1. A method for reconstructing a travel history for an individual, comprising: collecting a sample of breath exhaled by the individual; analyzing the sample to obtain a breath isotope ratio for at least one isotope; transforming the breath isotope ratio to a body water isotope ratio; and determining a travel origin by comparing the body water isotope ratio to a map model that correlates body water isotope ratios to geographic locations, said map model using at least one isotope source input associated with the geographic locations.