Fossils from South Australia are offering a surprising clue about the deep history of animal behavior.
Spriggina floundersi, an ancient organism that lived about 550 million years ago, may represent the oldest known example of "right-handedness" in animals, suggesting a preference for turning right emerged long before hands, feet, or widespread complex body plans.
What happened?
According to research published in the journal Scientific Reports, Spriggina floundersi may preserve the earliest identified sign of population-level handedness in animals. The study involved scientists from the American Museum of Natural History, Florida State University, Harvard University, and the University of California, Riverside, and was highlighted by Neuroscience News.
The evidence comes from Nilpena Ediacara National Park, where storms buried ancient seafloor communities and left them preserved in exceptional detail. Among the fossils at the site is Spriggina, an early bilaterally symmetrical animal with clearly defined left and right sides.
To test for a directional bias, the team compared shape differences in more than 100 exceptionally preserved specimens. About twice as many impressions looked bent to the left as to the right. Because the fossils are preserved as mirror images, however, a leftward bend in stone corresponds to an animal that would have bent right while alive.
Lead author Scott Evans, assistant curator of invertebrate paleontology at the American Museum of Natural History, described why the result matters.
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"When we talk about being right-or-left-handed, most people likely think about how they hold a pencil or kick a soccer ball," he said. "But our research shows that an animal without hands or feet, living over 500 million years ago, may have had its own version of handedness."
Why does it matter?
The discovery pushes a familiar trait much deeper into Earth's history. Handedness is often associated with humans and other modern animals, but this research suggests left-right behavioral bias may have much older evolutionary roots.
That could help scientists better understand how early animal bodies and behaviors developed during the Ediacaran Period, a pivotal era before the Cambrian explosion expanded life on Earth.
If one of these simple early animals consistently favored one side, it would suggest that biological asymmetry was already playing an important role in evolution.
The findings also offer a clearer picture of how life became more complex over time. Traits that seem ordinary today — from body symmetry to directional movement preferences — may have been emerging hundreds of millions of years before dinosaurs or mammals existed.
What's being done?
Scientists are continuing to use exceptionally preserved fossil beds to reconstruct how Earth's earliest animals lived. Sites such as Nilpena are especially valuable because they preserve entire communities buried in place, allowing researchers to study not only anatomy but also posture, movement, and ecological relationships.
By comparing large numbers of fossils rather than relying on a single unusual specimen, scientists can better determine whether a pattern reflects biology rather than chance. In this case, examining more than 100 Spriggina fossils strengthened the case for a true rightward preference across the population.
Protecting fossil-rich landscapes and supporting basic scientific work can help preserve evidence that answers major questions about how life evolved.
"It's a reminder that some of the traits we take for granted today have incredibly ancient origins," said study coauthor Mary Droser, a paleontologist at UC Riverside.
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