To determine an origin mark:

1. If a pokemon form has a previous evolution from within the same generation, 
    use the mark of the previous evolution. This should be recursive within the same generation.
2. If a pokemon form has no previous evolution from within the same generation, 
    look at the encounters of the pokemon form and use the mark of the earliest game you can encounter that form in.
3. If there are no encounters for the pokemon form,
    use the mark of the earliest game of the generation is marked as being introducted in.
4. If there is no mark for the earliest game of the generation,
    then it has no origin mark.