Inbred Law Professors?

I engaged in comment threads on Powerline--commenting on a Mirengoff post about Sen. Warren and the DNA test--asserting she had a false story.  As one might expect from my earlier post on the subject, I defended the test and, as you'd expect from the leanings of the website, got a lot of pushback from its devotees.

One point made was that Warren graduated from Rutgers Law.  I did a quick check of the (most of) women professors in Harvard Law and was a bit surprised by the results.  Some professors didn't include their education in their backgrounds, but most did.  Almost all of those I checked graduated from Harvard or Yale.  There was one graduate from Chicago and one from Texas in addition to Warren.

The predominance of Harvard/Yale bothers me--looks as if the system is rather inbred, at least at the law school level, less so at the undergrad level.  Also relevant is this: I noted in passing several cases where the professor had background in other fields, like history or math.