Humans were artificially evolved to an acme point when they came into contact with the Frozen Flame.
Besides, evolution takes place over longer expanses of time than the 14,300 gap we see between the first "modern" humans in Zeal and the last ones we see in 2,300 AD.
This is the Chronoverse, not our reality. Their technology developed at a drastically different pace, who's to say their evolution was completely the same as ours?
But did evolution really phase out magic? The Mystics and plenty of monsters use it, and Crono Co could after Spekkio 'taught' them. But then that brings the question of how exactly he gave them magic. All he did was point and tell them what element they were - which implies the magic was already a part of them - then mutter a silly incantation and battle. It seems more likely that he merely unlocked something dormant, which grew of its own accord.
Then that begs the question, is it possible to give magic to a nonmagical being, or one whose species never possessed magic? Robo, a nonmagical and nonliving being, could not learn or be given magic. Ayla, who was born before magic (or before the magic that Spekkio knew), also could not learn or be given magic. So what, then, are the requirements for learning or receiving magic? What exactly is magic? Is it the energy of life found in all things and all matter, as in the Golden Sun games? Or is it something you must be born into, a mere chance of blood?
But, I'm going off on a tangent. Perhaps the heat is getting to me and I've gone senile like dear old Belthasar. As for Gaspar's age... time to look to his (obviously limited) sprites for comparison. Gaspar's EoT sprites are shaded very nicely.. Both that and his Guru sprites look extremely old. First thing to understand is that character sprites in CT have a maximum of 12 colours, plus 2 for the weapon, plus one more for transparency. The palette must be chosen so that the same colours can be used in different places for different effects, like a hair colour being used in clothing, yet looking nothing like hair.
Guru Gaspar's hair and mustache use dark, desaturated blues and greys. It is difficult to tell which part of EoT Gaspar is his mustache, but it looks like it has white or some very pale yellow for a highlight, then the browns and yellows of his cane for shadow. It could just be the light from his lamp post. Thing is, the highlight colour on his shoes looks like one of the shadow colours from Guru Gaspar's hair and sash. Not identical, but close. I can't see anywhere else this blue was used in EoT Gaspar.
(If you're too lazy to read examination of a sprite, skip here)
So, either it's just extremely harsh lighting under that lamp, or Gaspar really did lose his blue hair.