My research characterizes molecular and isotopic compositions of sedimentary organic matter as a tool for reconstructing ancient environmental conditions.  My current projects utilize carbon and deuterium signatures of biomarkers - the molecular remains of algae and plants - to trace hydroclimate and ecosystem fragmentation in eastern Africa during major junctures in human evolution, ca. 6-to-1 million years ago.  In tropical lake systems, deuterium composition of biomarkers reflects local water cycle dynamics, which in turn are sensitive to seasonality, precipitation intensity and monsoon circulation.  Carbon isotope compositions are also linked to hydroclimate through the influences of water on plant community composition and structure.  Recently, I have become interested in the utility of ‘landscape biomarkers’ – such as n-alkylresorcinols – preserved in ancient soils towards mapping wetland environments and spatial distributions of water.  This quantitative approach to environmental reconstruction may provide powerful insights into the immediate selective pressures experienced by early humans.