First there was Arceus, then there was Psyduck! Psyduck are a mystical race of Pokemon who live on Psyduckia, because that is Arceus' will. One day Giratina got angry and in his rage, sprawled a majority of the Psyduck into the cosmos. Psyduck can naturally survive space, so they descended to earth and transformed into the other 714 Pokemon and the humans. Earth Psyduck devolved their ability to hold infinite knowledge, and suffered from a case of permanent severe migraine. The migraine suppressed their Psychic types, thus dooming them to be water types only. One day, the ultimate Psyduck will descend and call us. They will then
unlock our true power and we shall ascend to Psyduckia.
Psyduck devolves into a weaker form, Golduck. People obviously like Golduck less than the mighty Psyduck.