Levels

Childhood — XP 0-24

Newborn whelps are born with 0 XP and have to learn how to get their feet under them before they can do anything.
Level Zero colonists are able to participate in Chapter One of Story Mode as well as Foraging and Diplomacy, but they can't breed or benefit from Crucibles.

Young Adults — XP 25-99

Adults, can breed and participate in Crucibles.
This is the level that starter colonists, rng recruits, and natives begin as.

Prime Adults — XP 100+

They have a minimum of one whelp per breeding, so long as infidelity isn't involved.
They earn the Benefit of Age which doubles their base RP after other RP bonuses if you mention it.
— For example: A piece of art counts for 5 XP.
— They earn that XP and its RP equivalent of 5 RP. Your colony has Research+ so you get another 5 RP.
— The original RP is then doubled due to BoA, resulting in a total of 15 RP.
— Benefit of Age applies only to colonists owned by the artist/writer.