

No, there’s tons of records of barter in ancient Egypt, and it actually lasted until the Greeks came and forced the use of silver drachmae on them.
Gift economies existed too, but they weren’t universal. Just helping family and close friends out was universal, but it sounds like you’re thinking of more than that.
A human absolutely could walk 100 miles, and people often have. The weight thing needs to be scaled for body size, but you can carry quite a bit while doing it, too.
The only maybe-counterexample anthropologists talk about is actually sled dogs. Horses run out of steam faster. Presumably they know about camels too.