Without roads, maps, or the tools people have today, small groups of nomads moved from place to place in search of food. why might these groups migrate to different regions?

If they don't know what's ahead, they would have to guess based on movement of animals and how it looks like from afar off. This means that different people would have different opinions about which way to go to, and they would split into smaller group to travel towards their own destination

hope this helps