Overview
- A Nature paper analyzing microfossils from Australia’s McArthur and Birrindudu basins shows the oldest-known eukaryote fossils — about 1.7 billion years old — lived on oxygenated seafloors, implying mitochondria were present by that time.
- The Australian team matched fossil taxa to specific habitats using sedimentology and oxygen‑sensitive geochemical proxies such as iron, vanadium, molybdenum, uranium and pyrite and found deeper waters were largely anoxic and dominated by simple bacteria.
- A separate Science Advances report describes a diverse White Sea Ediacaran assemblage in Canada’s Mackenzie Mountains dated near 567 million years that includes Dickinsonia, Funisia and Kimberella and yields the oldest firm fossil evidence for animal locomotion and sexual reproduction.
- The Canadian fossils were preserved in deep‑water offshore sediments, supporting a model in which early animals first evolved in relatively stable, deeper marine environments before spreading shoreward.
- Researchers say both discoveries change habitat and timing assumptions about the rise of complex life but stress limits of soft‑tissue preservation and call for more field sampling, multiple geochemical proxies and continued collaboration with Indigenous stewards of the Canadian sites.