Post by grrraaahhh on Nov 10, 2010 19:47:59 GMT -9
DNA Analysis Reveals Rapid Population Shift Among Pleistocene Cave Bears
ScienceDaily (Feb. 25, 2007) — Studying DNA obtained from teeth of ancient cave bears, researchers have been able to identify a shift in a particular population of the bears inhabiting a European valley in the late Pleistocene era. The findings illustrate the ability of DNA sequence analysis to reveal aspects of animal population dynamics in the distant past and potentially illuminate the influence of human migrations in animal population changes. The new work, reported by a collaborative group of researchers including Michael Hofreiter of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, appears in the February 20th issue of the journal Current Biology, published by Cell Press.
Post by grrraaahhh on Nov 10, 2010 19:48:31 GMT -9
Climate Change Wiped Out Cave Bears 13 Millennia Earlier Than Thought
ScienceDaily (Dec. 7, 2008) — Enormous cave bears, Ursus spelaeus, that once inhabited a large swathe of Europe, from Spain to the Urals, died out 27,800 years ago, around 13 millennia earlier than was previously believed, scientists have reported.
"Our work shows that the cave bear, among the megafauna that became extinct during the Last Glacial period in Europe, was one of the earliest to disappear," said Dr Martina Pacher of the Department of Palaeontology at the University of Vienna. "Other, later extinctions happened at different times within the last 15,000 years."
Post by grrraaahhh on Nov 10, 2010 19:49:01 GMT -9
Public release date: 24-Aug-2010 [ Print | E-mail | Share Share ] [ Close Window ]
Contact: SINC firstname.lastname@example.org 34-914-251-820 FECYT - Spanish Foundation for Science and Technology
True causes for extinction of cave bear revealed
The cave bear started to become extinct in Europe 24,000 years ago, but until now the cause was unknown. An international team of scientists has analysed mitochondrial DNA sequences from 17 new fossil samples, and compared these with the modern brown bear. The results show that the decline of the cave bear started 50,000 years ago, and was caused more by human expansion than by climate change.
"The decline in the genetic diversity of the cave bear (Ursus spelaeus) began around 50,000 years ago, much earlier than previously suggested, at a time when no major climate change was taking place, but which does coincide with the start of human expansion", Aurora Grandal-D'Anglade, co-author of the study and a researcher at the University Institute of Geology of the University of Coruña, tells SINC.
According to the research study, published in the journal Molecular Biology and Evolution, radiocarbon dating of the fossil remains shows that the cave bear ceased to be abundant in Central Europe around 35,000 years ago.
"This can be attributed to increasing human expansion and the resulting competition between humans and bears for land and shelter", explains the scientist, who links this with the scarce fossil representation of the bear's prey in the abundant fossil record of this species.
In order to reach their conclusions, the team of scientists, led by the Max Planck Institute for Evolutionary Anthropology (Germany) studied mitochondrial DNA sequences from bear fossils in European deposits (Siberia, Ukraine, Central Europe and the Iberian Peninsula, specifically Galicia), and carried out a Bayesian analysis (of statistical probability).
The scientists also made comparisons with the modern brown bear (Ursus arctos) and with fossil samples of this species of bear, and managed to show why one became extinct and the other did not. In order to demonstrate this, the study analysed 59 cave bear DNA sequences and 40 from the brown bear, from between 60,000 and 24,000 years ago for the cave bear and from 80,000 years ago up to the present day for the brown bear.
Decline of the caves, extinction of the bears
The impoverishment of ecosystems during the last glacial maximum was "the 'coup de grace' for this species, which was already in rapid decline", the author explains.
The present day brown bear did not suffer the same fate and has survived until today for one simple reason – brown bears did not depend so heavily on the cave habitat, which was becoming degraded, and this is why they did not follow the same pattern as the cave bears.
"Brown bears rely on less specific shelters for hibernation. In fact, their fossil remains are not very numerous in cave deposits", the Galician researcher says.
The definitive extinction of the cave bear "broadly" coincides with the last cooling of the climate during the Pleistocene (between 25,000 and 18,000 years ago), which may have led to a reduction in shelter and the vegetation that the animals fed on.
The cave bear inhabited Europe during the Late Pleistocene and became definitively extinct around 24,000 years ago, although it held out for a few thousand years longer in some areas, such as the north west of the Iberian Peninsula, than in other places. This ursid was a large animal, weighing 500 kg on average, and was largely a herbivore. The bear hibernated in the depths of limestone caves, where the remains of individuals that died during hibernation slowly accumulated over time.
Stiller, Mathias; Baryshnikov, Gennady; Bocherens, Herve; Grandal D'Anglade, Aurora; Hilpert, Brigitte; Muenzel, Susanne C.; Pinhasi, Ron; Rabeder, Gernot; Rosendahl, Wilfried; Trinkaus, Erik; Hofreiter, Michael; Knapp, Michael. "Withering Away-25,000 Years of Genetic Decline Preceded Cave Bear Extinction" Molecular Biology and Evolution 27(5): 975-978, mayo de 2010. doi:10.1093/molbev/msq083
Post by grrraaahhh on Nov 10, 2010 19:51:42 GMT -9
Ursus rossicus from the South Siberia
A B S T R A C T
The skull, mandibles and cheek teeth of U. rossicus from four localities of the South Siberia are examined. This species inhabited the steppe regions in early Middle and Late Pleistocene. By odontological characters it is more close to U. r. rossicus from Krasnodar, than to U. rossicus uralensis from Kizel Cave in Ural. Discriminant analysis, based on measurements of lower cheek teeth of the cave bears from seven sites of Europe and Siberia, demonstrated that U. rossicus most resembles morphometrically U. savini. As a result of cladistic analysis employed 17 characters of skull, limb bones, and dentition, the phylogenetic tree has been obtained for 7 species of the genus U r s u s. A four species of the cave bears are included in the subgenus Spelearctos: U. savini, U. rossicus, U. deningeri and U. spelaeus.
Pleistocene small cave bear (Ursus rossicus) from the South Siberia, Russia
Post by grrraaahhh on Apr 17, 2011 21:20:35 GMT -9
From Cave Bear Ecology and Interactions with Pleistocene Humans:
Human ancestors (Homo spp.), cave bears (Ursus deningeri, U. spelaeus), and brown bears (U. arctos) have coexisted in Eurasia for at least one million years, and bear remains and Paleolithic artifacts frequently are found in the same caves. The prevalence of cave bear bones in some sites is especially striking, as these bears were exceptionally large relative to archaic humans. Do artifact-bear associations in cave deposits indicate predation on cave bears by early human hunters, or do they testify simply to early humans' and cave bears' common interest in natural shelters, occupied on different schedules? Answering these and other questions about the circumstances of human-cave bear associations is made possible in part by expectations developed from research on modern bear ecology, time-scaled for paleontologic and archaeologic applications. Here I review available knowledge on Paleolithic human-bear relations with a special focus on cave bears (Middle Pleistocene U. deningeri) from Yarimburgaz Cave, Turkey. Multiple lines of evidence show that cave bear and human use of caves were temporally independent events; the apparent spatial associations between human artifacts and cave bear bones are explained principally by slow sedimentation rates relative to the pace of biogenic accumulation and bears' bed preparation habits. Hibernation-linked behaviors and population characteristics of cave bears, based on osteometric, isotopic, and age and sex structure analyses, indicate that they depended heavily on seasonal food supplies, which were rich in resistant plant materials and cryptic, gritty foods. There is little evidence of direct ecological interaction among Pleistocene humans and cave bears.
Description: A nearly complete skull in total length of about 472 mm of an adolescent male of about 2-3 years of age, which brain case or nasal sutures and other ones are not fused. The lower jaws are composed ones from other individuals, which are also lacking most of the incisive teeth. The left mandible lacks the P4. The left one has a modern lost of the ramus. The skull (Figs. 2-4) is lacking all incisive teeth, but has all P4-M2 and the canini. The latter are damaged modernly on their tips. The parietals have open foramina on both sides each, which are below a saggital crest depression. The tooth morphology is perfectly preserved in such an early adult cave bear (Fig. 4), only one tip of the right P4 is broken of modern. www.ssj.sk/pdf/ACS_47_S1/ACS_47_S103.pdf