I would have thought it axiomatic that nomads, in multiple areas of the world, were the first traders.
Nomads would most likely bring some item(s) with them either not found or rare in some place they travel to, and trade them for some item found in the area they travel to; often an item rare or not found in their homeland. The naturalness of it is without question; not a “revelation”.
I agree, other than that the usual idea of how change or "progress" was in slow, "logical" steps -- nomads aren't hunter-gatherers, they're generally herders; traders who travel all the time and do nothing but trade are, uh, nomadic; and markets where trades take place are and were found in settled places, which were made possible through agriculture and animal husbandry... uh-oh, sounds like irreducible complexity strikes again!