Before modification by darius_sedai at 14/11/2016 10:08:10 PM
There probably used to be. But three thousand years of living in the backyard of Aes Sedai means that any women with the ability to channel or learn were found centuries ago, and were trained or sent away. Channeling men would also all be found, for sure. And Aes Sedai don't have children. The result would be a methodical and complete removal of channeling ability from the local population.
but given that Tar Valon is the largest and most powerful city there must be some level if immigration population. For instance we know that Moiraine's banker, Ilain Dormaile, in New Spring is Cairheinin and the seamstress, Tamore Alkohima was Domani ... seems like there are probably quite a few industries in Tar Valon that would draw people from all over the continent. Not to mention all the trade that passes through probably creates a more than a few babies that aren't strictly from local genetic sources.
I see the point you are making, and it was essentially true in the reverse in the Two Rivers where isolation bred the ability powerfully, but Tar Valon would have a constant influx of new blood so it would probably be fairly representative of the general population.