Reconstructing paleoecology for critical transitions in hominin evolution

了解与古人类化石相关的古生态学可以促进对决定人类谱系进化的因素的了解。在这个多学科项目中，研究人员重建了350万至330万年前人类祖先化石从沉积物中恢复的地区的古生态。他们根据三个地点的动物组合进行了高分辨率的区域级分析，这些地点的总面积为3000平方公里，并重建了人属起源之前的古生态环境。该项目促进了本科生和研究生的培训以及国际研究合作。与该项目相关的科学传播和K-12科学教育活动旨在提高人们对科学和人类起源研究的兴趣，并突出跨学科科学和研究背后人员的多样性。该项目测试了与人属的出现、南方古猿阿法种的明显灭绝以及共存的古人类物种的古生态背景有关的假设。实地考察是为了完善相关剖面的地层和年龄，并在不同地点之间进行高分辨率的动物区系比较。项目动物系专家完善哺乳动物化石分类学，收集和分析地学和古生态数据，进行高分辨率、大尺度的古环境重建，评估人属出现和南方古猿阿法种消失之前的生态系统变化。对于样品中的每个化石物种，估计了体重，饮食和底物使用的功能特征。通过牙釉质同位素（δ13C和δ18O）特征、介面磨损指数和脱质指数来估计饮食。通过对应分析来比较来自连续时间箱的动物组合，以及跨地点与现代社区的动物组合，研究小组估计了三个地点之间不同的生物和非生物因素，并探讨了这些模式如何与南方古猿阿法种的消失和人属的出现相一致。此外，物种聚类分析还用于检查出现的生物地理模式，考虑分类起源，假设扩散模式，并估计区域古生态模式。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Understanding the paleoecology associated with hominin fossils can advance knowledge about the factors that determined the evolution of the human lineage. In this multidisciplinary project, the researchers reconstruct paleoecology for regions where human ancestor fossils have been recovered from sediments between 3.5 and 3.3 million years ago. They conduct high-resolution, regional-level analyses based on the faunal assemblages from three sites that have a combined area of 3000 square kilometers and reconstruct the paleoecological context immediately preceding the origin of the genus Homo. The project advances undergraduate and graduate training and international research collaborations. Science communication and K-12 science education activities related to the project are designed to increase interest in science and human origins studies and highlight interdisciplinary science and the diversity of people behind the research. This project tests hypotheses related to the emergence of Homo, the apparent extinction of Australopithecus afarensis, and the paleoecological context of co-existing hominin species. Fieldwork is conducted to refine the stratigraphy and age of relevant sections and conduct high-resolution faunal comparisons between sites. Project faunal experts refine the taxonomy of mammalian fossils, collect and analyze taphonomic and paleoecological data, conduct high-resolution, broad-scale reconstruction of paleoenvironment, and assess ecosystem changes prior to the appearance of Homo and disappearance of A. afarensis. For each fossil species in the sample, functional traits of body mass, diet and substrate use are estimated. Diet is estimated through enamel isotopic (δ13C and δ18O) signatures, mesowear and hypsodonty indices. Using correspondence analysis to compare faunal assemblages from the successive time bins and across sites with modern communities, the team estimates biotic and abiotic factors that differed among the three sites and explores how these patterns align with the disappearance of A. afarensis and the appearance of Homo. In addition, species cluster analyses are used to examine biogeographic patterns that emerge, consider taxonomic origins, hypothesize patterns of dispersal, and estimate regional paleoecological patterns.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.