The introduction of fixed agriculture was the basis for civilization. As a general rule hunting and gathering doesn't provide a secure source of food for a community. Over an extended period of time, H&G usually inhibits the growth of the tribe.
The domestication of animals and the introduction of agriculture allowed people to make plans for their future. In fact, agriculture REQUIRED them to plan ahead. A new idea to a H&G people. In order to plan for planting and harvesting, the people needed to have some type of calendar.
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