As is said, every strong channeller in the book we know the origins of had the spark, in a similar way that there are too many weak channellers around now. I just don't see Maria's remarks being true (to at least what RJ put in the books). I appreciate this makes all of what I'm going to say next irrelevant if you believe what Maria says makes sense in context with the books but for me it doesn't.

I dislike using one bell curve to visualise all channelers, I much prefer a male and a female curve on the same graph which have different peaks either side of the "average". If it's anything like physical sexual dimorphism in humans then those peaks could be closer to 33 for females and 66 for males anyway (working off purely upper body strength studies, it could be a bit closer).

Again if you separated out the female channelers into those with the spark and without (This goes back to me not believing Maria). If you need to be a wilder to have a decent chance of being above AOL average and wilders have been continually ignored for 3000 years it's very possible that you're simply looking at the wrong side of the bell curve for people born without the spark.

If you accept Maria's statement then I fully understand that what I've said isn't applicable but I personally just can't accept what she says when the books to me say otherwise.