Science
567-Million-Year-Old Fossils Rewrite the Story of When Animals First Moved and Reproduced
Every animal alive today — from jellyfish to hummingbirds to humans — traces its ancestry back to a mysterious group of soft-bodied organisms that lived on the ancient seafloor more than half a billion years ago. Now, a spectacular new fossil site in Canada's Northwest Territories is forcing scientists to rewrite the timeline of that early animal evolution. The fossils, dated to 567 million years old, push back the origins of animal movement and sexual reproduction by as much as 10 million years.
The discovery, published in Science Advances and led by researchers from the American Museum of Natural History, Dartmouth College, and the University of Oxford, comes from a remote site in the Mackenzie Mountains of Canada's Northwest Territories. The fossils belong to the Ediacaran biota — the first complex multicellular organisms to appear on Earth, which lived between 575 and 539 million years ago. What makes this particular find extraordinary is both its age and its environment: these organisms thrived in deep-water settings far below the reach of sunlight, suggesting that complex animal life may have originated in the deep ocean rather than in shallow coastal waters.
Three key facts about this discovery:
Evidence of movement 567 million years ago. Among the fossils are trace fossils — preserved tracks and burrows left by organisms moving across the seafloor. These are among the oldest unambiguous signs of animal locomotion ever found, indicating that even some of Earth's earliest animals were capable of deliberate, coordinated movement. The fossils show organisms that could crawl, burrow, and potentially feed by moving through microbial mats on the ocean floor, challenging the long-held assumption that Ediacaran organisms were mostly stationary filter-feeders.
Sexual reproduction earlier than thought. Some of the fossils display features consistent with reproductive structures, including what appear to be propagules — small offspring that budded off from parent organisms. This suggests that sexual or asexual reproduction was already well established among Ediacaran communities, pushing back the evolutionary timeline for complex reproductive strategies by millions of years. The fossils include rangeomorphs and frond-like organisms that show clear size gradients and clustering patterns consistent with population-level reproduction.
Deep-water setting changes the narrative. Perhaps most significantly, these fossils were preserved in sediments deposited in deep water — hundreds of meters below the ocean surface, in an environment far from sunlight. Most previously known Ediacaran fossil sites represent shallow-water environments. The fact that such complex ecosystems existed in the deep ocean suggests that early animal diversification was not limited to sunlit coastal zones, and that the deep ocean may have been a crucible for early animal evolution. The site preserves multiple generations of organisms in life position, giving paleontologists an unprecedented window into how Earth's first animal communities were structured.