TY - JOUR A1 - Maslin, Mark A. A1 - Shultz, Susanne A1 - Trauth, Martin H. T1 - A synthesis of the theories and concepts of early human evolution JF - Philosophical transactions of the Royal Society of London : B, Biological sciences N2 - Current evidence suggests that many of the major events in hominin evolution occurred in East Africa. Hence, over the past two decades, there has been intensive work undertaken to understand African palaeoclimate and tectonics in order to put together a coherent picture of how the environment of Africa has varied over the past 10 Myr. A new consensus is emerging that suggests the unusual geology and climate of East Africa created a complex, environmentally very variable setting. This new understanding of East African climate has led to the pulsed climate variability hypothesis that suggests the long-term drying trend in East Africa was punctuated by episodes of short alternating periods of extreme humidity and aridity which may have driven hominin speciation, encephalization and dispersals out of Africa. This hypothesis is unique as it provides a conceptual framework within which other evolutionary theories can be examined: first, at macro-scale comparing phylogenetic gradualism and punctuated equilibrium; second, at a more focused level of human evolution comparing allopatric speciation, aridity hypothesis, turnover pulse hypothesis, variability selection hypothesis, Red Queen hypothesis and sympatric speciation based on sexual selection. It is proposed that each one of these mechanisms may have been acting on hominins during these short periods of climate variability, which then produce a range of different traits that led to the emergence of new species. In the case of Homo erectus (sensu lato), it is not just brain size that changes but life history (shortened inter-birth intervals, delayed development), body size and dimorphism, shoulder morphology to allow thrown projectiles, adaptation to long-distance running, ecological flexibility and social behaviour. The future of evolutionary research should be to create evidence-based meta-narratives, which encompass multiple mechanisms that select for different traits leading ultimately to speciation. KW - human evolution KW - East Africa KW - palaeoclimatology KW - hominin KW - pulsed climate variability framework Y1 - 2015 U6 - https://doi.org/10.1098/rstb.2014.0064 SN - 0962-8436 SN - 1471-2970 VL - 370 IS - 1663 PB - Royal Society CY - London ER - TY - JOUR A1 - Foerster, Verena A1 - Vogelsang, Ralf A1 - Junginger, Annett A1 - Asrat, Asfawossen A1 - Lamb, Henry F. A1 - Schäbitz, Frank A1 - Trauth, Martin H. T1 - Environmental change and human occupation of southern Ethiopia and northern Kenya during the last 20,000 years JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Our understanding of the impact of climate-driven environmental change on prehistoric human populations is hampered by the scarcity of continuous paleoenvironmental records in the vicinity of archaeological sites. Here we compare a continuous paleoclimatic record of the last 20 ka before present from the Chew Bahir basin, southwest Ethiopia, with the available archaeological record of human presence in the region. The correlation of this record with orbitally-driven insolation variations suggests a complex nonlinear response of the environment to climate forcing, reflected in several long-term and short-term transitions between wet and dry conditions, resulting in abrupt changes between favorable and unfavorable living conditions for humans. Correlating the archaeological record in the surrounding region of the Chew Bahir basin, presumably including montane and lake-marginal refugia for human populations, with our climate record suggests a complex interplay between humans and their environment during the last 20 ka. The result may contribute to our understanding of how a dynamic environment may have impacted the adaptation and dispersal of early humans in eastern Africa. (C) 2015 Elsevier Ltd. All rights reserved. KW - Archeology KW - Paleoclimate KW - African humid period KW - Push factor KW - Adaption KW - Migration KW - Hunter-gatherers KW - Foragers KW - Pastoralism KW - Chew Bahir Y1 - 2015 U6 - https://doi.org/10.1016/j.quascirev.2015.10.026 SN - 0277-3791 VL - 129 SP - 333 EP - 340 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Trauth, Martin H. A1 - Bergner, Andreas G. N. A1 - Foerster, Verena A1 - Junginger, Annett A1 - Maslin, Mark A. A1 - Schäbitz, Frank T1 - Episodes of environmental stability versus instability in Late Cenozoic lake records of Eastern Africa JF - Journal of human evolution N2 - Episodes of environmental stability and instability may be equally important for African hominin speciation, dispersal, and cultural innovation. Three examples of a change from stable to unstable environmental conditions are presented on three different time scales: (1) the Mid Holocene (MH) wet dry transition in the Chew Bahir basin (Southern Ethiopian Rift; between 11 ka and 4 ka), (2) the MIS 5-4 transition in the Naivasha basin (Central Kenya Rift; between 160 ka and 50 ka), and (3) the Early Mid Pleistocene Transition (EMPT) in the Olorgesailie basin (Southern Kenya Rift; between 1.25 Ma and 0.4 Ma). A probabilistic age modeling technique is used to determine the timing of these transitions, taking into account possible abrupt changes in the sedimentation rate including episodes of no deposition (hiatuses). Interestingly, the stable-unstable conditions identified in the three records are always associated with an orbitally-induced decrease of insolation: the descending portion of the 800 kyr cycle during the EMPT, declining eccentricity after the 115 ka maximum at the MIS 5-4 transition, and after similar to 10 ka. This observation contributes to an evidence-based discussion of the possible mechanisms causing the switching between environmental stability and instability in Eastern Africa at three different orbital time scales (10,000 to 1,000,000 years) during the Cenozoic. This in turn may lead to great insights into the environmental changes occurring at the same time as hominin speciation, brain expansion, dispersal out of Africa, and cultural innovations and may provide key evidence to build new hypotheses regarding the causes of early human evolution. (C) 2015 Elsevier Ltd. All rights reserved. KW - Paleoclimate KW - East Africa KW - Human evolution KW - Lakes KW - Sediments Y1 - 2015 U6 - https://doi.org/10.1016/j.jhevol.2015.03.011 SN - 0047-2484 VL - 87 SP - 21 EP - 31 PB - Elsevier CY - London ER - TY - JOUR A1 - Ebert, Thomas A1 - Trauth, Martin H. T1 - Semi-automated detection of annual laminae (varves) in lake sediments using a fuzzy logic algorithm JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Annual laminae (varves) in lake sediments are typically visually identified, measured and counted, although numerous attempts have been made to automate this process. The reason for the failure of most of these automated algorithms for varve counting is the complexity of the seasonal laminations, typically rich in lateral fades variations and internal heterogeneities. In the manual counting of varves, the investigator acquired and interpreted flexible numbers of complex decision criteria to understand whether a particular simple lamination is a varve or not. Fuzzy systems simulate the flexible decision making process in a computer by introducing a smooth transition between true varve and false varve. In our investigation, we use an adaptive neuro fuzzy inference system (ANFIS) to detect varves on the basis of a digital image of the sediment. The results of the application of the ANFIS to laminated sediments from the Meerfelder Maar (Eifel, Germany) and from a landslide-dammed lake in the Quebrada de Cafayate of Argentina are compared with manual varve counts and possible reasons for the differences are discussed. (C) 2015 Elsevier B.V. All rights reserved. KW - Varve KW - Lake sediment KW - Image processing KW - Fuzzy logic KW - MATLAB KW - Statistics Y1 - 2015 U6 - https://doi.org/10.1016/j.palaeo.2015.05.024 SN - 0031-0182 SN - 1872-616X VL - 435 SP - 272 EP - 282 PB - Elsevier CY - Amsterdam ER -