Changing genitalia

On 28 oktober 2018

Changes in genitalia are studied in current evolutionary theory. Professor Schilthuizen, Naturalis Leiden, for instance dedicates his life to the diversity of sexual organs (of bugs). His line of inquiry can be interpreted as (genetic) adaptations of the penis as a consequence of changing female genitalia.  Genitalia seem to be the most fast changing organs in evolution. The broad frame of reference in current evolutionary theory is that the penis has to adapt genetically because otherwise insemination and reproduction is obstructed. Hence the ‘race’ for genetic variation and alteration of genitalia.

But what if genetical and phenotypical changes in female genitalia do not require genetic adaptations of the penis? What if changing female genitalia require behavioural changes of the male sexual partner?

In line with biosemiotic theory the Sexual and Social Intelligence Hypothesis takes the position that (emotional) perception and meaning are strong motivation for behavioural adaptions. The SSIH presumes that in the human species adjustments to ever changing female genitalia have been of behavioural kind. In humans the anatomical and physiological changes in genitalia are paramount.

Actually the changes in genitalia -with reference to other primates- can be interpreted as completely reversed. The clitoris changed from an internal organ (in the vagina) to an external organ between the labia. The oestrus changed from visible to invisible for the male. The crus clitoris and the corpus cavernosum are internally positioned and no longer linked to the bloodstream, but part of the brain and spinal cord. In the SSIH these very obvious and prominent features are called ‘a total transformation of female genitalia’resulting in a completely different anatomical and physiological structure and feature’.

The SSIH states that humans are the (genetical) exception to the primate rule. Human female genitalia are aberrant when compared to the sexual organs of other related primates. The medical and biological facts imply that human evolution bares a genetic component (a penis with glans and corpus cavernosum) but also a neurobiological (liquor system) component and a behavioural (making love instead of having sex) component. The SSIH states that human evolution can be reconstructed along changes and behavioural adaptations as a consequence of ever changing genitalia.

In any case ‘the human male-female struggle for reproduction’ transformed in consecutive adaptations of sexual organs is not as unambiguous as the generally accepted evolutionary paradigm supposes.

Within the biosemiotic paradigm adapting = behaviour and creating new habits. In the SSIH this biosemiotic paradigm is inverted tot questions as:

Which changes in female sexual anatomy have caused adaptations in sexual behaviour?

How did humans change their sexual behaviour from having sex (penetrating the female) to making love?

Under which selection pressure did the human sex organs became inseparable from the liquor system?

How did the human genitalia evolve into separated structures as reproductive organs (ovary and uterus and testikels and germ cells) on the one hand, and sexual organs (clitoris and glans and corpora cavernosa) on the other hand?

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