HELPING THE OTHERS REALIZE THE ADVANTAGES OF GAS PISTON AR PISTOL UPPER

The e book 'Guns, germs and steel' launched me to the fact that the Sahara desert actually isolated Sub-Saharan Africa from the developments elsewhere given that the beginning of civilization till European colonialism. My primary question: Is that this legitimate? Ended up there main isolated exchanges of information?Is so, where? And why didn't it