hi! It would be worth x-posting this question to medical experts in /r/AskScience (Medicine category). As for this sub, you may be interested in these earlier posts

• Why did circumcision catch on in places like the US, Canada and Australia but not in Europe?

• How did circumcision grow from a practice of Judaism into a popular practice in Western medicine?

• Why did the Marines require you to be circumcised to join up in in the 1940s?

• How did medical circumcision of male infants become the norm in the United States?

• Why did American doctors in the late 19th Century/Early 20th century believe that masturbation led to insanity and that circumcision was a viable cure for masturbation?

Of course it's biased in favor of personal body autonomy, but there is an annotated timeline of the history of circumcision in /r/intactivists/wiki.

There's also a rudimentary answer to the question Why is genital cutting so popular in the US?

There are also Medical Associations' Statements Against Involuntary Non-therapeutic Genital Cutting that show that US recommendations for parental choice in cutting are considered ethically questionable or even completely unethical by medical authorities in cultures with less ignorance about the foreskin.

Does it reduce sensation in that area?

Is the foreskin sensory tissue? How could the destruction of sensory tissue do anything other than reduce what can be felt?

"Sensation" might not mean exactly what you think it does though considering the fact that most studies have found a slightly higher rate of premature ejaculation among modified men (Masood, 2005; Waldinger, 2005; Richters, 2006; Bollinger & Van Howe, 2011; Zwang, 1997).

Here is a history of circumcision.

In short, the procedure became "popular" (although no babies got to vote!) in the Victorian era as an anti-sexuality measure. That had roots in the medieval era, to wit:

With regard to circumcision, one of the reasons for it is, in my opinion, the wish to bring about a decrease in sexual intercourse and a weakening of the organ in question, so that this activity be diminished and the organ be in as quiet a state as possible....

The bodily pain caused to that member is the real purpose of circumcision....

The fact that circumcision weakens the faculty of sexual excitement and sometimes perhaps diminishes the pleasure is indubitable. For if at birth this member has been made to bleed and has had its covering taken away from it, it must indubitably be weakened.

The sages, may their memory be blessed, have explicitly stated: "It is hard for a woman with whom an uncircumcised man has had sexual intercourse to separate from him."

• Moses ben Maimon (Maimonides), Guide of the Perplexed, Part III, Chapter 49 Source: This page of quotes on the pleasures of the foreskin.

I'm curious why you're asking about this after your son's birth? Most people want to investigate it before the birth.

It was started in the US to prevent masturbation: http://en.m.wikipedia.org/wiki/John_Harvey_Kellogg#Masturbation_prevention Has benefits that are negated with condoms and antibiotics: http://www.webmd.com/sexual-conditions/guide/circumcision#4 And removes a large amount of nerves: http://commons.wikimedia.org/wiki/File:Sorrells.gif Also, there's the fact that your kid might not like the fact that it was done to them. ^^^Like ^^^me.