I am not sure I would be very successful as a Stone Age human.  First of all, I think they’d kill me as soon as they saw me because I would not look as they expect.  If for some reason they didn’t, I would have to live amongst them.  I am allergic to almost everything, I am a vegetarian, and I have limited use of one arm and one leg.  I doubt I would survive long!

Probably I would die.  Like the previous answerer, I've gone camping.  But these people have live their whole lives "camping."  I couldn't teach them thing one about that.  My best hope would be if I could teach them something from modern times so as to make myself useful to them.  But what would that be?  I can't think of anything I could teach them that would help and so they'd have very little incentive to help me out.

I would hope that, if I found myself marooned on an island with some Stone Age humans, I would have the resourcefulness and flexibility to adapt to the situation and learn the skills I would need to survive.

Obviously, none of us can truly know how we would react unless we are actually faced with such a set of circumstances. However, I have had experience with camping and have some knowledge of plants that could be used for food, construction of rudimentary shelter from natural materials, and first aid. I also think I could use pantomime and other forms of communication to hopefully establish to others that I was not a threat.