Search results for "evolution"
showing 10 items of 11096 documents
Seasonal and habitat effects on the nutritional properties of savanna vegetation: Potential implications for early hominin dietary ecology.
2019
The African savannas that many early hominins occupied likely experienced stark seasonality and contained mosaic habitats (i.e., combinations of woodlands, wetlands, grasslands, etc.). Most would agree that the bulk of dietary calories obtained by taxa such as Australopithecus and Paranthropus came from the consumption of vegetation growing across these landscapes. It is also likely that many early hominins were selective feeders that consumed particular plants/plant parts (e.g., leaves, fruit, storage organs) depending on the habitat and season within which they were foraging. Thus, improving our understanding of how the nutritional properties of potential hominin plant foods growing in mo…
Timber Logging in Central Siberia is the Main Source for Recent Arctic Driftwood
2015
Abstract Recent findings indicated spruce from North America and larch from eastern Siberia to be the dominating tree species of Arctic driftwood throughout the Holocene. However, changes in source region forest and river characteristics, as well as ocean current dynamics and sea ice extent likely influence its spatiotemporal composition. Here, we present 2556 driftwood samples from Greenland, Iceland, Svalbard, and the Faroe Islands. A total of 498 out of 969 Pinus sylvestris ring width series were cross-dated at the catchment level against a network of Eurasian boreal reference chronologies. The central Siberian Yenisei and Angara Rivers account for 91% of all dated pines, with their oute…
Conjunctive use of spectral gamma-ray logs and clay mineralogy in defining late Jurassic-early Cretaceous palaeoclimate change (Dorset, U.K.).
2006
Abstract Detrital clay mineralogy is controlled by weathered source rock, climate, transport and deposition that in turn influence the spectral gamma-ray (SGR) response of resultant sediments. Whilst a palaeoclimate signal in clay mineralogy has been established in some ancient successions, the SGR response remains contentious, largely because the data sets have yet to be collected at the same or appropriate vertical scales to allow comparison. In addition, the influence of organic matter on SGR is not always considered. Here, we present clay mineralogical, total organic carbon (TOC) and SGR analyses from the late Jurassic and early Cretaceous of the Wessex Basin, a period of previously doc…
Évolution rétrograde de Neospathodus au cours de la crise Permo - Triasique
2016
The Permian - Triassic evolution of platform conodonts (Gondolellidae) consists mainly in developing the carina and the platform. During the sublethal environmental stress conditions subsequent to the Permian - Triassic extinction, the Wuchiapingian - Griesbachian Clarkina lineage is replaced by the primitive looking platform-lacking Dienerian - Aegean Neospathodus kummeli - Kashmirella timorensis lineage. Moreover, above Jinogondolella denticulata, end of the Capitanian Jinogondolella lineage, “Neospathodus” arcucristatus, an atavistic blade-like homeomorph that lacks a platform, underlies Protoclarkina crofti, of the base of the anagenetic Clarkina lineage. These primitive-looking forms a…
High-resolution geochemical and biotic records of the Tethyan 'Bonarelli Level' (OAE2, latest Cenomanian) from the Calabianca-Guidaloca composite sec…
2004
Abstract High-resolution micropalaeontological and chemostratigraphic records for the upper Cenomanian portion of the Calabianca–Guidaloca composite section (NW Sicily) provide new insight into the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean. The Bonarelli Level equivalent was identified on the basis of lithology and well constrained by calcareous plankton biostratigraphy and radiolarian assemblages, as well as by the δ 13 C curve showing a marked positive excursion (up to 4.7‰). The Bonarelli Level equivalent deposition is characterized by highly eutrophic conditions as testified by radiolarian proliferation. Black shale samples from the Calabianca–Guidaloca composi…
Griesbachian and Dienerian (Early Triassic) ammonoid faunas from Northwestern Guangxi and Southern Guizhou (South China).
2008
30 pages; International audience; Intensive sampling of the Luolou (northwestern Guangxi) and the Daye (southern Guizhou) Formations in South China leads to the recognition of a regional Griesbachian and Dienerian ammonoid succession for this key palaeobiogeographical area. The new biostratigraphical sequence comprises the upper Griesbachian ‘Ophiceras beds' and the lower Dienerian ‘Proptychites candidus beds', which are separated from the uppermost Dienerian ‘Clypites beds' by an unfossiliferous interval. These faunas contain some taxa with wide geographic distribution (e.g. Ambites, Pleurambites, Pleurogyronites, Proptychites candidus), thus facilitating correlation with faunal succession…
Early Pliocene continental vertebrate fauna at Puerto de la Cadena (SE Spain) and its bearing on the marine-continental correlation of the Late Neoge…
2017
In this paper, we synthesize sedimentological, magnetostratigraphic and paleontological data from the continental vertebrate site of Puerto de la Cadena (Murcia, SE Spain), in order to clarify its age. The study site is located on the northern edge of the Carrascoy mountain range, in the upper part of the Cigarrón Unit. The end-Messinian discontinuity has been detected at the base of this unit, which indicates it has an early Pliocene age. Abundant remains of small and large vertebrates, including rodents, lagomorphs, primates, carnivorans, perissodactyls, artiodactyls, proboscideans, testudines, squamats, and crocodiles, have been found in this area. Some of these elements are of African o…
Bone diagenesis in arid environments; An intra-skeletal approach
2014
Bone trace element content and isotopic composition are closely related to human nutrition. The investigation of archaeological bone geochemistry can help us to better understand the relationship between past populations and their environment alongside cultural practices as inferred from dietary reconstruction. However, dietary in- formation may be altered post-mortem by diagenetic processes in soil. In this study, bone mineralogy (Ca/P, sec- ondary minerals, organic matter content and bone apatite crystallinity), histology, element content (Mg, Na, F, Sr, Ba, Mn, Fe, La, Ce and U) and stable isotope composition (δ13Candδ18O carbonate) were investigated at the intra- individual scale in ord…
Influence of dissolved organic matter on rare earth elements and yttrium distributions in coastal waters
2010
International audience; Data collected during this study indicate that dissolved Y and REE (rare earth element) behaviour can be monitored through shale-normalised ratios. Relationships occurring between these ratios suggest that leaching from lithogenic materials is the main source of REE in the studied area. This process involves riverine detrital matter in the inner area of the Gulf of Palermo. Features of shale-normalised patterns and the relationship recognised between dissolved Fe and Y/Ho suggest that REE are released from Fe-rich coatings of atmospheric dust. Observed similarities between dissolved Fe and chlorophyll- content suggest that leaching of Fe-rich atmospheric particulates…
Dental calculus indicates widespread plant use within the stable Neanderthal dietary niche.
2018
The ecology of Neanderthals is a pressing question in the study of hominin evolution. Diet appears to have played a prominent role in their adaptation to Eurasia. Based on isotope and zooarchaeological studies, Neanderthal diet has been reconstructed as heavily meat-based and generally similar across different environments. This image persists, despite recent studies suggesting more plant use and more variation. However, we have only a fragmentary picture of their dietary ecology, and how it may have varied among habitats, because we lack broad and environmentally representative information about their use of plants and other foods. To address the problem, we examined the plant microremains…