1. He just harvested the wild grains.
2. The hunter-gatherer went from place to place in search of food.
3. As the crops began to give better yields, this reduced his need to go in search of animals and wild plants.
4. This was followed by an attempt to grow food by scattering the spare grains.

The transition of early humans from a hunter-gatherer, nomadic way of life to settled agriculture is traced in this passage. 

The lifestyle of early humans is introduced in Statement 2, which sets the scene and is therefore the opening sentence.Statements 4 and 1 form a logical pair because of the action-result dynamic. 4 tells us something that the early men did, and 1 gives us a result of what happened as a consequence.  Statement 3 is a logical conclusion to the dialogue, as it sums up the gradual shift that is discussed in the passage. 

The most logical sequence is therefore 2413.