All nitrogen does not come from the food we eat. Elemental nitrogen is inherent in the human body. Have vegetarian bone fragments been subjected to isotope measurements?
Wait, are you saying that we're born with a lifetime supply of nitrogen ?
Or that humans fix nitrogen from the atmosphere ?
No, but I am saying that Nitrogen is obviously an element of the human body for a reason. I.E evolutionary survival.
Wow, I am so glad somebody finally did it! You totally debunked all those idiot egg-head scientists using isotopic analysis. You better write the journal of Osteoarchaeology and let them know how misguided they have been for publishing all those flawed studies. I bet you will be the next Darwin, providing the scientific community with such valuable insight. I can't believe no one thought of it before, there isn't even controversy over the method. You have such a deep grasp of their research, I bet you will make them all look like fools.
Or maybe you have just have a confused understanding of an isotope. Lets go over the definition:
Stable isotopes are chemical isotopes that are not radioactive (they have not been observed to decay, though a few of them may be theoretically unstable with exceedingly long half-lives). By this definition, there are 256 known stable isotopes of the 80 elements, which have one or more stable nuclides. A list of these is given at the end of this article. About two thirds of the elements have more than one stable isotope. One element (tin) has ten stable isotopes.
Different isotopes of the same element (whether stable or unstable) have nearly the same chemical characteristics and therefore behave almost identically in biology (a notable exception is the isotopes of hydrogen—see heavy water). The mass differences, due to a difference in the number of neutrons, will result in partial separation of the light isotopes from the heavy isotopes during chemical reactions and during physical processes such as diffusion and vaporization. This process is called isotope fractionation. For example, the difference in mass between the two stable isotopes of hydrogen, 1H (1 proton, no neutron, also known as protium) and 2H (1 proton, 1 neutron, also known as deuterium) is almost 100%. Therefore, a significant fractionation will occur.
Commonly analysed stable isotopes include oxygen, carbon, nitrogen, hydrogen and sulfur. These isotope systems have been under investigation for many years in order to study processes of isotope fractionation in natural systems because they are relatively simple to measure. Recent advances in mass spectrometry (i.e. multiple-collector inductively coupled plasma mass spectrometry) now enable the measurement of heavier stable isotopes, such as iron, copper, zinc, molybdenum, etc.
Stable isotopes have been used in botanical and plant biological investigations for many years, and more and more ecological and biological studies are finding stable isotopes (mostly carbon, nitrogen and oxygen) to be extremely useful. Other workers have used oxygen isotopes to reconstruct historical atmospheric temperatures, making them important tools for climate research.
You see, there is such a thing as isotopic signatures, the distribution of certain stable isotopes (there are 256 known stable isotopes of the 80 elements) and chemical elements within chemical compounds. This can be applied to a food web to make it possible to draw direct inferences regarding diet, trophic level, and subsistence. Isotope ratios are measured using mass spectrometry, which separates the different isotopes of an element on the basis of their mass-to-charge ratio. Bone recovered from archaeological sites can be analyzed isotopically for information regarding diet and migration. Tooth enamel and soil surrounding or clinging to the remains may also be used in isotopic analysis. To obtain an accurate picture of palaeodiets, it is important to understand processes of diagenesis (no doubt something you have mastered) that may affect the original isotopic signal. Carbon and nitrogen isotope composition are used to reconstruct diet, and oxygen isotopes are used to determine geographic origin. Strontium and lead isotopes in teeth and bone can sometimes be used to reconstruct migration in human populations and cultural affinity.
Perhaps next time, instead of being so abrasive and rude, you could simply say, "Hey, I am having some trouble understanding how researchers use nitrogen isotopes to differentiate between food sources. Could someone explain it for me?" Those types of approaches tend to be better received.
Edited by Skotkonung, 15 December 2009 - 07:26 AM.