No Evidence? There is a srong argument to support this as stated in*HH*"during the Era of Chaos a transformation took place involving the Zora descendants"
Now if you look at the timeline, the era of chaos happens in between Skyward Sword and the Minish Cap and due to there being no game in between the Minish Cap and*SS*I think we can only relate the ancestors of the Zoras to be the Parella. There are obvious similarities between the two as both are semi aquatic race and they reside within a lake. Now if I remember correctly there was no aquatic race seen in the Minish Cap so one can at the moment only interpret that the Zora/Parella were outside the boundary's of the Minish Caps world or they were simply hidden.
As for why they evolved or adapted, in my opinion hey had to adapt to a major event. In this case I refer back to the Era of Chaos, as it stated that some part of transformation took place at this time I think it could have been due to the danger the Parella could have been in so they might have had to move from Lake Floria to another location (Zoras Domain) Now since Parella could only reside in water it seems maybe they evolved human features to move locations and ultimately save the aquatic tribe.
