Department of Sociology, Anthropology and Social Work, Seton Hall University, South Orange, New Jersey.
Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey.
Am J Phys Anthropol. 2019 Jul;169(3):403-421. doi: 10.1002/ajpa.23846. Epub 2019 May 3.
Australopithecus anamensis has comparable δ C values to Ardipithecus ramidus, and both have been characterized as C feeders in open woodland habitats similar to "savanna" chimps. Unlike Ar. ramidus and "savanna" chimps, A. anamensis shows a derived dentognathic morphology for tough foods and a dental microwear pattern similar to the C -C -mixed-feeding A. afarensis. Here I test the hypothesis that changing the variables (ε , δ C δ C values) used to calculate the percentage of dietary C foods (%C diet) by 1-2‰ does not make a substantial difference for hominin diet reconstructions [van der Merwe, Masao, & Bamford, 2008, South African Journal of Science 104:153-155].
I estimate vegetation structures for A. anamensis with pedogenic carbonate and faunal enamel δ C values from the Pliocene Omo-Turkana Basin (4.2-3.9 Ma). I recalculate A. anamensis' %C diet based on new body size-dependent estimates of the ε value and alternative δ C and δ C values.
The Pliocene Omo-Turkana Basin shows evidence for dietary resources with a wide range of δ C values including canopy-driven C depleted ground C foods. Alternative equation variables changed by 1-2‰ yield higher C estimates for A. anamensis (15-31%) than previously thought (0-10%). The choice of δ C and δ C values for estimating %C is not a perfunctory task and potentially explains the δ C isotopic equifinality of A. anamensis and "savanna" chimps.
My integrative diet model reconciles the carbon isotopic data with the dentognathic and microwear evidence of A. anamensis' diet and suggests that "savanna" chimps are not proper dietary analogs of A. anamensis. A foraging strategy across heterogeneous habitats of the Pliocene Omo-Turkana Basin incorporating an array of C-depleted and C-enriched C foods and a portion of C resources may have served as one of the selective pressures for A. anamensis, the earliest habitual biped [van der Merwe et al., 2008, South African Journal of Science 104:153-155].
南方古猿源泉种的 δ¹³C 值与阿法南方古猿相近，且两者都被描述为在类似于“稀树草原”黑猩猩的开阔林地栖息地中以 C 类食物为食。与阿法南方古猿和“稀树草原”黑猩猩不同的是，南方古猿源泉种表现出一种用于坚韧食物的衍生齿颌形态和类似于以 C 类食物为主混合食性的阿法南方古猿的牙齿微观磨损模式。在这里，我通过 1-2‰来测试假设，即改变用于计算饮食中 C 类食物百分比（%C 饮食）的变量（ε，δ¹³C，δ¹³C 值）不会对人类饮食重建产生实质性影响[van der Merwe，Masao 和 Bamford，2008，南非科学杂志 104:153-155]。
我根据上新世奥莫-图尔卡纳盆地（4.2-3.9 百万年前）的土壤碳酸盐和动物群牙釉质 δ¹³C 值来估计南方古猿源泉种的植被结构。我根据新的、与身体大小相关的 ε 值和替代 δ¹³C 和 δ¹³C 值，重新计算了南方古猿源泉种的%C 饮食。
上新世奥莫-图尔卡纳盆地的证据表明，其饮食资源具有广泛的 δ¹³C 值范围，包括由树冠驱动的 δ¹³C 贫化的地面 C 类食物。替代方程变量的变化为 1-2‰，会导致对南方古猿源泉种的 C 估计更高（15-31%），高于之前的估计（0-10%）。选择用于估计%C 的 δ¹³C 和 δ¹³C 值不是一项敷衍的任务，并且可能解释了南方古猿源泉种和“稀树草原”黑猩猩的 δ¹³C 同位素等价性。
我的综合饮食模型将碳同位素数据与南方古猿源泉种的齿颌和微观磨损证据的饮食相协调，并表明“稀树草原”黑猩猩不是南方古猿源泉种的合适饮食模拟物。在上新世奥莫-图尔卡纳盆地的异质生境中，采用一系列 δ¹³C 贫化和 δ¹³C 富集的 C 类食物以及一部分 C 资源的觅食策略可能是南方古猿源泉种的一个选择性压力之一，南方古猿源泉种是最早习惯两足行走的物种[van der Merwe 等人，2008，南非科学杂志 104:153-155]。
