The fear of savanna predators may have driven Australopithecines to walk upright, potentially using weapons like sticks for defense and hunting.

“I personally suspect that it's caused by many things but one of the things that I think probably it is caused by is literally the fear that australopithecines would have felt when they went out across the open savanna you know worried they're gonna be attacked and I think that in order to respond to that fear they would have brought with him a weapon and so we know that that our ancestors that far back couldn't plan for the future they couldn't say well tomorrow I'm gonna need acts or tomorrow I'm gonna feel why but they could plan for the now and so if they were scared they could say well I'm gonna bring a big stick with me so that way I cause I'm scared and I want to stand off anybody and so that would have put pressure on you to walk upright if you want to hold something in your hand but it also would have given you an advantage when a hunting opportunity didn't come along so now you've got this big spear that you've chewed the edge down or a big Club that you could whack things with”