Imagine that winter is almost here. You and your clan have picked and eaten all the edible plants around you for miles.
You compete for food with other humans, but also with other animals. The herds are getting smaller every day. It’s time for you and your clan to leave. You'll spend tonight in a shelter made of reeds and branches found near your campsite.
Life was nicer last summer and fall. You could find tasty food so quickly that it only took a few hours to get the day's supply. Your clan might come back here next summer. But right now you’re heading for places where you found food last winter. You’re hoping that works.