Great Question!
According to The effect of male circumcision on sexuality “Masturbatory difficulty increased after circumcision in 63%.” There you have your answer, uncircumcised males would spend all their time sanding wood (i.e., self-pleasure), resulting in lower birth rates, or it put the survival of the tribe at risk. Of course, I’m kidding; however, it does beg the obvious question concerning the physiological effects.
I have read, although difficult to measure, the assertion that over 20,000 specialized erotogenic nerve endings are packed into the foreskin. Surveys on the same seem quite subjective, and debated. Although the following links do provide a good amount of supportive references for the coloration of nerve density and erogenous zones. http://www.noharmm.org/advantage.htm, and http://www.cirp.org/library/anatomy/winkelmann/
Concerning the argument in favor of circumcision most site immunological benefits. There again, there is evidence to support just the opposite that the “protective effect of the natural anatomy.” provides mechanisms against infection. Therefore, this contradicts the hygiene argument, and presupposition that the people of that time were too ignorant to keep their junk clean and free of sand. http://www.cirp.org/library/disease/HIV/
As a differential mark, I agree with the comments, I’m not sure where this would practically be demonstrated.
What I struggle with is the theocratic justifications. I believe one can make a strong argument given the current understanding of medicine, and science, concluding that keeping the foreskin intact has merit in uncompromised anatomy’s, albeit the procedure is still contested. Personally, I feel shortchanged (not shorted mind you) knowing several inches of highly sensitive skin was removed without my consent. But why was god so concerned with nudity, sex, and the penis in the first place? Why not pick another body part or feature to change for the purposes of sealing the deal, and marking his people? I’m thinking back hair would have been a much better selection if we had to remove anything. Or for that matter, why not add instead of subtracting, who would turn down adding a few more inches to ones penis 😊