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I'm not getting into a statistical debate about normality and +/- 2 standard deviations etc. As of the moment, the very large majority of adults are heterosexual, and while reliable figures are hard to obtain (!), I'll bet that a large majority of people do not indulge in anal sex, and that a largeish majority of people actually disapprove of it.
There is a range of normality, but the possibilities in this case are quite narrow. Eventually I expect homosexuality will be made compulsory, but as of the moment, it isn't.