I know some are definitely mentioned in Pokedexes and other sources, Pokemon like Cleffa/Clefairy/Clefable, and Lunatone and Solrock. It wouldn't surprise me if there were more, but I assume some originated here because there are ancient Pokemon that have been around for millions of years, Anorith/Armaldo, Lileep/Cradily, Omanyte/Omastar, Kabuto/Kabutops, Aerodactyl, and so on. Relicanth is another one that's not changed its form in millions of years.
Overall, some, but not all Pokemon originated in space. Just my coupla coins.