# Scientists Find Oldest Known Eukaryote Fossils, 1.75 Billion Years Old, in Australian Rock Cores

*2026-09-27 22:00 UTC · Science · 1 min read*

> A 1.75-billion-year-old cache of over 12,000 microfossils from Australia shows early complex cells lived only where oxygen was present, the oldest known eukaryote fossils on record.

Researchers led by Maxwell Lechte and Leigh Anne Riedman, publishing in Nature, examined mudstone drill cores from hundreds of meters below Australia's Northern Territory and identified more than 12,000 microfossils. The oldest date back 1.75 billion years, making them the oldest confirmed eukaryote fossils on Earth.

The team dissolved the rock samples and examined the organic residue under a microscope, cross-checking it against chemical indicators of ancient oxygen levels. Eukaryote fossils turned up only in samples from oxygen-rich settings, ranging from coastal mudflats to the open sea, while oxygen-poor layers held nothing but simple prokaryotic microbes.

The pattern backs a long-standing hypothesis that oxygen availability was the trigger for the evolutionary leap from simple to complex cells, addressing a puzzle about how all complex life, including humans, ultimately got its start.

## Sources

- [sciencedaily.com](https://www.sciencedaily.com/releases/2026/09/260925005447.htm)

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TechTools News · https://techtools.cz/tools/news/article/2451-scientists-find-oldest-known-eukaryote-fossils-1-75-billion-years-old-in
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