Teenagers who run away from home to live in the wilderness may become feral. As they become more and more feral, they gain some supernatural powers (a la Peter Pan - ability to fly, things they imagine come true - possibly quite powerful), but at the expense of their humanity and ability to speak, comprehend complex subjects, etc. Maybe they have a leader: the most feral of them all.
A regression into a fantasy childlike state.
The size and number of knots in hair, tied around neck, or hanging from belt could signify family, importance, worship, guild affiliations. Being able to translate the meaning of the size and placement of knots can give you a a large understanding of who somebody is.
May be used in a more barbaric society. Where in cities peoples clothes and crests show who they are, barbarians have no need for this so use knots.