Note that ratios are generally higher in the marine system

In arid areas, where rainfall is less than about 400 nun per annum, terrestrial systems, too, may yield elevated d N. 

Carbon and nitrogen isotope analyses today are a routine part of the study of human skeletal remains. They are usually calculated along with radiocarbon measurements at dating laboratories. There are other isotopes that may also be of interest in the study of diet such as hydrogen and sulfur, but these are less well understood. 

There are other methods for investigating past diet as well and our first example discussed below illustrated one of them - the use of antigen-antibody reactions. This is a very special case where the preservation of unusual human remains makes possible the preservation of proteins that reveal evidence for cannibalism. 

Marlar, R.A., B.L. Leonard, B.R. BiUman, P.M. Lambert, J.E. Marlar. 2000. Biochemical evidence of cannibalism at a prehistoric Puebloan site in southwestern Colorado. Nature 407 25-26. 

Cannibalism is an emotionally charged topic. Because of strict cultural taboos against cannibalism, many people do not want to believe it was practiced in the past in spite of the fact that there are a number of historically documented examples from various places around the globe. 

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Fig. 7.11 Carbon and nitrogen isotopes in terrestrial and marine food chains. Note that ratios are generally higher in the marine system...

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