Fig. 3.

Nursing histories from time-resolved Sr/Ca variation in Middle-Upper Paleolithic deciduous teeth. NEA, Neanderthal; UPMH, Upper Paleolithic modern human. The elemental profiles (Sr/Ca; Ba/Ca for comparison) were analyzed within enamel closest to the enamel–dentine junction (EDJ); [U] is reported as diagenetic alteration proxy for all fossil specimens (15) (SI Appendix, Text S4 and Fig. S13); diagenetically affected sections are grayed out. All are plotted relative to secretion time (in days); the birth event is highlighted by a vertical line in each plot. Elemental ratios are reported mass (weight)-based, not as mol/mol (15). The compositional profiles were smoothed with a locally weighted polynomial regression fit (LOWESS), with its associated SE range (±3 SE) for each predicted value. (A) Comparison between two contemporary individuals with known feeding histories, MCS1 (exclusively breastfed) and MCS2 (exclusively formula-fed); t1, transitional period, i.e., first time solid food starts; t2, progressively reduced breastfeeding during day; t3, transitional period ends, end of breastfeeding. (B) Nadale 1: the slight decrease of Sr/Ca indicates exclusive breastfeeding until the end of crown formation (4.7 mo). (C) Fumane 1: Sr/Ca variation indicates breastfeeding until 4 mo of age (fully comparable with MCS1 sample; SI Appendix, Fig. S6). (D) Riparo Broion 1: Sr/Ca profile indicates exclusive breastfeeding until 5 mo of age. (E) Fumane 2: 55 d of available postnatal enamel shows exclusive breastfeeding. (F) Comparative Sr/Ca profiles of all fossil specimens adjusted to the birth event; the interpolated modeled profiles were calculated based on those portions unaffected by diagenesis ([U] < 0.05 ppm), with strong smoothing parameters to reveal the biogenic signal. Riparo Broion 1, the specimen most affected by diagenesis, retains the overall outline of a breastfeeding signal (A). Further details are provided in Materials and Methods.