I find it quite disgusting that seemingly intelligent people can't accept that some people are homosexual and some aren't, it isn't an illness or a condition.

Who are these seemingly intelligent people?

Or, as I suggested, women who display 'masculine' characteristics – or interests, for that matter.

I'm old fashioned

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Looking at it from a purely scientific point of view IF a "gay" gene does exist (yet to be proven) chances are that it would be recessive as it would not be conducive to the success of the species. One could argue that the estimated 10% occurrence of homosexuality in the population is somewhat higher than would be expected if this was the case and hence nurture could be an influence, however it might be that the "gay" gene is associated with another effect that is beneficial in some way e.g. in the way that the gene for sickle cell anaemia is associated with improved resistance to malaria.

As for high pitched voice, masculine looks etc., these are sexual characteristics that are controlled by hormones and response to hormones is controlled by your genes. Sometimes lack of the appropriate receptors to these hormones due to a genetic quirk can lead to a male foetus developing into a baby that appears to have the physical characteristics of the opposite sex and lead to them being raised as girls. It is not inconceivable that if a "gay" gene does exist that it may be linked to a gene that controls response or production of sex hormones.

All the above is hypothetical.

It should be noted that homosexuality occurs in a wide number of species at varying levels of occurence and what part nurture or genetics takes place in these instances is unknown.