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Monday, August 1, 2011

Fall of the Neanderthals: Volume of Modern Humans Infiltrating Europe Cited as Critical Factor




Science Daily  — New research sheds light on why, after 300,000 years of domination, European Neanderthals abruptly disappeared. Researchers from the University of Cambridge have discovered that modern humans coming from Africa swarmed the region, arriving with over ten times the population as the Neanderthal inhabitants.

The most plausible answer to this long-debated question has now been published in the journal Science by two researchers from the Department of Archaeology at Cambridge -- Professor Sir Paul Mellars, Professor Emeritus of Prehistory and Human Evolution, and Jennifer French, a second-year PhD student.The reasons for the relatively sudden disappearance of the European Neanderthal populations across the continent around 40,000 years ago has for long remained one of the great mysteries of human evolution. After 300 millennia of living, and evidently flourishing, in the cold, sub-glacial environments of central and western Europe, they were rapidly replaced over all areas of the continent by new, anatomically and genetically 'modern' (i.e. Homo sapiens) populations who had originated and evolved in the vastly different tropical environments of Africa.
By conducting a detailed statistical analysis of the archaeological evidence from the classic 'Perigord' region of southwestern France, which contains the largest concentration of Neanderthal and early modern human sites in Europe, they have found clear evidence that the earliest modern human populations penetrated the region in at least ten times larger numbers than those of the local Neanderthal populations already established in the same regions. This is reflected in a sharp increase in the total number of occupied sites, much higher densities of occupation residues (i.e. stone tools and animal food remains) in the sites, and bigger areas of occupation in the sites, revealing the formation of much larger and apparently more socially integrated social groupings.
Faced with this dramatic increase in the incoming modern human population, the capacity of the local Neanderthal groups to compete for the same range of living sites, the same range of animal food supplies (principally reindeer, horse, bison and red deer), and the same scarce fuel supplies to tide the groups over the extremely harsh glacial winters, would have been massively undermined. Additionally, almost inevitably, repeated conflicts or confrontations between the two populations would arise for occupation of the most attractive locations and richest food supplies, in which the increased numbers and more highly coordinated activities of the modern human groups would ensure their success over the Neanderthal groups.
The archaeological evidence also strongly suggests that the incoming modern groups possessed superior hunting technologies and equipment (e.g. more effective and long-range hunting spears), and probably more efficient procedures for processing and storing food supplies over the prolonged and exceptionally cold glacial winters. They also appear to have had more wide-ranging social contacts with adjacent human groups to allow for trade and exchange of essential food supplies in times of food scarcity.
Whether the incoming modern human groups also possessed more highly developed brains and associated mental capacities than the Neanderthals remains at present a matter of intense debate. But the sudden appearance of a wide range of complex and sophisticated art forms (including cave paintings), the large-scale production of elaborate decorative items (such as perforated stone and ivory beads, and imported sea shells), and clearly 'symbolic' systems of markings on bone and ivory tools -- all entirely lacking among the preceding Neanderthals -- strongly point to more elaborate systems of social communications among the modern groups, probably accompanied by more advanced and complex forms of language.
All of these new and more complex behavioural patterns can be shown to have developed first among the ancestral AfricanHomo sapiens populations, at least 20,0000 to 30,000 years before their dispersal from Africa, and progressive colonisation (and replacement of earlier populations) across all regions of Europe and Asia from around 60,000 years onwards.
If, as the latest genetic evidence strongly suggests, the AfricanHomo sapiens and European Neanderthal populations had been evolving separately for at least half a million years, then the emergence of some significant contrasts in the mental capacities of the two lineages would not be a particularly surprising development, in evolutionary terms.
Professor Sir Paul Mellars, Professor Emeritus of Prehistory and Human Evolution at the Department of Archaeology, said: "In any event, it was clearly this range of new technological and behavioural innovations which allowed the modern human populations to invade and survive in much larger population numbers than those of the preceding Neanderthals across the whole of the European continent. Faced with this kind of competition, the Neanderthals seem to have retreated initially into more marginal and less attractive regions of the continent and eventually -- within a space of at most a few thousand years -- for their populations to have declined to extinction -- perhaps accelerated further by sudden climatic deterioration across the continent around 40,000 years ago."
Whatever the precise cultural, behavioural and intellectual contrasts between the Neanderthals and intrusive modern human populations, this new study published in Sciencedemonstrates for the first time the massive numerical supremacy of the earliest modern human populations in western Europe, compared with those of the preceding Neanderthals, and thereby largely resolves one of the most controversial and long-running debates over the rapid decline and extinction of the enigmatic Neanderthal populations.

Largest-Ever Map of Plant Protein Interactions



The image shows an Arabidopsis plant overlaid on a network map of protein-protein interactions. The clusters of colours represent "communities" of interacting proteins that are enriched in specific plant processes. (Credit: Image courtesy of Joseph R. Ecker, Salk Institute for Biological Studies / Plant Photo: Joe Belcovson, Salk Institute for Biological Studies / Network map: Mary Galli, Salk Institute for Biological Studies and Matija Dreze, Center for Cancer Systems Biology at the Dana-Farber Cancer Institute)
Science Daily—An international team of scientists has described their mapping and early analyses of thousands of protein-to-protein interactions within the cells of Arabidopsis thaliana , a mustard plant variety that is to plant biology what the lab mouse is to human biology.

The four-year project was funded by an $8 million National Science Foundation grant, and was headed by Marc Vidal, Pascal Braun, David Hill and colleagues at the Dana Farber Cancer Institute in Boston; and Ecker at the Salk Institute. "It was a natural collaboration," says Vidal, "because Joe and his colleagues at the Salk Institute had already sequenced the Arabidopsis genome and had cloned many of the protein-coding genes, whereas on our side at the Dana Farber Institute we had experience in making these protein interaction maps for other organisms such as yeast.""With this one study we managed to double the plant protein-interaction data that are available to scientists," says Salk Institute plant biologist Joseph Ecker, a professor in the Plant Molecular and Cellular Biology Laboratory. "These data along with data from future 'interactome' mapping studies like this one should enable biologists to make agricultural plants more resistant to drought and diseases, more nutritious, and generally more useful to mankind."
In the initial stages of the project, members of Ecker's lab led by research technician Mary Galli converted most of their accumulated library of Arabidopsis protein-coding gene clones into a form useful for protein-interaction tests. "For this project, over 10,000 'open reading frame' clones were converted and sequence verified in preparation for protein-interaction screening," says Galli.
Vidal, Braun, Hill and their colleagues systematically ran these open reading frames through a high quality protein-interaction screening process, based on a test known as the yeast two-hybrid screen. Out of more than forty million possible pair combinations, they found a total of 6,205 Arabidopsis protein- protein interactions, involving 2,774 individual proteins. The researchers confirmed the high quality of these data, for example by showing their overlap with protein interaction datafrom past studies.
The new map of 6,205 protein partnerings represents only about two percent of the full protein- protein "interactome" forArabidopsis, since the screening test covered only a third of allArabidopsis proteins, and wasn't sensitive enough to detect many weaker protein interactions. "There will be larger maps after this one," says Ecker.
Even as a preliminary step, though, the new map is clearly useful. The researchers were able to sort the protein interaction pairs they found into functional groups, revealing networks and "communities" of proteins that work together. "There had been very little information, for example, on how plant hormone signaling pathways communicate with one another," says Ecker. "But in this study we were able to find a number of intriguing links between these pathways."
A further analysis of their map provided new insight into plant evolution. Ecker and colleagues Arabidopsis genome data, reported a decade ago, had revealed that plants randomly duplicate their genes to a much greater extent than animals do. These gene duplication events apparently give plants some of the genetic versatility they need to stay adapted to shifting environments. In this study, the researchers found 1900 pairs of their mapped proteins that appeared to be the products of ancient gene-duplication events.
Using advanced genomic dating techniques, the researchers were able to gauge the span of time since each of these gene-duplication events -- the longest span being 700 million years -- and compare it with the changes in the two proteins' interaction partners. "This provides a measure of how evolution has rewired the functions of these proteins," says Vidal. "Our large, high-quality dataset and the naturally high frequency of these gene duplications in Arabidopsis allowed us to make such an analysis for the first time."
The researchers found evidence that the Arabidopsis protein partnerships tend to change quickly after the duplication event, then more slowly as the duplicated gene settles into its new function and is held there by evolutionary pressure. "Even though the divergence of these proteins' amino-acid sequences may continue, the divergence in terms of their respective partners slows drastically after a rapid initial change, which we hadn't expected to see," Vidal says.
In the July 29 issue of Science researchers from theArabidopsis interactome mapping study reported yet another demonstration of the usefulness of their approach. Led by Jeffery L. Dangl of the University of North Carolina at Chapel Hill, they examined Arabidopsis protein interactions with the bacterium Pseudomonas syringae (Psy) and a fungus-like microbe called Hyaloperonospora arabidopsidis (Hpa). "Even though these two pathogens are separated by about a billion years of evolution, it turns out that the 'effector' proteins they use to subvert Arabidopsis cells during infection are both targeted against the same set of highly connected Arabidopsisproteins," says Ecker. "We looked at some of these targetedArabidopsis proteins and found evidence that they serve as 'hubs' or control points for the plant immune system and related systems."
Ecker and his colleagues hope that these studies mark the start of a period of rapid advancement in understanding plant biology, and in putting that knowledge to use for human benefit. "This starts to give us a big, systems-level picture of howArabidopsis works, and much of that systems-level picture is going to be relevant to -- and guide further research on -- other plant species, including those used in human agriculture and even pharmaceuticals,"Ecker says.
The "Arabidopsis Interactome Mapping Consortium" consists of over 20 national and international laboratories that contribute to this study with support from a number of funding agencies including the National Science Foundation and the National Institutes of Health.

மிகப்பெரிய விண்வெளி கல் சீனாவில் கண்டுபிடிப்பு



பூமியில் சில தருணங்களில் விண்வெளி கற்கள் விழுவது உண்டு. அவ்வாறு விழுந்த அதிசய விண்வெளி கல் ஒன்றை சீன நிபுணர்கள் தற்போது கண்டுபிடித்து உள்ளனர்.
சீனா மற்றும மங்கோலியாவை பிரிக்கும் அல்டாய் மலைப்பகுதியில் இந்த விண்வெளிக் கல் கண்டுபிடிக்கப்பட்டு உள்ளது. இந்த புதிய விண்வெளி கல் 2.2 மீற்றர் நீளமும், 1.25 மீற்றர் உயரமும் கொண்டதாக உள்ளது.
உலகிலேயே மிகப் பெரிய 3வது விண்கல்லாக இந்த கல் உள்ளது. இந்த விண்வெளி கல் நமது பூமியில் உள்ள கல்லை விட கடினமாக இருந்தது. அட்லாய் மலைப்பிராந்தியத்தின் 10 ஆயிரம் அடி உயரத்தில் விண்வெளிக் கல் இருந்தது. இந்த விண்வெளிக் கல் மேற்பரப்பு, கறுப்பு, சிவப்பு என பல வண்ணங்களை பிரதிபலித்தது.
இந்த விண்வெளிக் கல்லை எதிர்பாராத விதமாக தான் கண்டுபிடித்தோம் என ஷாங்போலின் தெரிவித்தார். இவர் பெய்ஜிங் கண்காணிப்பக விண்வெளி கல் ஆய்வு நிபுணர் ஆவார்.
விண்வெளிக் கல் இரும்பு சார்ந்ததாக இருக்கும் என ஷாங்போலின் தெரிவித்தார். சூரியக் குடும்பம் உருவாகும் தருணத்தில் 450 கோடி ஆண்டுகளுக்கு முன்னர் விண்வெளி கிரகங்கள் சேதம் அடைந்து இந்த கற்கள் உருவாகி இருக்கலாம் என நிபுணர்கள் கூறுகிறார்கள்.
1808 ஆம் ஆண்டு அவுஸ்திரேலியாவிலும், 1923 ஆம் ஆண்டு நமீபியாவிலும் மிகப் பெரிய விண்வெளிக் கல் கண்டுபிடிக்கப்பட்டது குறிப்பிடத்தக்கது.