Where do Texas governors come from?

From ABC News comes this quote of Texas Governor - and GOP presidential candidate - Rick Perry, replying to a young boy and his mom:

"Here your mom was asking about evolution, and you know it's a theory that's out there, and it's got some gaps in it. In Texas we teach both creationism and evolution in our public schools," Perry said.  "Because I figure you're smart enough to figure out which one is right."

But obviously, Perry himself isn't that smart.

So, OK, this kid might indeed be smarter than Rick Perry. But if all schoolchildren are that smart, where do Texas governors come from?