Yoonies are human-like creatures, more or less equally split into 4 castes, but the only difference is how they are viewed by various members in society:
Farmers, who are thought to be stronger and most robust in Yoonie society, but not so intelligent. The most visible are older males of the species, with a penchant for wearing plaid, dungarees and straw hats. Farmers think they are the most important group in Yoonie society (and beyond) as without the products they provide, society would fall apart in a hungry, naked mess.
Tradesmen, who are thought to be more dexterous and fastidious than their counterparts, tend to be looked upon as very anti-social, that their work takes precedence over social activities. Their jobs tend to be viewed as very dirty, as they always have dirty, calloused hands. Tradesman think they are the most important group in society, as without them things would literally fall apart.
Merchants, who are thought to be more charismatic than the other members of the Yoonies, are also viewed as very greedy and selfish, that a fast buck is better than anything else to them. They tend to be fatter than other Yoonies, due to spending so much time behind a desk, but wear more expensive clothing. Merhcants think they are the most important group in society, as otherwise there would be no money with which to survive if they were not there.
Intellectuals, who are thought to be more intelligent and wise than the other Yoonies, but also viewed as haughty and dismissive of others who are not as smart as they are. They tend to stay indoors, wearing long, white robes for no apparent reason, discussing their ideas and experimenting. They think they are the most important group in society, as without them, everybody would still be using stone tools.
While there are no barriers to movement between the groups, such a thing is frowned upon, but accepted. An individual cannot be in two castes simultaneously, and will be pressured by members of both castes to give one of them up.
Each of the four castes elects a member to the Yoonie Council, which acts as the overall ruling body in Yoonie society. There are also individual councils within each of the group, making decisions specific to them. The national and caste councils don't share a remit, and any member of a group that is served on a caste cannot serve on the national council, and vice versa.
