I had a dream that there was this species of gigantic creature that lived natively in outer space. (It looked kind of like Tin Man. There was another TNG episode with a creature that lived in deep space. This thing looked more like that, but I can’t remember enough about it to look it up).
Anyway, we discovered that this creature could travel in time as well! I became very concerned. People didn’t understand my concern. After all, this creature looked so harmless. So I explained: My concern was evolution. Things that have an ability to increase their relative proportions will come to dominate. Normally, every species is competing to increase its proportional representation. But in the case of a time traveling species? Nobody else will have a chance! No matter how docile this specimen seemed, their descendants will come to dominate all of time and space, so that they will be the only species in all of existence!
My friend (I forget who was my companion in this dream) pointed out that some species co-evolve with others. For example, domestic corn will not try to kill us, because it is to their evolutionary advantage for us to increase, so that they can increase as well.
We went to the Time Travel Studies department at Michigan State University to talk to a professor about this. He suggested that we go back in time and set it up so that, even at the beginning of time, these space creatures had a symbiotic relationship with us. So we hitched a ride on one of these creatures and worked to set up a symbiotic relationship.
Then, we decided to come back to see if we had successfully protected the future. We came back to Earth to see what the differences were from what we remembered.
Everything seemed to be pretty much the same except that dogs made nests in trees.