Terrestrial climate and ecosystem dynamics in SE Africa during the emergence, persistence and extinction of archaic hominids in the late Pliocene and early Pleistocene based on cores from IODP Expedition 361

为了详细了解非洲东南部在上新世晚期至更新世早期的陆地生态系统和气候演变，以及古人类进化的外部边界条件，该项目旨在在IODP站点U1478(莫桑比克海峡)生成4-2 Ma和2-0.8 Ma(作为后续建议的新要素)的新的陆地植被记录。在方法上，将通过对U1478遗址拼接的材料进行孢粉学(花粉和孢子丰度，以及基于花粉的气候重建)、元素地球化学(X射线荧光扫描)和有机生物标记物(δ13C蜡、δDWAX、TEX86)分析的综合方法来实现项目目标。迄今为止(即在15个项目月之后)，工作包1至3产生了：(1)过去4 Ma的连续X射线荧光记录，用于通过旋回地层学建立年龄模型，并使控制U1478地点沉积物元素含量的过程得以重建；(2)轨道尺度分辨率的4至2 Ma连续孢粉记录，并通过基于孢粉的气候定量重建而得到加强。第一个项目阶段中最重要的发现包括大约2.8 Ma时植被的根本重组的证据；它的标志是从稀树草原到Fynbos生物群的周转，与上新世晚期的北半球早期冰川事件相同。第三个项目年将专门用于工作包4，它将产生：(I)4-2 Ma间隔的叶蜡δ13C记录，这将使人们能够深入了解非洲东南部C3和C4植物的分布，因此，将在限制人类进化关键间隔期间降水变化的大小方面发挥关键作用；(Ii)2-0.8 Ma间隔的新的轨道尺度分辨率花粉记录，与U1478站点和附近MD96-2048岩心已有的花粉数据相结合，将产生自上新世以来非洲东南部在轨道尺度分辨率上的第一个连续花粉记录；(3)项目成果的综合。总而言之，孢粉和元素地球化学替代数据的整合将使我们能够详细评估林波波河流域生态系统和气候变化的特征、时间、规模和节奏，从而可以评估自上新世以来“人类摇篮”地区的生态系统和气候变化。因此，不仅有可能澄清特别强烈的环境变化的间隔是否与原始人的出现和灭绝的步骤重合，而且还可能确定这种变化的确切性质。这一信息将为正在进行的关于环境强迫和人类进化之间潜在因果联系的讨论提供新的线索。

To gain detailed insight into the terrestrial ecosystem and climate evolution – and thus the extrinsic boundary conditions for the evolution of archaic hominids – in SE Africa during the late Pliocene to early Pleistocene, the project aims to generate new terrestrial vegetation records for the intervals 4–2 Ma and (as a new element within this follow-up proposal) 2–0.8 Ma at IODP Site U1478 (Mozambique Channel). Methodologically, the project goal will be reached through an integrated approach based on palynological (pollen and spore abundances, and pollen-based climate reconstructions), element- geochemical (XRF scanning) and organic biomarker (δ13Cwax, δDwax, TEX86) analyses of material from the splice of Site U1478. To date (i.e., after 15 project months), Work Packages 1 to 3 have yielded: (i) a continuous XRF record for the past 4 Ma that was used for age-model development by means of cyclostratigraphy, and has also enabled the reconstruction of processes controlling the elemental content of the sediments at Site U1478; (ii) a continuous pollen record from 4 to 2 Ma at orbital-scale resolution, which is augmented by quantitative pollen-based climate reconstructions. The most important finding within the first project phase comprises evidence for a fundamental reorganization in vegetation at c. 2.8 Ma; it is marked by a turnover from savanna to fynbos biomes, coeval with the early Northern Hemisphere glaciation events of the late Pliocene. The third project year will be dedicated to Work Package 4 that will yield: (i) a leaf-wax δ13C record for the 4–2 Ma interval, which will allow insight into the distribution of C3 and C4 plants in SE Africa and, hence, will be pivotal in constraining the magnitude of precipitation change during critical intervals of hominid evolution; (ii) a new orbital-scale resolution pollen record for the 2–0.8 Ma interval, which in combination with the already available pollen data from Site U1478 and nearby core MD96-2048 will yield the first, continuous pollen record off SE Africa since the Pliocene at orbital-scale resolution; (iii) a synthesis of the project results. In summary, the integration of palynological and element geochemical proxy data will allow detailed assessment of the character, timing, magnitude, and tempo of ecosystem and climate variability in the Limpopo River catchment, and thus in the ‘Cradle of Humankind’ region, since the Pliocene. As such, it will become possible not only to clarify whether intervals of particularly strong environmental change coincided with steps in hominid emergence and extinction, but also to identify the exact nature of this change. This information will shed new light on the ongoing discussion on potential causal links between environmental forcing and human evolution.