Marine life forms that subsisted on Earth 3 billion years ago have been unearthed in Australia. In the Farrell Quartzite in Pilbara Craton in the northwestern part of the country, a team of researchers led by Christopher House from Pennsylvania State University found groups of tiny plankton.
Two types of microplankton were found in the Australian sediment: some shaped like spindles, and others that had spheroidal morphology—like elliptical spheres. They were between 20 and 60 microns long, which, although very tiny—as small as a grain of sand—represents an usually large and complex form of life for being so ancient. Today’s microplankton, living 3 billion years later, are around the same size.
House and colleagues used carbon isotope ratios to determine that the microfossils were in fact biologically viable—they weren’t simply inorganic matter that appeared to be fossils; they were once metabolic forms of life. The microfossils were most likely tiny autotrophic plankton—they could make organic compounds necessary for life out of inorganic sources and didn’t have to depend on the availability of certain compounds that others are limited by for survival. They lived in an ocean that once covered the land in which their remains were discovered.
Other spindle-like microplankton have been discovered from 3.4 billion years ago from different areas on Earth, including South Africa and other areas of Australia—indicating that this body plan remained consistent for a very long period of time. Not only that, but it spread out across the world as once of the oldest and most stable and sustainable forms of life.
Read more about this ancient microplankton in the journal Geology.
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