Renata Netto spends a lot of time on beaches. The Brazilian scientist is an ichnologist, a specialist in the traces of ancient animal behaviors preserved in fossilized footprints, trackways, burrows, nests and other impressions. These “trace fossils” do not hold the animal itself, but a kind of geological memory of its presence on Earth, 60,000 or 600,000 or 600 million years ago. Many trace fossils are entombed in cliffs; the fragile fossils cannot come to the lab, so researchers must study them in the field.

In this episode, Renata recounts sharing beaches with surfers and bargaining for paving stones full of trace fossils. She describes the lost world of Earth’s first large multicellular life, the enigmatic Ediacaran Biota, which lived 635–542 million years ago, and the beauty of a shrimp burrow.