There was a long article about the utility of beauty in evolution; and why "beauty" exists, even if its evolutionary "advantage" is not manifest. The podcast seemed a bit rambling; a more mathematical view point seems to reconcile all that. No idea which fraction of that is BS
1) Mutations in observable properties of organisms happen (those can be traced back to genetic mutations, or othe underlying mechanisms: 'epigenetics' etc..)
2) Such mutations are likely to persist unless they lead to, or significantly contribute to, extinction. I.e. mutations are likely to persist if they are advantageous from a utalitarian perspective, but can persist also if they are neutral, or slightly (but non-traumatically) negative in that respect.
Diversity exists when a) it can originate; b) it does not lead to extinction.
3) The space of "organisms not bound for near-term extinction" is set by environmental boundary conditions that change with space and time. (Environment: both climate, location and "other organisms"). Evolution takes time, and hence the space of all survivable diversity is not fully filled.
