The herd has moved but they're are not many animals left.
Perhaps we will have to find a new one.
We already have enough food for winter
During Paleolithic times, nomads and groups of people moved from place to place often to find somewhere that had food and water. Living was also a struggle because without permanent homes, these people were often attacked by hostile animals.
Moving into Neolithic times, people finally discovered farming and started to construct permanent homes and discovered farming. They had a surplus of food which they did not have to worry about the Winter time which they had enough to eat.
Finally, civilization. People after many years, communities joined to make cities. And sense their were cities there was civilization.