Have you considered asking /r/AskAnthropology as well?

Predators are earning their living. They canNOT afford to be injured by the prey. They have to be around for the next 100 or so hunts. As such, a fight between a human and predator would probably go on only as long as the predator thought it could win easily. Put something sharp in its eye and even a BIG predator stops to think. No meal is worth the loss of an eye.

Spears are spectacularly good weapons. If the shaft is strong enough to be grounded (rare, as such a shaft is heavy and you don't expect to meet a large predator every day) nothing can charge a human and get a way with it.

While the Gurkhas used steel, it was not unheard of for a single Gurkha to kill a tiger. The techinque was to get the animal to charge. Dodge (VERY fast) and clip off a paw with those wonderfully sharp chopping knives they all carried. Didn't always work, but it could be done.

As /u/Hinmatoowyalahtqit mentioned, this is more of an anthropology or even biology question than a history question. However, I guess it is relevant to the history of hunter-gatherers. Anyway...

Individually, humans were certainly weak to predator animals. However, there are a few things worth considering here. The first is that humans are essentially predators ourselves; our eyes are on the front of our faces, to facilitate chasing prey (as opposed to herbivores, such as deer, who have their eyes on the side of their faces so they can constantly scan an area around them). Generally speaking, animals like bears, wolves, or lions won't go after us unless we're alone or wounded or otherwise compromised.

So the second strength that humans have in the wild is community. Groups of animals can cooperate together, of course, but early humans had both hand-sign language and vocalized language and could strategize things like ambushes and traps; such as a lone human leading a predator into an ambush, or groups of humans herding/chasing prey animals off of a cliff and collecting the meat at the bottom.

The third advantage that humans have is we are the best long distance runners on the planet. Cheetahs, deer, and other animals can sprint very fast, but humans can keep up a constant pace for days if they have to (there are a few reasons for this, but one of them is our ability to sweat and regulate body temperature; deer and stuff will literally overheat if you keep chasing them). This is how some of the earliest hunting was accomplished, called persistence hunting. A hunter or group of hunters would chase a prey animal until it collapsed from exhaustion, then casually walk up to it and strangle it. This was how people hunted before any tools, snares, spears, darts, slings, whatever. Our ability for distance running worked to a degree defensively as well. Humans would probably have to work hard to outrun a charging bear but we were capable of crossing vast distances relatively quickly compared to many predators.