Study Finds 1.7 Billion-Year-Old Eukaryotes Lived in Oxygenated Shallow Seas
Updated
Updated · Astrobiology News · May 23
Study Finds 1.7 Billion-Year-Old Eukaryotes Lived in Oxygenated Shallow Seas
3 articles · Updated · Astrobiology News · May 23
Nature-published research led by McGill and UC Santa Barbara says the earliest known eukaryotes inhabited oxygenated, near-shore seafloor environments about 1.7 billion years ago.
Rock chemistry from northern Australian fossils dated roughly 1.75 billion to 1.4 billion years ago showed oxygen-bearing seawater, using oxygen-sensitive elements such as iron to reconstruct the habitat.
The finding challenges the long-held view that early complex life evolved in oxygen-poor settings or drifted in the open ocean, instead pointing to benthic, aerobic lifestyles from an early stage.
Researchers said eukaryotes likely remained on the seafloor and did not spread widely into open oceans until about 1 billion years later, a shift that would have reshaped the biosphere.
If oxygen was key to complex life, why did our ancestors stay on the seafloor for another billion years?
Ancient rocks reveal our ancestors needed oxygen. What other secrets in stone could rewrite the story of life?
Does our oxygen-dependent origin mean the search for complex alien life on oxygen-poor worlds is futile?
Early Eukaryotes Thrived in Oxygenated Shallow Seas: Fossil and Geochemical Insights from Northern Australia
Overview
Recent research has revealed that the oldest well-accepted eukaryote fossils were found in the McArthur and Birrindudu basins of Australia's Northern Territory, dating back between 1.75 and 1.4 billion years ago. At that time, this region was a shallow inland sea with lagoons and mudflats, where oxygen was just starting to build up in the ocean, though atmospheric oxygen remained extremely low. These discoveries show that early eukaryotes thrived in coastal environments with some oxygen, offering new insights into the habitats and conditions that supported the rise of complex life on Earth.