Elements in Baby Teeth Reveal Breast-Feeding History

CAMBRIDGE, MASSACHUSETTS—By measuring the ratios of barium to calcium in the layers of enamel and dentin in baby teeth, Manish Arora of Harvard University’s School of Public Health says that it is possible to determine how long a child had been breast fed. Before birth, very little barium is deposited into the developing teeth. The barium level spikes and stays high after birth when breast milk becomes the source of nutrition. When solid food is introduced, the levels change again. To test the technique, Arora analyzed a 100,000-year-old Neanderthal baby tooth from Belgium. He estimates that the child was breast fed exclusively until seven months of age, when its diet was supplemented with solid food, and that weaning occurred at 14 months of age. Breast feeding is “a major determinate of child health and immune protection, so breast-feeding is important both from the point of view of studying our evolution as well as studying health in modern humans,” he explained.