Tracking human travel using stable oxygen and hydrogen isotope analyses of hair and urine

Abstract

The stable oxygen and hydrogen isotope compositions of organic samples are increasingly being used to investigate patterns of animal migration. Relatively few studies have applied these techniques to modern humans, despite a variety of potential forensic applications. We analyzed drinking water and food at two geographic locations, East Greenbush, New York (USA) and Fairbanks, Alaska (USA), with different delta(18)O and deltaD values for precipitation and tap water. Foods varied widely in measured delta(18)O and deltaD values, but not systematically by purchase location. We measured delta(18)O and deltaD values of scalp hair from five residents at each location. We used a mixing model to establish the proportion of oxygen and hydrogen in head hair derived from drinking water ( approximately 27% and approximately 36%, respectively). Finally, we analyzed the delta(18)O and deltaD values of facial hair and urine from a subject who traveled from Fairbanks to East Greenbush, on to the UK and back to Fairbanks. Urine delta(18)O and deltaD values responded immediately and strongly to travel-related change in drinking water, and were well described by a single-pool turnover model. Beard hair delta(18)O values tracked changes in urine delta(18)O closely, and oscillated between the values for the resident populations in both locations. In contrast, beard hair deltaD values did not track changes in urine deltaD as well, and retained a signature of the traveler's permanent residence. Our findings show that the delta(18)O and deltaD values of urine and facial hair (specifically delta(18)O) can provide a record of the geographical movements of humans.