Enamel Ca isotope analyses of hominin teeth

Aim/rationale:
This proposal stems from an inclusive and international effort to solve the conundrum of weaning strategies among South African hominins (A. africanus, P. robustus, early Homo) using calcium isotope systematics in the enamel of dm2 and M1 teeth. The project relies on:
1) Evidence-based variations of enamel Ca isotope compositions according to known weaning status in modern humans linked to the consumption, or not, of always extremely Ca isotope-fractionated milk.
2) Preliminary results obtained for South African early Homo showing extended duration of breastfeeding that remains to be challenged for A. africanus and P. robustus.
3) Minimal, almost non-destructive, micro-sampling (<300 m) of tooth enamel from dm2 (n=4) and M1 (n=13) specimens that will be processed in the vault of the Evolutionary Studies Institute, Wits.
4) South African cutting-edge isotope mass spectrometry (Sapphire CC-MC-ICPMS) and clean room facilities at the School of Geosciences, Wits, to purify and measure Ca stable isotope compositions. No export permit is thus required.
5) The comparison of the hominin Ca isotope compositions with those from an unprecedented collection of enamel samples (n =132) from Pan and Gorilla specimens that will constitute the pongid referential and complement that already exists for modern humans.
6) The stringent selection of tooth specimens based on undisputable diagnosis, little-to-no-wear, that are always isolated, preferentially broken, and associated with existing -CT tomography scans or age-at-death information.

Methodology (short):
All the enamel samples will be processed for Ca isotope measurements at Wits Isotope Geoscience Laboratory. The procedure of metal separation and purification using column chromatography will be processed in the Class 10-100 (10-100 particles in 1 m3) laminar-flow fumehoods dedicated for the separation and purification of metals, including Ca. The Ca isotope measurements will be carried out by means of the Sapphire (Nu Instrument, Wrexham, UK) collision-cell multi-collector inductively-coupled mass spectrometer (CC-MC-ICPMS) at Wits Isotope Geoscience Laboratory.