IQ and Education

As discussed on Mankiw's latest post, I'm having some serious problems with Charles Murray's articles (2) (3). I understand the idea that IQ could create an upperbound as to how far education can take a person. My problem is he seemingly pulls these IQ constraints from a top hat. He writes:
"There is no magic point at which a genuine college-level education becomes an option, but anything below an IQ of 110 is problematic. If you want to do well, you should have an IQ of 115 or higher. Put another way, it makes sense for only about 15% of the population, 25% if one stretches it, to get a college education."

Where do these numbers come from? I didn't see a cite. Am I just not seeing it? This just smacks of elitism to me. ...Or maybe I just don't have the IQ to grasp it. Couldn't it just as well be that a typical 4 year college is worthwhile and useful to everyone with an IQ of at least 100, or maybe 90? Who's to say where that bound is?

Beyond that, I do believe 'g' exists. What I DON'T buy into at all is the idea that once you reach a given education level, all formal education after that is pointless or (personally) inefficient due to your IQ. People always have room to improve - they always have room for intellectual growth, no matter what their IQ.

One problem with IQ as a measure is that it is a very narrow definition of innate intelligence. There are lots of different kinds of intelligence. Luckily our colleges understand this which is why, more and more, fields and disciplines are creatively expanded to work different peoples' brains. Besides, people also need to have the 'free will' to dream.

The Rudy's of the world need to try, and if they fail, they may just be more the wiser for it.