How Bacteria Nearly Destroyed All Life

From by Alan Bellows.


The sea was host to a plethora of anaerobic microorganisms, but there were also a few members of a newly evolved variety: cyanobacteria. These adapted bacteria were the first to use water and sunlight for photosynthesis, producing oxygen as a by-product of their metabolism.

The cyanobacteria were a struggling minority at first, but scientists believe that these new microbes began to dominate with the help of meltwater from a few glaciers scattered across the young continents. These glaciers spent centuries scraping across the Earth collecting minerals, ultimately depositing their rich nutrient payloads into the oceans. The cyanobacteria flourished in the presence of the increased minerals, and the rapidly growing population was soon venting increasingly large amounts of its poisonous waste oxygen into the environment.

The underwater oxygen began to chemically react with the abundant iron, eventually scrubbing the seas clean of the element through oxidation. This series of developments was nothing short of an ecological disaster– oxygen was poisonous to most of primitive Earth's inhabitants, and many bacteria relied on the iron as a nutrient.

Once the oceans' supply of iron was exhausted, oxygen began to seep from the sea into the air. The free oxygen they produced reacted with the air, gradually breaking down the methane which kept the Earth's atmosphere warm and accommodating. It took at least a hundred thousand years– a short duration in geological terms– but the Earth was eventually stripped of her methane, and with it her ability to store the heat from the sun. Temperatures fell well below freezing worldwide, and a thick layer of ice began to encase the oxygen-saturated planet.

Almost every living thing on Earth died as a result of this massive bacteria-induced climate change, an event known as the oxygen catastrophe.

The survivors of the oxygen catastrophe eventually adapted to consume the abundant oxygen and produce carbon dioxide. This greenhouse gas very gradually made its way into the atmosphere, increasing in concentration and nudging temperatures back into the hospitable range over millions of years.


One man's meat is another man's poison. Just a line separates life from death.


blog comments powered by Disqus