Fossils found in Canada, possibly 890 million years old, may be oldest sign of animal life on Earth


Writing in the journal Nature, Turner leaned on those recent discoveries to describe how the fossils may have formed when sponges, measuring a few millimeters to a centimeter across, became mineralized. The soft tissue was first to fossilize, encasing the 3-D network of collagen-like fibers that formed the sponge’s skeleton. Over time, these skeletal fibers decayed, leaving hollow tubules that filled up with calcite crystals.