An Emotional Response
The vast majority of life works just fine with sensors hooked up to instant responses, the ‘deep troughs’ that keep things going. It’s not very complex or flexible though, and certainly favors stability over mobility.
The next step is to add a layer that reacts to situations before they fully manifest. This distributed layer is awesome because it adds a dimension that hasn’t been present before: anticipation.
A scent in the water? That correlates with (thank you DNA) food! Make that scent stronger and you’ll find dinner.
Most folks call this emotions and it runs deep. These are the depths of the ocean of intelligences because it is a body-wide adaptation, present in the vast majority of complex systems that make up an organism.
An interesting thing about emotion is that it can cause bodily changes without actually encountering the thing. So fear of fire can cause the heart to race, even if you only smell smoke. And if done long enough, or severe enough, epigenetic alterations in the deep troughs can occur.