If you were going to 20k B.C while we were still at the height of our primitiveness, and you were sent back to somewhere in Europe (say Germany) with your regular survival utensils (a knife, water bottle and a zippo lighter) and a backpack containing something of your choosing, what would that be?
I think I'd take back some yeast. That way I'd be able to brew alcohol for disinfecting and maybe bump medicine forward thousands of years.
P.S just for the sake of it, you're sent back into some friendly and welcoming tribe so you're not spending all your time scrounging for food. You have people to watch your back. That way, you can get down to business, and be history's first scientist if you choose to.
"People Aren't against you; they're for themselves"
"If you don't want people looking down at you then grow up"
"If you know the rules to the game, play; 'cause when we die we all know we'll be going the same way"