You know, the concepts behind evolution are, by no means limited to Genetic Replicators (genes).
Anything that can in any way affect the probability of more of them existing in the future is subject to the same evolutionary forces.
If there is a pattern that people tend to find aesthetically pleasing, then it is more likely to be imitated.
Ideas can spread and evolve.
I believe that Religion is one of the best examples of a meme (evolving idea) that I can think of.
Much of the complexity of the universe comes from two thing.
The first is what I just explained: essentially evolutionary pressures shaping (if not as the only factor, as a major one at lease) virtually everything.
There are an infinite number of internally consistent sets of laws of physics. There is a limited number of simple ones, so statistically, a very complex system will exist in any given universe. The laws of physics are astoundingly complex, but all this complexity, coupled with its massive size, and extremely massive amount of time that all the different forces and pressures have had, extreme complexity is bound to emerge.