BOW
Forget the 'cross' part. Learn to make and use simple longbows and (not so simple) fletched arrows, bowstrings, and pressure-flaked arrowheads.
That, and a knife and spear made using the same technology, got our ancestors through the last bottleneck.
I have been a SEE trainer and am an American native. Trust me on this, and realize that to master the 'simple' bow may take a lifetime.
Major advantage: you make it when you need it.
Best way to get food is seashore gathering, snare and wild plant foods.
Know how to make a fire?
[edit on 2-3-2008 by Chakotay]