1.75-Billion-Year-Old Fossils Prove Earliest Complex Life Were Seafloor Dwellers!

In a landmark study published in Science (June 2026), researchers have described exceptionally preserved 1.75-billion-year-old fossils from the McDermott Formation in northern Australia that represent the oldest known complex multicellular organisms — and they were firmly anchored to the ancient seafloor.

The fossils, named Benthosphaera australis, consist of centimeter-scale, frond-like structures with distinct holdfasts, branching filaments, and possible reproductive structures. High-resolution CT scans and geochemical analysis confirm they were benthic (seafloor-dwelling) eukaryotes that lived in shallow marine environments during the late Paleoproterozoic.

Lead author Dr. Erica Barlow (University of New South Wales) states: “These are not simple microbial mats. They show clear differentiation into holdfasts, stems, and fronds — the hallmark of true multicellularity. At 1.75 billion years old, they predate all previously accepted complex fossils by at least 150 million years.”

The discovery is significant because it demonstrates that complex multicellular life evolved in stable seafloor habitats rather than in the water column. The organisms appear to have been sessile filter-feeders or pH๏τosynthesizers, occupying a niche similar to later Ediacaran biota but vastly earlier.

This finding pushes back the timeline for the emergence of multicellularity and suggests that the transition from simple prokaryotes to complex eukaryotes occurred in benthic marine settings where oxygen levels were rising. It also challenges models that placed the origin of complex life much later, during the Neoproterozoic.

As more Paleoproterozoic sites are examined, these Australian fossils promise to rewrite the earliest chapters of eukaryotic evolution — proving that the first complex organisms were already sophisticated seafloor residents 1.75 billion years ago.