Why did humans develop agriculture around 8500 B.C. and not before? One thing to keep in mind while answering such a question is that agriculture didn’t “spring up” fully formed. Humans slowly developed agriculture through a process of trial and error. Furthermore, there were periods when humans used aspects of both hunter-gatherer and agricultural society. Sometimes, hunter-gatherers adopted agriculture for a few centuries and then returned to their old practices.
In attempting to answer the question of why agriculture first emerged around 8500 B.C., the chapter makes an important qualification: agriculture did not emerge fully formed: rather, societies only experimented with some agriculture. It would be some time after 8500 B.C. before any society’s food sources were entirely agricultural.
In the last 10,000 years, it’s become increasingly difficult to be a hunter-gatherer, for a number of reasons. Wild foods have become considerably less available in that time, and most of the world’s large mammal species have gone extinct. Another theory about why humans turned toward agriculture is that agriculture can support larger populations; humans were motivated to experiment with agriculture because it promised to feed them enough to survive. Agriculture also depended upon the existence of technologies like the hoe and the awl that didn't exist before about 10,000 years ago. So gradually, environmental changes and the rise of human technology and population density incentivized the use of agriculture.
The decision to pursue agriculture instead of hunter-gatherer practices was motivated by practicality more than anything else—humans came to recognize that their best chance of feeding themselves involved growing crops, not killing large (wild) mammals.