The original question however was: How can we get from a uniform gas distribution to such an extremely clumpy system in the first place? This puzzling question has not be addressed here yet, at all.
I think it has --- see message #3.
I am not a physicist (don't worry, I'm sure several of 'em will turn up any minute now). But I think the point is this: a
perfectly uniform distribution of gas would indeed never become "clumpy". But this state is unstable: that is, any small deviation from perfect uniformity will be accentuated rather than reduced over time.
Edited by Dr Adequate, : No reason given.