During the Paleolithic Era, early Humans hunted and gathered food. Every so often they would move from place to place in search of more animals to hunt and more fruit/berries to gather. This method was very slow and inefficient. Because of the lack of food and shelter many Humans died.
Surplus of food
We have more fooooood.
Around 8000 B.C.E Early Humans invented framing and Domestication. This caused a huge event called the Agricultural Revolution. Because of the Agricultural Revolution there was a huge boom in the population. The population increase was caused by many different factors. This was the start of the Neolithic Era.
Trading for goods
I want the fish for the chicken
Because of the Agricultural Revolution Humans didn't have to be Nomads anymore. Because of this Early Humans made permanent shelters instead of temporary ones. The houses Early Humans made were way nicer than the temporary ones.
Farming and domestication was so effective, that people had way more food than they needed. This caused humans to have longer and healthier lives. This also caused an increase in population, which ultimately lead to villages and cities.
After the Agricultural Revolution, Humans and Civilizations started trading with one another. This started many towns and villages because of the easy access between different people. This also lead to the interaction and relations between of different civilizations.