The Extremists

4000 MYA

Bacteria are Earth's first life forms. They continue to dominate environmental evolution in the twentieth century. Ancient bacteria (archae) thrive in extreme environments typical of Archaen (early) Earth.

Heat- and acid-loving microbes flourish in boiling muds, hot springs, deep-sea vents, and ash ejecting volcanoes. Some loll in waters as hot as 113 degrees C [230 degrees F]. Some freeze at temperatures as high as 55 degrees C [131 degrees F]! Some bacteria abide in pools of concentrated sulfuric acid.

Twentieth-century microbial methane makers thrive in oxygen-free sediments inside animals and in sewage. Producing all the methane in Earth's atmosphere, these bacteria help prevent oxygen levels from reaching an explosive concentration.

Top: Extremists bask in this sulfuric-acid-rich river, Rio Tinto, Huelva, Spain. (Photograph by Annabel Lopez © Ricardo Amils)

Bottom: Extremist microbes inside tube worms form the cornerstone of this 20th century deep-sea hydrothermal vent system. (Photograph courtesy JASON Foundation for Education)

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