Answer:
The agricultural revolution happened because hunter-gatherers saw that wild plants can be planted and be grown, being a near reliable source of food. The Sumerians in Mesopotamia, modern-day Iraq, were the first and were part of what was known as the Fertile crescent. If it had not happened, people would still be nomadic and we would not have surplus(extra) food. Entire civilizations would not exist, because they would still be nomadic. Their would be people everywhere with the same culture that the civilizations had, but there would be no borders. Populations would still be low, and some species could even cease to exist due to overhunting. But however, disease would not spread so easily.