PHOSPHORUS LEVELS PREDICT GENOMIC NOVELTY PRODUCTION IN THE NEOPROTEROZOIC: A PRELIMINARY MATHEMATICAL MODEL

To estimate the likelihood of complex life on other planets, we need to understand the processes responsible for the evolution of animals. However, while several studies have investigated potential environmental and genomic catalysts for metazoan evolution, the interplay of these factors has been less explored. In particular, it remains difficult to quantify how environmental factors modulate rates of genomic evolution. Here we describe a preliminary mathematical model that predicts rates of genomic change as a function of nutrient concentration and correlated changes in primary productivity and ecosystem structure. Model parameters (including microbial cell density, cell diameter, genome size, and viral load) were averaged and bracketed using work from previous studies. Initial model outputs—driven by recently estimated phosphorus concentrations—suggest an approximately ten-fold change in genomic novelty production rates before and after the Cryogenian. Our model implies that genomic change in a given microbial population, per unit volume per unit time, should increase as a function of phosphorus concentration. This finding supports the role of a changing phosphorus cycle in the evolution of complex eukaryotes, and provides a key step in modeling the interplay between the geochemical and genomic drivers of macroevolutionary change in deep time. Similar models could use geochemical cues to predict maximum rates of genomic change on other planets, facilitating the search for complex extraterrestrial life.