----- At least it's better than the other side of the discussion: "there is no biological basis". A twin study is very powerful, it's not something you dismiss as easily as you make it sound. But it's expected, this reply. I do the same. If you show me a reconstruction of old monkey skulls I will likely say it was a bad study.

 ** These kind of studies are only relevant on scientific circles where few empirical data is obtained and analyzed. Give that study to any geneticist and you'll get laughed at. Heck, i'm going to give it to my thesis professor (pHD in molecular genetics, organic chemistry and genetic engineering) and see his reaction. I'll be back with is reply tomorrow. 

Unless you show me some solid empirical study on how that kind of behaviour really is presented on the genomic level (and such a study can be done on Mice), it still frivolous, in the scientific level.  

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You're making a fundamental error here. I know from my own field (medicine) that hundreds of diseases and personality disorders were proven to be hereditally determined long before any elaborate DNA sequencing of humans was available. A huge share of these studies were, and still are, based on twin studies. They've so far been essential for science on nature vs nurture.

You still don't seem to understand or accept that strong causality links between genetics and traits such as behaviour can be proved without any detailed analysis of DNA whatsoever.

There's no reason for a geneticist to laugh at this particular study.

I'll laugh at the study then.

You can't have a sociological study based upon twins.

Why? Because they have the same freaking up bringing. Same mother and father, brothers and sisters. They learn the same values, go to the same school, they learn the same things. How do you know the fact they lived in the same house and went to the same school did not cause it? What is your proof that genetics were the cause?

And you can't compare hereditary diseases to sociological behaviors. Why? Because those diseases are proven to be rooted in DNA, while sociological behaviors haven't been proven to be in DNA once.

Wrong. A twin study provides an extremely strong genetic aspect. It's the fundamental purpose of them.

Let me lay it out for those who might not get the point of twin studies:

* Identical twins = identical genome.

* You split the twins in separate groups. Each pair of twins were separated at birth or at a very young age, and thus have been influenced by different environmental factors. 

* Any statistically significant similarities found between the groups - whatever parameter you decide to study; traits such as body length, disease, success in education, religious activity, criminal behaviour, happiness, homosexuality - can be attributed to inheritance.

* Any differences between the groups can be attributed to environmental influence.

So for this study, you got 4,000 twins that were separated at birth.

I don't buy that. For a minute.

Well of course that makes sense. But since the twins were NOT separated, you can't determine which was the root, genes or environment! That makes the whole study invalid.

General question..

If homophobia was an instinct, why would it even exist? There was no threat that the homosexuals were going to stop the breeding heterosexuals from passing on their genetic material, and that IS what the following generations are based off of, right?

This is only theory, but I believe homophobia is an offset of "false memory" (Studies showed that people who were convinced enough that a fale event actually happened, start to believe, and often "remember" portions of that false event), and a need to belong within a group. I would deem homophobia very little chance, if any, of being inherited.

I looked it up. The process that I was trying to think of is called Confabulation. 

"In psychology, confabulation is the spontaneous narrative report of events that never happened. It consists of the creation of false memories, perceptions, or beliefs about the self or the environment usually as a result of neurological or psychological dysfunction."

Wow, this is like something out of Nineteen Eighty-Four.