Take note, crime scene investigators: Researchers may have found a way to figure out where a person has been—and even hints about what they've been eating—simply by zapping their hair with an ultraviolet laser. In one demonstration of the new set-up, reported online this month in Rapid Communications in Mass Spectrometry, the team burned three 50-micrometer holes in a horse hair (above). Subsequent analyses of the vaporized material revealed variations in the carbon isotope ratios incorporated into the hair as it grew. Those changes were caused by subtle changes in the horse's diet—for instance, the isotope ratio in oats the horse ate 1 week ago may be quite different from the ratio in alfalfa it consumed last month, when the follicle was producing a different segment of the same hair. Besides providing insights into dietary changes, analyses of the ratios of carbon, nitrogen, and oxygen isotopes in hair samples from animals can provide hints about their migratory habits. For humans, such techniques could help discern changes in the recent travel habits of a criminal suspect or help identify the place of origin for an unidentified set of remains.
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