Saturday, January 13, 2007


Intelligent Design: 'A War on Science' (BBC Horizon Video - 49 mins)

BBC Horizon: 'A War on Science' was broadcast on BBC Two at 2100GMT on Thursday, 26 January 2006

From the BBC News report "Britons unconvinced on evolution":

Just under half of Britons accept the theory of evolution as the best description for the development of life, according to an opinion poll.

Furthermore, more than 40% of those questioned believe that creationism or intelligent design (ID) should be taught in school science lessons.

The survey was conducted by Ipsos MORI for the BBC's Horizon series.

Its latest programme, 'A War on Science', looks into the attempt to introduce ID into science classes in the US.

From the BBC Horizon 'A War on Science' webpage:

When Charles Darwin published his theory of evolution nearly 150 years ago, he shattered the dominant belief of his day - that humans were the product of divine creation. Through his observations of nature, Darwin proposed the theory of evolution by natural selection. This caused uproar. After all, if the story of creation could be doubted, so too could the existence of the creator. Ever since its proposal, this cornerstone of biology has sustained wave after wave of attack. Now some scientists fear it is facing the most formidable challenge yet: a controversial new theory called intelligent design.

In the late 1980s Phillip Johnson, a renowned lawyer and born-again Christian, began to develop a strategy to challenge Darwin. To Johnson, the evidence for natural selection was poor. He also believed that by explaining the world only through material processes was inherently atheistic. If there was a god, science would never be able to discover it.

Johnson recruited other Darwin doubters, including biochemist Professor Michael Behe, mathematician Dr William Dembski, and philosopher of science Dr Stephen Meyer. These scientists developed the theory of intelligent design (ID) which claims that certain features of the natural world are best explained as the result of an intelligent being. To him, the presence of miniature machines and digital information found in living cells are evidence of a supernatural creator. Throughout the 90s, the ID movement took to disseminating articles, books and DVDs and organising conferences all over the world.

To its supporters, intelligent design heralds a revolution in science and the movement is fast gaining political clout. Not only does it have the support of the President of the United States, it is on the verge of being introduced to science classes across the nation. However, its many critics, including Professor Richard Dawkins and Sir David Attenborough, fear that it cloaks a religious motive - to replace science with god. [Video]

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Kenya: Evangelicals Wage Anti-Evolution War

A bronze sculpture [stands] at the entrance of the Museum. It details the development of man.

Kenya's world-class collection of hominid bones - primates belonging to a family of which the modern human being is the only species still in existence - is at the centre of a silent but intense war being waged by a section of the evangelical churches.

The priceless National Museums of Kenya* (NMK) fossils pointing to man's evolution risk being relegated to the abyss as a section of the Church renews its war on science insisting that the evolution theory contradicts the biblical story of creation.

Bishop Boniface Adoyo** of Nairobi Pentecostal Church (NPC), Christ is the Answer Ministries, is championing the 'hide-the-fossils' campaign, which has left scientists and historians perplexed.

...[Evolutionary] theory says man evolved from ape-like furry creatures with tails which moved on four limbs.

But Adoyo dismisses the theory as "mere speculations".

He argues that the theory presents assumptions as facts. He says it takes more faith to believe in the theories than that God created man. "These are just speculations yet we believe in them. ...Man is uniquely created; there is nothing concrete about the evolution theory and that is why we as Christians are uncomfortable with the museum's plans to display the hominids and narrate the story of evolution as if it is the truth," he explains.

Continued at "Kenya: Evangelicals Wage Anti-Evolution War" [Creationism]


*"Louis Leakey established the Institute of Primate Research IPR in 1960 [at NMK] with monkeys as models to understand human evolution and as a facility for collection and studies of East African primates. Since its inception, IPR has expanded tremendously in both physical and researches facilities and is now focused on the breeding and use of non-human primate study, prevent and or treat human diseases under the auspices of the animal welfare. The Institute has out door and indoor housing facilities for breeding colonies of about 270 primates.

IPR is an institution of the National Museums of Kenya NMK and is currently located in 400 acres of Ololua natural tropical forest near Karen, approximately 20kms from Nairobi. IPR is a non-profit making organization,which undertakes research on bio-medical/animal welfare and conservation aspects using East African Primates.

The Institute undertakes research in basic and applied aspects using monkeys. IPR is involved in collaborative and contract research in association with academic and industry at the international level.The institute is recognized as a World Health Organization WHO collaborating center in Human Reproduction and Tropical Disease Research" (See "Overview of Primate facilities at the Institute of Primate Research")


**Info on Bishop Boniface Adoyo from Christ is the Answer Ministries:

"Bishop Adoyo joined the staff at Nairobi Pentecostal Church in 1986, serving in various ministry positions. In 1990 he was appointed associate pastor of NPC Valley Road under then Senior Pastor, Rev Dennis White of the Pentecostal Assemblies of Canada. When Rev. White moved to launch NPC Karen, Rev. Adoyo assumed leadership as Senior Pastor of NPC Valley Road, becoming the first Kenyan Senior Pastor.

In January 1999 as part of a dream of Rev.White a historic transition took place from missionary leadership to Kenya leadership and Rev. Adoyo became the Pastor Overseer of NPC churches. On 28th, August 2004 he was consecrated as Bishop of Christ is the Answer Ministries."


An earlier post on this topic from Tuesday, September 05, 2006: "Furious evolution debate hits Kenyan museum (Nairobi)"

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Hofmeyr Skull Is First Fossil Proof of Human Migration Theory

Anthropology: A 36,000-year-old skull from South Africa provides the first fossil evidence that modern humans left Africa 70,000 to 50,000 years ago to colonize Eurasia, new research suggests.

'Up until a few years ago, this was largely just a theory based on some genetics,' said Ted Goebel (info), an anthropologist at Texas A and M University who was not involved in the study.

"We're beginning to accumulate evidence from archaeology, from genetics, from physical anthropology that support this model or theory that modern humans spread out of Africa - 60,000 or 70,000 years ago," he said.

Scientists today can only theorize about how anatomically modern humans, who appeared in East Africa by 195,000 years ago, spread across the continent to the Middle East, Asia, Australia, and Europe.

...This theory is bolstered not only by this latest discovery but also by a separate find (*see below) in Russia, in which human teeth and artifacts have been dated to around the same age as the South Africa skull.

...The study was led by Frederick E. Grine (info)

Continued at "Skull Is First Fossil Proof of Human Migration Theory, Study Says" (National Geographic)


Based on the journal Science paper:

Late Pleistocene Human Skull from Hofmeyr, South Africa, and Modern Human Origins


The lack of Late Pleistocene human fossils from sub-Saharan Africa has limited paleontological testing of competing models of recent human evolution. We have dated a skull from Hofmeyr, South Africa, to 36.2 plus or minus 3.3 thousand years ago through a combination of optically stimulated luminescence and uranium-series dating methods. The skull is morphologically modern overall but displays some archaic features. Its strongest morphometric affinities are with Upper Paleolithic (UP) Eurasians rather than recent, geographically proximate people. The Hofmeyr cranium is consistent with the hypothesis that UP Eurasians descended from a population that emigrated from sub-Saharan Africa in the Late Pleistocene.


*Info on the Russian find was posted yesterday in "Earliest Evidence Of Modern Humans In Europe Discovered By International Team"

See the Washington Post's 'Science Notebook' entry "Ancient Skull Gives Credence To 'Out of Africa' Hypothesis"

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Friday, January 12, 2007


Rafflesiaceae: Family found for gigantic flowers (+ Video)

The 200-year-old mystery of where some of the world's largest flowers sit in the botanical family tree has finally been solved by scientists.

To their surprise, the plants, which have up to 1m-wide (3ft), blood-red, rotten-flesh stinking flowers, belong to a group bearing tiny blooms.

The Rafflesiaceae were tricky to place because of their unusual features, the team reports in the journal Science.

Such traits include the fact that they are rootless, leafless and stemless.

...And the strange plants, which can be found growing on the jungle floor in southeast Asia, are also parasitic. Eschewing the process of photosynthesis, the Rafflesiaceae bed down in the tissue of the tropical grape vine, feasting upon the nutrients it provides.

...Charles Davis (lab), assistant professor of organismic and evolutionary biology at Harvard University and lead author of the Science paper, said: "These plants are so strange - almost extra-terrestrial - wherever they were placed [within the family tree] there would be a lot of explaining to do."

Continued at "Family found for gigantic flowers" (BBC Science News UK)


Based on the paper:

Floral Gigantism in Rafflesiaceae

Charles C. Davis et al.

Published Online January 11, 2007
Science DOI: 10.1126/science.1135260


Species of Rafflesiaceae possess the world's largest flowers (up to 1 m in diameter), yet their precise evolutionary relationships have been elusive, hindering our understanding of the evolution of their extraordinary reproductive morphology. We present results of phylogenetic analyses of mitochondrial, nuclear, and plastid data showing that Rafflesiaceae are derived from within Euphorbiaceae, the spurge family. Most euphorbs produce minute flowers, suggesting that the enormous flowers of Rafflesiaceae evolved from ancestors with tiny flowers. Given the inferred phylogeny, we estimate that there was a ca. 73-fold increase in flower diameter on the stem lineage of Rafflesiaceae, making this one of the most dramatic cases of size evolution reported for eukaryotes.


Video of Rafflesia 'in the wild':

Also see the 2004 open access/free paper from Proceedings of the National Academy of Sciences (PNAS):

Mitochondrial DNA sequences reveal the photosynthetic relatives of Rafflesia, the world's largest flower

Todd J. Barkman et al.

PNAS | January 20, 2004 | vol. 101 | no. 3 | 787-792


All parasites are thought to have evolved from free-living ancestors. However, the ancestral conditions facilitating the shift to parasitism are unclear, particularly in plants because the phylogenetic position of many parasites is unknown. This is especially true for Rafflesia, an endophytic holoparasite that produces the largest flowers in the world and has defied confident phylogenetic placement since its discovery over 180 years ago. Here we present results of a phylogenetic analysis of 95 species of seed plants designed to infer the position of Rafflesia in an evolutionary context using the mitochondrial gene matR (1,806 aligned base pairs). Overall, the estimated phylogenetic tree is highly congruent with independent analyses and provides a strongly supported placement of Rafflesia with the order Malpighiales, which includes poinsettias, violets, and passionflowers. Furthermore, the phylogenetic placement of Mitrastema, another enigmatic, holoparasitic angiosperm with the order Ericales (which includes blueberries and persimmons), was obtained with these data. Although traditionally classified together, Rafflesia and Mitrastema are only distantly related, implying that their endoparasitic habits result from convergent evolution. Our results indicate that the previous significant difficulties associated with phylogenetic placement of holoparasitic plants may be overcome by using mitochondrial DNA so that a broader understanding of the origins and evolution of parasitism may emerge.

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Recent 'Intelligent Design The Future' Podcasts

Recent 'Intelligent Design The Future' podcasts/webcasts from the Center for Science and Culture include:

The Making of a Darwin Dissenter Part I
January 10, 2007 04:23PM

On this first of a two part ID The Future, CSC's Casey Luskin interviews CSC Fellow Dr. Geoffrey Simmons on what makes him skeptical Darwinian evolution. Dr. Simmons has a BS in biology; coursework completed for MS in microbiology, University of Illinois; an M.D., University of Illinois Medical School; Internship and Residency in Internal Medicine, LAC-USC Medical Center; Boarded in Internal Medicine since 1974. He is a licensed and practicing physician in Eugene, Oregon, and the author of the forthcoming book Billions of Missing Links (Amazon Astore UK | US).

Does Darwinism Lead to Moral Relativism?
January 08, 2007 03:43PM

On this episode of ID The Future, CSC senior fellow Dr. John West examines whether or not Darwinian evolution supports a traditional view of morality as is often claimed. In his new book Darwin's Conservatives (Amazon Astore UK | US), Dr. West addresses how Darwin's theory, contrary to some of its conservative champions, manifestly does not reinforce the teachings of conservatism. According to West, Darwinism promotes moral relativism rather than traditional morality.

What Do People Mean When They Talk About 'Evolution'?
January 05, 2007 12:05PM

On this episode of ID The Future the CSC's Robert Crowther looks at the different meanings of the word evolution and explains the importance of clearly defining evolution when discussing the subject.

PBS' "Think Tank" Video Explaining the Differences Between intelligent design, Darwinism and creationism
January 03, 2007 12:27AM

On this episode of ID The Future we are highlighting a second clip from PBS' Think Tank with Ben Wattenberg that features CSC Director Dr. Stephen Meyer explaining the differences between intelligent design, Darwinism and creationism.

How To Define Intelligent Design
January 01, 2007 04:23PM

On this episode of ID The Future CSC director of communications Robert Crowther discusses how to define intelligent design and why so many mainstream definitions of the theory are incorrect.

Dr. Stephen Meyer Discusses his Peer-Reviewed Science Article about Intelligent Design on PBS' "Think Tank"
December 29, 2006 09:00AM

On this episode of ID The Future we are featuring a clip from PBS' Think Tank with Ben Wattenberg. CSC Director Dr. Stephen Meyer appeared on the program and in this segment discusses the publication of his article "The Origin of Biological Information and the Higher Taxonomic Categories" in the peer-reviewed biology journal the Proceedings of the Biological Society of Washington, published out of the Smithsonian Institution. The publication of the article led to harassment and discrimination against the editor of the journal, evolutionary biologist Dr. Richard Sternberg. (See "Congress slams Smithsonian's anti-religious attacks")

The Top Intelligent Design Stories of 2006
December 27, 2006 02:03AM

On this episode of ID The Future, CSC's Casey Luskin interviews Access Research Network's Dennis Wagner about the intelligent design news stories of 2006. Access Research Network (ARN) has compiled a list of the top intelligent design stories of the past year. The list spans the globe and includes such highlights as:

* 60% of U.S. Medical Doctors Doubt Macroevolutionary Theory
* Fly Eye Important Blueprint for Creating Better Video Systems
* Europeans Question the Value of Teaching Macroevolution
* Over 600 Scientists Express Skepticism of Darwinian Evolution
* Scientists Conduct New Research Using Intelligent Design Theory.


At the time of writing there are 79 podcasts available.

From PBS' Think Tank: Intelligent Design vs. Evolution and Intelligent Design vs. Evolution part 2

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Earliest Evidence Of Modern Humans In Europe Discovered By International Team

Modern humans who first arose in Africa had moved into Europe as far back as about 45,000 years ago, according to a new study by an international research team led by the Russian Academy of Sciences and the University of Colorado at Boulder.

The evidence consists of stone, bone and ivory tools discovered under a layer of ancient volcanic ash on the Don River in Russia some 250 miles south of Moscow, said John Hoffecker, a fellow of CU-Boulder's Institute of Arctic and Alpine Research. Thought to contain the earliest evidence of modern humans in Europe, the site also has yielded perforated shell ornaments and a carved piece of mammoth ivory that appears to be the head of a small human figurine, which may represent the earliest piece of figurative art in the world, he said.

'The big surprise here is the very early presence of modern humans in one of the coldest, driest places in Europe,' Hoffecker said. 'It is one of the last places we would have expected people from Africa to occupy first.'

A paper by Michael Anikovich and Andrei Sinitsyn of the Russian Academy of Sciences, Hoffecker, and 13 other researchers was published in the January 12 issue of the journal Science [1].

The excavation took place at Kostenki, a group of more than 20 sites along the Don River that have been under study for many decades. Kostenki previously has yielded anatomically modern human bones and artifacts dating between 30,000 and 40,000 years old, including the oldest firmly dated bone and ivory needles with eyelets that indicate the early inhabitants were tailoring animal furs to help them survive the harsh climate.

Most of the stone used for artifact construction was imported from between 60 miles and 100 miles away, while the perforated shell ornaments discovered at the lowest levels of the Kostenki dig were imported from the Black Sea more than 300 miles away, he said. "Although human skeletal remains in the earliest level of the excavation are confined to isolated teeth, which are notoriously difficult to assign to specific human types, the artifacts are unmistakably the work of modern humans," Hoffecker said.

The sediment overlying the artifacts was dated by several methods, including an analysis of an ash layer deposited by a monumental volcanic eruption in present-day Italy about 40,000 years ago, Hoffecker said. The researchers also used optically stimulated luminescence dating - which helps them determine how long ago materials were last exposed to daylight - as well as paleomagnetic dating based on known changes in the orientation and intensity of Earth's magnetic field and radiocarbon calibration.

Anatomically modern humans are thought to have arisen in sub-Saharan Africa around 200,000 years ago.

Kostenki also contains evidence that modern humans were rapidly broadening their diet to include small mammals and freshwater aquatic foods, an indication they were "remaking themselves technologically," he said. They may have used traps and snares to catch hares and arctic foxes, exploiting large areas of the environment with relatively little energy. "They probably set out their nets and traps and went home for lunch," he said.

While there is some evidence Neanderthals once occupied the plains of Eastern Europe, they seem to have been scarce or absent there during the last glacial period when modern humans arrived, he said. The lack of competitors like the Neanderthals might have been the chief attraction to the area and the reason why modern humans first entered this part of Europe, Hoffecker said.

"Unlike the Neanderthals, modern humans had the ability to devise new technologies for coping with cold climates and less than abundant food resources," he said. "The Neanderthals, who had occupied Europe for more than 200,000 years, seem to have left the back door open for modern humans. "

The ivory artifact believed to be the head of a small figurine, discovered during the 2001 field season, was broken and perhaps never was finished by the person who began crafting it more than 40,000 years ago, said Hoffecker. "This is a really interesting piece," he said. "If confirmed, it will be the oldest example of figurative art ever discovered."

Buried under 10 feet to 15 feet of silt, the artifacts at Kostenki include blades, scrapers, drills and awls, as well as sturdy antler digging tools known as mattocks that resemble crude pick-axes, he said. Mattocks have been found at other Old World sites and the arctic and were used to dig large pits for the storage of foods and fuel, although traces of such pits have yet to turn up at the lowest levels of Kostenki, he said.

Large animal remains at Kostenki include mammoth, woolly rhinoceros, bison, horses, moose and reindeer. A bone chemistry analysis from 30,000-year-old human remains indicates a high consumption of freshwater aquatic foods - either water birds, fish, or both - more evidence for efficient food gathering techniques, he said.

The study also included researchers from the University of Arizona, the Kostenki Museum-Preserve in Kostenki, the University of Illinois-Chicago, Boston University, the University College London and the Institute of Environmental Geology, Climate and Geoengineering in Rome. Research at Kostenki has been funded by the Leakey Foundation and the National Science Foundation.

Except for some early sites in the Near East, the oldest evidence modern humans outside of Africa comes from the Australian continent roughly 50,000 years ago, said Hoffecker, who was awarded an honorary doctorate from the Russian Academy of Sciences in 2006. Several modern human sites in south-central Europe may be almost as old as Kostenki, he said.

Source: University of Colorado at Boulder January 11, 2007


[1] Based on the paper:

Early Upper Paleolithic in Eastern Europe and Implications for the Dispersal of Modern Humans

Science 12 January 2007:
Vol. 315. no. 5809, pp. 223 - 226
DOI: 10.1126/science.1133376


Radiocarbon and optically stimulated luminescence dating and magnetic stratigraphy indicate Upper Paleolithic occupation - probably representing modern humans - at archaeological sites on the Don River in Russia 45,000 to 42,000 years ago. The oldest levels at Kostenki underlie a volcanic ash horizon identified as the Campanian Ignimbrite Y5 tephra that is dated elsewhere to about 40,000 years ago. The occupation layers contain bone and ivory artifacts, including possible figurative art, and fossil shells imported more than 500 kilometers. Thus, modern humans appeared on the central plain of Eastern Europe as early as anywhere else in northern Eurasia.


A recent post (Tuesday, December 05, 2006):

Neanderthal Women Joined Men in the Hunt

"A new explanation for the demise of the Neanderthals (background info), the stockily built human species that occupied Europe until the arrival of modern humans 45,000 years ago, has been proposed by two anthropologists at the University of Arizona..."

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Thursday, January 11, 2007


Scientists discover stage at which an embryonic cell is fated to become a stem cell

Cambridge scientists have discovered the stage at which some of the cells of a fertilised mammalian egg are fated to develop into stem cells and why this occurs. The findings of the study, which overturn the long-held belief that cells are the same until the fourth cleavage (division) of the embryo, are reported in today's edition of Nature.

After fertilisation, the cells of the embryo at first undergo equal, symmetrical divisions and unequal, asymmetrical ones that direct smaller daughter cells towards the inside of the embryo. These become the inner cell mass of stem cells. Previously, it was believed that the mammalian embryo starts its development with identical cells and only as these inside and outside cells form do differences between cells first emerge.

However, research led by Professor Magdelena Zernicka-Goetz (homepage), University of Cambridge, has revealed evidence to suggest that differences between the embryonic cells are already apparent at the 4-cell-stage.

Continued at "Scientists discover stage at which an embryonic cell is fated to become a stem cell" [Epigenetics]


Based on the Letter to Nature:

Histone arginine methylation regulates pluripotency in the early mouse embryo

Opening Paragraph

It has been generally accepted that the mammalian embryo starts its development with all cells identical, and only when inside and outside cells form do differences between cells first emerge. However, recent findings show that cells in the mouse embryo can differ in their developmental fate and potency as early as the four-cell stage. These differences depend on the orientation and order of the cleavage divisions that generated them. Because epigenetic marks are suggested to be involved in sustaining pluripotency, we considered that such developmental properties might be achieved through epigenetic mechanisms. Here we show that modification of histone H3, through the methylation of specific arginine residues, is correlated with cell fate and potency. Levels of H3 methylation at specific arginine residues are maximal in four-cell blastomeres that will contribute to the inner cell mass (ICM) and polar trophectoderm and undertake full development when combined together in chimaeras. Arginine methylation of H3 is minimal in cells whose progeny contributes more to the mural trophectoderm and that show compromised development when combined in chimaeras. This suggests that higher levels of H3 arginine methylation predispose blastomeres to contribute to the pluripotent cells of the ICM. We confirm this prediction by overexpressing the H3-specific arginine methyltransferase CARM1 in individual blastomeres and show that this directs their progeny to the ICM and results in a dramatic upregulation of Nanog and Sox2. Thus, our results identify specific histone modifications as the earliest known epigenetic marker contributing to development of ICM and show that manipulation of epigenetic information influences cell fate determination.

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A previously unrecognized group of Middle Jurassic triconodontan mammals from Central Asia

An open access article from Naturwissenschaften:


Ferganodon narynensis gen. et sp. nov. is represented by a lower molariform tooth from the Middle Jurassic (Callovian) Balabansai Svita in Kyrgyzstan. The new genus is allied with Klamelia zhaopengi Chow and Rich 1984 from the Middle Jurassic Shishugou Formation in Xinjiang, northwest China to the new family Klameliidae based on parallelogram-shaped lower molariforms, imbricating rather than interlocking of cusps e-d-f, by a peculiar distolabial cingulid cusp, and by vertical folding of the enamel on the labial crown side. The new family Klameliidae fam. nov. is most similar to Gobiconodontidae by the structure of the molariform teeth and represents a previously unrecognized radiation of eutriconodontan mammals possibly endemic to Central Asia.


There are three vertebrate localities within the Middle Jurassic Balabansai Svita in the northern Fergana Valley, Kyrgyzstan that have produced remains of mammals: (1) Sarykamyshsai 1 (site FTA-30), 3–4 km east of the town of Tashkumyr (lower, gray to greenish colored part of the Balabansai Svita, Callovian); (2) Tashkumyr 1 (site FTA-131), left bank of the Naryn River close to the town of Tashkumyr (bonebed within a calcareous sandstone of the lower part of the Balabansai Svita, Callovian); and (3) Dzhiddasai (site FBX-23), 5 km west of the town of Tashkumyr (upper, red colored part of the Balabansai Svita, Callovian; see Averianov et al. 2005 for a more detailed description of localities). More than 20 mostly fragmentary mammalian teeth were recovered so far from these localities. The mammal fauna is dominated by docodonts, represented by an isolated molar of Tashkumyrodon desideratus Martin and Averianov 2004 from Sarykamyshsai 1 and by a lower molar and several upper molar fragments of a new docodont from the Tashkumyr 1 bonebed that is similar to Dsungarodon zuoi Pfretzschner and Martin, 2005 from the Late Jurassic (Oxfordian) Qigu Formation in the Junggar Basin, Xinjiang, northwestern China. This locality produced also one almost complete and several fragmentary teeth referable to one or two taxa of Eutriconodonta. The most complete eutriconodontan tooth is described here and attributed to a new taxon within the newly established family Klameliidae fam. nov.

Continued via "A previously unrecognized group of Middle Jurassic triconodontan mammals from Central Asia" [Fossil]

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Wednesday, January 10, 2007


Why doesn't the immune system attack the small intestine?

Answering one of the oldest questions in human physiology, researchers at Dana-Farber Cancer Institute have discovered why the body's immune system* - perpetually on guard against foreign microbes like bacteria - doesn't attack tissues in the small intestine that harbor millions of bacteria cells.

In a study in the February issue of Nature Immunology, and which is currently available on the journal's Web site as an advanced online publication, investigators led by Shannon Turley (info), PhD, of Dana-Farber identify an unlikely group of peacemakers: lymph node cells that instruct key immune system cells to leave healthy tissue alone. The finding, which illuminates a previously unknown corner of the human immune system, may lead to new forms of treatment for autoimmune diseases such as Type 1 diabetes and multiple sclerosis.

'We've discovered that cells not generally thought of as part of the immune system actually play an important role in protecting the intestine from immune system attack,' says Turley. 'Because the cells are found in lymph nodes throughout the body, they may offer a way of suppressing a variety of autoimmune diseases,' which result from immune system assault on healthy tissue.

The immune system distinguishes between normal and foreign agents by small proteins, called antigens, on the cell surface. In parts of the body, such as the pancreas, that are sheltered from the outside environment, cells known as dendritic cells display the antigens of their normal neighbors in a way that puts the immune system 'at ease.' By reading those antigens without being on alert, the immune system's T cells learn that such cells are off-limits to attack.

Continued at "Why doesn't the immune system attack the small intestine?"


Based on the paper:

Peripheral antigen display by lymph node stroma promotes T cell tolerance to intestinal self

The intestinal epithelium functions to absorb nutrients and to protect the organism against microbes. To prevent autoimmune attack on this vital tissue, T cell tolerance to intestinal self-antigens must be established. Central tolerance mechanisms involve medullary thymic epithelial cells (mTECs), which use endogenously expressed peripheral-tissue antigens (PTAs) to delete self-reactive thymocytes. The prevailing model for the induction of peripheral tolerance involves cross-presentation of tissue antigens by quiescent dendritic cells. Here we show that lymph node stromal cells present endogenously expressed PTAs to T cells. Moreover, antigen presentation by lymph node stroma is sufficient to induce primary activation and subsequent tolerance among CD8+ T cells. Thus, lymph node stromal cells are functionally akin to mTECs and provide a direct strategy for purging the peripheral repertoire of self-reactive T cells. [Abstract]


*Immune systems are generally characterized by their ability to distinguish between self and non-self cells, tissues, or molecules, and to eliminate the non-self (for review see Janeway 2001). The mammalian immune system is an incredibly complex and intricate system that can recognize non-self and provide protection from a wide variety of pathogens. While there is a high degree of interconnectivity between its components, the immune system can be loosely divided into two subsystems, the innate and the adaptive immune systems. In general, innate immunity is a non-specific, inducible response to pathogens. It is immediate in action, yet short-lived. On the other hand, the adaptive immune system is much more specific, but takes longer to activate. It also features immunological memory, and can augment itself to respond more quickly and with greater specificity to future infections of similar pathogens. Both systems work together to provide protection against a diverse and rapidly-evolving array of pathogens.

While much is known about the evolution of the immune system, the details of its origin remain to be elucidated. The innate immune system is the more ancient of the two systems, with roots deep in the deuterostome branch of the bilaterians, roughly one billion years ago. Conversely, the adaptive immune system appeared more recently and quite suddenly, around 450 million years ago with the emergence of the gnathostomes, more commonly called the jawed vertebrates. Because of its high degree of complexity and interconnectivity, the mammalian immune system has been labeled as "irreducibly complex", and its evolution and origin through "Darwinian" mechanisms challenged. [From Evolving Immunity]

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Amphibians - the comeback kings of evolution

From New Scientist: Amphibians bounced back spectacularly from a series of mass extinctions during their evolution, according to a new genetic analysis.

In the present day, biologists see amphibians as sentinels of environmental change. The extreme sensitivity of their skin makes them more prone than other organisms to soaking up toxins and suffering from fungal infection, and provides little protection from ultraviolet radiation, which causes genetic mutation.

Many amphibian populations have declined in recent years. At least 43% of populations of amphibian species are declining, some research suggests (see, for example, Global frog crisis defies explanation).

That said, a look at their latest evolutionary tree reveals that amphibians have a remarkable capacity to bounce back from environmental changes, says Kim Roelants of Vrije University in Brussels, and colleagues.

Continued at "Amphibians - the comeback kings of evolution"


Based on the Proceedings of the National Academy of Sciences (PNAS) paper:

Global patterns of diversification in the history of modern amphibians

The fossil record of modern amphibians (frogs, salamanders, and caecilians) provides no evidence for major extinction or radiation episodes throughout most of the Mesozoic and early Tertiary. However, long-term gradual diversification is difficult to reconcile with the sensitivity of present-day amphibian faunas to rapid ecological changes and the incidence of similar environmental perturbations in the past that have been associated with high turnover rates in other land vertebrates. To provide a comprehensive overview of the history of amphibian diversification, we constructed a phylogenetic timetree based on a multigene data set of 3.75 kb for 171 species. Our analyses reveal several episodes of accelerated amphibian diversification, which do not fit models of gradual lineage accumulation. Global turning points in the phylogenetic and ecological diversification occurred after the end-Permian mass extinction and in the late Cretaceous. Fluctuations in amphibian diversification show strong temporal correlation with turnover rates in amniotes and the rise of angiosperm-dominated forests. Approximately 86% of modern frog species and >81% of salamander species descended from only five ancestral lineages that produced major radiations in the late Cretaceous and early Tertiary. This proportionally late accumulation of extant lineage diversity contrasts with the long evolutionary history of amphibians but is in line with the Tertiary increase in fossil abundance toward the present. (Abstract)

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