The only known? I guess the problem is that "socialism" means a billion things to people, from "don't be so greedy all the time and help others out" to "specific governments Eastern Europe etc.". But I don't even buy that early Christians were the first example of that, I think exploitation is the invention, not socialism. Anyway, open source software is really just an example of this:
> If nature has made any one thing less susceptible than all others of exclusive property, it is the action of the thinking power called an idea, which an individual may exclusively possess as long as he keeps it to himself; but the moment it is divulged, it forces itself into the possession of every one, and the receiver cannot dispossess himself of it. Its peculiar character, too, is that no one possesses the less, because every other possesses the whole of it. He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. That ideas should freely spread from one to another over the globe, for the moral and mutual instruction of man, and improvement of his condition, seems to have been peculiarly and benevolently designed by nature, when she made them, like fire, expansible over all space, without lessening their density in any point, and like the air in which we breathe, move, and have our physical being, incapable of confinement or exclusive appropriation. Inventions then cannot, in nature, be a subject of property.
-- Thomas Jefferson, letter to Isaac McPherson (13 Aug. 1813)
And if you look at the date you'll notice these thoughts are real old hats :P Doesn't take away from them of course, to the contrary... it's about time we actually implement the wisdom we have. But let's not think any of it is or should be new.