I said it was possible, not that everyone could do it, or that it had a purpose. My point is to illustrate that it is possible to do, and possible to be happy living this type of life, as many of our ancestors probably were and African tribesman as well. You're right that there are too many of us for the Earth to provide for, but nonetheless the human race would still survive, just in a smaller number.

As far as killing animals goes you can make traps/snares and some weapons can be fashioned without using anything other than your hands (i.e. spears, atlatls, clubs, "throwing sticks," etc.) Once materials are gathered, flintknapping can also be used to fashion sharp tips for spears and arrows for bows. Stones can be sharpened against each other to be create knives and other tools needed.