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Abstract: The northeastern Qinghai-Tibetan Plateau (QTP) lies at the convergence of the Asian winter and summer monsoons and westerlies, making it an ideal place for studying the effects of climatic change, owing to its fragile ecological environment and unique geographical location. This paper reports on a multi-proxy analysis consisting of magnetic susceptibility, total organic carbon content (TOC), pollen, grain size, and geochemical parameters from the peat deposit in the Gonghe Basin to reconstruct the Holocene millennial-scale climatic variation. The results indicate that the climate tended to be warm and humid since 10.0 cal ka BP, but it deteriorated obviously (cold and dry) in 8.6–7.1 cal ka BP. The regional optimal warm and humid period was from 7.1–3.8 cal ka BP, although there were frequent climatic fluctuations during that time. Thereafter, the climate became cold and dry. 10 millennial-time-scale cold events were recorded, which were coincident with climatic records from deep sediments in the North Atlantic Ocean, ice cores, lakes, peat, and aeolian deposits in the QTP. In addition, we discovered that the southwestern monsoons forced by solar insolation in the Holocene have crucial effects on regional climatic change, and the millennial-scale cold fluctuations are possibly related to the thermohaline circulation (THC). [Copyright &y& Elsevier]

Abstract: Research into the links between climatic change and hominin evolution has generated numerous hypotheses. In recent years, methodological refinement of, and increased research effort directed towards, reliable proxies for palaeoclimatic change have provided a growing body of data with which to test such hypotheses. Whilst many archaeologists are aware of these data, few are cognizant of the wealth of techniques developed by theoretical biologists over the last half-century to explicitly address the evolutionary consequences of adaptation to temporally heterogeneous environments. The current paper expands and adapts one such technique for use with empirical data, and applies it to a global palaeoclimatic record spanning the last five million years, in order to discern the potential impact of environmental heterogeneity on hominin evolution during this period. Of particular interest are the contributions of climatic change, associated with directional selection, and climatic variability, associated with selection for phenotypic plasticity. At this macro-scale, results suggest an early peak in selection for plasticity at approximately 2–2.7 mya, combined with three major shifts in directional selection at approximately 3.3–3.4, 1.4–1.5, and 0.5–0.6 mya. These results are employed to relate the fossil and archaeological records to a number of environmental hypotheses of human evolution. In particular, it is argued that the origins of the genus Homo and the spread of Oldowan technology are associated not with a major turnover pulse, but with a period of selection for phenotypic plasticity. [Copyright &y& Elsevier]

Abstract: Australia has not always been arid, and the central desert was once well watered. This paper traces the changes in climate and vegetation, leading to the present aridity. At the beginning of the Cenozoic, continental Australia had a warm and humid climate, and the vegetation was mainly meso–micro-thermal (warm to cool temperate) rainforest. Central Australia experienced seasonal rainfall and there may have been limited aridity in the northwest. By the mid–late Eocene, rainforest in central Australia was restricted to the well-watered valley bottoms, with sclerophyll vegetation on the slopes and ridges. In the latest Eocene–earliest Oligocene, there was an abrupt cooling of ocean waters and the diversity of megathermal angiosperms decreased. The early–mid-Miocene was warm–humid and there was a considerable diversity of forest types. Woodlands and Casuarinaceae forests became more common. Central Australia was seasonal, with a very warm season of high evaporation. In Western Australia, regular flows in the palaeodrainage systems had stopped by the mid-Miocene and this marked the first major step towards aridity. The late Miocene was cool and dry, with a major reduction of rainforests and an increase of Eucalyptus/casuarinaceous sclerophyll forests in inland southeastern Australia. Regular burning became a feature of the eucalypt forests. Rainforest persisted, however, along the east coast and highlands of Australia. Central Australia became more arid with dry woodland and chenopod shrublands. Rainforests continued to decrease during the Pliocene and grasslands developed in central northern Australia. By the early Pleistocene, the modern climatic regime had been established, but precipitation was higher than today. Cycles of open, shrubland/grasslands/herbfields and wooded vegetation accompanied the arid glacial and humid interglacial cycles (respectively). About 0.5Ma, there was a change to a drier climate, but it was still wetter than today. The last glacial period was particularly harsh, and the present interglacial period is drier than the previous interglacial. Aridity has thus increased in a number of steps, following the first major step towards aridity in the early Miocene. Distinctive elements of the vegetation can be traced back to times when the arid zone was humid and supported rainforest. The elements, which have remained in arid regions, are the few that could tolerate or adapt to the drier climates. The taxa, which could not cope with these changing conditions, were eliminated from the arid regions. [Copyright &y& Elsevier]