A Walk Through Time


Community Living

3500 Million Years Ago

The benefits of community life impress microbes early on. One microbe's waste in another's lunch. Eating, reproducing, and making waste are consistent features in the continual development of life. Microbial mats form richly layered ecosystems, and under the right conditions, these become stromatolite bacterial skyscrapers.

The blue-greens live in the top layers, slipping in and out of UV-light shielding sheaths to gather solar energy. Cyanobacteria produce prodigious amounts of food. "Consumer" bacteria, immune to oxygen, quickly join the cyanobacteria. Beneath them live mixed populations of consumers and producers, each possessing unique diets and tolerances for oxygen, light, and sulfides.

Top: This fossil stromatolite sings the benefits of bustling, layered microbial community life in Warrawoona, northwest Australia, 3,500 MYA. (Photograph by J. William Schopf)

Bottom: The living microbial mat is from Matanzas, Cuba. (Photograph by Peter Westbroek)

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