Saw this on a forum I frequent, and thought it would make a great topic for my next religion post.
Unlike others, this will be a short post.
Cavemen existed. I don't know of many people that would argue that. The point of contention is when did they roam the earth? Some would say hundreds of thousands of years ago. All of that is without evidence, as there were no observers, and no hard evidence there was anything around more than about 10,000 year ago.
That said, there is debate about how one might be saved prior to Christ's arrival on earth. Here is a link that summarizes it beautifully. So, essentially speaking, if a caveman believed in God, they were saved. Because God had given us a Promise (that Jesus would fulfill), and that promise was His manifested Grace, and there is not scripture that would indicate that salvation is by anything other than God's Grace.