Agreed. I can't imagine that people with even stone tools wouldn't figure out "hey, staying dry is nice" and make at least primitive roofs. A simple thatched or

Agreed. I can't imagine that people with even stone tools wouldn't figure out "hey, staying dry is nice" and make at least primitive roofs. A simple thatched or broad-leaf roof (e.g., palm/banana leaves) is not exactly hard technology to figure out.