A Late Pleistocene Demographic Winter Due to Global Warming?

随着持续的气候危机和全球生物多样性的侵蚀，现在首要关注的是更好地了解生态系统如何对长期的气候和人为压力做出反应。在晚更新世(约50,000-12,000年前)，许多哺乳动物巨型动物物种(即体重44公斤)经历了显著的种群数量下降(“瓶颈”)，甚至全部物种灭绝(如猛犸象、洞熊)，这与各大洲重大的气候变化和人类数量的增加相吻合。包括古遗传学和地球化学在内的新技术的发展，正开始帮助我们理解这些人口崩溃及其生态后果。然而，气候和人为因素对这些人口变化的相对影响在许多情况下仍然存在争议。其中一个原因是，用现有方法评估过去人口动态的关键方面(例如生育率)十分复杂。然而，最近的研究表明，骨骼中的钙在繁殖和乳酸程度不同的同种个体之间存在同位素差异。这一发现为研究基于化石遗骸的生殖行为和生育率随时间的变化提供了一个独特的机会。PleistoDEM将针对来自欧洲和北美不同地点的一系列现代物种和化石物种，如驯鹿、猛犸象和洞熊，这是使用这些技术进行的第一次大规模研究。CA同位素分析将被整合到一个更广泛的多代理框架中，包括稳定的光和锶同位素系统，以便在过去生态、环境和流动性的高分辨率画面中考虑再生率和行为。这一开创性的项目将提高我们对晚更新世生态变化的理解，这反过来将为预测和面对未来的生态变化提供坚实的基础。

With the ongoing climate crisis and global erosion of biodiversity, it is now of prime concern to better understand how ecosystems react to long-term climatic and anthropogenic stressors. In the late Pleistocene (~50,000-12,000 years ago), numerous species of mammalian megafauna (i.e. weight > 44 kg) experienced significant population declines ('bottlenecks'), or even total species extinction (e.g. woolly mammoths, cave bears), that coincided with major climatic changes and the growing presence of human populations in all continents. The development of new techniques, including paleogenetics and geochemistry, are beginning to help us understand these demographic collapses and their ecological consequences. However, the relative impacts of climatic and anthropogenic factors on these demographic changes remain debated in many cases. One reason for this arises from the complexity of assessing key aspects of past population dynamics (e.g. fertility rates) with currently available methods. However, recent studies have shown that the calcium (Ca) in the skeleton is isotopically different between conspecific individuals that reproduce and lactate to different extents. This discovery provides a unique opportunity to study reproduction behaviors and aspects of fertility rates through time based on fossil remains. PleistoDem will target a range of modern and fossil species, such as reindeers, mammoths and cave bears, from different locations in Europe and North America, representing the first largescale study using these techniques. Ca isotopic analyses will be integrated in a broader multi-proxy framework including stable light and strontium isotopic systems, in order to consider reproduction rates and behaviors within a high-resolution picture of past ecology, environment and mobility. This ground-breaking project will improve our understanding of Late Pleistocene ecological changes, which in turn will provide a solid base to anticipate and face future ecological changes.