Answer:
dwindling food supplies
Step-by-step explanation:
Nomadism is a form of life that was present in human groups, especially before the Agricultural Revolution. It is a human practice of groups that, instead of living fixed in one place, scatter around the territory looking for food. Their walk revolves around the natural resources available: when they were depleted, they moved to other places. Between 1 million years and 10,000 years, humanity lived in a nomadic way. According to this reasoning, we can say that the correct answer to your question is "dwindling food supplies".