What could threaten a primitive man expelled from the tribal community?

At that time, it was very difficult to survive alone. The communities greatly increased the chances of survival. Together, it was much easier to get food, build dwellings, defend against enemies and animals. The exile had a rather slim chance that he would find another community and be accepted there. Otherwise, he could only count on gathering and hunting small animals. There were chances of stealing what they needed from their former fellow tribesmen or other communities. In case of illness, no one would look after him. It is quite problematic to protect yourself from a large predator on your own. Most likely, he would have died in a fairly short time.