Testing the Sample Preparation Method and Oxygen Isotopic Analysis of Tooth Enamel for the Reconstruction of the Birth Seasonality of Ovicaprines (the Case of Teeth from Istykskaya Cave, Eastern Pamir)

Testing the Sample Preparation Method
and Oxygen Isotopic Analysis of Tooth Enamel
for the Reconstruction of the Birth Seasonality of Ovicaprines
(the Case of Teeth from Istykskaya Cave, Eastern Pamir)

doi:10.17746/1563-0110.2024.52.2.047-054

K.A. Babina^1–3, S.V. Shnaider¹, А.А. Bragina^{2, 3}, and Е.V. Parkhomchuk^{2, 3
1}ZooSCAn International Research Laboratory, CNRS–IAET SB RAS, IRL 2013, Pr. Akademika Lavrentieva 17, Novosibirsk, 630090, Russia
²“AIsotopes” Isotope Research Laboratory, Institute of Archaeology and Ethnography, Siberian Branch, Russian Academy of Sciences, Pr. Akademika Lavrentieva 17, Novosibirsk, 630090, Russia
³Novosibirsk State University, Pirogova 2, Novosibirsk, 630090, Russia

Cyclic variations of Δ¹⁸O along the growth line of M2 and M3 molars provide information about the seasonality of enamel formation and thereby about reproductive seasonality in animals, taking into account the time of tooth eruption and full enamel maturation. Determination of birth seasonality of small ruminants is relevant to the reconstruction of pastoralist strategies. Two peaks of reproductive activity per year are one of the most reliable indicators of human control of the small ruminants. As part of this work, for the first time in Russia, a method of sample preparation and analysis of oxygen isotope ratios in the tooth enamel of small ruminants is proposed. Traditionally, breeding seasonality was evaluated by the isotopic analysis of carbonates, the content of which in dental enamel is only 4 %. According to a new approach, oxygen from a sample is converted to gaseous CO by the interaction of enamel with carbon in a helium flow under 1300 °C, enabling one to measure d18O in all components of the dental enamel, including phosphates, which make up 90 % of enamel mass and are resistant to diagenesis. In this study, four sample preparation protocols depending on the degree of preservation of teeth and their age were tested: (A) cleaning and sampling of enamel, (B) treatment by H2O2, (C) treatment by NaOCl and CH3COOH, and (D) extraction of Ag3PO4. Results show that for assessing seasonality breeding, it suffices to evaluate the lowest and the highest 818O along the tooth growth line. If the preservation of sample is good, minimal chemical treatment is enough to observe these extremes.

Keywords: Isotopic analysis, oxygen, stable isotope ratio, farming, animal breeding, sheep, Central Asia