Yu Itahashi

We determined the carbon and nitrogen isotope compositions of biologically important 21 amino acids and 7 nucleobases, which are used as working standards. These isotopic compositions were determined using a high-sensitivity elemental analyzer coupled to an isotope ratio mass spectrometer (nano-EA/IRMS) without chemical derivatization. The values were calibrated against internationally recognized reference materials. The δ ¹³ C values for amino acids range from − 33 to − 9‰, and δ ¹⁵ N values range from − 9 to + 9‰. For nucleobases, δ ¹³ C ranges from − 32 to − 8‰, and δ ¹⁵ N ranges from − 9 to + 6‰. Analytical precision was better than ± 0.3‰ for δ ¹⁵ N and ± 0.5‰ for δ ¹³ C. Determined δ ³⁴ S values for cysteine and methionine are also reported with a precision of ± 0.2‰. Cross-validation of δ ¹⁵ N values using gas chromatography/IRMS (GC/IRMS) confirmed the consistency with nano-EA/IRMS and GC/IRMS within 0.8‰. The dataset provides a practical working standard to support compound-specific isotope analysis (CSIA), facilitating method development, calibration and data comparability in archeological, ecological, geochemical and biochemical research. In addition to reporting reference data, we outline a streamlined and standardized workflow encompassing sample treatment, compound isolation and isotope measurement. This framework aims to support standardized procedures in CSIA, accommodating both derivatized and underivatized approaches depending on analytical needs. We also present an isotope systematics that summarizes the structural and isotopic characteristics of representative carbon-, nitrogen- and sulfur-bearing compounds, including amino acids, nucleobases and other biochemically important compounds. These frameworks also support compound-level analyses of amino acids, nucleobases and related biomolecules. Together, the reference materials dataset, the standardized workflow and the isotope systematics provide a foundation for reproducible and integrated isotopic applications across broader research fields such as archeology, ecology and geochemistry in the field of Earth and planetary sciences.

We developed a novel technique for the accurate radiocarbon dating of single amino acids from archaeological human and animal remains. Despite the extensive use of bulk collagen for radiocarbon dating of archaeological bones, obtaining accurate dates can be difficult in some cases due to unremovable C contamination in collagen. To obtain a reliable, uncontaminated age, we developed a purification method for analysing hydroxyproline, a major amino acid in bone collagen. This method uses two purification processes: liquid–liquid extraction and recrystallization after high-performance liquid chromatography. This purification method substantially reduced the contamination by exogenous C in the isolated amino acids. The reliability of the method was demonstrated by radiocarbon dating an archaeological bone with a known date of death. This method enables compound-specific radiocarbon dating of amino acids with < 100 μg of C, reducing collagen and bone sample consumption relative to previous approaches. This method is expected to enable the extensive application of radiocarbon dating to degraded archaeological bones that were previously unusable. In addition, our technique of isolation and purification of amino acids is useful for the isolation of compounds for the radiocarbon analysis from diverse organic tissue beyond collagen and other organic molecules in marine sediments targeted by studies in the field of Earth and planetary science.

Significance: We studied goose bones from Tianluoshan—a 7,000-y-old rice cultivation village in the lower Yangtze River valley, China—using histological, geochemical, biochemical, and morphological approaches. Our analyses reveal an early stage of goose domestication at Tianluoshan. The goose population seemed to have been maintained for several generations without the introduction of individuals from other populations and might have been fed cultivated paddy rice. These findings indicate that goose domestication dates back 7,000 y, making geese the oldest domesticated poultry species in history.

Objective: The inhabitants of several sites in the Upper Tigris Valley, such as Hakemi Use, domesticated animals and cereals during the Pottery Neolithic period, while the inhabitants in this valley were hunter–gatherers in the Pre‐Pottery Neolithic period, consuming freshwater and terrestrial food resources. However, there is considerable uncertainty surrounding whether or not changes in dietary food composition accompanied the shift in food production away from foraging. In order to reveal the impact of the development of agriculture on the human diet over the Pre‐Pottery and Pottery Neolithic periods in this region, we analyzed the isotopic compositions of amino acids from the farmers at the Hakemi Use Pottery Neolithic site, and compared them with those from the Pre‐Pottery hunter–gatherers in the close region.Materials and Methods: Herein, we report the nitrogen isotopic compositions of amino acids, as well as both carbon and nitrogen isotopic compositions of bulk collagen, from human and faunal remains collected from Hakemi Use.Results: Whereas freshwater resources were consumed by hunter–gatherers in this region during the Pre‐Pottery period, the δ¹⁵N values of glutamic acid (δ¹⁵N_Glu) and phenylalanine (δ¹⁵N_Phe) suggest that freshwater food resources were rarely consumed by inhabitants following the development of agriculture.Discussion: Despite living in similar settings by the Tigris as its inhabitants during the Pre‐Pottery period, the farmers of the Pottery Neolithic period depended less on freshwater resources for their diets relative to the hunter–gatherers of the Pre‐Pottery Neolithic period.

We have improved a method for isolation and purification of individual amino acids for compound-specific radiocarbon analysis (CSRA). To remove high-performance liquid chromatography (HPLC) eluent blanks from isolated amino acid fractions prior to the radiocarbon (Δ¹⁴C) measurement, each fraction was filtered through a membrane filter and then washed with diethyl ether twice. Radiocarbon measurements on standard amino acids processed and purified with the above method using elemental analyzer–accelerator mass spectrometry resulted in Δ¹⁴C values that were in strong agreement (R² = 0.998) with the original Δ¹⁴C value of each amino acid standard. From these measurements, we calculate dead and modern carbon contamination contributions as 1.2 ± 0.2 and 0.3 ± 0.1 μgC, respectively, which are consistent with direct assessments of HPLC procedural blanks of 1.0 ± 0.8 μgC per sample. These contamination constraints allow correction of measured Δ¹⁴C values for accurate and precise CSRA and are widely applicable to future archeological and biogeochemical studies.