The inhabitants (mountaineers) are divided into rigid hereditary castes:
The crew are the upper caste, descended from the individuals who piloted the colonized vessel and hold power through their monopoly on organ transplantation.
The original colonists signed the "Covenant of Planetfall" at gunpoint as they were awakened from hibernation, agreeing that this outcome was just recompense for the labors of the crew during the voyage. As a result their descendants are the lower caste.
This repressive system was overthrown, and the former inequality appears to have disappeared.