Inferring

I think the Nomads moved from place to place because they over hunted or the herds moved to new lands to find more food. The nomads are not farmers, farmers have crops to look after. The nomads did find seeds but did not know what to do with them.
 They moved  from place to place to find a new place to live. They moved seasonally to find food like animals and territory. Animals also moved to find food like grass, and fruit so the hunters followed the animals and the gatherers went to find fruit, and wild plants and I think the gatherers also collected nuts. The reason the hunters and gatherers survived is because they followed the animals so they could have food.
Too many people means more hunting and houses so they have to migrate. Hunters and gatherers learned how to plant seeds so they don't have to move from place to place but some times they still have to hunt.