Anal sex is probably just a spandrel

A spandrel is described like this:

“Evolutionary biology uses the term spandrel for features of an organism arising as byproducts, rather than adaptations, that have no clear benefit for the organism’s fitness and survival.”

It seems likely that anal sex is a spandrel in that sense. It is possible because an accident of anatomy allows a structure which normally passes faeces to also receive an erect penis.

I am familiar with arguments that homosexuality has some genetic value, but I have never seen an argument that homosexual activity itself has some adaptive value (presumably it is actually maladaptive). It is most likely that anal sex (performed on men or women) is simply a spandrel in a biological sense. In the case of anal sex performed on men, another accident of anatomy – the position of the prostate gland – enables sexual stimulation and erection on the part of the receiving man (reportedly). Presumably that is another “spandrel”.

5 responses to this post.

  1. there r many women n men who enjoy anal better than pussy.
    what comes by mutual adjustment is supremely heavenly.
    I love doing n getting done > orals.
    thanks for descriptive post….


  2. Posted by Julian O'Dea on November 26, 2015 at 3:34 am

    “Based on an extensive review of the research, Voeller (1991) estimated that at least 10% of sexually active American women engage in receptive anal intercourse with some regularity. Halperin (1999) pointed out that even if this estimate is inflated twofold, anal intercourse occurs among more women annually than among MSM [men who have sex with men]—four million versus one million, respectively.”

    So, it is possible that most anal sex acts are heterosexual; although the homosexual men that indulge in it may perform the act more frequently, so it is hard to be sure.


  3. Posted by Julian O'Dea on October 1, 2017 at 10:14 am

    “About 37 percent of women and 5 percent of men have had receptive anal intercourse in their adult lives”

    [Incidentally, I wonder if the fact that nearly a third of women have had receptive anal sex (and other data suggest that 10% of sexually active women have it regularly) might help to explain why modern women are more accepting of gays and gay sex.]


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