A study uses stable calcium isotopes to assess weaning practices in humans. Weaning practices can provide insights into the health and demography of present and past human populations. However, the study of prehistoric and historic weaning practices has been hampered by a lack of direct evidence of weaning behavior in archeological and fossil records. To identify biomarkers that would enable the reconstruction of human weaning practices, Théo Tacail and colleagues analyzed stable calcium isotopes (44Ca/ 42Ca) from the enamel of 51 deciduous teeth from 12 modern humans; mammalian breast milk has low levels of 44Ca compared with the average Western diet. The authors found that the enamel became enriched in 44Ca during the transition from prenatal to postnatal development. During the first 5–10 months of life, the proportion of 44Ca relative to 42Ca increased in tooth enamel for individuals who were either not breastfed or breastfed only for short periods, whereas the calcium isotope ratio did not change over the same period in individuals who were breastfed for more than 12 months. According to the authors, the observed variations in calcium isotope ratios in enamel record a transition from placental nutrition to an adult-like diet, reflect the duration of breastfeeding, and may help glean insights into weaning practices in past hominins. - Read at PNAS
Article #17-04412: “Assessing human weaning practices with calcium isotopes in tooth enamel,” by Théo Tacail et al.