Early dispersal of modern humans in Europe and implications for Neanderthal behaviour

The appearance of anatomically modern humans in Europe and the nature of the transition from the Middle to Upper Palaeolithic are matters of intense debate. Most researchers accept that before the arrival of anatomically modern humans, Neanderthals had adopted several 'transitional' technocomplexes. Two of these, the Uluzzian of southern Europe and the Chatelperronian of western Europe, are key to current interpretations regarding the timing of arrival of anatomically modern humans in the region and their potential interaction with Neanderthal populations. They are also central to current debates regarding the cognitive abilities of Neanderthals and the reasons behind their extinction. However, the actual fossil evidence associated with these assemblages is scant and fragmentary, and recent work has questioned the attribution of the Chatelperronian to Neanderthals on the basis of taphonomic mixing and lithic analysis. Here we reanalyse the deciduous molars from the Grotta del Cavallo (southern Italy), associated with the Uluzzian and originally classified as Neanderthal. Using two independent morphometric methods based on microtomographic data, we show that the Cavallo specimens can be attributed to anatomically modern humans. The secure context of the teeth provides crucial evidence that the makers of the Uluzzian technocomplex were therefore not Neanderthals. In addition, new chronometric data for the Uluzzian layers of Grotta del Cavallo obtained from associated shell beads and included within a Bayesian age model show that the teeth must date to ~45,000-43,000 calendar years before present. The Cavallo human remains are therefore the oldest known European anatomically modern humans, confirming a rapid dispersal of modern humans across the continent before the Aurignacian and the disappearance of Neanderthals.     

Effect of natural iron fertilization on carbon sequestration in the Southern Ocean

The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization--an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below--as invoked in some palaeoclimatic and future climate change scenarios--may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.     

Neanderthals in central Asia and Siberia

Morphological traits typical of Neanderthals began to appear in European hominids at least 400,000 years ago and about 150,000 years ago in western Asia. After their initial appearance, such traits increased in frequency and the extent to which they are expressed until they disappeared shortly after 30,000 years ago. However, because most fossil hominid remains are fragmentary, it can be difficult or impossible to determine unambiguously whether a fossil is of Neanderthal origin. This limits the ability to determine when and where Neanderthals lived. To determine how far to the east Neanderthals ranged, we determined mitochondrial DNA (mtDNA) sequences from hominid remains found in Uzbekistan and in the Altai region of southern Siberia. Here we show that the DNA sequences from these fossils fall within the European Neanderthal mtDNA variation. Thus, the geographic range of Neanderthals is likely to have extended at least 2,000 km further to the east than commonly assumed.     

Effects of prescribed fall burning on a wetland plant community, with implications for management of plants and herbivores

An important contemporary challenge for adaptive resource management is assessing both the direct and indirect effects of management activities by designing appropriate monitoring programs and sound analysis methods. Here we evaluate the effects of prescribed fall burning on a wetland plant community that is managed primarily for spring-migrating geese. During late fall in 2 consecutive years, we burned vegetation in 4 replicate blocks (2.3 ha each) that traversed a natural moisture and associated vegetation gradient. We used ordination, gradient analysis, and contingency table analysis to evaluate how annual changes in relative abundance of plants were affected by burning as well as other important ecological factors. Burning increased species diversity of plants, especially in the 2 wetter vegetation zones, but had no effect on species richness or on the proportion of native plant species. Wetland plant species responded to prescribed burning independently, and their response often differed by vegetation zone and with annual variation in flooding. Burning enhanced the abundance of native foxtail barley ( Hordeum jubatum ) and reduced the abundance of introduced swamp timothy ( Crypsis shoenoides ). Saltgrass ( Distichlis spicata ), a native plant species, was usually less abundant following burning, although the level of response was different for each of the 3 vegetation zones. Two other introduced plant species, quackgrass ( Elytrigia repens ) and reed canarygrass ( Phalaris arundinaceae ), were less abundant after fall burning, especially when spring flooding was more extensive. Wild geese using the experimental blocks for feeding clearly preferred burned sites, suggesting that fall burning can enhance wetland use by geese during spring. Given that simple manipulations such as burning and flooding of a wetland system may often produce complex results, we suggest that on-going management schemes be regularly evaluated with field experiments such as those conducted in this study.     

Multifunctionality of extracellular and cell surface heparan sulfate proteoglycans

Heparan sulfate proteoglycans are a remarkably diverse family of glycosaminoglycan-bearing protein cores that include the syndecans, the glypicans, perlecan, agrin, and collagen XVIII. Members of this protein class play key roles during normal processes that occur during development, tissue morphogenesis, and wound healing. As key components of basement membranes in organs and tissues, they also participate in selective filtration of biological fluids, in establishing cellular barriers, and in modulation of angiogenesis. The ability to perform these functions is provided both by the features of the protein cores as well as by the unique properties of heparan sulfate, which is assembled as a polymer of N-acetylglucosamine and glucuronic acid and modified by specific enzymes to generate specialized biologically active structures. This article discusses the structures and functions of this amazing family of proteoglycans and provides a platform for further study of the individual members.