By Sid Perkins
Chemical analyses of teeth, possibly including fossilized ones, can provide clues about the age at which a child was weaned, a milestone in life that may reveal information about how the human species and its predecessors evolved.
Unlike living bone, which contains a substantial amount of protein such as collagen, tooth enamel is about 98 percent mineral. Therefore, atoms in the enamel — especially those deep within a tooth — don’t tend to swap with those in the environment as they fossilize, says Louise T. Humphrey, an anthropologist at the Natural History Museum in London. Studies have shown that changes in the ratios of various isotopes in teeth record evidence of nutritional stress, movement from one location to another and exposure to heavy metals such as mercury, she notes.
Recently, Humphrey and her colleagues scrutinized baby teeth that had been shed by modern-day children to see if the effects of significant changes in their diet had been preserved. Some of the children had been fed formula from birth, others had been breastfed exclusively and others transitioned from mother’s milk to formula or other foods when they reached a few weeks or months of age.
Because various foods have differing ratios of calcium, a major component of tooth enamel, and strontium, the dietary changes should show up in teeth, the researchers had speculated.