The Fossil Record of Animal Behavior and Cognition across the Phanerozoic
thesisposted on 2020-12-01, 00:00 authored by Shin-nan (Shannon) Hsieh
The way animals interact with physical and biotic environments is heavily mediated through their behavior. Behavior is in turn dependent on cognition – the ability to respond to and use information. The origins and evolution of cognition and behavior are of intense interest to biologists, but behavioral biology has only recently been integrated with paleontology. This thesis ties together several case studies in how the fossil record informs our understanding of animal behavior and cognition through the broad swath of its history. First, I examine the rise of cognitive complexity as viewed through nervous system and sensory system anatomy, and its associated behavioral sophistication beginning in the Cambrian. I also compare how cognitively complex Cambrian ecosystems were compared to later ones, as well as which life modes are most associated with cognitive complexity. Second, I survey the representation of animal behavior based on the paleontological literature, analyzing which major behavioral categories and which animal taxa are disproportionately overrepresented in the record. The theoretical reasons why they might be represented are also discussed. Next, I focus on a particular form of evidence for past behaviors left after the behavior-producers are no longer present – trace fossils, such as burrows and tracks. I review and discuss a specific type of behavior, farming in non-human organisms, viewed through the lens of trace fossils and their modern analogues. Lastly, I experimentally examine, using marine snails on an intertidal mudflat, if surface locomotion trails can be used as a reliable predictor of the population of trace-making animals that produced them.