First postulate | behavioural adaptation

On 29 oktober 2018

Contrary to current evolutionary theory the SSIH states that as a consequence of radical differentiation in the female sex organs the male has adapted by changing his sexual behaviour.

Schilthuizen -and others- suppose that changes in female genitalia stipulate selection on male diversity of the penis. If for instance the vagina is lengthened (like often noted in bugs), the male with the longer penis can fertilize the female. The changes in female genitalia invoke Natural? or Sexual? selection on penis length. But the male (bug) does not have to alter his sexual behaviour. His sexual behaviour, penetrating and ejaculating, ‘having sex’ is the same as ever. The male adaptation to changes in female genitalia can be seen as individual genetical fate or fortune, as an inborn individual feature of the male (bug). Biological diversity within the (bug) species favours the males with genes for a longer penis.

The evolutionary changes in human females are of a different kind. These changes are not about vagina lenght or about curves and twists to the ovary that prevent fertilization. The most striking change in human female genitalia is the differentiation in sex organs (brain and spinal cord) and reproductive organs (uterus and ovary). In general every random male with an erected penis can fertilize a random female by ejaculating. Penis length is not a critical factor for reproduction in humans.

The Sexual and Social Intelligence Hypothesis postulates that due to the specific changes in human female genitalia  human evolutionary development can be found in male adaptation to the female sex organs, not to the female reproductive organs. The female sex organs have become critical for evolutionary adaptations in humans. This postulate in the SSIH switches the current evolutionary perspective from reproduction to sex in primates, more specifically in human primates.

It raises questions like: What purpose did sex organs have in our human evolution? How have sex organs, attached to brain and spinal cord, influenced human evolutionary development? Under which selection pressure are human males? On which criteria did human females select their sexual partner? Where in the human evolution did sexual adaptation shift from Natural selection into Sexual selection?

How could the human male have adapted to changes in female sex organs? Is his adaptation a behavioural one, or a genetical one? Includes the male adaptation to changes in the female sex organs neurobiological and neuropsychological elements like perception? Meaning? Intentionality?

This postulate in the SSIH puts sex, sexual behaviour and sexual adaptation in the core of human evolution. It shifts the line of inquiry for unraveling human evolution from reproduction to sex. From Natural selection to Sexual selection. From genes for reproductive organs to genes underlying sexual behavioural features.

Comments are closed.