You travel back in time, back to cave man era. To the most advanced yet immensely primitive tribe at the time. There you see, a large Amazonian tribe, full of mute, tall, muscular women who have already mastered fire and hunting. Their beauty is as great as their strength, having long silky hair. They only lack one thing, men. They have never seen a man before, yet somehow mysteriously keep reproducing.

You spy on this tribe, and with your modern technology, you could do anything you want with them. Perhaps teach them? Make them the strongest and longest lasting tribe and alter time itself?