Twiggly the Gnome
Legend
I think you’ll find everyone is descended from Halfllngs. Though evolution has nothing to do with it. They used the power of the Pristine tower to alter themselves and turn themselves into the races we know and love today.
People seem to be under the misconception that gnomes are extinct on Athas. The truth is that they never existed on that world. It's impossible to derive anything as noble as the gnomish race from such base stock as halflings.