Researchers have uncovered a major fossil site in Canada’s Northwest Territories that could reshape scientific understanding of when sexual reproduction first appeared on Earth.
The fossils date to the Ediacaran Period, more than 500 million years ago, when some of the earliest large and complex organisms lived in ancient oceans. Scientists said the discovery may push back evidence of sexual reproduction and animal movement by 5 million to 10 million years.
The study was published in Science Advances and led by researchers from the American Museum of Natural History and Dartmouth. Researchers found more than 100 fossils in the Mackenzie Mountains on the traditional lands of the Sahtú Dene and Métis communities, which provided guidance and permission for access to the site.
Ancient fossils point to early reproduction
Among the most important discoveries was Funisia, a tube-shaped marine organism that lived in tightly packed clusters on the seafloor.
Researchers believe Funisia may provide the oldest known fossil evidence of sexual reproduction. Scientists said the organism likely reproduced by releasing sperm and eggs into the surrounding seawater, similar to the spawning behavior seen in modern corals.
Some fossils from the site are estimated to be about 567 million years old. That makes them significantly older than previously documented fossils from the White Sea assemblage, a major group of Ediacaran organisms previously known only from Europe, Asia, and Australia.
Researchers said the finding suggests sexual reproduction and other complex animal behaviors may have evolved far earlier than scientists once believed.
Early animals lived in ancient oceans
The fossil site also included several organisms never before identified in North America.
One of them was Dickinsonia, a flat-bodied organism that moved across the seafloor while likely absorbing nutrients through its underside. Researchers also uncovered Kimberella, an organism with a muscular foot used to scrape food from the ocean floor. Scientists widely interpret it as an early relative of mollusks.
Another fossil, Eoandromeda, may represent an ancient comb jelly with eight spiral-shaped arms. Ediacaran organisms lived before most animals evolved shells or bones, making their fossils extremely rare. Researchers said special environmental conditions were needed to preserve the soft-bodied impressions found at the site.
Deep-water origins may explain early evolution
The study also revealed that these organisms lived in deeper-water marine environments than previously recognized for the White Sea assemblage.
Researchers said the finding supports a growing theory that early animal evolution may have begun in stable offshore waters before later spreading into shallower coastal regions.
Scott Evans, lead author of the study and assistant curator of invertebrate paleontology at the American Museum of Natural History, said deep oceans may have provided stable conditions with fewer fluctuations in oxygen and temperature.
Researchers added that hundreds of feet of rock above the fossil-bearing layers may still contain undiscovered fossils, giving the remote Canadian site major potential for future discoveries about the origins of complex animal life on Earth.
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