A team led by paleontologists at the American Museum of Natural History and Dartmouth College has uncovered more than 100 fossils in Canada’s Mackenzie Mountains after a decade of expeditions by helicopter and foot. The find is rewriting the earliest chapters of animal life, not because the animals are older than anyone thought, but because of where they lived.
The fossils belong to the Ediacara Biota, the strange, soft-bodied organisms that represent the first direct record of multicellular animal life on Earth. They date to roughly 567 million years ago and were found in a deep-water setting on the continental slope, persistently below storm wave base. That detail matters: this particular assemblage, known as the White Sea assemblage, had previously been documented only in shallow continental-shelf environments, and never before on the paleocontinent of Laurentia, the ancient core of North America.
A menagerie of squishy pioneers
Among the specimens are six groups never before recorded in North America. The most celebrated are the large, flat, mat-like Dickinsonia, which glided along the seafloor absorbing bacteria and algae through its underside, and Kimberella, a seafloor scraper with a muscular foot, considered an early relative of mollusks and potentially the oldest known fossil bilaterian, an animal with a front, back, and symmetrical sides.
The site also yielded Funisia dorothea, an immobile tube-dweller found in dense clusters, whose coordinated release of sperm and eggs into the water column provides the oldest fossil evidence of sexual reproduction. Trace fossils in the form of parallel grooves, known as Kimberichnus, record the grazing marks of moving animals. Together, the evidence pushes back the origins of animal movement and sexual reproduction by five to ten million years.
The age rests on rhenium-osmium geochronology of underlying formations, dated to 567.3 plus or minus 3.0 million years and 566.9 plus or minus 3.5 million years, combined with chemostratigraphic correlation. The expedition team, working with the Sahtu Dene and Metis, whose traditional lands include the site, cataloged the specimens at the Prince of Wales Northern Heritage Centre in Yellowknife.
A challenge to the textbook sequence
For decades, paleontologists have organized the Ediacara Biota into three successive assemblages, Avalon, White Sea, and Nama, presented as a tidy chronological handover. The new find blurs those boundaries. These White Sea fossils overlap in time with the older Avalon assemblage, meaning the two communities coexisted for millions of years rather than replacing one another.
The team argues the deep-water setting supports a pattern of offshore origination: complex animal life may have first evolved in stable, deep offshore waters, where temperature and oxygen were steady, and only later spread toward the shallows. That trajectory runs opposite to the pattern seen later in evolutionary history, when innovations typically appear in shallow water first.
The same group’s earlier work had hinted at this idea, but never with fossils of this quality from a deep-water Laurentian site. The find roughly doubles to quintuples the number of taxa documented in the Mackenzie Mountains region.
Why the caveats matter
The boldest claims rest on thin material. The only Kimberella specimen is a single, incomplete posterior fragment, and the authors themselves frame the oldest-bilaterian designation as tentative. The age of the fossil beds themselves is not directly measured; no radiometric date exists for the fossil horizon, so the 567-million-year figure depends on dating nearby layers and chemical correlation. Experts not involved in the study, including paleontologists at UC Riverside and Yale, called the deep-to-shallow trajectory unusual in animal history and said the find extends early animals deeper in time, but independent confirmation at other sites has not yet arrived.
The site is far from exhausted. Fossil-bearing layers continue for hundreds of meters (hundreds of feet) of rock across Yukon, the Northwest Territories, and British Columbia, and the team planned a new field season in British Columbia this summer. If the offshore-origination hypothesis holds, the next chapters of the animal story may be written in even deeper, older waters.
Sources
- Evans, S.D., Sperling, E.A., Lau, K.V., Strauss, J.V. “Discovery of White Sea assemblage fossils from Laurentia.” Science Advances 12(21): eaed9916 (2026). DOI: 10.1126/sciadv.aed9916
- AMNH press release, “Fossil Trove Expands Range of Squishy Early Animals,” May 20, 2026
- Dartmouth Faculty of Arts & Sciences, “Fossils Push Back Origins of Animal Movement by Millions of Years,” June 9, 2026
- Scientific American, May 20, 2026
- The Conversation / Phys.org, May 2026