Hierarchical random walks in trace fossils and the origin of optimal search behavior

How best to search for food in heterogeneous landscapes is a universal problem facing mobile organisms. Diverse modern animals use a random search strategy called a Lévy walk, composed of many small move steps interspersed by rare long steps, which theoretically is optimal for locating sparse resources. Here, we find the first evidence, to our knowledge, that extinct animals, in this case 50 My-old sea urchins, used a Lévy-like search strategy. Our results are important because they indicate Lévy walks likely have an ancient origin and may arise from simple behaviors observed in much older fossil trails. This foraging strategy may have adapted in response to decreased food availability after productivity collapse associated with past climate change and mass extinctions.