A lively debate at Charles Stross' comment section on limits to human intelligence.
I'm not sure I understand his hypothesis. Language also lets us simplify things into symbols, and then operate upon them more efficiently. Not only can you teach me to better peel a banana, but in doing so, you might have helped me solve another problem I've been having, like skinning rabbits or something. I see language as a multiplier of knowledge.So we only need to be smart enough to understand and use the cognitive tools created by our most intelligent outliers.
Yes, you can learn a lot and become more efficient but does that make you more intelligent? Where are natural selection's pressures to evolve more brain tissue? Is learning through the means of language a short-cut for gaining knowledge in stead of the evolution of intelligence? I believe that since the discovery of language human intelligence/stupidity hasn't changed at all.