I don't think I would make a very good caveman. I'm not sure how the set of genes floating around inside me right now ever made it past the Neanderthal period.
For one thing, my natural eyesight is terrible. I am completely dependent on vision-correcting lenses, which have only been around for seven centuries or so. Caveman Bret would have had trouble distinguishing his mate from, say, a charging saber-tooth tiger. A mistake in that regard could lead to him embracing a tiger or running his mate through with a spear, neither of which is an optimal situation for the propagation of his genetic material.
My memory is really bad as well. In prehistoric times, with no means of writing or recording information, that would have been trouble. Caveman Bret probably would have frozen to death during the winter because he forgot how to make fire.
I also don't think I'm the type of guy that can go find a mate, club her over the head, and drag her back to the cave for some procreation. Caveman Bret would have spent his days huddled silently in a corner of his cave, hoping a potential mate would accidentally stumble in and be impressed with the tidy decor. That plan was probably as unsuccessful in ancient times as it is now.
From an evolutionary standpoint, I should not exist. Maybe I'm a mutant.