Though not often considered a living fossil, cyanobacteria have been kicking around for practically forever and will continue to do so well into the future. In fact, like many other strains of bacteria, they're one of the most successful groups of organisms this planet has ever seen, and include some of the first life forms to evolve on Earth. Stromatolites — layered structures formed in shallow water by the trapping, binding, and cementation of microorganisms, especially cyanobacteria — provide the most ancient records of life on Earth dating back an astounding 3.5 billion years.