I think it comes to perspective. If you were born during that time, you would've been able to adapt and survive, it's part of how we are coded as humans and as an organism. Our main goal is to survive hence we are engineered to want to have sex etc. Anyways besides that point, in the case we teleported back to that time and had to live as a caveman, it could be a struggle and depending on the level of a persons mental and attitude they would either survive or not survive :x