Here’s the problem: Flint flakes have long been taken as evidence that our prehistoric ancestors knew how to use tools. Way back, when we (“we” being humans) were still more animal than otherwise, it seemed that our hirsute forbears had mastered the use of razor-sharp stone flakes to butcher animals—and each other. But modern-day monkeys have been observed creating such flakes by banging rocks together—only they do not then make use of the flakes. They’re just breaking rocks to get at the minerals inside them. See the potential conundrum?
Lacking direct evidence that those flakes were being sued—and said evidence would constitute bones bearing clear markings of butchering—scientists can’t be sure if our apelike progenitors were using those flints to cut things or if they were just breaking rocks for the sake of breaking rocks. (For that matter, maybe it wasn’t them creating the shards, anyway; it could have been monkeys.) How to tell if the stone knives—for that is essentially what they were—were being used as weapons or just being left on the ground, a danger if stepped on but otherwise ignored. We know that our forebears, and the offshoots of the human family tree, had the temperament to use the knives on each other and on their prey, but did they yet possess the intellect?