I have finally been inspired by Marley’s post to ask the question that has been on my mind for quite a while.
First, I need to clarify my own belief about homosexual orientation. I do not believe that a man or a woman simply chooses to be homosexual. For many years, I have not known why this happens - and still don’t - but have tended towards the idea that the way a child is brought up has a lot to do with it.
The findings of studies into identical twins who were separated at birth and raised independently reveal that if one is gay, then the other twin is found to be gay only about half of the time. Despite this, many people argue that the root cause of homosexual orientation is genetic. In order to derive this conclusion from the data, a variable needs to be posited, and that variable is the dormant homosexual gene. In other words, in that proportion of the population who have a homosexual gene - usually estimated as 10%, though why only 10% of the population should have that “mutation” has not been satisfactorily explained, as far as I know - the gene is only expressed in around half of the individuals. The reason is usually given as an unknown factor in the environment. In the old days, I guess people would have said the way your parents brought you up.
All the uncertainty and ignorance about this would be of only academic interest to many people were it not for the (contested) fact that Christianity considers the commission of homosexuality acts to be a sin. Thus, it is an issue of importance to many people beyond scientists. Simply put, for many Christians, if people are born with a homosexual orientation the whole picture changes. Either, one must say that it’s not a sin (between consenting adults in a loving relationship, at any rate) or that the orientation is not “wrong” but acting on it is - which seems harsh and a bit of a fudge.
I have noted (perhaps too sensitively) that some posters prefer the word “biological” to describe homosexual orientation to “genetic”. Is there any difference between the two and if so what significance is there in that? But let this be more than an argument about words.
Those wishing to pit me or approach this in a non-scientific manner, please open a Pit thread.
Those wishing to argue theology, please open another thread in GD or refer to one of the many existing threads.
This is some old data which may have been disproven since then. But, I seem to recall studies which show the thalamus (at least I think it was the thalamus) in homosexual men to be significantly smaller in comparison to heterosexual men.
I’m just trying to answer the OP.
The possible difference between a genetic predisposition versus a bilogical predisposition is that a person can have a biological “abnormality” (see footnote)
that is NOT genetic in its cause. A person can have a heart defect that is simply random in the sense that their family has never shown evidence of it being a genetic disorder.
While it is true that some heart defects ARE genetic, that doesn’t make it absolute.
There may be some genetic reason but not necessarily. I think along the lines of nature PLUS nurture in most cases when attempting to explain a persons life.
I used the word abnormality in the strictest biological sense. I do NOT in anyway consider a person’s sexual preference, their inclinations or practices to be either normal OR abnormal. Who in the fuck am I to say what is normal?
I’m a freak myself. I just don’t happen to be gay.
I hope that came out right.
Given that homosexuals are a rather small portion of the population - I think 10% was Kinsey’s estimate and it’s probably way too high - you’re wrong to say “only” there. That’s a pretty strong correlation.
Yes. “Genetic” means it’s caused by one’s genes. “Biological” is broader and includes factors that are not genetic. An older post of mine with some links and details. I’m neither a biologist nor a geneticist, so the information in there is not my own.
Right. I mention in every “is homosexuality genetic?” topic around here that annaplurabelle cites the ‘prenatal wash’ as the factor that seems to have the most influence on sexual orientation.
Yesterday’s newspaper here had a small article about some Italian scientist having reached the conclusion that genetic disposition to male homosexuality are passed down solely through the mother, and the reason that it has not been selected out of the genepool is that those particular traits that make males homosexual (and thus presumable are detrimental in males) are beneficial in females as women with them tended to have more babies.
Just as genetically identical twins do not have identical birthmarks or fingerprints (these developing in utero), so the configuration of the impossibly complex neural network in their skulls is not identical. Similarly, one twin could be monopolising certain chemicals and hormones to the detriment of the other.
Evolutionarily, I heard of some research a while ago which tentatively suggested that certain indicators correlating with homosexuality in boys, when they appeared in girls, were correlated with a lower age for puberty. This would make the “cause of homosexuality” evolutionarily advantageous overall. Anyone hear anything more on this?
What is “prenatal wash”? That term, in quotes, produces exactly one result on google* and it’s a ringtone website.
[sub]*Does that make it a googlewhack or do those have to be without quotes?[/sub]
S/MI’ll agree with your statement that IdTwins don’t have identical prints with reservation. While it is true that id twins fingerprints aren’t EXACTLY identical, it could also be argued that idTwins themselves aren’t identical in their appearance. Their prints are identical in that they have the same BASIC patterns and that it usually takes identification beyond what is considered normal in distinguishing the two. The differences are accounted for by the nurture aspect of their lives. Which you made reference to.
BUT if you had the ability to control these variables then they would most likely be indistingushable from one another. So to simply say, “they don’t have identical fingerprints” is simplistic IMHO. There have been cases where twins prints were so identical that the differences weren’t significant enough to measure.
Really? I didn’t know that, t-keela - I always assumed that fingerprints were formed when the skin kind of “shrank” into that pattern in what was an essentially random manner. Many thanks. (I assume birthmarks are as random as I believed them to be?)
heh man I hate to burst your bubble dude but id twins are pretty much identical. They have the same DNA. In about 50% of the cases where a twin actually has a birthmark. The other twin will have the same birthmark. BUT It will be on the OPPOSITE side of his/her body.
Now mind you, this isn’t 100% for all monozygotic twins. but then not all twins even have a birthmark, not everyone does. But their hand and feet prints will be the same and their fingerprints while they might not be technically identical they are uausally VERY similar and any birthmarks are also found on their twin.
Actually Id Twins are “opposites”. Thus the print differences and other normally identifying markings etc. whatever are also “identical”.
S/M Check this thread out and add your 2 cents worth. I think you might at least find the concept interesting. I wouldn’t normally post this kinda request but you seem like somebody that can look at things with an open mind without going off on a rant.
Having done a bit of research in biometrics, I’m a little dubious about this - while it’s true that fingerprints, iris patterns etc. are not entirely epigenetic, there’s also considerably more variation between twins than you’d think, to the point where identical twins present no real problem to biometric systems. You don’t even need a pair of identical twins to evaluate this - examine the fingerprints of your own hands, or compare the iris patterns of each eye. For example, my middle finger on either hand has a pattern which even at a very basic level is considerably different to the other. The other corresponding pairs are more similar, but by no means identical even to my untrained eye. While in a general sense they will look the same, at the detail level they exhibit just about as much variability as is seen in the general population.
Here’s a paper (warning, postscript - google text cache here) studying the capability of a typical fingerprint system on monozygotic twins, which shows only a slightly degraded capability - about a 1% drop in successful ID rates for a given error rate.
Dead Badger While I agree with you, just as I did w/ S/M identical twins fingerprints are not identical. What I said was that they are VERY similar and usually need to be subjected to stricter testing than with the general population. BUT if you could control the variables that are found in their normal lives then their prints would be so similar as to be a non-issue.
I could provide a list of cires to back up my point here but I didn’t realize that Uncle Cecil had already addressed this issue. enjoy
I think the jest of the story is that it is possible for identicle twins to actually have identical prints and that they are undoubtedly similar despite whatever factors may be involved.
What’s hardly conclusive? Search for some old threads, like the one I linked to, and you’ll see more people citing studies and going into depth. I can’t do that. But in the meantime I don’t know what you’re being skeptical of.
man I hate to burst your bubble dude but id twins are pretty much identical. They have the same DNA. In about 50% of the cases where a twin actually has a birthmark. The other twin will have the same birthmark.