What were the earliest known life forms on Earth?

The earliest known life forms on Earth may date back as far as 4.1 billion years based on graphite inside a single zircon grain from Australia. Direct fossil evidence includes stromatolites found in 3.48-billion-year-old geyserite, as well as various microfossils discovered in ancient rocks. These discoveries suggest life emerged shortly after the formation of Earth's oceans and are studied alongside analogous extreme ecosystems like hydrothermal vents.

What we know

• The earliest possible evidence of life on Earth is up to 4.1 billion years old, based on biologically fractionated graphite inside a single zircon grain from the Jack Hills range in Australia. [2] · medium confidence
• The earliest directly known life forms are stromatolite fossils found in 3.480-billion-year-old geyserite within the Dresser Formation of Western Australia. [2]
• Microfossils of microorganisms have been discovered in 3.465-billion-year-old Apex chert rocks and in 3.42 billion-year-old hydrothermal vent precipitates from Barberton, South Africa. [1, 2]
• Stratigraphic evidence of life includes 3.7-billion-year-old metasedimentary rocks containing graphite from the Isua Supracrustal Belt in Greenland. [2] · medium confidence

Still open

• Whether the graphite inside the 4.1-billion-year-old zircon grain is definitively of biological origin remains a subject of ongoing investigation.

Where to go next

• how it workedHow did stromatolites form?
• how we knowWhat are the oldest fossil sites on Earth?
• whenWhen did the oceans form on Earth?
• the bigger pictureWhat are extremophiles and hydrothermal vent ecosystems?
• an unexpected connectionHow do scientists search for extraterrestrial life?

Sources

• [1]earliest known life form (Wikidata Q29572919) · CC0 1.0
• [2]Earliest known life forms · CC BY-SA 4.0
• [3]Extraterrestrial life · CC BY-SA 4.0
• [4]Outline of life forms · CC BY-SA 4.0
• [5]Life on Earth · CC BY-SA 4.0