Before we respond to the question "is religion man-made," we'd have to ask "is it made?" Of course it is: universes were "made," and so are all objects, all perceptions which involve the brain, which "makes" them into something graspable.

If the question means, "did religion come about because a supernatural finger like the one extending Michelangelo's bearded Father-God?" reached out and said "here is religion; you can have it? " The answer is no. Or "was religion made somewhere 'out there' in physically distant heavens? the answer would again be "no."

What humans do with what they receive is always "man-made," "humanly constructed," whether this means forming images in the brain, creating artistic expressions, inventing lawnmowers, or writing books of philosophy. So long as we are talking about anything connected with the human, we cannot evade questions involving brain cells, the ability to create those symbols, the impulse to invent rituals. Religious people are not, or should not be, offended by such questions or the answers about something being 'man-made."

"Religions" usually involve complexes of scripts, sacrifice, stewardship, mission, and institution-building. Of course, these are "made by humans." Religious people do not believe they have exhausted the subject when they affirm that "social constructions of reality" exist, also in the realm that gets named "religion." After they have affirmed something like that, the fun begins, and what is valuable in perceptions called 'religious' begins.