During the day they would hunt or gather food. Some people would have like jobs where they would have to make primitive tools made out of stone and primitive weapons used for hunting. Others would take care of the food and use skins of animals like mammoths to make tents or clothes or similar things.
The aquaducts supplied Rome with freshwater.
It is the transportation industry that is most directly affected by the ruling in Gibbons v. Ogden, since the ruling stated that the same power to regulate commerce can be used to regulate navigation.