If you're curious about that question, run, don't walk to your local bookstore or library and get "Guns, Germs, and Steel" by Jared Diamond. Amazing book.
He ended up writing the book after he visited New Guinea and made some friends among the tribesmen there, who struck him as very intelligent people, despite having a very primitive society, and one of them asked basically the same question you asked.
That book has been on my Amazon "Wish List" for far too long. Now with that glowing recommendation I'm gonna have to get it.