These bizarre fossils represent some of the earliest moving, sexually reproducing life ever discovered

These unusual fossils are among the earliest evidence of moving, sexually reproducing life forms.

By Jack Tamisiea edited by Sarah Lewin Frasier

Currently, the remote Northwest Territories in Canada are blanketed with snow-covered mountains. However, over half a billion years ago, this region was an ancient seabed housing a variety of Earth’s earliest complex life forms, including wrinkled pancake-like creatures, fleshy fronds, and spiral-shaped organisms.

Recently, researchers uncovered a significant collection of fossils that challenge our understanding of when these extraordinary creatures emerged in evolutionary history. Detailed in the journal Science Advances, these fossils also hint that the deep sea may have been the nurturing environment for complex life.

Discovered in Canada’s MacKenzie Mountains, these fossils offer a rare glimpse into the Ediacaran period, which predates the Cambrian explosion of life. To access the site, lead author Scott Evans, a paleontologist at the American Museum of Natural History, and his team underwent a 14-hour drive followed by a helicopter journey.

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Although the journey to retrieve the fossils was challenging, the findings were invaluable. The team gathered over 100 fossils of peculiar, soft-bodied organisms that mark key stages in life’s evolution. According to Evans, these fossils resemble animals more familiar to us today. “They move around, and some of them reproduce sexually,” he explains.

Among these ancient organisms were Dickinsonia, which ingested algae through its underside without a mouth, and Kimberella, a creature that scoured the seafloor and may have ties to modern mollusks. The site also contained fossils of Funisia, spongelike tubular entities that were some of the first to reproduce sexually, likely by releasing sperm and eggs into the water like contemporary corals.

These fossils date back 567 million years, pushing the timeline of early animals further back. Mary Droser, a paleontologist at the University of California, Riverside, who was acknowledged in the study but not directly involved, points out that the Ediacaran has traditionally been seen as having distinct animal groupings, with simpler stationary species giving way to more complex life forms around 559 million years ago. This new evidence, however, shows that these groups coexisted for millions of years.

This site also provides vital environmental context for the emergence of early animals. The lack of wave-induced ripples in the rocks suggests that this area might have been the ocean floor.

The evidence from this site supports the idea that the first animals emerged in deep-sea settings, according to Lidya Tarhan, a Yale University paleontologist not part of the study. She suggests that these fossils back earlier theories that life gradually transitioned from deep waters to shallower regions, which is considered atypical in the evolution of animals.

While the ocean’s deep areas may seem harsh due to their cold and dark conditions, Evans notes that the deep sea is more stable in terms of temperature and oxygen levels compared to shallower waters. “That stability might have been an ideal place for animals to first appear and evolve,” Evans comments. “If you can find one constant temperature, you’re set.”

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