There is sufficient evidence throughout history that people are "evolving" and gaining hightened abilities, reflexes and insight. Growing up, you learn about legendary warriors who could slay one thousand men without taking a scratch or blinking, sure, it's obvious exageration, but they were most likely based off of true events (the Black Knight might be a bad example, but it's late and i cant think of anything else at the moment)
but it's not just back then, there is evidence all around us that people are gaining "New Type" abilities (ill let you know when i find some)



screw it, do you believe that people are becoming New Types or not?
dont just say yes because you love Gundam, have decent backup evidence.

the stories have been around for ages.
Gundam was released in the late 70's.
Gundam just gave it a decent name, tons of publicity, and more interested onlookers (because i cant think of a better word right now...)