endurance doesn't help much when you need to out-sprint something that wants to eat you.
True, but Ghostavo is pointing out the other evolutionary advantage we have over pretty much any other animal. Everyone remembers the big brain, but possibly even before it, we had a major advantage when it came to hunting.
In fact I seem to remember reading a theory once that humans evolved tool use not just in order to make us better at hunting our prey but in order to prevent other animals poaching our kills.
While I'll agree with you that without tools and alone a human is very easy prey, the simple fact is that humans were rarely alone and without tools.
It's only recently that humankind have become so assured of their mastery over the animal kingdom that we don't constantly have a weapon within easy reach to deal with any large predatory animal stupid enough to **** with us.