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Descent of Man In this lecture, beginners can familiarize themselves with basic information and terms used to describe the evolution of humanity beginning with the origin of primates through the comings and goings of Genus Homo. |
Links to Ancient Man in DNA Find?
Posted: Sunday, July 29, 2001
(All Africa) If the find at a local World Heritage Site is authenticated, it could be the oldest such sample yet extracted. Two researchers claim that they have extracted the DNA of a 1,8-million-year-old hominid from microscopic traces of blood found on stone tools excavated at the Sterkfontein Caves.
It is a discovery, scientists say, that could revolutionise the study of ancient DNA and the origins of mankind.
"The DNA we have found is something between a chimpanzee and a human, which suggests a hominid," explains Wits University micro archaeologist Bonnie Williamson.
Williamson and Professor Tom Loy of the University of Queensland believe that this DNA sequence is that of either our direct ancestor Homo habilis or Paranthropus robustus. If their findings are verified it would be the oldest DNA yet extracted.
The oldest DNA so far sequenced and independently verified is from a 50 000-year-old woolly mammoth.
"We strongly suspect that the DNA that we have is that of a hominid, but we still want to conduct more research to verify our claim," says Loy, who plans to publish the findings in a leading scientific journal soon. [More]
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Posted: Sunday, July 29, 2001
The genetic history of a group of populations is usually analyzed by reconstructing a tree of their origins. Reliability of the reconstruction depends on the validity of the hypothesis that genetic differentiation of the populations is mostly due to population fissions followed by independent evolution. If necessary, adjustment for major population admixtures can be made. Dating the fissions requires comparisons with paleoanthropological and paleontological dates, which are few and uncertain.
A method of absolute genetic dating recently introduced uses mutation rates as molecular clocks; it was applied to human evolution using microsatellites, which have a sufficiently high mutation rate. Results are comparable with those of other methods and agree with a recent expansion of modern humans from Africa. An alternative method of analysis, useful when there is adequate geographic coverage of regions, is the geographic study of frequencies of alleles or haplotypes.
As in the case of trees, it is necessary to summarize data from many loci for conclusions to be acceptable. Results must be independent from the loci used. Multivariate analyses like principal components or multidimensional scaling reveal a number of hidden patterns and evaluate their relative importance. Most patterns found in the analysis of human living populations are likely to be consequences of demographic expansions, determined by technological developments affecting food availability, transportation, or military power.
During such expansions, both genes and languages are spread to potentially vast areas. In principle, this tends to create a correlation between the respective evolutionary trees. The correlation is usually positive and often remarkably high. It can be decreased or hidden by phenomena of language replacement and also of gene replacement, usually partial, due to gene flow. http://www.pnas.org/cgi/content/full/94/15/7719
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Earth: the real planet of the apes Posted: Friday, July 27, 2001
Recently, two candidates for the earliest known hominid have emerged, both tantalisingly close to the last common ancestor with the chimps. Last year, a Kenyan-French team led by Brigitte Senut and Martin Pickford unveiled "Millennium Man", a six-million-year-old chimpanzee-like creature whose existence was pieced together from 13 fossils. Remains from at least five males and females, including an arm, a fingertip, a jaw fragment and, crucially, a leg bone, suggested that Orrorin tugenesis walked on two legs.
According to its discoverers, from the Kenyan Palaeontology Expedition, its teeth were more like those of modern humans than any apes. Its strong femur suggested that it walked upright, but its powerful upper arm bone hinted that it might also have been at home in the trees.
Senut and Pickford, who made the finding in Kapsomin in the Tugen hills of Kenya's Baringo district, argued that its similarities with Homo sapiens made it a contender for the title of direct ancestor.
But as Millennium Man was being unveiled at a press conference, a rival team from America was working on another find, which also came from the dawn of humanity.
This time, the fragments of bones were found in the Middle Awash region of Ethiopia and were dated at between 5.8 million and 5.2 million years old. The finds, reported in Nature this month, included a piece of collarbone, several hand and foot bones and a jawbone with teeth, also with features more in common with hominids than any ape. [More]
More Links:
Scientists unearth six million-year-old remains in Africa
19 November 2000: [UK News] Channel 4 dispels myths surrounding mankind's lost cousins
23 March 2000: Miniature monkey is missing link in man's family tree
10 February 2000: Stone Age man wasn't so dumb
23 December 1999: Ape man's arm points to our evolution
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Mt. Etna A Blast For Temple University Geologist Posted: Friday, July 27, 2001
(Science Daily) Temple University geology professor Dr. Gene Ulmer sits in his home and closely watches the continued eruptions of Sicily’s Mt. Etna volcano on his television. "I wish I were still there," he says, wistfully.
Ulmer was there, watching from an erosional valley only three miles from Mt. Etna’s summit, when the volcano violently erupted and spewed forth ash and lava at 1:33 p.m. on June 19. "It was a very exciting moment," says Ulmer, who is now at home nursing an infection he picked up at Mt. Etna, but was in the nearby town of Nicolosi in June with one of his graduate students, Mark Manna, after attending an international meeting on geo-thermal and volcanic energy in Italy. "Within 10 minutes, there was such a dust cloud that everything was obscured. But what went on through the afternoon, it just sounded like continual thunder as the lava was booming its way out of the top of the volcano."
Ulmer and Manna are part of a team from Temple, Penn State, and Princeton Universities working on a National Science Foundation-funded research project to develop a sensor that can be used to monitor and predict such volcanic eruptions.
"That’s why we were in Italy at this meeting," he says. "Mark was presenting a paper on his thesis research." [More]
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Researchers First To Catalogue Interactions Of An Organism's Proteins Posted: Friday, July 27, 2001
(Science Daily) In recent years, researchers have made significant scientific advancements by decoding the entire genetic blueprint – the genome – of several organisms, including humans. That work, however, is only a first step in understanding how living things are put together and how they operate.
Now, a team of scientists at North Carolina State University has played a key role in the first analysis of the function of all of an organism's important proteins, the main building blocks of all living organisms. That peer-reviewed research, headed by a team of scientists from Yale University, is described in the July 27 edition of the journal Science.
Proteins are the complex molecules created to carry out the instructions in an organism's genes, encoded in DNA, for how that organism grows and functions. Research on how those proteins work, called "proteomics," is an emerging field of scientific study.
The Yale-NC State proteomics project analyzed how 5,800 proteins in yeast interact with each other, with DNA and with lipids, the molecules that make up the membranes surrounding cells. [More]
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Star With Midriff Bulge Eyed By Astronomers Posted: Friday, July 27, 2001
For the first time ever, a star spinning so fast its mid-section is stretched out has been directly measured by an ultra-high-resolution NASA telescope system on Palomar Mountain near San Diego.
"Measuring the shape of this star, Altair, was as difficult as standing in Los Angeles, looking at a hen's egg in New York, and trying to prove that it's oval-shaped and not circular," said Dr. Charles Beichman, chief scientist for astronomy and physics at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Altair is a well-known member of the Summer Triangle, clearly visible in the summer night sky across the United States. Scientists using the Palomar Testbed Interferometer, which links multiple telescopes, measured the star's radius at different angles on the sky. They noticed the size of the star varied with changing angles, which was the first tip-off that Altair is not perfectly round.
"This surprising observation led to a bit of challenging detective work to properly interpret the data," said principal investigator Dr. Gerard van Belle of JPL. "We measured the size of another star, Vega, at the same time, which didn't change with angle, so we knew this wasn't just a fluke of the telescope."
Previous studies of Altair raised the prospect that the star might have midriff bulge, but never before had the shape been measured directly. Earlier measurements of the star's spectrum, or light-wave pattern, had hinted that Altair was rotating very fast. When a gaseous orb, like a star, spins fast enough, it tends to expand at the middle, like a beach ball that is squeezed at the top and bottom.
Altair is a perfect example -- it rotates at least once every 10.4 hours, and the new Palomar observations reveal the diameter at its equator is at least 14 percent greater than at its poles. For a star that spins slowly, this effect is miniscule. For example, our Sun rotates once every 30 days and has an equator only .001 percent greater in diameter than its poles.
By measuring Altair's size at separate positions along its edge, van Belle and his colleagues determined that Altair rotates at a speed of at least 210 kilometers per second (470,000 miles per hour) at the equator. Future studies may pin down the speed more precisely.
"Determining the shape of another star helps us learn about the forces that control the shape and structure of all stars, including our star, the Sun," Beichman said. "This tells us more about the Sun's behavior and ultimate fate."
The Palomar Testbed Interferometer has three 50-centimeter (20-inch) telescopes. To study Altair, the telescopes were used two at a time. The combined light from the telescope pairs provided sharpness comparable to a telescope as large as a football field.
"Altair is the twelfth brightest star in the sky -- you'd think that everything there is to know about this star would have been discovered already," said co-investigator Dr. David Ciardi of the University of Florida, Gainesville. "It's a good example of the surprises you're going to encounter when you are able to look at even familiar stars with unprecedented resolution."
The Palomar Testbed Interferometer is paving the way for the Keck Interferometer, Space Interferometry Mission and Terrestrial Planet Finder, all part of NASA's Origins program. The program will hunt for Earthlike planets that might harbor life around other stars. "In the long run, we'll use these interferometric capabilities to search for planets around nearby stars. This is an important first step," said Beichman.
Van Belle and Ciardi co-authored the Altair paper, scheduled to appear in the October 1 issue of the Astrophysical Journal, with Robert Thompson of JPL and the University of Wyoming, Laramie; Dr. Rachel Akeson of the JPL/Caltech Infrared Processing and Analysis Center, Pasadena, Calif.; and Dr. Elizabeth Lada of the University of Florida, Gainesville.
Their research was funded by NASA's Office of Space Science, Washington, D.C., along with the National Science Foundation. Palomar Observatory is owned and operated by the California Institute of Technology in Pasadena, which also manages JPL for NASA. The Palomar Testbed Interferometer was designed and built by a team of JPL researchers led by Drs. Mark Colavita and Michael Shao. Funded by NASA and managed by JPL, the interferometer is located at the Palomar Observatory near the historic 200-inch Hale Telescope.
Images and animation of Altair are available at http://www.jpl.nasa.gov/images/stars/index.html . Information on the Palomar Testbed Interferometer is available at http://huey.jpl.nasa.gov/palomar . Information on NASA's Origins Program is available at http://origins.jpl.nasa.gov .
Editor's Note: The original news release can be found at http://www.jpl.nasa.gov/releases/2001/release_2001_150.html
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The First Galaxy Without One Or The Smallest Black Hole Yet? Posted: Monday, July 23, 2001
NEW BRUNSWICK/PISCATAWAY, N.J. - Rutgers astronomers have made a provocative discovery -- the first galaxy without a supermassive black hole (SBH) at its center or the smallest black hole ever detected in the center of a galaxy. They used the Hubble Space Telescope to observe the galaxy M33, one of the nearest neighbors to the Milky Way galaxy at a relatively short distance of 3 million light-years. By using Hubble's high-resolution instruments, the investigators were able to see details at a scale that is at least 10 times finer than was ever possible in the past from the ground.
A paper describing this research, "No Supermassive Black Hole in M33?" by Professor David Merritt, Assistant Professor Laura Ferrarese and Assistant Research Professor Charles Joseph, all of Rutgers' department of physics and astronomy, is being published online by the journal Science, as part of the Science Express web site, on July 19. (See http://www.sciencexpress.org)
Merritt, who leads the Supermassive Black Hole Research Group at Rutgers, is a theorist who has worked extensively on the interaction of black holes with galaxies; Ferrarese discovered two of the first supermassive black holes external to the Milky Way; and Joseph is a key member of Hubble's Instrument Development Team for the Space Telescope Imaging Spectrograph, the instrument used for the observations on which the current research was based.
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Minor Mutations In HIV Virus Have Major Impact Posted: Friday, July 20, 2001
Source: Massachusetts General Hospital (http://www.mgh.harvard.edu/)
BOSTON - Researchers at Massachusetts General Hospital (MGH) published a study in this week's Nature indicating that HIV can mutate key proteins in order to hide from an immune attack, and once these mutations occur they persist.
"The virus is gradually evolving and learning how to evade the immune system," says the senior author of the study Bruce Walker, MD, of the Partners AIDS Research Center at MGH. "This study shows for the first time that minor mutations in the virus can have a major impact on the ability of the immune defenses to recognize it."
When HIV infects a cell, the cell alerts the immune system that it contains a foreign invader by displaying viral protein fragments on the cell surface. This is a suicide signal that alerts the immune system to kill the infected cell. The immune response that is generated is dependent on the ability to recognize the displayed HIV fragment. Walker and his colleagues have found that the virus can mutate these targeted regions and in doing so evade this attack.
"Our study indicates that the virus can learn how to evade the immune response in one person, and that it retains this ability even after it is transmitted to the next person," says Philip Goulder, MD, the lead author on the study. When this happens, the immune system is forced to use a second-line attack strategy that was less effective in containing the virus in the patients studied. These studies, which were performed in HIV-infected mothers who transmitted virus to their infants, showed that the infected infants are less able to control the virus because of mutations that occurred in the mothers. The effects of these mutations were particularly apparent in the children since they inherit key elements of their immune systems from their parents, and thus there is a strong chance that they will be programmed to target the same regions that the mother targeted. In mothers in whom mutations had already arisen, the children could not target the virus effectively.
The authors also examined adults who recently had been infected with HIV by sexual transmission, and found that the viruses presently being transmitted have already evolved to be able to avoid a number of important immune responses. Once these mutations arise, they do not appear to revert to the original strain, suggesting that escape mutations are likely to accumulate as the epidemic progresses.
The findings have significant implications for vaccines that are presently in development. "Vaccines being tested today are based on strains that were isolated a number of years ago, " says Walker. "These vaccines are attempting to induce immune responses to regions of the virus that may have already mutated, and thus the immune responses may be less effective." In the same way that influenza virus evolves to escape detection by immune responses and requires new vaccines to be made on a regular basis, HIV also is evolving. The extent to which this will affect present vaccine candidates is not known, but the present study indicates that this is something that will need to be monitored very closely.
The current work was supported by the Medical Research Council (UK), the NIH, the Doris Duke Charitable Foundation, the Lloyd Foundation and the Elizabeth Glaser Pediatric AIDS Foundation and a number of private donors.
The Massachusetts General Hospital, established in 1811, is the original and largest teaching hospital of Harvard Medical School. The MGH conducts the largest hospital-based research program in the United States, with an annual research budget of more than $300 million and major research centers in AIDS, the neurosciences, cardiovascular research, cancer, cutaneous biology, transplantation biology and photo-medicine. In 1994, the MGH joined with Brigham and Women's Hospital to form Partners HealthCare System, an integrated health care delivery system comprising the two academic medical centers, specialty and community hospitals, a network of physician groups and nonacute and home health services.
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Chandra Detects Halo Of Hot Gas Around Milky Way-Like Galaxy Posted: Friday, July 20, 2001
Source: NASA/Marshall Space Flight Center (http://www.msfc.nasa.gov)
The first unambiguous evidence for a giant halo of hot gas around a nearby, spiral galaxy much like our own Milky Way was found by astronomers using NASA's Chandra X-ray Observatory. This discovery may lead to a better understanding of our own galaxy, as well the structure and evolution of galaxies in general.
A team of astronomers, led by Professor Daniel Wang of the University of Massachusetts, Amherst, observed NGC 4631, a spiral galaxy approximately 25 million light years from Earth with both Chandra and NASA's Hubble Space Telescope.
While previous X-ray satellites have detected extended X-ray emission from this and other spiral galaxies, because of Chandra's exceptional resolution this is the first time that astronomers were able to separate the individual X-ray sources from the diffuse halo. Chandra found the diffuse halo of X-ray gas to be radiating at a temperature of almost 3 million degrees.
"Scientists have debated for over 40 years whether the Milky Way has an extended corona, or halo, of hot gas," said Wang, lead author of the paper which appeared this month in The Astrophysical Journal Letters. "Of course since we are within the Milky Way, we can't get outside and take a picture. However, by studying similar galaxies like NGC 4631, we can get an idea of what's going on within our own galaxy."
The Chandra image reveals a halo of hot gas that extends for approximately 25,000 light years above the disk of the galaxy. One important feature of the X-ray emission from NGC 4631 is that it closely resembles the overall size and shape seen in the radio emission from the galaxy. This indicates that there may be a close connection between the outflows of hot gas, seen in X-rays, and the galaxy's magnetic field, revealed by radio emission.
The Hubble image of NGC 4631 shows filamentary, loop-like structures enclosing enhanced X-ray-emitting gas and emanating from regions of recent star formation in the galaxy's disk. These data clearly show the hot gas is heated by clusters of massive stars and is now expanding into the halo of the galaxy.
"What we see in NGC 4631 can be thought of as the bursting flames of a gigantic cosmic camp fire," said Wang. "Using Chandra and Hubble together, we really get a complete story of what is happening in this galaxy."
NGC 4631 is a galaxy that has high amounts of star formation, possibly triggered by interaction with neighboring galaxies. Such star formation might have created the conditions necessary to heat the gas seen by Chandra, as vast amounts of energy are released from supernovae and massive stars in star-forming regions - enough to lift the gas out of the plane of the galaxy.
These new results provide important clues about the cycling of energy and mass in a galaxy like our own Milky Way and about the evolutionary history of galaxies, which are thought to be more active in star formation in the past than at the present.
###
Other members of the research team include: Stefan Immler, University of Massachusetts; Rene Walterbos, New Mexico State University; James Lauroesch, Northwestern University, Evanston, Ill., and Dieter Breitschwerdt, Max Plank Institute, Germany.
Chandra observed NGC 4631 with its Advanced CCD Imaging Spectrometer (ACIS) instrument, which was developed for NASA by Pennsylvania State University, University Park, and Massachusetts Institute of Technology, Cambridge. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program, and TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass.
Images associated with this release are available at:
http://chandra.harvard.edu
and
http://chandra.nasa.gov
Editor's Note: The original news release can be found at
http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2001/01-248.html
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Missing black hole forces galaxy rethink Posted: Friday, July 20, 2001
(Reuters) Astronomers have found a galaxy that is missing a vital component at its heart - a supermassive black hole. The discovery challenges the prevailing view that these black holes are crucial to galaxy formation.
Supermassive black holes have more than a million times the mass of the Sun and astronomers have found them in every one of the thirty or so galaxies they have examined, usually by observing the gravitational effect they have on stars.
But David Merritt and colleagues at Rutgers University in New Jersey, US, have used the Hubble Space Telescope to image the centre of a disc shaped galaxy called M33. They calculated that the largest black hole it can possibly contain is thousands of times smaller than the smallest supermassive black hole.
Astronomers already knew that M33 was a strange shape - it's a regular disc, without the bulge in the middle that most galaxies display. In general, the smaller the bulge is, the smaller the black hole in the middle of a galaxy. But Merritt's upper limit on the mass of M33's black hole is much smaller than was expected.
Douglas Richstone of the University of Michigan, who has been a prominent champion of the role of black holes in galaxy formation, said he did not understand how bulgeless galaxies like M33 could have formed without a supermassive black hole. "I think it's a problem for the black hole story," he said.
Chicken and egg
The conventional model of how galaxies form is that in the early Universe, gas clouds collapse to form supermassive black holes. Other parts of the gas cloud then swirl into orbit around the black holes and stars are born.
But Merritt says M33 may be the first hard evidence that astronomers have been getting the chicken and egg the wrong way round. "M33 looks like a fairly young galaxy," he says. He thinks it is possible that a supermassive black hole may yet form in M33, although astronomers are not sure whether this would be typical.
Richstone disagrees. Despite the confusion, he is glad that one aspect of the current model survives intact, the relationship between the galactic bulge and the mass of the black hole. He thinks the solution to the problem will come from understanding better how the unusual, bulgeless disc galaxies form.
The limits on the size of M33's black hole are published in Science Express.
Related Stories from New Scientist:
Most violent explosions in Universe caused by the birth of black holes
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Massive Dust Storm Has Erupted On Mars Posted: Monday, July 16, 2001
(NASA Science News) A massive dust storm --the largest in 25 years and still growing-- has erupted on Mars. It's so big that amateur astronomers using modest telescopes can see it from Earth. And the cloud has raised the temperature of the frigid Martian atmosphere by a stunning 30 degrees Celsius. This story includes movies of the ongoing storm and explains how Martian dust storms can grow so large.
FULL STORY at http://science.nasa.gov/headlines/y2001/ast16jul_1.htm?list501692
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Grounding Language In Perceptual Categories Posted: Friday, July 13, 2001
Using neural nets to simulate learning and the genetic algorithm to simulate evolution in a toy world of mushrooms and mushroom-foragers, we place two ways of acquiring categories into direct competition with one another: In (1) "sensorimotor toil," new categories are acquired through real-time, feedback-corrected, trial and error experience in sorting them. In (2) "symbolic theft," new categories are acquired by hearsay from propositions - boolean combinations of symbols describing them. In competition, symbolic theft always beats sensorimotor toil.
We hypothesize that this is the basis of the adaptive advantage of language. Entry-level categories must still be learned by toil, however, to avoid an infinite regress (the "symbol grounding problem"). Changes in the internal representations of categories must take place during the course of learning by toil. These changes can be analyzed in terms of the compression of within-category similarities and the expansion of between-category differences. These allow regions of similarity space to be separated, bounded and named, and then the names can be combined and recombined to describe new categories, grounded recursively in the old ones. Such compression/expansion effects, called "categorical perception" (CP), have previously been reported with categories acquired by sensorimotor toil; we show that they can also arise from symbolic theft alone.
The picture of natural language and its origins that emerges from this analysis is that of a powerful hybrid symbolic/sensorimotor capacity, infinitely superior to its purely sensorimotor precursors, but still grounded in and dependent on them. It can spare us from untold time and effort learning things the hard way, through direct experience, but it remain anchored in and translatable into the language of experience.
Continue: http://www.cogsci.soton.ac.uk/
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Blocking "Engulfment" Gives Dying Cells New Lease On Life Posted: Friday, July 13, 2001
Source: Cold Spring Harbor Laboratory (http://www.cshl.org/)
Multicellular life is a balance between cell survival and cell death. The genetically programmed death of cells is a normal part of embryonic development and occurs throughout the lifetime of organisms to rid abnormal (e.g. pre-cancerous) and surplus cells from the body. Research at Cold Spring Harbor Laboratory now reveals that under special circumstances, cells programmed to die during nervous system development can be brought back from the brink of death. This finding has important implications for the treatment of neurodegenerative disease, stroke, and cancer.
The study, to be published July 12 in Nature, focused on the developing nervous system of a favored experimental organism: the soil nematode worm Caenorhabditis elegans. Cell survival and cell death during development in this animal is highly stereotyped. Among different embryos, cells in corresponding positions virtually always share the same fate. Because the worms are transparent, the fate of all cells—living, dead, or dying—can be followed relatively easily and filmed by using a video camera attached to a microscope.
Under normal circumstances, dead cells are engulfed by neighboring cells to eliminate them from the embryo. Until now, the engulfment process was viewed as an after-the-fact, disposal operation. Cold Spring Harbor Laboratory researchers Daniel Hoeppner and Michael Hengartner, together with Ralf Schnabel of the Institute for Genetics (Braunschweig, Germany), studied how the death and "burial" (engulfment) processes are coördinated during development of the C. elegans nervous system. They made two interesting discoveries.
First, the scientists found that when they weakened the genetically programmed signal for cells to die, most cells still died (65%) and an expected cohort of cells survived (15%). Surprisingly, however, a few cells (5%) proceeded all the way to death's door but at the very last stage before death (stage 3 of 4), they reverted to a normal appearance and survived.
Second, the researchers found that blocking engulfment in animals with a genetically weakened cell death signal increased the number of cells that escaped death to nearly 20%. Moreover, some 40% of cells slated for death in these animals survived outright, never displaying signs of death. In essence, when the engulfment machinery was disabled, cells lived that otherwise would have died. This finding indicates that the engulfment machinery actively contributes to cell killing, rather than merely eliminating dead cells.
Because many features of programmed cell death and engulfment are conserved between C. elegans and humans, the scientists suggest that modulating the activity of the engulfment machinery in humans might be an effective therapy for neurodegenerative disease, stroke, and cancer.
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Striking Difference Between Matter And Antimatter Posted: Friday, July 13, 2001
Source: Stanford University (http://www.stanford.edu)
Physicists Find A New, Striking Difference Between Matter And Antimatter
An international collaboration of physicists conducting experiments at the Department of Energy's Stanford Linear Accelerator Center (SLAC) has discovered a second fundamental difference between the behavior of matter and that of antimatter. They observed this intriguing phenomenon -- known as charge-parity (CP) violation and first seen decades ago in experiments with another particle -- in disintegrations of heavy, short-lived subatomic particles called B mesons. The collaboration reported its result in a paper submitted July 5 for publication in Physical Review Letters, a leading scientific journal.
"After 37 years of searching for further examples of CP violation, physicists now know that there are at least two kinds of subatomic particles that exhibit this puzzling phenomenon, thought to be responsible for the great preponderance of matter in the Universe," said Princeton University physicist Stewart Smith, spokesman of the collaboration. "We are poised for further discoveries that should open up new directions for particle physics."
The international collaboration includes more than 600 scientists and engineers from 73 institutions in Canada, China, France, Germany, Great Britain, Italy, Norway, Russia and the United States. They built and have been operating the sophisticated 1,200-ton detector, named BABAR, which was used to make the discovery.
The detector records subtle distinctions between decays of B mesons and those of their antimatter counterparts, called anti-B mesons. Both are more than five times heavier than protons and survive just over a trillionth of a second. Physicists employed the detector to observe an unmistakable difference, or asymmetry, between the rates at which B and anti-B mesons decay into a special set of specific final states.
From these measurements, they calculated a parameter called sin 2b (sine two beta), which expresses the degree of asymmetry between matter and antimatter. A non-zero value of this parameter is clear evidence for CP violation among B mesons.
In the paper just submitted, the BABAR collaboration reported measuring a value of sin 2b = 0.59 ± 0.14, which is substantially different from zero. There are now fewer than 3 chances in 100,000 that the actual, physical asymmetry could be consistent with zero.
This BABAR result is easily the most precise measurement of sin 2b reported to date. Earlier measurements made at Fermi National Accelerator Laboratory, the Japanese National Laboratory for High-Energy Accelerator Research (KEK), and at SLAC by the BABAR collaboration are consistent with the present result but not as accurate. The value just reported agrees with expectations based on the Standard Model, today's dominant theory of particle physics.
The precision of the BABAR result was made possible by the outstanding performance of the PEP-II B Factory at SLAC. Built in collaboration with the Energy Department's Lawrence Berkeley and Lawrence Livermore National Laboratories, this pair of 2.2-kilometer storage rings collides unequal-energy beams of electrons and their antimatter counterparts, called positrons. Piermaria Oddone, now deputy director of the Berkeley lab, first proposed this innovative experimental approach, which greatly enhances the accuracy of many B meson measurements.
"The B Factory has performed beyond expectations, permitting the BABAR collaboration to make the world-class measurements on B mesons," said SLAC Director Jonathan Dorfan, who played a pivotal role in designing and building this particle collider. Since it began operating in June 1999, the B Factory has produced more than 32 million pairs of B mesons, from which data the present BABAR result was extracted.
The mysterious phenomenon of CP violation was first discovered in a 1964 experiment led by James Cronin and Val Fitch at the Brookhaven National Laboratory. Their group observed this behavior in decays of subatomic particles called K mesons, which are about one tenth as heavy as B mesons and live much longer; the two physicists shared a Nobel Prize for the discovery.
Several observations of CP violation have since occurred in experiments with K mesons. But until the recent BABAR discovery, no other subatomic particles had clearly exhibited this exceedingly rare phenomenon. Having this second striking example of CP violation should aid theorists trying to understand what causes it.
Scientists are interested in this puzzling behavior because it can help explain the abundance of matter in the Universe. In 1967, Russian theorist Andrei Sakharov used CP violation to suggest how the present matter-dominated Universe could have emerged from one that contained exactly equal amounts of matter and antimatter during the earliest moments of the Big Bang.
The Stanford Linear Accelerator Center is a national laboratory for high-energy physics and synchrotron-radiation research operated by Stanford University on behalf of the U.S. Department of Energy. The Department's Office of Science funded the construction of the B Factory at $177 million and contributed about 60 percent of the cost of the BABAR detector, with the remainder coming from foreign sources. "The foreign contributions to this experiment, both monetary and scientific, have been absolutely crucial to its success," noted former BABAR spokesman David Hitlin of the California Institute of Technology.
Editor's Note: The original news release can be found at
http://www.stanford.edu/dept/news/pr/01/cp3.doc711.html
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Early Humans Lived In Forests Instead Of Grasslands Posted: Friday, July 13, 2001
University Of Illinois At Urbana-Champaign (http://www.uiuc.edu/)
Soil Suggests Early Humans Lived In Forests Instead Of Grasslands
CHAMPAIGN, Ill. — Carbon isotope evidence in almost 6-million-year-old soils suggests that the earliest humans already were evolving in – and likely preferred – humid forests rather than grasslands, report a team of scientists working in Ethiopia.
The discovery challenges long-held beliefs, beginning with Darwin, that humans did not evolve into upright beings and thrive until expanding tropical grasslands forced our chimpanzee-like ancestors out of dwindling forests about 4 million to 8 million years ago.
Hominid fossil sites from the later Pliocene period (2.5 million to 4.2 million years ago) previously had been found in savanna habitats. Researchers had been confident that the slightly earlier hominids living in the late Miocene also would be found in the savanna.
"The expectation was that we would find hominids in savanna grassland sites that date back to about 8 million years ago. That hasn’t happened," said anthropologist Stanley H. Ambrose of the University of Illinois. "All older hominids have been found in forested environments."
The analysis was of fossil soils from paleontological sites in the Middle Awash region of Ethiopia’s rift valley, where the remains of a new subspecies of Ardipithecus ramidus have been discovered. They date to the late Miocene period (5.4 million to 5.8 million years ago). Scientists from four institutions report their findings in a pair of papers that appear in the July 12 issue of the journal Nature.
Ambrose collected fossil soil samples from the layers containing the newly found hominids. One of the fossils was found by team member Leslea Hlusko, also a UI professor of anthropology. Ambrose performed geochemical studies on the samples in his UI laboratory.
The region where the fossils were found is now a hot, dry semi-desert occupied by nomadic camel herders. At the time the area formed, it was higher in elevation, cooler, wetter and more forested.
Ambrose’s geochemical technique allows for an environmental reconstruction of soils by examining the carbonate nodules (caliche) in the samples. The nodules reflect the types of plants that grew in the soils. Tropical grasses contain more of the heavy isotope of carbon than do trees, shrubs and leafy plants. The nodules from these late-Miocene hominid fossil sites contain low levels of carbon 13, which is consistent with trees and woody plants. They also contain oxygen isotope ratios that are indicative of a cool, humid climate. "These hominids were living in the forest, despite the fact that grasslands were available," Ambrose said.
The new findings, he said, require a fundamental reassessment of models that invoke a significant role for global climatic change and/or adaptation to savanna habitats in the origin of hominids.
Ambrose’s findings appear in a paper cowritten with seven other researchers: Tim White, Yohammes Haile-Selassie and Paul R. Renne of the University of California at Berkeley; Giday WoldeGabriel and Grant Heiken of the Los Alamos National Laboratory in New Mexico; William K. Hart of Miami University in Oxford, Ohio; and Berhane Asfaw of the Rift Valley Research Service in Addis Adaba, Ethiopa.
The National Science Foundation and the University of Illinois Research Board provided funding for Ambrose’s research.
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Huge Genetic Variation Found in Human Beings Posted: Thursday, July 12, 2001
WASHINGTON (Reuters) - The notion of a uniform genetic blueprint for human beings took a tumble on Thursday, as the most detailed examination yet of variations in the genetic makeup of people detected unexpectedly large individual differences.
Researchers with Genaissance Pharmaceuticals Inc. of New Haven, Connecticut, found astonishing variance at the genetic level in 82 unrelated people primarily from four racial backgrounds -- white, black, Asian and Hispanic.
In studying 313 genes -- out of the 30,000 identified by human genome scientists -- the Genaissance researchers found that for each gene, there actually are on average 14 versions that can be inherited by a given person from parents.
The researchers said their findings should cause scientists to rethink the definition of the human genome, or genetic map. [More]
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Earliest Human Ancestors Discovered In Ethiopia Posted: Thursday, July 12, 2001
Source: National Science Foundation (http://www.nsf.gov/)
Discovery Of Bones And Teeth Date Fossils Back More Than 5.2 Million Years
Anthropologists have discovered the remains of the earliest known human ancestor in Ethiopia, dating to between 5.2 and 5.8 million years ago and which predate the previously oldest-known fossils by almost a million years. The previous discovery of the 4.4-million-year-old Ardipithecus ramidus was up to this point the oldest known hominid, the primate zoological family that includes all species on the human side of the evolutionary split with chimpanzees.
The fossil finds, reported in the July 12 issue of Nature, were made by National Science Foundation (NSF)-funded scientists over a four-year period in Ethiopia's Middle Awash study area, about 140 miles northeast of the capital, Addis Ababa. To the team of scientists, the discovery represents more evidence to confirm Darwin's conclusion that the earliest humans, or hominids, arose in Africa.
Yohannes Haile-Selaissie, a paleontologist at the University of California at Berkeley, made the recent fossil discoveries from these earliest creatures. Working under lead researcher and Berkeley colleague Tim D. White, Haile-Selaissie found a jawbone and teeth in December, 1997. More fossils were found, the last a tooth, uncovered in January, 2001.
The area where this hominid discovery took place has been the focus of much recent attention. Eleven hominid specimens have been recovered from five late Miocene localities within the Middle Awash region.
"The new fossils come from the oldest of the patches of exposed sediment at Saitune Dora, Alayla, Aas Koma and Digiba Dora," White said. "These bones and teeth were difficult to find on surfaces that are littered with stones ranging from pebbles to boulders."
The study of the Middle Awash has been ongoing since 1981 under the joint direction of White and Desmond Clark of UC-Berkeley, Giday WoldeGabriel of Los Alamos National Laboratory and Ethiopian researchers Berhane Asfaw and Yonas Beyene.
The researchers explain that about six million years ago, the Middle Awash region was already a well-defined rift valley characterized by intense earth movements, with active volcanoes nearby. "It is hard to imagine life would go on normally under such hostile environmental conditions -- Ardipithecus and the other animals inhabiting the area were real survivors," WoldeGabriel said.
White says that an accurate portrayal of these creatures is not yet possible because an intact skull or limb bones have not yet been found. Researchers estimate the size of the skeletal bones and the lower jaw is roughly the same size as a modern chimpanzee.
"This is an exciting development," says Mark Weiss, program director of physical anthropology at NSF. "Not only are we gaining insights into the anatomy of what may be some of our earliest ancestors, but we are seeing a better picture of the environment in which they lived. I'm really looking forward to further finds by White and his colleagues." White has received close to $1.2 million in NSF funding for his work since 1995.
The age of these newly found fossils was determined by the Berkeley Geochronology Center by employing an argon-argon laser heating method -- a process that determines the time elapsed since volcanic ashes and lavas were erupted by measuring the argon gas trapped in the rock after it cools. "The argon dating results were corroborated by geomagnetic polarity data, then further confirmed by biochronological analysis of the primitive fossil animals found with the human ancestor remains," White explains.
"These fossils are strong evidence that that lines leading to chimpanzees and humans had already split well before five million years ago," Haile-Selaissie concludes.
Editor's Note: The original news release can be found at
http://www.nsf.gov/od/lpa/news/press/01/pr0157.htm
http://www.nature.com/nsu/010712/010712-14.html
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Beginning Friday the 13th, four planets will form equilateral triangle Posted: Thursday, July 12, 2001
Around 4:30 a.m. local time on Friday, July 13th, Venus, Saturn, and the red star Aldebaran will form a compact equilateral triangle hovering 25 degrees above the eastern horizon. How high is that? If you hold your clenched fist at arm's length it spans an angle about 10 degrees wide. So, you can find the celestial threesome about two and a half "fists" above the horizon.
The brightest member of the grouping, Venus, is so brilliant it's often mistaken for an airplane or a UFO. But if you stare at Venus for a few moments you'll see it doesn't blink, twinkle, or move abruptly like a spacecraft -- it really is a planet! Venus glares so because it's close to Earth and its global clouds reflect much of the sunlight that falls on them. Yellow-hued Saturn is 10 times wider than Venus, but 50 times dimmer in Earth's night sky because Saturn lies in the outer solar system. Aldebaran, even more distant at 71 light years, is a giant reddish-colored star 40 times wider than the Sun that could swallow 40 billion Venus-sized planets. [More]
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The "book of life" may be missing half of its words Posted: Thursday, July 12, 2001
WHEN the papers containing the first attempts to sequence the human genome were published earlier this year, some people purported to be shocked. The cause of their shock was the number (or, rather, the lack of number) of genes that it took to carry the blueprint for a human being. One paper, published by the publicly funded Human Genome Consortium (prop. Francis Collins, of America's National Institutes of Health), came up with a figure of 31,000. The other, the product of Celera, a private company (prop. Craig Venter), suggested around 26,000.
Within the margins of error expected of such cutting-edge research, that sounded like a consensus. The reason that many people were sceptical was that it was little larger than the figures previously arrived at for nematode worms (19,000) and fruitflies (13,600). Surely, these scientists argued, people are a lot more complex than worms and flies. And that should mean that they must have many more genes.
A paper just published in Genome Biology suggests that the sceptics might be right, after all. Bo Yuan, of Ohio State University, in Columbus, and his colleagues, suspect that the human genome contains not 30,000 genes, but more than twice that figure. Their estimate, arrived at using a different approach from that employed by Celera and the Human Genome Consortium, is 65,000-75,000. [More]
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Earliest Human Ancestors Discovered In Ethiopia Posted: Thursday, July 12, 2001
Earliest Human Ancestors Discovered In Ethiopia; Discovery Of Bones And Teeth Date Fossils Back More Than 5.2 Million Years
Anthropologists have discovered the remains of the earliest known human ancestor in Ethiopia, dating to between 5.2 and 5.8 million years ago and which predate the previously oldest-known fossils by almost a million years. The previous discovery of the 4.4-million-year-old Ardipithecus ramidus was up to this point the oldest known hominid, the primate zoological family that includes all species on the human side of the evolutionary split with chimpanzees.
The fossil finds, reported in the July 12 issue of Nature, were made by National Science Foundation (NSF)-funded scientists over a four-year period in Ethiopia's Middle Awash study area, about 140 miles northeast of the capital, Addis Ababa. To the team of scientists, the discovery represents more evidence to confirm Darwin's conclusion that the earliest humans, or hominids, arose in Africa.
Yohannes Haile-Selaissie, a paleontologist at the University of California at Berkeley, made the recent fossil discoveries from these earliest creatures. Working under lead researcher and Berkeley colleague Tim D. White, Haile-Selaissie found a jawbone and teeth in December, 1997. More fossils were found, the last a tooth, uncovered in January, 2001.
The area where this hominid discovery took place has been the focus of much recent attention. Eleven hominid specimens have been recovered from five late Miocene localities within the Middle Awash region.
"The new fossils come from the oldest of the patches of exposed sediment at Saitune Dora, Alayla, Aas Koma and Digiba Dora," White said. "These bones and teeth were difficult to find on surfaces that are littered with stones ranging from pebbles to boulders."
The study of the Middle Awash has been ongoing since 1981 under the joint direction of White and Desmond Clark of UC-Berkeley, Giday WoldeGabriel of Los Alamos National Laboratory and Ethiopian researchers Berhane Asfaw and Yonas Beyene.
The researchers explain that about six million years ago, the Middle Awash region was already a well-defined rift valley characterized by intense earth movements, with active volcanoes nearby. "It is hard to imagine life would go on normally under such hostile environmental conditions -- Ardipithecus and the other animals inhabiting the area were real survivors," WoldeGabriel said.
White says that an accurate portrayal of these creatures is not yet possible because an intact skull or limb bones have not yet been found. Researchers estimate the size of the skeletal bones and the lower jaw is roughly the same size as a modern chimpanzee.
"This is an exciting development," says Mark Weiss, program director of physical anthropology at NSF. "Not only are we gaining insights into the anatomy of what may be some of our earliest ancestors, but we are seeing a better picture of the environment in which they lived. I'm really looking forward to further finds by White and his colleagues." White has received close to $1.2 million in NSF funding for his work since 1995.
The age of these newly found fossils was determined by the Berkeley Geochronology Center by employing an argon-argon laser heating method -- a process that determines the time elapsed since volcanic ashes and lavas were erupted by measuring the argon gas trapped in the rock after it cools. "The argon dating results were corroborated by geomagnetic polarity data, then further confirmed by biochronological analysis of the primitive fossil animals found with the human ancestor remains," White explains.
"These fossils are strong evidence that that lines leading to chimpanzees and humans had already split well before five million years ago," Haile-Selaissie concludes.
Editor's Note: The original news release can be found at http://www.nsf.gov/od/lpa/news/press/01/pr0157.htm
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Brain-Development Timeline For Mammalian Species Posted: Wednesday, July 11, 2001
Source: Cornell University (http://www.cornell.edu/)
ITHACA, N.Y. -- A team of Cornell University neurobiologists has modeled key milestones in brain development across nine mammalian species, from hamsters to humans. They have, for example, pinpointed the date after conception when the cells that make up the retina of the eye are formed. The neurobiologists found pretty much what they expected -- an evolutionarily conserved pattern of sequence and timing. But they also found a few curious exceptions, such as the discovery that the human brain is relatively developed at birth.
Knowing precisely how development in rodent brains can be translated to other species, the researchers hope, might reduce the number of higher animals required for research and should make transgenic mice an even more valuable animal model in biomedical research. And because brain (neural) development milestones are remarkably consistent in mammals, the researchers' mathematical model is able to fill in the blanks in one species, Homo sapiens , where experimentation is unthinkable.
One product of the model -- 95 neural development milestones for hamsters, rats, mice, spiny mice, ferrets, cats, monkeys and humans -- is reported in the July 2001 issue of Neuroscience (Vol. 105/1, pp. 7-17) by Barbara Clancy, Richard B. Darlington and Barbara L. Finlay of Cornell's Department of Psychology.
"We're happy that this model will improve estimation of the timing of milestones in brain development, particularly for humans," says Clancy, a postdoctoral associate in biopsychology. "This also should permit data on the well-studied rat to be applied to the recent burst of genetic studies in mice.
The model works because of the striking stability in the order and relative timing of neural events across many mammalian species, including human infants. Although their rather unwieldy bodies might disguise it, the model shows that the brains of human infants are relatively developed at birth.
This legitimizes something that many new parents have bragged about all along -- their baby really is quite precocious." However, Clancy says, "we're a little disappointed that some events we humans think are important just don't fit. We hoped we could use the mammalian model to advise when humans should wean their young but no such luck. If humans followed the time course set by brain development, we would wean our young immediately after birth, and of course our kids have other ideas."
The "weaning problem" is likely related to another peculiarity in mammalian development, Clancy notes: Relative to the sequence of neural development events, the times required for gestation and dates of birth are "all over the map, or rather, all over the calendar."
Some kinds of mammals are born with their eyes open, while others can't open their eyes until hours or days after birth, she says, citing an example familiar to anyone who has raised babies and kittens.
The only other event that doesn't fit the developmental patterns, the Cornell neurobiologists report, is a huge surge in the production of synapses (the junctions where brain cells communicate), an event that begins just before birth in the developing brains of primates, including humans.
For all other milestone events, the model accurately "predicted" the post- conception (PC) time, where the PC time was known from actual experiments with animals. (Accurate prediction of known facts is a critical test for mathematical models. The model's correlation, between predictions and known facts, was 0.9900, a nearly perfect relationship that indicates high accuracy.)
For example, the PC time of peak development of the amygdala (the almond-shaped section in the front of the brain's temporal lobe that is involved in emotions such as fear) was predicted by the Cornell model to be 14.3 days in rats, whereas previous experiments put amygdala development at 15 days. Similarly accurate predictions were found for amygdala development in two other thoroughly studied species, mice and macaque monkeys.
And for species with no experimental data on that part of the brain (including hamsters, rabbits, ferrets, cats and humans) the model made predictions, based on the general developmental pattern in all mammals. Thus, the PC time of peak amygdala cell development in the human fetus should be about PC 50 days, according to the Cornell model -- although no ethical scientist would ever conduct experiments to confirm that prediction.
"That's the beauty and power of statistical science," Darlington says. "Because the sequence and timing pattern of neural development has been conserved throughout the evolution of mammals, no animals were sacrificed to compile this data.
This model could very well result in fewer animals being used in research, and human experimentation will not be needed to increase our understanding of events in our own neural development that we need to know about."
The new model is an outgrowth of a mathematical equation first determined and reported in 1995 by Darlington, a behavioral statistician and professor of psychology, and Finlay, professor and chair of the Cornell Department of Psychology. Now the model can be used by any neuroscientist to extend predictions of neural development milestones to any other mammalian species.
The study was supported by a grant from the National Institutes of Health and a postdoctoral research fellowship from the National Institute of Mental Health.
"Sorry, we just can't use this model to settle the perennial question: How old is that dog in people years?" Finlay says. "But if you give us a minute, we can tell you exactly when a fetal dog's amygdala appears."
Related World Wide Web sites:
o Neuoscience journal: http://www.elsevier.com/locate/neuroscience
o Cornell Dept. of Psychology: http://comp9.psych.cornell.edu/
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New early human fossils Posted: Wednesday, July 11, 2001
Late Miocene hominids from the Middle Awash, Ethiopia
YOHANNES HAILE-SELASSIE
Department of Integrative Biology and Laboratory for Human Evolutionary Studies, Museum of Vertebrate Zoology, 3060 VLSB, University of California, Berkeley, California 94720, USA
Molecular studies suggest that the lineages leading to humans and chimpanzees diverged approximately 6.5-5.5 million years (Myr) ago, in the Late Miocene. Hominid fossils from this interval, however, are fragmentary and of uncertain phylogenetic status, age, or both. Here I report new hominid specimens from the Middle Awash area of Ethiopia that date to 5.2-5.8 Myr and are associated with a wooded palaeoenvironment.
These Late Miocene fossils are assigned to the hominid genus Ardipithecus and represent the earliest definitive evidence of the hominid clade. Derived dental characters are shared exclusively with all younger hominids. This indicates that the fossils probably represent a hominid taxon that postdated the divergence of lineages leading to modern chimpanzees and humans. However, the persistence of primitive dental and postcranial characters in these new fossils indicates that Ardipithecus was phylogenetically close to the common ancestor of chimpanzees and humans.
These new findings raise additional questions about the claimed hominid status of Orrorin tugenensis, recently described from Kenya and dated to 6 Myr. [More]
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How tools and meat-eating made us human Posted: Wednesday, July 11, 2001
THE world’s oldest stone tools were made by hominids who selected their raw materials carefully and understood how they could be used, new finds from Ethiopia have shown. While little is known about the first toolmakers, they seem to have used their new skills to obtain a meat-rich diet.
Sites on the Kada Gona river in northeastern Ethiopia have yielded numerous stone flakes and cores, the Ethiopian archaeologist Sileshi Semaw reports in the Journal of Archaeological Science. Based on radioisotopic argon-argon dating and the correlation of the Earth’s ancient magnetic field with the deposits in which the tools were found, he dates them to between 2.6 and 2.5 million years ago.
The tools were largely made from trachyte, a stone which flakes neatly when struck with a stone hammer to give sharp-edged fragments that can be used immediately for cutting and scraping. Less than half of a random sample of potential toolmaking materials from near the sites of East Gona (EG) 10 and 12 proved to be of trachyte, while 70 per cent of the artefacts were of this material. [More]
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Hubble spies exotic double cluster Posted: Wednesday, July 11, 2001
(CNN) A prominent double cluster in a nearby galaxy, captured in stunning detail by the Hubble Space Telescope, represents a kind of object unlike anything in our own Milky Way galaxy.
The cosmic oddity, located in the Large Magellanic Cloud, a satellite galaxy to the Milky Way, is the star attraction in a new Hubble image released by international scientists on Tuesday.
The double cluster, known as NGC 1850, is a dense collection of juvenile, globular-like stars, and the second brightest star cluster in the Large Magellanic Cloud. The celestial phenomenon has no equivalent in our galaxy, Hubble scientists said.
"These objects are different from what we find in our galaxy in that they are at the same time very compact, rather massive and recently formed," said Nino Panagia, one of the astronomers who studied NGC 1850. [More]
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Staph Bacteria Are Prolific Gene Swappers Posted: Tuesday, July 10, 2001
Source: NIH/National Institute Of Allergy And Infectious Diseases (http://www.niaid.nih.gov/)
When some disease-causing bacteria encounter a new obstacle, they simply swap DNA with their relatives to acquire the genes needed to overcome it. And they do so quite readily, according to scientists from the National Institute of Allergy and Infectious Diseases (NIAID).
The research reveals how Staphylococcus aureus, the common "staph" bacterium responsible for several human infections, has repeatedly adapted to novel environments and conditions. The research offers new approaches to antibiotic and vaccine design, and answers long-standing questions about the origins of both diseases: toxic shock syndrome (TSS) and antibiotic-resistant infections. "We have long wondered how TSS and methicillin-resistant staph strains took hold in the population," says study director James Musser, M.D., Ph.D., a bacteria researcher from NIAID's Rocky Mountain Laboratories in Hamilton, Mont. "The debate among microbiologists has been, did isolated strains pick up new genes once and then spread through the population, or did the bacteria acquire the genes on multiple occasions? Our research clearly shows the second explanation is correct."
The discovery likely settles the debate, Dr. Musser explains, and raises a concern about how easily bacteria can become dangerous. S. aureus is a common microbe that often causes no illness. Some strains can cause diseases, however, including TSS, food poisoning and impetigo. The bacteria can infect the skin, blood, urinary tract and wounds, and are a common source of infections acquired in hospitals. Most people are unknowing S. aureus carriers, intermittently harboring the bacteria on their skin or in their nose and throat, even in the absence of illness.
Whether or not a particular S. aureus strain causes disease depends largely on its genes. Different strains can survive different environments, and Dr. Musser's team sought to learn how genes have been exchanged between strains. In the study reported in today's online edition of the Proceedings of the National Academy of Sciences, first author Ross Fitzgerald, Ph.D., and colleagues from Dr. Musser's lab compared the genes of 36 different S. aureus strains to determine which genes help each strain survive.
Dr. Musser's team used a technique called DNA microarray analysis to rapidly screen their samples. Upon analyzing the results, the researchers discovered nearly a fourth of the genome was dispensable, consisting of genes that were not required for the bacteria's basic life processes. These so-called contigency genes provide flexibility in the bacterium's ability to cause disease in humans, cows and other organisms, explains Dr. Musser.
The TSS outbreak among menstruating women in the late 1970's likely occurred because of a change in the host environment brought on by new, hyperabsorbable tampons. Similarly, methicillin resistance emerged only after S. aureus was repeatedly exposed to the antibiotic. Dr. Musser's research suggests the bacteria adapted to the changes by picking up contingency genes on multiple occasions, showing how easily new bacterial strains can appear and spread through the population.
The discovery opens new avenues for research in pathogenic bacteria. "We are now looking to see if particular strains are adept at transferring or picking up genes so that we can know which strains we should be hypervigilant about," says Dr. Musser. His laboratory is also comparing different strains to select proteins they have in common for additional research. "DNA microarrays provide a finer microscope for dissecting bacterial genetics, and permit a rational strategy for vaccine and drug design."
NIAID is a component of the National Institutes of Health (NIH). NIAID supports basic and applied research to prevent, diagnose, and treat infectious and immune-mediated illnesses, including HIV/AIDS and other sexually transmitted diseases, tuberculosis, malaria, autoimmune disorders, asthma and allergies.
Reference:
Fitzgerald JR et al. Evolutionary genomics of Staphylococcus aureus: insights into the origin of methicillin-resistant strains and the toxic shock syndrome epidemic. This article is available online at http://www.pnas.org/papbyrecent.shtml. This article is not yet available in print.
Press releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at http://www.niaid.nih.gov.
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Galactic cannibalism in action Posted: Thursday, July 5, 2001
Andromeda: One of the closest and largest galaxies to ours
Astronomers have found evidence that a nearby galaxy has been devouring its close neighbours.
Deep field observations of the Andromeda galaxy show that its outer regions contain a stream of stars torn away from one of its small companion galaxies. It adds to growing evidence from our own Milky Way that many galaxies grow and evolve by absorbing their minor brethren.
Such a detailed view is only possible for the nearest galaxies, but scientists expect that when techniques improve they will detect more examples of galactic cannibalism.
These observations are the most detailed ever made of the outskirts of one of the closest galaxies to ours.
The mighty Andromeda galaxy, similar to our own Milky Way galaxy but larger, is 2 million light-years distant (19 million million million kilometres or 12 million million million miles). More
M31 is the famous Andromeda galaxy, our nearest large neighbor galaxy, forming the Local Group of galaxies together with its companions (including M32 and M110, two bright dwarf elliptical galaxies), our Milky Way and its companions, M33, and others.
Visible to the naked eye even under moderate conditions, this object was known as the "little cloud" to the Persian astronomer Al-Sufi, who described it 964 AD in his Book of Fixed Stars; it must have been observed by Persian astronomers as early as 905 AD, or earlier. Charles Messier was obviously unaware of this early report and ascribed its discovery to Simon Marius, who was the first to give a telescopic description in 1612. Unaware of both Al Sufi's and Marius' discovery, Giovanni Batista Hodierna independently rediscovered this object before 1654. Edmond Halley, however, in his 1716 treat of "Nebulae", accounts the discovery of this "nebula" to the French astronomer Bullialdus (Ismail Bouillaud), who observed it in 1661; but Bullialdus mentions that it had been seen 150 years earlier (in the early 1500s) by some anonymous astronomer (according to R.H. Allen, 1899/1963).
It was longly believed that the "Great Andromeda Nebula" was one of the closest nebulae. William Herschel believed, wrongly of course, that its distance would "not exceed 2000 times the distance of Sirius" (17,000 light years); nevertheless, he viewed it at the nearest "island universe" like our Milky Way which he assumed to be a disk of 850 times the distance of Sirius in diameter, and of a thickness of 155 times that distance.
It was William Huggins, the pioneer of spectroscopy, who noted the difference between gaseous nebula with their line spectra and those "nebulae" with continuous spectra, which we now know as galaxies. More
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Whales are one of evolution's great enigmas Posted: Tuesday, July 3, 2001
After life went to all the trouble of adapting to dry land, some mammals decided life was better in the water after all. Philip Gingerich of the University of Michigan has discovered a number of fossils that shed light on the gradual transformation of a furry, four-legged, land-dwelling carnivore into the whales that we know. In the December 22 issue of Publications of the National Academy of Science, he announced the oldest whale fossil yet know, a 53.5-million-year-old creature called Himalayacetus. The creature seemingly lived in a predominantly salt-water environment along the edge of the long-vanished Tethys Sea. It challenges the conventional notion that whales first made the transition to water by hunting for fish in fresh-water rivers.
Introduction to the Cetacea
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Giant world detected in deep space Posted: Tuesday, July 3, 2001
www.ifa.hawaii.edu
Astronomers have found one of the largest objects ever detected orbiting the Sun. It was seen in a deep space survey looking for bodies circling our star out near Pluto, the most distant planet. Only planets are larger than this new object, dubbed 2001 KX76.
The icy, reddish world is over a thousand kilometres across and astronomers say there may be even larger objects, bigger than planet Pluto itself, awaiting discovery.
"What we have seen may be only the tip of the iceberg," co-discoverer Dr Lawrence Wasserman said.
The world - it is big enough to be called a world - has a typical reddish hue and is probably covered in ice. It orbits the Sun beyond Neptune in the so-called Kuiper Belt - a region that extends far beyond the known planets.
Since 1992, over 400 Kuiper Belt Objects (KBOs) have been detected. Their discovery has revolutionised our view of the distant reaches of our Solar System. It is the sheer size of 2001 KX76 that is exciting astronomers.
"When we spotted it, we just wrote 'wow' on the image," Lawrence Wasserman, of the Lowell Observatory in Arizona, US, said. "We knew right away it was a big one." More
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Brain Parses "Movies Of Our Lives" Posted: Tuesday, July 3, 2001
Washington University In St. Louis (http://www.wustl.edu/)
Brain Parses "Movies Of Our Lives" Into Small Meaningful Chunks
St. Louis, June 29, 2001 -- With so much of our modern lives dominated by movies and television, it's easy to think of perception as a continuous, unedited, uncut version of the world around us. But new research from Washington University in St. Louis suggests that while we are watching the "movies" of our daily lives, the brain is automatically dividing them into smaller, meaningful units.
Jeffrey M. Zacks, Ph.D., assistant professor of psychology in Arts and Sciences, and colleagues, identified a network of brain areas that is activated during the perception of boundaries between events.
"We found regions of activity in the brain that track the process of identifying parts of continuous events, whether or not people are aware of those parts or even know anything about them," said Zacks. The study is published in the June 2001 issue of Nature Neuroscience.
The researchers observed local brain activity using functional magnetic resonance imaging (fMRI) while participants watched movies of common, everyday goal directed activities, such as making the bed, doing the dishes, or ironing a shirt. In the first scan, participants were instructed to passively watch the movies. These scans revealed that the brain automatically parses continuous events into smaller segments even in the absence of explicit instructions to do so.
"To answer the question about whether event segmentation is an ongoing process, we needed data from when people were not performing any task. So we had them just sit and watch the movies," Zacks said. "The fact that changes in brain activity occurred during the passive viewing of movies indicates that this is how we normally perceive continuous events, as a series of segments rather than a dynamic flow of action."
In two later scans, the same movies were shown again, but participants were instructed to press a hand-held button every time they identified a specific small task -- rinsing, washing, drying, for instance -- that was a necessary component of the larger activity. In one of the later scans, participants were asked to divide the movie into the largest units that were natural and meaningful to them; in the other scan, the smallest units.
These later scans allowed the researchers to look at brain activity during the perception of boundaries between large and small events. "We found local changes in brain activity occurring at the same time people were identifying event boundaries, and throughout this network, changes were larger for large boundaries and smaller for small ones," Zacks said.
Similar changes were observed when participants were passively viewing movies, although to a lesser degree. These findings also confirm previous behavioral work on the hierarchical structure of event segmentation, whereby large meaningful segments correspond to groups of smaller meaningful segments.
The activated parts of the brain include a large bilateral region of the posterior cortex, and a smaller region in the right frontal cortex. The peak of activity in the posterior cortex is in the human MT (or V5) complex, an area responsible for understanding motion and human action.
Activity in the frontal cortex was localized to a part of the frontal eye field (FEF) that is associated with shifting attention. How we form our perceptions has long been a basic question in cognitive science. While much previous research has yielded interesting clues about how we form perceptions in space, much less is known about how we form perceptions across time.
These findings have important practical implications because insights into how the brain processes and perceives individual tasks and activities could be harnessed to suggest more direct and effective approaches to everything from elementary curricula to on-the-job training. "If we understand how the brain and mind chunk activity into tasks, we can design better tools for teaching people new activities," said Zacks.
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Brown Dwarfs Are Stellar Embryos Evicted By Siblings Posted: Monday, July 2, 2001
Source: University Of Colorado At Boulder (http://www.colorado.edu/)
According To Study, Brown dwarfs, essentially stunted stars, were most likely ejected from newborn, multiple-star systems before they had a chance to accumulate enough mass to ignite the hydrogen in their interiors and flower, according to a new study.
University of Colorado at Boulder astronomer Bo Reipurth said that most newborn stars are spawned in binary or multiple systems involving two, three, four, five or even more stars. Just as newborn mammals on Earth compete with each other for milk, newborn stars in multiple systems compete for gaseous matter that generates speedy growth, he said.
"What we are proposing is that brown dwarfs don’t require special conditions to form," said Reipurth, a research professor at CU-Boulder’s Center for Astrophysics and Space Astronomy. "Most stars in our Milky Way Galaxy began either as binary or multiple-star systems, and soon after birth a tug-of-war starts between stellar embryos over which ones can accumulate the most star-forming material."
Whether singly or in small groups, stars form out of dense cores that collapse, resulting in a powerful rain of gaseous material falling toward the stars’ centers, he said. The more massive star embryos generally move around the center of such cores, allowing them to accrete more matter and bulk up.
"The smaller and weaker star embryos are constantly flung out of the central feeding ground by gravitational slingshots, and thus grow slower," Reipurth said.
Reipurth and Cathie Clark of the Institute of Astronomy in Cambridge, England, co-authored a paper on the subject in the July 2001 issue of The Astronomical Journal, published by the American Astronomical Society.
"Amazingly, calculations show that the gravitational horseplay between stellar embryos almost always end up with the lightest member being violently flung out of the little group," said Reipurth. Sometimes the kick merely sends it into an extended orbit around the other embryos, but more often it is completely booted out of the system.
"While we know the eventual outcome, it is impossible to precisely predict when such an ejection will occur," he said. "There is an element of randomness in this process, much like a lottery." After 50,000 to 100,000 years, many of these multiple-star systems have decayed, leaving behind smaller binary or multiple-star systems.
Stars require roughly 8 percent of our sun’s mass to begin the process of nuclear ignition, said Reipurth. "If they don’t make it, they don’t ignite. If such small star embryos are ejected by their siblings so early that they have not built up the necessary mass and fuel, they become brown dwarfs," he said.
"With better luck in the disintegration lottery, a brown dwarf could have become a normal star, shining for billions of years. But without nuclear ignition, brown dwarfs are left to merely glimmer darkly forever," he said.
Binary stars are very common, but scientists have puzzled for years over why brown dwarfs are rarely found as close companions to normal stars, Reipurth said. "Our model can now explain that, because a stellar embryo very close to one that succeeds in becoming a star would normally also get sufficiently fed to become a star."
During the last year, astronomers have pinpointed several brown dwarfs that are distant companions to normal stars. "These are brown dwarfs that also were kicked out, but not quite strongly enough to avoid the pull of their siblings," he said.
Close examination with large telescopes of free-floating brown dwarfs has shown that some are binaries, Reipurth said. "These are two small stellar embryos which formed a pair before they got ejected together. Widely spaced pairs of stellar embryos are more unlikely to survive an ejection intact, consistent with the observation that all known binary brown dwarfs are relatively close to each other."
The last few years have seen a flurry of discoveries of giant planets orbiting other stars, and it has been hotly debated whether such giant planets are simply very small brown dwarfs. "This is not the case," said Reipurth.
"Even though brown dwarfs failed in the end to become stars, they still were formed the same way as stars. In contrast, giant planets are frequently found as very close companions to stars, implying they grew as planets from circumstellar disks like planets in our own solar system."
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Where There's Soup, There's Life Posted: Monday, July 2, 2001
Source: Geological Society Of America (http://www.geosociety.org/)
Where there's soup, there's life. But we're talking gourmet soup. That is, gourmet geochemical "primordial soups" in hot springs and hydrothermal springs in the oceans that support novel chemolithotrophic thermophiles. If we can understand these heat-loving little critters, then we may confirm what microbial ecologist Anna-Louise Reysenbach suspects;they were the earliest ancestors of all life.
Early Earth was a hot environment, and it's possible that some of the life that we see today in hot springs in places like Yellowstone National Park and at deep-sea hydrothermal springs along mid-ocean ridges may share some common metabolic features with their early Earth ancestors. So determining what life exists in hot springs today is one of the first steps to define what early life on a hot planet may have been like.
These thermophiles "living in hot springs are microscopic, and are hard to identify just by looking at them under the microscope," explained Reysenbach from Portland State University. She uses biogeochemical, molecular, and microbiological approaches to study the ecology of thermophiles.
"Essentially there are two ways to identify these microbes; either by trying to grow them, or by using molecular techniques that identify an evolutionarily conserved gene, a sort of fingerprint, of the organism. Using a combination of these approaches, we have been able to grow a very prevalent and important member of hydrothermal ecosystems.
"This group of organisms are chemolithoautotrophs, they use inorganic energy and carbon sources, and are the deepest lineage within the universal tree of life," she explained. "Although the trunk and base of the tree of life are much debated, these few pieces of evidence suggest that this group of organisms may be a good proxy for studying early Earth life. Understanding how these organisms fossilize, what remaining biological signatures they may leave behind, how they precipitate minerals etc. will perhaps help us interpret the rock record here on Earth and other planets more effectively."
The important member of this group is the Aquificales, a deeply-rooted lineage that is common in both terrestrial and deep-sea hydrothermal systems. Reysenbach looks forward to receiving the genome of one of the isolates, "Persephonella marina," which will be available in a few months.
"I think it will definitely show what type(s) of carbon fixation pathways this organism has, how it gets some of it's essential elements, N, C, P, etc.," she said. "What I am also very interested in is how different or similar it is to its relative Aquifex. When the genome sequence of Aquifex was released, it rocked the boat a little, since it showed that this organism is a VERY modern organism...and not what some thought would be typical of a 'primitive' -ancestral organism."
Reysenbach will present her research "Gourmet Geochemical "Primordial Soups" at Hydrothermal Vents Support Novel Thermophilic Chemolithotrophs: Implications for the Evolution of Life on Early Earth" on Wednesday, June 27, at the Earth Systems Processes conference in Edinburgh, Scotland. The Geological Society of America and the Geological Society of London will co-convene the June 24-28 meeting.
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