Evolution Thought

It has long been thought that organisms adapt to their environment, taking up certain ecological niches.  According to this train of thought, plants would adapt to utilize an untapped niche, feces.  It could then be hypothesized that plants evolved to utilize the nutrients found in the fecal matter.  What would that mean about other organisms?  Perhaps it was the organisms that adapted to the plants.  If an animal were to excrete a stool high in certain nutrients beneficial to plants, the local plants around the animal would grow in more abundance.  This increase in plant life could have then increased that animal's chance of survival by supply some sort of benefit, such as an increased food supply.  Over vast amounts of time, this relationship could have help nudge an animal's evolution in a certain direction.  Just a fun idea to ponder.