Discovery Pushes Back Complex Animal Origins by 4 Million Years

Scientists have uncovered more than 700 fossils in southwestern China's Yunnan Province that reveal complex animal life emerged at least four million years earlier than previously thought, during the late Ediacaran period around 539 million years ago. The discovery, from a site known as the Jiangchuan Biota, shows a diverse ecosystem of early animals with features once believed to appear only in the subsequent Cambrian explosion.

The research, conducted by teams from Oxford University's Museum of Natural History and Department of Earth Sciences, along with Yunnan University, was published on April 2, 2026, in the journal Science. For decades, experts had dated the rapid diversification of complex animals to the Cambrian period, starting about 535 million years ago, when simple, flat organisms evolved into three-dimensional forms capable of active movement and predation. These new fossils, dating from 554 to 539 million years ago, indicate that many major animal groups, including bilaterians with bilateral symmetry and early relatives of modern vertebrates, had already begun evolving.

Among the specimens are wormlike creatures anchored to the seafloor by stalks and discs, some...