Forschungsthema
Advanced time-series analysis to provide a spatiotemporal framework for the evolution, expansion and technological innovation of Homo sapiens
The archaeological, morphological and genetic findings show that Homo sapiens emerged and evolved from reproductively semi-isolated populations, connected by sporadic gene flow through green corridors and networks which change in the course of climate change. This projects aims at creating a spatiotemporal paleoclimatic framework for testing current hypotheses about a multiregional origin of our species. The principal research questions addressed by the project are: (1) How do spatiotemporal climate fluctuations affect human evolution, expansion and innovation? and (2) How does the physical character of the landscape affect human evolution, expansion and innovation? The project's goals may lead to important insights into the environmental changes occurring at the same time as speciation, brain expansion, dispersal of H. sapiens out of Africa and cultural innovations. The project's quantitative reconstructive approach will also provide the necessary data to validate and improve current ecological models for the living conditions of early humans. The results will also help to expand paleoanthropological investigations into neglected areas of Africa that at least at times provided favorable conditions for humans.
Trends, rhythms and events in East African climate (DFG)
This projects aims at statistically analyzing the long (~278 m) sediment record of the Chew Bahir basin, as part of the ICDP-funded Hominin Sites and Paleolakes Drilling Project (HSPDP). The aim of the project is (1) to establish a robust age-depth model for the sediment cores, (2) to correlate the Chew Bahir record with other records within and outside HSPDP, (3) to detect trends, rhythms and events in the environmental record of the basin, and (4) identify recurrent, characteristic types of climate transitions in the time series, as compared with the ones of the other HSPDP sites and climate records outside HSPDP. This task is handled by a doctoral student, who will work in a team of specialists in the field of mathematical geosciences at the University of Potsdam and the Potsdam Institute for Climate Impact Research, but will benefit also from the larger Chew Bahir and HSPDP projects. The Doctoral Student, expected to be trained as an earth scientists with a pronounced fascination with mathematical methods, will use linear techniques to establish an age model and to detect climate shifts and cycles. He/she is expected to understand the sediment and proxy forming processes in the basin as well as he/she is expected to be equipped with solid knowledge in statistics and programming. He/she will use nonlinear methods to detect more complex or hidden processes within the data. The results of the project will help to illuminate the role of climate change (timing, nature, abruptness, magnitude, and synchronicity of these shifts especially the transitions between Glacial and Interglacial) in the evolution of mammalian (including hominin taxa) during the Pleistocene.
Suguta Valley Project (DFG)
We proposed two-week expeditions to investigate the late Cenozoic structural inventory and lacustrine history of the remote Suguta Valley, northern Kenya. The first objective of this study is the mapping and analysis of faults to better understand the structural evolution, spatiotemporal trends in depositional environments, and drainage networks in the Northern Kenya Rift. The second objective is to sample lacustrine strata and paleosoils, datable tephras, and volcanic flows to reconstruct the environmental history of the region. This study will close a crucial 200-km-long gap in the tectonic and sedimentary record of the East African Rift System. This new information will provide data needed for better assessing of environmental changes in the course of the volcano-tectonic evolution and superposed climate fluctuations during the last five million years. Ultimately, new data from the Northern Kenya Rift is thought to help provide new insights into: (1) the role of volcano-tectonic processes along the rift axis in generating accommodation space and highly compartmentalized deposition environments for sediments; (2) the spatial and temporal synchronicity of the Early Holocene climate optimum in East Africa; (3) the role of the tropics in glacial-interglacial transitions during the Pleistocene; and (4) the linkages between Plio-Pleistocene climate changes and hominin evolution in East Africa. (DFG TR419/6-3)
Nonlinear Analysis of Hyperspectral Data (BMWi)
In semi-arid to sub-humid climates of the earth, extreme climate events cause high erosion rates in areas of extreme relief. The relationship between climatic factors, particularly rainfall and spatio-temporal variation of erosion in the lower latitudes are poorly understood, particularly because of the low data density. Remote sensing data such as precipitation data from the Tropical Rainfall Measuring Mission (TRMM) and environmental data from remote sensing partly overcome of this problem, in particular to quantify and determine the provenance of sediment transfers. This project aims at exploring the usability of nonlinear methods to better determine erosion, transport and sedimentation in remote areas with extreme relief. In the study areas in equatorial East Africa, this study is of particular importance as the flooding, surface erosion and mass movements in the course of global climate change has an extreme impact on human populations, agriculture and infrastractures. (BMWi 50EE1012/EnMAP)
Chew Bahir Coring Project (DFG)
We proposed to obtain up to ten replicate ca. 15-20 meter long continuous sediment cores along a north-south and an east-west transect through the Chew Bahir basin, Southern Ethiopian Rift These cores presumably include the deposits of the African Humid Period (~15 to 5 kyrs BP) providing us with information about the last dry-wet-dry cycle and associated environmental variations in East Africa. The analysis of these cores will provide the necessary information about sedimentary processes in the Chew Bahir as required for detailed planning of deeper drilling in the Southern Ethiopian Rift within the framework of the ICDP "Hominid Sites and Paleolakes Drilling Project" project. The first objective is to study the type and character of sediment in the basin, in particular with respect to the organic matter including pollen and biomarkers. The second objective is to determine the sedimentation rates and its variation in the Chew Bahir based on a high-resolution AMS 14C chronology on parallel carbonate and charcoal samples to estimate possible reservoir effects. The third objective is to test controversially-discussed hypotheses about the timing, magnitude and synchronicity of the African Humid Period across the continent including the possible abruptness and internal variability of this event and the influence of this important dry-wet-dry shift in the tropics on the biosphere. (DFG TR419/8-1)
Chew Bahir Drilling Project (DFG)
The overall goal of the six-year project is to test hypothesized linkages between climate and mammalian (including hominin) evolution in tropical-subtropical eastern Africa by the acquisition and analysis of long sediment core records of environmental change from the Chew Bahir basin. The anticipated time interval to be investigated by analysis of the cores is at least the last 500,000 yrs. This time interval includes the episodic presence of archaic Homo sapiens (<500 ka BP, including H. heidelbergensis andH. rhodesiensis), anatomically modern humans (AMH, since <200 ka BP), and H. sapiens sapiens (the subspecies including all modern humans, since ~100 ka BP). It also includes the first (apparently failed) dispersal of AMH from Africa (125-100 ka BP) and the successful "Out of Africa II (or III)" expansion at around 80-40 ka BP. We plan to obtain long (minimum 400 m) continuous drill core records of mostly lacustrine deposits spanning the full time interval of the evolution of our own species and its direct ancestors. All investigations of these cores are based on comprehensive experience in the analysis of short cores obtained in the same locality (see Chew Bahir Coring Project), provenance and remote sensing studies in the southern Ethiopian Rift, and precipitation statistics. This project contributes to the Hominin Sites and Paleolake Drilling Program led by A. Cohen (U Arizona).
Hominid Sites and Paleolakes Drilling Project (ICDP)
Understanding the temporal and causal relationship between climate and human evolution is an enduring scientific challenge. Past attempts to understand this relationship have focused on outcrops containing hominin fossils and artifacts, or by using ocean and lake core records to help interpret the hominin fossil record. However, outcrop records are discontinuous and weathered, and deep sea cores integrate environmental histories over vast areas and are far from the hominin fossils. We propose a new approach, combining the advantages of obtaining drill core records of lake deposits close in age and location to hominin localities with the easier logistics of targeting shallow depth paleolake deposits on land, accessible by a truck-mounted drill rig. Drill cores from lakes have yielded exceptionally well-resolved records of climate change, and the approach we propose in HSPDP is strongly informed by the experience and results of deep lake drilling for collecting high-resolution paleoclimate records. Similar records can be collected from lake beds now on-land. Through an anthropology-geoscience community collaboration, the HSPDP Steering Committee has identified several high-priority basins in East Africa, where world-class paleoanthropological sites are situated near thick and highly resolved lacustrine deposits.
Age-Depth Modeling (DFG)
The age models of fluvio-lacustrine sedimentary sequences are often subject of discussions in paleo- climate research. The techniques employed to build an age model are very diverse, ranging from visual or intuitive estimation of the age-depth relationship over linear or spline interpolations between age control points to sophisticated Bayesian techniques also taking into account the most likely deposition times of the type of sediment within the sequence. All these methods, however, fail in detecting abrupt variations in sedimentation rates, including the possibility of episodes of no deposition (hiatus), which is the strength of the method presented in this work. The new technique simply compares the deposition time of equally thick sediment slices from the differences of subsequent radiometric age dates and the unit deposition times of the various sediment types. The percentage overlap of the distributions of these two sources of information, together with the evidence from the sedimentary record, helps to build an age model of complex sequences including abrupt variations in the rate of deposition including one or many hiatuses.
Bioturbational Signal Distortion of Paleoceanographic Time Series (DFG)
Bioturbation (or benthic mixing) causes significant distortions in marine stable isotope signals and other palaeoceanographic records. Although the influence of bioturbation on these records is well known it has rarely been dealt systematically. This project in modeling, quantifying and deconvolving bioturbation in deep-sea sediments.
DNA-Metabarcoding of Plankton in East Africa (DFG)
Lake-sediment cores provide natural archives of past environmental changes, traditionally analyzed with sedimentological, geochemical and paleontological methods. More recently, samples from sediment cores have also been subjected to molecular DNA analysis, targeting either the living community of soil microbes or remnants of organisms that inhabited the lake and/ or its surface sediment in the past. The project proposed here aims at evaluating the possibility for DNA metabarcoding in the Chew Bahir sediment cores, combining state-of-the-art techniques of environmental genomics and ancient DNA analysis. The principal research questions addressed by the project are: (1) How far back in time can DNA remnants in the Chew Bahir sediment cores be extracted and analyzed? (2) How congruent are the results of PCR-based vs. hybridization- capture-based metabarcoding? and (3) What are the long-term trends and shifts in the plankton communities in the Chew Bahir record? The results of this project will provide an important contribution to the understanding of interactions between the environment and the biosphere in the past, particularly in sediments, in which microscopically recognizable organic remains are scarce or absent. Furthermore, we expect important methodological advances in the study of sediments of tropical lakes, which will be in future projects of great importance.