We are using 87Sr/86Sr in dental enamel to investigate the birthplaces and migrations of 18th century enslaved Africans buried in NYC, but need to better understand, for modern populations, whether Sr isotopes in teeth match the landscape on which individuals lived when those teeth were developing. We are doing two studies to assess this question: (1) dental 87Sr/86Sr in childrens’ teeth from six Solis, Mexico villages (the site of a long-term Mexican government nutrition study) where the landscape comprises modern calc-alkaline lavas, and (2) in sheep bones, bedrock and streamwaters from Iceland, whose lavas approximate the planet’s low 87Sr/86Sr endmember. The Solis data are eye-opening: ranges in 87Sr/86Sr for groundwater, soils and bedrock match one another (0.7045 to 0.7055) but do not match the teeth. The teeth range from 0.7065 to 0.7085. a reflection of the tortilla-rich local diet and the Sr-rich CaO (from CaCO3) added to the cornmeal to improve its digestibility. These results underscore the need to assess the importance of exotic foods (e.g.: seafood) and food additives even in ancient time. Most of our analysed NYC burials with decoratively filed tooth modifications (an indication of birth in Africa) have 87Sr/86Sr much higher (up to 0.723) than NYC values (~0.7115) suggesting possible origins in the Rb-rich ancient cratons (high 87Sr/86Sr) of west Africa. Others burials, with values lower than the NYC value (near 0.709), may reflect a seafood Sr source, and/or origins in carbonate terrains in Africa or the New World or possibly origins in the less radiogenic (lower 87Sr/86Sr) volcanic islands of the Caribbean.