The Onset and Evolution of Early Hominin Meat Consumption (HoMeCo) - The position of Plio-Pleistocene hominins in African paleo-food webs based on nitrogen isotopes in tooth enamel

饮食变化，特别是动物资源的整合，被认为是人类进化的关键事件。然而，我们人类祖先的营养行为的直接证据仍然难以捉摸。肉类消费的最早迹象包括粗糙的石器和化石骨骼上可能的切割痕迹（3.4至3.3 Ma）。然而，他们的起源和假设，南方古猿的形状和使用工具之前出现的人属存在很大的争议。氮（N）同位素测量胶原蛋白从化石骨和牙本质提供了关键的见解，在现代生态系统中的物种的饮食行为和最近的地质过去（<120 kyr）。然而，由于成岩蚀变，这种分析仅限于保存特殊的地点。与骨骼或牙本质不同，牙釉质中的有机物通过其高度矿化的结构而免受改变，可能保存数百万年的同位素信号，但到目前为止，牙釉质中的低有机物含量阻碍了N同位素分析。最近，我和我的同事开发了一种新的氧化-反硝化方法，用于分析~5 mg牙釉质中矿物结合氮的同位素组成，其与传统方法相比需要少100倍以上的N。我们建立了釉质N记录的同位素组成的饮食和保存在喂养实验和自然生态系统中的营养信号。此外，我分析了动物化石的牙齿从Sterkfontein成员4（~2.6至2.2马），包括七个南方古猿的试点研究。南方古猿个体间的釉质氮同位素值变化很大，但没有达到食肉动物的值，表明该分类群主要以植物为基础的饮食。这个数据集为更好地理解早期人类的营养行为迈出了第一步。在这个项目中，我将使用釉质氮同位素数据来重建上新世-更新世人类肉类消费的开始和进化，包括来自非洲东部和南部的14种南方古猿、肯尼亚人、傍人和人属。我将生成两个早期人类的稳定的碳、氮和氧同位素数据集（约200年）。130个个体）和相关动物（食草动物，食肉动物和杂食动物，包括非人类灵长类动物;约。2000人），以评估其喂养生态。我将瞄准东非裂谷系的六个关键地点和南非人类摇篮的五个洞穴矿床。这些地点跨越4.2至1.4 Ma，这是气候引起的环境变化和人类（饮食）适应的关键时期。这个前所未有的N同位素数据集将大大有助于我们了解我们早期祖先饮食行为的区域，时间和分类变化。我将评估动物资源消耗的发生，进化和重要性，以及饮食灵活性在早期人类类群灭绝和适应性辐射中的作用。

Dietary change, specifically the incorporation of animal resources, is considered a key event in human evolution. However, direct evidence for the trophic behavior of our hominin ancestors remains elusive. The earliest signs of meat consumption include crude stone tools and possible cut marks on fossil bones (3.4 to 3.3 Ma). However, their origin and the assumption that Australopithecus shaped and used tools prior to the emergence of Homo are heavily debated.Nitrogen (N) isotopes measured in collagen from fossil bone and dentin provide key insights into the dietary behavior of species in modern ecosystems and the recent geological past (<120 kyr). However, due to diagenetic alteration, such analyses have been limited to sites with exceptional preservation. Unlike bone or dentin, organic matter in tooth enamel is protected from alteration by its highly mineralized structure, potentially preserving isotopic signals over millions of years, but low organic matter content in enamel has so far prevented N isotope analysis.Recently, my colleagues and I developed a novel oxidation-denitrification method for analyzing the isotopic composition of mineral-bound nitrogen in ~5 mg enamel, which requires over 100-fold less N compared to traditional approaches. We established that enamel N records the isotopic composition of diet and preserves a trophic signal in both a feeding experiment and in natural ecosystems. Additionally, I analyzed teeth of fossil fauna from Sterkfontein Member 4 (~2.6 to 2.2 Ma), including seven australopithecines for a pilot study. Australopithecus shows a large variation in enamel N isotope values between individuals, but does not reach carnivore values, indicating a primarily plant-based diet for this taxon. This dataset provides a first step towards better understanding the trophic behavior of early hominins.In this project, I will use enamel N isotope data to reconstruct the onset and evolution of meat consumption of Plio-Pleistocene hominins, including 14 species of Australopithecus, Kenyanthropus, Paranthropus and Homo from eastern and southern Africa. I will generate stable carbon, nitrogen, and oxygen isotope datasets for both early hominins (ca. 130 individuals) and associated fauna (herbivores, carnivores, and omnivores including non-hominin primates; ca. 2000 individuals), to assess their feeding ecology. I will target six key-localities in the East African Rift System and five cave deposits in the South African Cradle of Humankind. These sites span 4.2 to 1.4 Ma, a critical period of climate-induced environmental change and hominin (dietary) adaptation. This unprecedented N isotope dataset will contribute significantly to our understanding of regional, temporal and taxonomic variation in the dietary behavior of our early ancestors. I will evaluate the onset, evolution and importance of animal resource consumption, as well as the role of dietary flexibility in the extinction and adaptive radiation of early hominin taxa.