Fossils from Canada show animals moved and mated

A newly described trove of 567-million-year-old fossils from Canada’s MacKenzie Mountains pushes back when complex animals began moving and reproducing sexually. The findings, published in Science Advances, also point to the deep sea as a stable starting place

Snow-covered peaks in Canada’s remote Northwest Territories hide a very different world—one that existed more than half a billion years ago on an ancient seafloor. When researchers set out for the MacKenzie Mountains. the trip was long and unglamorous: a 14-hour drive followed by a helicopter flight to reach the fossil site.

It was a gamble worth taking. The team collected more than 100 fossils of soft-bodied creatures, many preserved as detailed imprints on slabs of mud-colored rock. Dated to 567 million years ago. the fossils mark a milestone that changes how scientists think about when complex animal life began to move and reproduce.

The study was described today in the journal Science Advances. and it centers on a set of creatures that look more like animals familiar to modern biology than the earliest Ediacaran forms long known from museum drawers. Lead author Scott Evans. a paleontologist at the American Museum of Natural History. points to the behavior the fossils suggest: “They move around. and some of them are reproducing sexually.”.

Among the best known is Dickinsonia. the frisbeelike early complex organism that lacked a mouth and instead absorbed bacteria and algae as it moved along the seafloor. Another is Kimberella, shaped like a teardrop, which scraped across the sea bottom and may be related to modern mollusks. The site also yielded Funisia—spongelike, tubular organisms that were among the first creatures to reproduce sexually.

For Funisia, the evidence points toward a reproductive strategy that would have required coordination in the water: scientists think these organisms sent sperm and eggs into the water column, much like today’s corals do.

That combination—movement plus sexual reproduction—pushes the timeline deeper than before. The fossils “extends early animals deeper in time. ” says Mary Droser. a paleontologist at the University of California. Riverside. who was not involved with the paper but is mentioned in its acknowledgments. Droser notes that the Ediacaran period has often been divided into distinct groupings of animals. beginning with simpler stationary species and then shifting to more complex creatures around 559 million years ago. These new fossils challenge that tidy separation. Instead, Droser says the new evidence shows that those animal groups lived side by side for millions of years.

There’s another question the fossils answer in the way rocks can: where did this early animal life begin?. The team argues that the deep sea wasn’t just where these creatures ended up—it was where they got started. Based on the site’s rocks. which do not preserve ripples or other signs of waves. the researchers posit that the area was once the ocean floor.

That matters because the early evolution of animals has been debated in terms of geography and pacing. Lidya Tarhan. a paleontologist at Yale University. who was not involved with the study. says the fossils support earlier hypotheses that proposed early life gradually moved from the deep to the shallows. But she also describes the deep-to-shallow trajectory as “unusual in the evolutionary history of animals.” In other words: if animals first emerged in a stable. cold. dark environment. it complicates the story of how quickly the rest of the ocean—and eventually other habitats—was colonized.

Evans offers a reason the deep sea could have been a better incubator than it sounds. The deep ocean, he says, has less variation in temperature and available oxygen than shallow environments. “That stability might have been a really great place for animals to first show up and evolve,” Evans says. “If you can figure out one temperature, you’re good to go.”.

Put together, the fossils do more than add new names to an old evolutionary timeline. They show that complex animal life—moving through sediment. scraping surfaces. absorbing food. and releasing sperm and eggs—was already happening at 567 million years ago. And they do it from a deep-sea setting where conditions would have been steadier than in waters battered by waves.

For scientists trying to reconstruct how the earliest animals lived, these slabs of ancient mud are more than remnants. They’re evidence of an early world where movement and mating were already part of the evolutionary experiment—one that seems to have started far from the bright shallows most people imagine when they picture life’s breakthrough moments.

Ediacaran early animals sexual reproduction deep sea Dickinsonia Kimberella Funisia MacKenzie Mountains Science Advances paleontology evolution