Isotopes are different forms of the same chemical element. For example, three types of carbon are different isotopes because they have different numbers of neutrons in their atomic nuclei. Thus the common form of carbon is carbon-12, with six protons and six neutrons in its nucleus; the rarer carbon-13 has six protons and seven neutrons, while the radioactive carbon-14 has six protons and eight neutrons.
Chemically, all the isotopes of an element act the same, but because of
their differences in weight, some may preferentially end up in certain substances.
Plants and animals, to a degree, reflect the isotopic makeup of the geographic areas
where they live and the diets they eat. In recent years, techniques for correlating the
isotopic makeup of teeth and bones have produced evidence as to where people and
animals originated and what they ate. For example, a bronze-age burial in England
showed that the person had grown up in the Alps. What mysteries would be solved by such
studies on the early inhabitants of our own desert Southwest?
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.