The seven percent difference between the stable carbon isotope ratios for the marine and the terrestrial carbon reservoirs is found to persist throughout the food chains on Canada's Pacific coast. Therefore, a measurement of the delta ¹³C values for ancient human collagen gives a direct determination of the relative amounts of marine and terrestrial foods consumed by an individual. Preliminary results suggest that a similar difference exists between the ¹⁵N values of the marine and terrestrial food chains, and that this difference is also passed on to the human consumer.