But it is the organism which builds the shell, not the shell that builds the organism. In theory I don't see why an organism couldn't at least produce an iron shell in the same way, but I don't presume that is at all correct. The lack of iron shelled organisms would suggest that there is some other reason. When you say that it's just because it was easier for things to evolve the way they did, I don't see any difference between that and what I am saying, which is that biological quality experiences may not be so easy or even possible to access without biology as it has actually evolved. Craig > > -- > Stathis Papaioannou > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To view this discussion on the web visit https://groups.google.com/d/msg/everything-list/-/1MMcAZANCDcJ. To post to this group, send email to firstname.lastname@example.org. To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/everything-list?hl=en.