I suppose I'll add a little more to the caste system. Plato's Republic gives us the basic timarchy (caste society). It's pretty rudimentary but surprisingly realistic. Instead of paining myself to create my own, I'll build off of Plato's.
Let's start at the top and work our way down, shall we?
At the top of the pyramid we have the Master caste (for lack of a better name). Early on in it's development the best of human genetics worm their way into the ruling class and blossom. Eugenic morals and beliefs have always been more prevelant in rich people. This would be further aided by the advancing genetics market, allowing one's genes to be tweaked, and later on replaced. As technology progressed, cybernetics make their way onto the comercial market. Of course, this sort of technology and the procedures to install it would be hideuosly expensive and only available to the extremely wealthy. Give this trend a few hundred years and the ruling class are a superhuman amalgam of man and machine free from the constraints of an aging body. With all these resources at their disposal, the Master Caste would be the pinacles of physical beauty, atheleticism, inteligence, and just about every sort of human attribute ad naseum. This isn't to say that they would be without fault. Materialims would run rampant among the Masters. Everyone of them would have their own treasure trove, every part of which is disposable. To them everything is a comodity and nothing is sacred. For example, starting a family would require no more than a visit to a designer baby parlor. With this sort of materialism comes obscene greed, and with greed comes conflicts over just about every social schism imaginable. This would be one of the leading factors for the Fall. Enough on them for now.
The next rung down is the Guardian Caste. These are the super hero's of civilization: Soldiers, police, rescuers, etc. This caste would enjoy just about all the physical benefits of the Master Caste (top genetics, cybernetics), with one exception; This Caste would have been created by the master caste, and thus would have limited free will. They follow the orders of their commanding officers and superior officials to the fullest extent of their abilities and without question.
Then we move down to the Logistics Caste. Today's data entry nerds, systems administrators, cubical slaves, accountants and their contemporaries are the ancestors of this group. Just plain old human genetics here, and nothing fancy like cybernetics. Only excelent clerks bred for centuries to punch numbers and file records.
On a slightly lower level than the Logicians is the Artisan Caste. Here is where we find the galaxy's craftsmen, artists, drivers, and every other average joe. This is the largest caste, composing about 60% of the galactic population. It is comparatively as diverse and dynamic as todays general public.
And finaly at the bottom of the social structure is the Labor Caste. This group does all of the work that is excessively dirty, dangerous, and exhausting. All of the Laborers are genejacks; genetically altered to work as hard as possible for as long as possible. Their work is their life. They are incapable of forming a personality, interacting socially, conceiving emotion, or feeling pain. Their job is all they know.
This again, can be built on and altered. But for now it's a good working guidline.
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