Even thought it did not happen all at once, what discovery signifies the beginning of the neolithic age?

The discovery of agriculture. Before the Neolithic period, men and women were dependent on hunting, fishing, and gathering wild berries or plants. That is why agriculture became so important for the humankind: we were not just able to collect food, but also to produce it by cultivation. It was also the beginning of domestication, the development of better stone-tools and the establishment of the first permanent villages.