I study foundational questions in evolutionary theory, by building toy models to incorporate mechanistic phenomena within population genetic models, and by applying model insights to bioinformatic data. Two of my central research interests are i) the robustness and evolvability of biological systems, and ii) how best to describe fitness in a density-dependent and frequency-dependent world. Specific systems include prions, evolutionary capacitance, the evolution of error rates, and the birth of protein-coding sequences from non-coding DNA. I am especially interested in the error-prone nature of molecular (eg transcription, translation, folding) and other developmental processes. Errors in the present can mimic future mutations, and so when selection against the consequences of present errors is strong, this changes the distribution of possible mutations in ways that can have profound consequences. I am also interested in the tension between relative and absolute contests.