“…More broadly, as suggested by the observation that AARs in general display highly complex and interrelated evolutionary dynamics ( 5 , 10 ), these findings may also apply to AARs other than polyQ (S. Vaglietti and F. Fiumara, unpublished observations). The results of our analyses fit well with the view of molecular co-evolution as a driver of molecular co-adaptation, interactivity, and, ultimately, of organismal fitness ( 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ). Indeed, we found, first, that functionally related polyQ proteins, which display polyQ-length co-variation, also have higher degrees of physical interactivity.…”