Before Rand revealed the history of the Aiel, there were exactly zero Aiel followers of the Way of the Leaf. Now there is endemic depression among the Aiel, some of whom are leaving to join the Tuatha'an.

Even if this weren't the case, there is no way you can start with zero and end up with a remnant. A remnant is by definition a persistent fraction of a whole, but you cannot divide zero, you cannot have something persist that doesn't already exist.