One of the distinctions among languages is the tonal/atonal distinction. Dediu & Ladd (2007) suggest that this split between tonal and atonal languages is related to a recent mutation in the ASPM gene. In particular, people with the newer variant of this gene correspond closely to groups with atonal languages. The new variant of this gene is believed to have appeared between 14,100 and 500 years ago (most likely about 6k years ago). The mutation fixed itself very quickly in certain sub-populations, suggesting a selective sweep. If the new variant of this gene is strongly related to atonality in language, then one would also expect a divergence of the atonal languages from a tonal ancestor around the same time (14,100 to 500 years ago).
Is there evidence that atonal languages have tonal languages as ancestors? If so, did the seperation appear in the time frame of 14,100 to 500 years ago?