MacMeaties, I think the problem with your analogy (that of Chimps being stone age humans) is problematic.
Chimps are not "early stone age." You are comparing apples to oranges. The level of intelligence that a chimp displays is quite different than that of a human, however taking a child/infant human from the stone age and raising them as a modern human would work... Intelligence has *not* changed since the stone age, understanding (i.e. knowledge) has.
Your comparison of Chimps = less intelligent / users of tools = stone age humans would mean that Amish = fifteenth century technology = less intelligent, or Aboriginal/'native' peoples with technology != U.S.A. standards == less intelligent. The problem with this, other than being insulting, is that it has been proven untrue. Any human, from anywhere on Earth can receive the same level of education and be as knowledgeable as any other (with as much variation as within the U.S.)
It has also been suggested that actual "intelligence" hasn't changed over the past 5-10,000 years, but that human technology has; that our ability to learn and reason hasn't advanced with our technology, but has adapted to a different set of needs (instead of learning what is and isn't poisonous and what game can be hunted via what means, we learn fractions and science...)
Apples to oranges.
Humans had need to develop greater psychology and sociology amungst its groups. Their environment and social dynamics required this of them as they became more dependant on one another...
Chimps... Chimpanzees rape their women and murder their men. The women allow this so that thier offspring aren't murdered by the other males, for not being that males child... Their sociology is practically non-existent, not even to the level of village despots.
They have no reason to learn to speak (although that also likely has to do with anatomy, but they have learned and practically taught sign language), count or build weapons. Weapons? A chimp can rip a himan in half with its bare hands... The only reason they need their sticks and stones is for delicate work such as not digging up the ant nest to eat ants, or not crushing the nut into goo (but breaking it open to eat/drink).
Apples to oranges to pears.
Incidentally, while trying to teach another parrot to count single integers, humans ignored the fact that one of the others was "adding to the last number." Behavior never before witnessed, and believed not possible prior to the accidental discovery.
(Citations needed, but all of this was on Discovery/Science/Animal Planet a little over 10 years ago...)