Groups of people following a hunter-gatherer lifestyle are very dependent upon environmental conditions that are out of their control. If the animals they hunt migrate, the people must follow the animals if they want success in their hunting. If the seasons change, wild fruits or vegetables may not be available for gathering in a given location, forcing the people to move or to change their diet. If animals and plants decline due to drought, the people may be forced to leave the area in search of food in other places.
Over time, prehistoric groups began to change the conditions under which wild food-producing plants grew through such actions as
the use of fire to stimulate new growth; the protection of favorite plants; sowing seeds or parts of tubers without domestication; preparing soils; eliminating competitors; fertilizing; irrigating; concentration of plants; controlling of growth cycles; expansion of ranges;
Actual farming, the domestic growing of plants specifically intended for use as food, developed from these actions. The rise of agriculture enabled groups of people to establish permanent living locations, enhanced the development of settlements that became cities, and gave people time to develop other aspects of early human culture.