 Complete the following phrase:  The early acquaintance with a food-producing economy in the PontoCaspian Steppe is assigned to this period. The transition from a food-gathering to a food-producing economy through farming and stock-keeping, led to a profound social and cultural change. Hunting and river fishing have likely continued to play a significant role in subsistence, especially in the forest-steppe areas. This transition to animal husbandry played a critical role in the history of the rise of human society, and is a significant contributor to the 