fun trivia: nivkh/gilyak is the oldest surviving setlers of sakhalin island (more than 5000 bc), which far older than tunguistic people (a sub of mongoloid family, where ainu and orok originated, and probably japan also, but russian is caucasoid) which come very later (orok and ainu is migrated to sakhalin around 500 bc)... so they has complitely different culture than what soo far we have seen... sky burial is one of them and we might even explore more diverse culture we never seen....