On the origins of human beings.

The term cave man also means cave dwellers.  The question of early humans living in some peaceful golden age, no, violence was worse, not better.

Why were early humans cave dwellers.

People could not make fire so there was safety there.  Also we like sunlight but in some parts of the earth only so much sun was desired because of our sensitive skin which could easily get melanoma.

A driver of human ambition was being lower in some respects to some other animals and the invention of clothing was a rather big development in human evolution and still is.  Try going out naked today and you will run into trouble very fast.  Be a sharp dresser and maybe evolve faster?