“We only know a tiny proportion about the complexity of the natural world. Wherever you look, there are still things we don’t know about and don’t understand...”

― David Attenborough

Exciting things happen because there are so very many pieces to the jigsaw puzzle that is nature. Networks and hierarchies, structures and processes are all conjured into being over eons of time. There are no simple scripts to make this happen. The sheer complexity of the interactions between such large numbers of individual parts of a natural system, creates structure. And this is just as true of your immune system as it is of a rain forest. This 'technology' is everywhere about us. 

A lovely example of this way of looking at the world, is the story of the re-introduction of the wolf to Yellowstone National Park. Far from wiping out all prey species, the presence of the wolves beneficially reorganised the entire area - trees, rivers, animals  were all affected. You can see a video about it here.