Imagine that we are trying to work out how to move to other planets and how to live for millions of years. Now consider that the entire genetic blueprint for a human would fit inside an organism the size of a bacteria. A human egg cell is about the diameter of a human hair, 100 microns, but a human sperm head is about 5 microns. That sperm cell head at 5 microns contains all the genetic code of a complete intelligent adult human. Also in the range of .2 to 5 microns: Bacteria.
My idea is that a very advanced alien race could have invented the first bacteria that arrived on earth as a way to transport themselves to another world. Bacteria, which can live in space, survive radiation and near zero temperatures and can survive dormant as spores for 25 million years, repair their DNA and reproduce, would be like alien super sperm. Under the right conditions, as does a 5 micron human sperm cell, they grow into some large intelligent life form, perhaps the Grey aliens in the movies, or something with a form best adapted to the current environment.
Bacteria share genetic information (they learn) so we may just be in the phase where they are learning the best traits of life on this planet before they germinate into a new creature that takes over the planet.
Next step: I’d like a look at the genetic code of the oldest bacteria we’ve found.