Animals may have evolved vastly earlier than fossil evidence suggests

Key Points:

• A new study led by the University of Oxford suggests animals may have originated between 800 and 700 million years ago, far earlier than their first definitive fossils from around 590 million years ago in the Ediacaran period.
• Researchers analyzed exceptionally preserved microfossils from the Kheseen Biota in Mongolia, which, despite high-quality preservation and known animal presence elsewhere at that time, contained no identifiable animal fossils, challenging previous assumptions based on the Weng'an Biota fossil record.
• Molecular clock analysis, incorporating older fossil deposits and genetic data, supports an earlier animal origin, potentially predating or coinciding with the Cryogenian "Snowball Earth" glaciations, raising new questions about how extreme ice ages may have influenced early animal evolution.
• The study highlights that early animals were likely small, soft-bodied, and difficult to fossilize, suggesting their absence in older fossil records may be due to environmental and chemical preservation biases rather than their actual nonexistence.
• The researchers call for broader fossil searches across diverse environments and fossilization modes, integrating body fossils, trace fossils, and chemical biomarkers to better pinpoint the timing of animal origins, which remains uncertain.