actually, i have this huge Pokémon creation theory
Arceus came 1st, created the 6 Pokémon (groudon, dalgia, etc.) and a lot of mews. Grou and ky created earth, mew created the other Pokémon. Mew can transform from its own DNA, but if my theory is right, not into grou, kyo, ... and arceus. (And in man-made Pokémon)
I think I wrote this down somewhere, too lazy to type it all
Remember, there are a lot of mews but only 1 arceus, if mew can make every Pokémon, it would have made more then 1 arceus, groud, ky, ...
So my theory is: mew created all not-one-in-a-kind not-man-made Pokémon.