Animal History May Be 200 Million Years Longer Than Thought

An Oxford-led study in Science Advances argues that the absence of animal fossils in Mongolia's Kheseen Biota does not prove animals were absent then, since the deposit preserves microfossils just as well as China's 590-million-year-old Weng'an Biota. Using older geological constraints, molecular clocks push the possible origin of animals back to 800–700 million years ago, into the Snowball Earth era.

• Mongolia's Kheseen Biota preserves microfossils as well as China's 590-million-year-old Weng'an deposit, yet contains no animals
• Researchers examined over 140 samples using scanning electron microscopy
• Molecular clocks constrained by 850–730-million-year-old deposits estimate animal origins at 800–700 million years ago
• Biomarkers suggest sponges existed at least 650 million years ago