Brehnev welcomed Nixon to visit Moscow. The Soviet Union reacted to the standardization of relations amongst China and the United States by having Brehnev welcome Nixon to Moscow. President Nixon trusted that normalizing relations with china drive a wedge amongst China and the Soviet Union.
Answer:
Human groups became larger as they acquired new sources of foods. These new sources of foods allowed them to be able to support larger populations.
From hunter-gatherers, they became pastoralists, and from pastoralists, human gruops became farmers, when they learned how to practice agriculture.
Agriculture produced food surpluses, which led to the development of even larger human groups, and finally, civilizations.