Quoted By:
Both Mewtwo MegaEvolutions, along with MegaCharizardX are man-made Mega's.
Mewtwo's Mega's were created to push the limits and capabilities of the experiment. CharizardX's Mega was created scientifically, possibly alongside Mewtwo, in an attempt to remove Charizards flaws, and experiment with type changing.
Pic Related is the best image I have been able to find for this. It ties evidence found in Origins (The canon interpretation of Red's journey) to the theory.
