<p>As a mathematical demographer and statistician, I study systematic constraints and random influences that shape the structure of human populations. I am currently working on questions in the biodemography of longevity, building stochastic models to account for features of the patterns of rates of mortality at extreme ages shared between humans and other species. These include models grounded in evolutionary theories of senescence. I also work on a variety of problems that pose statistical challenges to demographers,including statistical adjustments to censuses and forecasts of kinship resources for the elderly, including effects of HIV/AIDS on elderly persons in Thailand and elsewhere. As former Chair of the Committee on Population of the National Research Council, I take an interest in forced migration, the demography of complex emergencies, and human rights. I serve on the Editorial Board of PNAS. During 2009-2010 I have been a Miller Professor in the Miller Institute for Basic Research in Science at UC Berkeley.</p>