Agriculture. and animal husbandry
Hunter gathers depend on food sources that are "natural" in the environment requiring no human effort to create. Food from animals comes from hunting wild animals that exist in the environment. Food from plants comes from seeds, nuts and fruit that grows wild.
Hunter, gatherers had to migrate as the food sources in an area were exhausted and the animals moved away from an area or were hunted out. It is thought that many large mammals in north America became extinct because of hunting by nomadic people.
Gatherers would harvest the naturally occurring food sources as they followed the hunters. Natural food sources tend to be seasonal. Black berries in the fall, Seed crops in the summer, roots in the spring, and in different locations. The Indians in California would move to the mountains in the fall to harvest acorns, then migrate out of the mountains in the winter.
Learning how to plant the crops that would grow food, and to select varieties that were more productive allowed the people to stay in one place. Animal husbandry was combined with agriculture. The herds of animals could be contained near the areas where crops were being raised providing meat to the community. Then some of the animals ( horses, lamas, cows, elephants) were trained in helping to grow and carry the crops. irrigation allowed planting of more and more productive crops near rivers.
With the development of agriculture and animal husbandry people were able to settle down and live in one place. Hunters, gatherers had to move from place to place to find food.