really, we didn't find proof of even CLOSE to human intelligence until all the " man eating predators", with brains the size of your thumb, basically ate each other, kind of like if Russia pulled nuclear war on America, we would kill each other out. and even since then we have had to adapt and change, and evolve, while the pea-brains went and got stuck in swamps or couldnt find food or etc. so, really, with the competition back then, as we know, being similar just alot wilder, to today. they really just needed to avoid the predators, who usually by then preferred deer or antelope, etc.
How does any prey species survive and continue to propulgate? They learn to survive. The keep watch, learn to stay away from hunting territory, run fast, learn how to fight back, learn to create homes more or less safe from predators, learn what the predators fear. And in the case of humans learn to hunt tbe predators in return. Before guns there were spears and knives. There are primitive tribes today who still hunt with spears some using an ingenious sort or 'sling shot' that can propel the spear almost as fast as a bullet.