陕北地区动物骨骼的脂肪酸单体碳同位素分析

COMPOUND SPECIFIC CARBON ISOTOPE ANALYSIS OF INDIVIDUAL FATTY ACIDS FROM ANIMAL BONES IN NORTHERN SHAANXI,CHINA

基于动物油脂的脂肪酸单体碳同位素模型开展古代样品的脂肪酸单体碳同位素分析可细化脂肪来源,有助于探究动物资源的加工利用、相关载体的使用功能及先民饮食策略,从而为古代人类的生活方式和古代社会的经济形态提供重要信息。目前该模型已得到国外诸多地区现代动物样品的验证,但其在中国的适用性尚不明晰。文章对陕北地区石峁遗址和高家洼遗址出土的动物骨骼开展了脂肪酸分析,并对其中1例缺乏形态鉴定特征的碎骨样本进行ZooMS(基于质谱的动物考古学)分析。结果显示,该碎骨样本的一系列特征肽段与鹿和绵羊的部分肽段相匹配,表明其为鹿或绵羊。家养动物(猪、普通牛、羊亚科)中,除2例绵羊显现出较强的C_(4) 饮食信号,应源于粟类作物副产品或人工采集的藜科植物消费;其余动物均表现为C_(3) /C_(4) 类混合特征,意味着存在野生C_(3) 植物的摄入。相比其他遗址,石峁遗址采取了相对粗放的家猪管理模式;而牛、羊饲养模式的多样化可能是先民在当地自然条件下对新兴家畜品种开展探索性饲养活动的反映。野生动物(梅花鹿、马鹿)中,2例鹿具有较高的δ^(13)C_(16:0) 和δ^(13)C_(18:0) 值,应有C_(4) 植物的摄入,表明龙山时代陕北地区先民与鹿存在互动关系。古代陕北地区C_(4) 植物对饮食的贡献使得该地区的动物脂肪酸单体碳同位素数据相对于前人建立的"δ^(13)C_(18:0) -δ^(13)C_(16:0) "分布模型存在正向偏移,但仍可通过计算Δ^(13)C值来区分该地区的动物脂肪来源(Δ^(13)C>0‰为非反刍动物体脂,-3.3‰<Δ^(13)C<0‰为反刍动物体脂)。

The application of compound specific carbon isotope model of animal individual fatty acids could be used to characterize more specifically the origin of animal fats in archaeological context,explore the processing and utilization of animal resources,the functions of related containers and the dietary strategies of humans,and provide information for ancient human lifestyle and socio-economic formation.Although the model has been verified by modern animal samples in some regions abroad,its applicability in China remain unclear.In this paper,GC-MS(Gas Chromatography-Mass Spectrometry)and GC-C-IRMS(Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry)were conducted on fatty acids of domestic animal bones(including Sus domesticus,Bos taurus and Caprinae(Ovis aries or Capra hircus,etc))and wild animal bones(including Cervus nippon and Cervus elaphus)unearthed from the Shimao site(38°34'20″N,110°19'31″E)and the Gaojiawa site(37°54'20″N,109°17'10″E)in northern Shaanxi.ZooMS(Zooarchaeology by Mass Spectrometry)technology was performed on a fragmented bone lacking morphological identification characteristics.The ZooMS result shows that a series of characteristic peptides(m/z 1105.3,1427.4,2131.6,2883.6,2899.6 and 3033.4)in the sample matched with partial peptides of deer(Cervidae)and sheep,indicating that this sample is deer or sheep.GC-MS analysis show that all the bone samples(n=29)have similar fatty acid distributions.C_(16:0) and C_(18:0) acids predominate,with minor amounts of branched chain fatty acids(e.g.,C15:0br~C17:0br)and long chain saturated fatty acids(e.g.,C14:0~C20:0,C22:0~C24:0).GC-C-IRMS results show that the meanδ^(13)C_(16:0) and δ^(13)C_(18:0) values of domestic pigs are-22.0±1.9‰and-20.8±2.0‰(n=5),indicating that they consumed wild C_(3) plants and millet byproducts or Chenopodiaceae plants collected intentionally.Compared with contemporary sites,the management of domestic pigs at the Shimao site was relatively extensive.Theδ^(13)C_(16:0) values of cattle and sheep/goats are averaged by-25.5±2.1‰(n=10)and-26.1±1.4‰(n=8),respectively,while the meanδ^(13)C_(18:0) values are-27.0±1.7‰(n=10)and-27.8±1.6‰(n=8)respectively,reflecting the combination of C_(3) and C_(4) plants in the diet structure.In addition,two sheep show strong C_(4) dietary signals,indicating the consumption of millet byproducts or Chenopodiaceae plants collected intentionally.The diversified raising patterns of cattle and sheep/goats might reflect the humans'exploratory raising activities on new livestock breeds under local resource conditions.Among the wild animals,two deer show relatively highδ^(13)C_(16:0) and δ^(13)C_(18:0) values,implying that there was an interactive relationship between humans and deer in northern Shaanxi during the Longshan period.The consumption of C_(4) plants in ancient northern Shaanxi makes the local compound specific carbon isotope data of animal individual fatty acids have positive offset compared with the"δ^(13)C_(18:0)-δ^(13)C_(16:0)"distribution model established by previous study.However,theΔ^(13)C value can still be used to characterize the origin of animal fats in northern Shaanxi,namelyΔ^(13)C>0‰indicates non-ruminant adipose fats while-3.3‰<Δ^(13)C<0‰indicates ruminant adipose fats.