Because circumcision reduces the diameter of the shaft immediately behind the glans and accentuates the coronal ridge, weve speculated that the practice of circumcision may have unwittingly modified the penis in ways that enable it to function as a more effective semen displacement device. My prediction would be that circumcised males ought to experience a lower incidence of being cuckolded.READERS: So why did human penises evolve to have foreskin at all then? The best way to think about most adaptations is in terms of cost/benefit ratios.Their widely-quoted study does not mention the foreskin.
I also examined an alternative hypothesis suggesting that MGM signals group commitment for collective action, particularly inter-societal warfare.
Although other forms of male scarification fit this model, the distribution of MGM is not predicted by frequency of inter-societal warfare. put forward a theory that the shape of the glans has evolved with the function of pumping a rival's sperm out of the vagina, tending to ensure that a child born after that intercourse is that of the man concerned and not an earlier one.
Genital mutilation, in this view, is just another way to win the sperm war.
In some forms of mutilation, the handicap to sperm competition is obvious.
Men who display this signal of sexual obedience may gain social benefits if married men are selected to offer social trust and investment preferentially to peers who are less threatening to their paternity.
Clitoridectomy and vaginal infibulation serve a parallel signaling function in women, increasing a husband's paternity certainty and garnering his increased investment.I suggest that MGM is likely to reduce insemination efficiency, reducing a man's capacity for extra-pair fertilizations by impairing sperm competition.MGM may therefore represent a hard-to-fake signal of a man's reduced ability to challenge the paternity of older men who are already married.GALLUP: The length of the foreskin is one of the most variable features of the human penis.When most uncircumcised males achieve an erection it pulls the foreskin back over the glans and back down the shaft of the penis, enabling the coronal ridge to do its business and scoop rival males semen away from the womans cervix. The idea could be tested by comparing the incidence of non-paternity between circumcised and intact males.So why do some societies insist on such a risky ritual for their men?