Two‐step vegetation response to enhanced precipitation in Northeast Brazil during Heinrich event 1

High resolution palynological and geochemical data of sediment core GeoB 3910‐2 (located offshore Northeast Brazil) spanning the period between 19 600 and 14 500 calibrated year bp (19.6–14.5 ka) show a land‐cover change in the catchment area of local rivers in two steps related to changes in precipitation associated with Heinrich Event 1 (H1 stadial). At the end of the last glacial maximum, the landscape in semi‐arid Northeast Brazil was dominated by a very dry type of caatinga vegetation, mainly composed of grasslands with some herbs and shrubs. After 18 ka, considerably more humid conditions are suggested by changes in the vegetation and by C_org and C/N data indicative of fluvial erosion. The caatinga became wetter and along lakes and rivers, sedges and gallery forest expanded. The most humid period was recorded between 16.5 and 15 ka, when humid gallery (and floodplain) forest and even small patches of mountainous Atlantic rain forest occurred together with dry forest, the latter being considered as a rather lush type of caatinga vegetation. During this humid phase erosion decreased as less lithogenic material and more organic terrestrial material were deposited on the continental slope of northern Brazil. After 15 ka arid conditions returned. During the humid second phase of the H1 stadial, a rich variety of landscapes existed in Northeast Brazil and during the drier periods small pockets of forest could probably survive in favorable spots, which would have increased the resilience of the forest to climate change.     

Out of Africa and into an ice age: on the role of global climate change in the late Pleistocene migration of early modern humans out of Africa

The results from two climate model simulations are used to explore the relationship between North Atlantic sea surface temperatures and the development of African aridity around 100,000 years ago. Through the use of illustrative simulations with an Earth System Climate Model, it is shown that freshwater fluxes associated with ice sheet surges into the North Atlantic, known as Heinrich events, lead to the southward shift of the intertropical convergence zone over Africa. This, combined with the overall increased aridity in the cooler mean climate, leads to substantial changes in simulated African vegetation cover, particularly in the Sahel. We suggest that Heinrich events, which occurred episodically throughout the last glacial cycle, led to abrupt changes in climate that may have rendered large parts of North, East, and West Africa unsuitable for hominin occupation, thus compelling early Homo sapiens to migrate out of Africa.     

The influence of abrupt climate change on the ice‐age vegetation of the Central American lowlands

Aim To investigate the effects of abrupt climate change in the North Atlantic on the vegetation history of lowland Central America. We use palynological evidence from a Central American lake on the Yucatan Peninsula to evaluate the effects of rapid climate changes during the last ice age, between 65 and 8 ka. Location Lake Petén‐Itzá, lowlands of northern Guatemala. Methods Sediment core PI‐6 was sampled at c. 170‐year resolution for pollen and charcoal analysis in order to construct a temporal sequence of environmental change. Uni‐ and multivariate statistical analyses were performed on the pollen dataset to test whether there was an association between Heinrich events in the North Atlantic and vegetation changes in the Central American lowlands. Results Pollen analysis revealed that the composition of plant assemblages on the Yucatan Peninsula varied in phase with rapid changes in North Atlantic climate. Pine savannas were the main vegetation type between c. 60 and 47 ka. These savannas gave way to pine–oak (Pinus–Quercus) forests in the latter half of the last ice age. Marked episodes of replacement of the pine–oak assemblage by xeric‐tolerant taxa occurred during Heinrich events. The Last Glacial Maximum (LGM) was characterized by mesic conditions. Main conclusions The pollen record from Lake Petén‐Itzá showed that vegetation changes associated with Heinrich events were more significant than those associated with the LGM. Each Heinrich event produced a characteristic shift towards xeric taxa. Although colder than Heinrich events, the LGM on the Yucatan Peninsula was relatively moist, and the presumed savannization of the landscape during the maximum cooling of the last glacial was not supported by our data. Our findings suggest alternative scenarios for plant diversification and genetic interchange during glacial times, and also indicate that vegetation in tropical continental settings was not as stable as previously thought.     

Axes, planes and tubes, or the geometry of embryogenesis

The paper presents selected figures of chick embryogenesis as depicted in the classic studies of Caspar Friedrich Wolff (1734–1794), Christian Heinrich Pander (1794–1865) and Karl Ernst von Baer (1792–1786). My main objective here is (1) to demonstrate how the imagery of Wolff, Pander and Baer attempted to project an image of a 3-dimensional rotating body into static figures on paper by means of linear contours, and (2) to ponder on the efficacy and pervasiveness of dots, lines and arrows for depicting embryogenesis.     

再论华南地区末次冰盛期植被类型

根据南海北部17940孔和台湾中部头社孔孢粉序列对比结果,首次提出了华南地区15—40kaBP期间的三个具代表性植物群1)以青栲类为主的亚热带常绿阔叶林为第1植物群,该植物群在MIS2阶段(20—15kaBP),为南海北部周边地区和台湾中部头社盆地周围地带性植被;2)以松属或桤木属为主的木本植物为第2植物群,对应于间冰阶,夏季风盛行,降水充沛,气候暖湿,高海面(高湖面);3)以蒿属或以禾草为主的草本植物为第3植物群,对应于冰阶,冬季风盛行,降水少,气候暖干,低海面(低湖面)。第2、3植物群在末次冰期时段呈交替出现,表现出东亚季风在本区的旋回特征。文中推论了LGM时段大陆架上的植被类型为陆架前缘的浅水区分布着红树林,裸露的陆架前后缘分别生长着草地、灌木丛和常绿阔叶林。最后,本文提出了蒿属峰值与北大西洋Heinrich事件的对比。     

Timescales and cultural process at 40,000 BP in the light of the Campanian Ignimbrite eruption, Western Eurasia

Significant new information shows that the Campanian Ignimbrite (CI) eruption from the Phlegrean Fields, southern Italy, was much larger than hitherto supposed and in fact one of the largest late Quaternary explosive events. The eruption can be dated to 40,000 calendar years ago, within the interval of the so-called Middle to Upper Paleolithic 'transition'. Its position can be precisely correlated with a number of other environmental events, including Heinrich Event 4 (HE4), the Laschamp excursion, and a particular cosmogenic nuclide peak. In view of this unique combination of factors, we studied the CI volcanic catastrophe with particular attention to its impact on climate and human ecosystems, including potential interference with ongoing processes of cultural evolution (biological evolution is best left aside for the moment). The contribution of this research is chronological and ecological. The CI volcanic event provides an unequalled means of correlating stratigraphic sequences across Western Eurasia, either directly or indirectly, and affords a unique opportunity to establish the age and climatic context of important archaeological sequences. Ecologically, the CI eruption inevitably interacted with the beginning of HE4 in terms of atmospheric feedback systems. Their combined forcing produced a sudden and at least hemispheric climatic deterioration; a 'volcanic winter' scenario cannot be ruled out. Paleolithic occupation was severely altered throughout the direct-impact zone of the eruption and likely along fringe areas in southern and southeastern Europe. The above observations call for a reconsideration of the processes and rhythms involved in the Middle to Upper Paleolithic 'transition'. A tentative model is suggested that links the exceptional environmental stress at 40,000 BP with processes already active in Paleolithic societies, leading to a period of accelerated change in cultural configurations. These eventually evolved into an Upper Paleolithic proper at a later date. The evidence to invoke allochthonous cultural input or invasionist scenarios is not considered compelling.     

Reinhart Heinrich (1946-2006): an annotated bibliography

Reinhart Heinrich contributed to many areas of theoretical biology, most notably to metabolic control analysis, a field that he helped to create, but also different aspects of modelling and to the evolution of enzyme catalysis. His interests were initially focussed on the erythrocyte, but subsequently broadened to encompass calcium oscillations, glycolytic oscillations, membrane processes and signal transduction. His publications are arranged here according to subject area, together with some introductory notes.     

The Case of Heinrich Wilhelm Poll (1877–1939): A German-Jewish Geneticist, Eugenicist, Twin Researcher, and Victim of the Nazis

This paper uses a reconstruction of the life and career of Heinrich Poll as a window into developments and professional relationships in the biological sciences in Germany in the period from the beginning of the twentieth century to the Nazi seizure of power in 1933. Poll’s intellectual work involved an early transition from morphometric physical anthropology to comparative evolutionary studies, and also found expression in twin research – a field in which he was an acknowledged early pioneer. His advocacy of eugenics led to participation in state-sponsored committees convened to advise on social policy, one of which debated sterilisation and made recommendations that led eventually to the establishment of the notorious Kaiser Wilhelm Institute for Anthropology, Human Heredity and Eugenics. However, his status as a prominent geneticist and, in particular, as a eugenicist had an ironic and ultimately tragic dimension. Heinrich Poll was of Jewish birth, and this resulted in his career being destroyed by an application of the population policies he had helped put in place.