How did the early people explain the proccesses of nature?

The Greeks explained it through the myth of Persephone. She was abducted by Hades and brought down to the Underworld. In the Underworld she ate a certain amount of pomegranate seeds (which is the food of the dead) and had to stay in the Underworld. Zeus then bargained for her life and she was allowed 6 months on Olympus with her mother. During the six months she's gone in the Underworld, Demeter (her mother) weeps and lets the earth die. Hence the seasons.