first they were hunter gatherer. they had to survive and gather food for them self. Like pigs and other things like berries. There homes could not be permanent because they kept moving place to place so they could survive. We call them nomads.
then they started to settle in and harvest crops they grew. If they did not get they would not be able to feed the group. they would take goats and cows and get milk from them to drink and to make cheese.
Then they started to make towns and socites. Then the bagan to trade and make currance. so if someone needs something they can trade for with somr thing the other person needs.