A newly discovered fossil site in southwest China is pushing back the known origins of animals, offering new insight into how complex life first emerged on Earth.
Researchers say the fossils show that many major animal groups evolved earlier than previously believed, before the start of the Cambrian Period. The findings suggest that the rise of complex animals was more gradual than the sudden burst once associated with early evolution.
The study was led by scientists from the Oxford University Museum of Natural History, the University of Oxford Department of Earth Sciences, and Yunnan University. It was published in the journal Science.
Earlier origins of animal life
For decades, scientists believed complex animals appeared during the Cambrian explosion around 535 million years ago. However, the new fossils show that this process had already begun at the end of the Ediacaran period.
The fossils, dated between 554 and 539 million years old, push the timeline of animal diversification back by at least 4 million years. Lead author Gaorong Li said the discovery fills a major gap in the fossil record and confirms that complex animals existed earlier than previously proven.
A transitional ecosystem captured in fossils
The fossils were found at the Jiangchuan Biota in Yunnan Province, where researchers recovered more than 700 specimens.
Scientists said the site captures a transitional ecosystem. It includes both simple Ediacaran organisms and early forms of animals linked to modern groups. Co-author Frankie Dunn said the fossils show a shift from flat, seafloor-bound life to organisms that moved through the water and fed actively.
Early ancestors of modern animals were identified
Among the most important discoveries were early members of deuterostomes, which later gave rise to vertebrates such as humans and fish. These fossils are the oldest known relatives of this group.
#Fossils from southwest China are rewriting the story of life on #Earth.
More than 700 specimens show complex animals existed millions of years earlier than thought—before the Cambrian explosion.
A major shift in evolution just got pushed back. pic.twitter.com/mJDBGXbddB
— Tom Marvolo Riddle (@tom_riddle2025) April 3, 2026
Researchers also identified early ancestors of modern starfish and acorn worms, part of the Ambulacraria. These organisms were attached to the seafloor and likely used tentacles to capture food.
Other fossils included worm-like bilaterians and possible early comb jellies. Many specimens showed unusual features not seen in known species from either the Ediacaran or Cambrian periods.
Co-author Luke Parry said the fossils reveal a key evolutionary transition, linking strange early life forms to animals that can be recognized today.
Fossils help resolve long-standing debate
The discovery helps address a long-running question in evolutionary biology. Genetic studies had suggested that animal groups evolved earlier than fossil evidence indicated, leading to a debate between “rocks” and “clocks.”
Researchers say the new fossils bring these lines of evidence into closer agreement by providing direct proof of early complex life.
Emily Mitchell of the University of Cambridge, who was not involved in the study, said the findings support the idea that a transitional stage must have existed before the Cambrian period.
Exceptional preservation reveals hidden details
The fossils are preserved as carbon-rich films, unlike most Ediacaran fossils, which appear as surface impressions. This rare type of preservation allows scientists to see fine anatomical details.
The preservation is similar to that seen at the Burgess Shale in Canada, one of the most important Cambrian fossil sites.
Co-author Ross Anderson said the lack of similar fossils at other sites may be due to preservation differences rather than their actual absence.
Years of fieldwork led to a breakthrough
The fossils were discovered by a team from Yunnan University, led by Peiyun Cong and Fan Wei, after nearly a decade of research.
Earlier work in eastern Yunnan had only revealed fossilized algae. Researchers said they eventually found sites where animal remains were preserved alongside plant life.
Professor Feng Tang of the Chinese Academy of Geological Sciences said the fossils provide strong evidence that diverse bilaterians existed at the end of the Ediacaran period.
Researchers say the discovery reshapes the timeline of early animal evolution and opens new questions about how complex life first developed.
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