Really? You've obviously never worked in retail! :) There are so many different types of intelligence, but I'm assuming you mean it in the cognitive way.
I think...and this is just my opinion...that we build on the knowledge of those before us and the more solid our foundation of knowledge, the faster we can advance. Also, as adults become more intelligent, their children "should" also benefit from having someone around who can answer their questions. I also believe that all of this instant information that we are able to obtain through the internet and such has an effect on what we know. I must look up thousands of things on the net a year...yet, I've only been to the library only a handful of times.