Lifespans were not all that long back then. Maybe someone had the bright idea to notice that women got infected a lot after having had sexual relations and that ...upon observation....men had dirty organs. Surely the nobler castes realized that in order to preserve their lineage, something would have to be done with that diseased organ. So they took off the extra flesh.
Lemme see what the internet has to say....
About one-third of males worldwide are circumcised. The procedure is most prevalent in the Muslim world and Israel (where it is near-universal), the United States and parts of Southeast Asia and Africa; it is relatively rare in Europe, Latin America, parts of Southern Africa and most of Asia. The origin of circumcision is not known with certainty; the oldest documentary evidence for it comes from ancient Egypt. Various theories have been proposed as to its origin, including as a religious sacrifice and as a rite of passage marking a boy's entrance into adulthood. It is part of religious law in Judaism and is an established practice in Islam, Coptic Christianity and the Ethiopian Orthodox Church.
So is there any current evidence that uncircumcised men...today...are a greater health risk?
Although the idea somehow caught on that circumcision has some protective function, it's utterly ridiculous to think that's why God required it of Abraham. People do the same thing with the ancient food laws, claim they are simply the best food for people to eat, and make up all kinds of rationalizations for why that is. However, in the New Testament both circumcision and the Jewish food laws are declared to be inapplicable to the Gentiles who are becoming believers. It's absurd to think Gentiles would have been excluded from practices that have to do with health.
Both circumcision and the food laws are presented in scripture in the context of setting Israel apart from her Gentile neighbors. Circumcision sealed the covenant with God, the food laws kept the people from eating foods sacrificed by the heathen nations to their demon gods. Also some foods are symbolic or "types" of demonic creatures. Trying to give all this a medical meaning is to give a worldly meaning where an unworldly meaning was intended and to obscure God's true purpose in creating for Himself a holy people, a people set apart from the other nations of this world.
Circumcision is also symbolic, symbolic of the removal of the "flesh" or the "world" from around the "heart" which is symbolic of the human spirit, thus releasing the human spirit which had been buried in the flesh. God is making for himself a spiritual people out of a fleshly people. This was fulfilled through the Messiah, Jesus Christ, as were all the other symbols and types of the Old Testament.
I would think transmission of STDs via orogenital suction might give one pause when crowing about disease prevention. NYS DOH just issued a health advisory regarding HSV. Really, how did anyone ever think this particular practice (mohel sucking the blood) was a good idea?