In which eon did single-celled organisms first form on Earth?
Biology · High School · Thu Feb 04 2021
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Single-celled organisms first appeared on Earth during the Archean Eon. The Archean Eon spans from about 4 billion years ago to 2.5 billion years ago. The earliest evidence of life, which includes fossil remains of single-celled microorganisms, dates from approximately 3.5 billion years ago. These single-celled forms of life are known as prokaryotes, which include bacteria and archaea.