Alright, I've had this theory for a long time, and have posted about it in several threads on here before. This time I'll be posting those thoughts here.
First off the basic premise of this theory. I beleive that Zygarde is connected to the core of the Earth, and that it influences Pokemon evolution including Mega Evolution.
First a quote from an recent post of mine
"The Earth's iron core produces the magnetic field of the planet too. For those that don't recall or didn't...