I'm fascinated by the earliest stages of cell evolution, including the origins of bacteria, archaea, eukaryotes, and the relationships between them. I am applying phylogenetic and comparative genomic approaches to reconstruct the common ancestors of these groups and to draw inferences about the conditions in which they evolved on the early Earth. Working back from modern genomes to understand ancient events challenges current methods to their limits, and so I work with statisticians to develop and apply new approaches that bring new kinds of data to bear on these challenging problems. These methods include non-stationary and non-reversible substitution models, which enable the root of a phylogenetic tree to be inferred as an integral part of the analysis. They also include probabilistic supertree and gene tree-species tree reconciliation approaches, which promise to harness genome-wide evolutionary patterns to resolve the most ancient parts of the tree of life.