[Nate]

Bacterial life is already pretty simple, indeed, many organelles in eukaryote cells are bacteria-like structures and are probably descended from them. If life elsewhere in the universe arises like ours, bacterial life is most likely. Bacteria where the only form of life on Earth for nearly 3 billion years, while multicellular life has existed less than 600 million. Life arose very quickly on Earth, suggesting it is likely, or at least easily achievable under the right circumstances. Multicellular life, conversely, seems much less likely (though that may be more due to the time it takes for bacteria to prepare the atmosphere for more complex life).

How do we know the history of bacteria on Earth? Do monocellular blobs of jelly fossilize?!