The origin of animals from a unicellular perspective

Metazoans appear to have evolved and diversified during an ~200 million year window (around 800-600 mya) during the Neoproterozoic Era. At this time, much of the Earth system was in flux - it included 70 million years of the global Snowball Earth glaciations, a massive influx of sediment and nutrients, and the rise of atmospheric oxygen. All of these have been proposed to be the cause of animal multicellularity but we do not know which, if any, of these earth system changes were important for the origin multicellularity. A unicellular prospect may help identify what was important for the origins of animals. The ecological changes that come with multicellularity involve changes in the dominant physics that the organisms experience. Here I explore what ecologically important shifts in physics occur due to the environmental changes occurring in the Neoproterozoic. Using the choanoflagellate Salpingoeca rosetta, I quantify how motility, feeding rates, and temperature-metabolic scaling, change as a function of temperature and viscosity and how their observed biology compares with a general mechanistic theory that shows how multicellularity can generate ecological advantages in high seawater viscosity. This work provides  some clues and testable hypotheses for how animal evolution could have proceeded during the time after their origin but prior to their fossil record.

Speaker: Carl Simpson, Stanford University

Attend in person or online (see weblinkj)