it possible for one identical twin to have Down Syndrome and the other not?

Idle Mind
12-18-09, 07:40 PM
No, I don't think so. The genetic abnormality that causes Downs Syndrome is a trisomy of chromosome 21 -- three copies of the chromosome in each cell, instead of two. So in order for this to happen, it would have had to obtain the extra copy from one of the parent gametes. Fusion of the gametes to form the zygote happens prior to the zygote spliting into two during the first cell division, which is when identical twin formation occurs.

I think.

Bishadi
12-23-09, 10:37 PM
Since you are born gay, if you are gay does that mean your identical twin would be gay as well?

a hemaphrodite is born gay.

(more cleft palet births then them folks)


all others learn it

Dywyddyr
12-24-09, 06:19 AM
a hemaphrodite is born gay.
Really?
So what sex, exactly, is a "hemaphrodite"?


(more cleft palet births then them folks)
So what?

Grim_Reaper
12-24-09, 07:42 AM
No, that's not a reasonable assumption.

And why would it not be reasonible?

Grim_Reaper
12-24-09, 07:44 AM
a hemaphrodite is born gay.

(more cleft palet births then them folks)


all others learn it

A Hermaphrodite it born Both Male and Female SO why on why would you say they were gay if they have both sets of Organs.

edenocp
12-24-09, 08:36 AM
no human is born gay

Dywyddyr
12-24-09, 09:00 AM
no human is born gay
Evidence?

Grim_Reaper
12-24-09, 09:14 AM
no human is born gay

I dont know about that. If they are not born Gay then what is it that makes them desire the same sex. Perhaps there Underware is too tight or they like to stick with what they know? What studies do you have that support your claim of no himan is born gay. With that statement doe that imply that other speices are born gay?

Orleander
12-24-09, 09:42 AM
no human is born gay

no human or no animal? Are you saying wild animals have also made the decision to be gay?