"Now, everything we know about terrestrial life tells us that life has a natural tendency to expand into all available space."
At the same time, it makes sense that more advanced life will try to be more efficient with its use of resources. This is a lot easier to do when you're smaller. Perhaps, they would try to minimize their size, allowing them _expand_ into _smaller_ space.
I'm sure this thought has been considered (e.g., see Men in Black 1), but I felt like sharing it anyway.
At the same time, it makes sense that more advanced life will try to be more efficient with its use of resources. This is a lot easier to do when you're smaller. Perhaps, they would try to minimize their size, allowing them _expand_ into _smaller_ space.
I'm sure this thought has been considered (e.g., see Men in Black 1), but I felt like sharing it anyway.