An interesting article titled “The Pb isotopic record of historical to modern human lead exposure,” appears in the journal Science of The Total Environment written by George D. Kamenov and Brian L. Gulson (vol. 490, pp. 861-870, 2014). George Kamenov is a University of Florida geology professor. The article describes how trace amounts of lead present in teeth can give clues about what geographical region the teeth (and the person) came from.
What is interesting about this article, is that the lead in the teeth can be used to pinpoint the geographic area where the teeth originated from. This is because lead is composed of four different isotopes which fluctuate in different rocks and soils around the world. As children grow they inhale dust and ingest soil which contains the different isotopes of lead. As tooth enamel forms during childhood, it locks in the lead signals from the environment.
The first molar has its enamel formed by around age 3, incisor and canine enamel is formed by around age 5, and third molar (wisdom teeth) enamel is formed by around age 8. If a child moves geographic regions during this time, the different teeth can persevere the lead in the environment and tell the story about what geographical region they are from.
After all the molars and teeth have their enamel form, if one moves to a different environment, the lead signals present in their teeth will be different than everyone else. The researchers state that teeth from the United States have distinct isotope signals from anywhere else. However, South America and European teeth can have some overlap. The researchers also state that modern and historic teeth are different due to the composition of lead changing over the past century because of mining activities and leaded gasoline.
The researchers feel that such techniques can help better determine how humans migrated across regions in the past. They also feel that such information can be useful for solving crimes and cold cases.