The biggest feature of Xahian culture are the castes into which the entire population is divided. There are seven castes; warrior, technical, engineer, farmer, mother, leader, worker. All but the worker caste is distinct and separate, their bloodlines kept pure by a combination of law and genetics. Generations of enforcement have resulted in only the best being born into that caste with everyone set into a role from birth to death. All Xahian are the product of in vitro fertilisation, with assayed embyros being implanted into members of the mother caste. Born in 'batches' of siblings, the younglings are trained and indoctrinated from birth into their caste with final assesments at age 10. Those who pass are assigned a role in their caste, those who fail are demoted into the worker caste, a caste made up soley of those whose genetics fail to make the grade. This is the fate of the majority of Xahians; only the best of a caste are entitled to contribute genetic material to produce the next generation Xahians and ensure their genetic legacy.