Site Links:
|
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. |
How Brain Draws And Re-draws Picture Of World
Posted: Thursday, November 27, 2003
Source: Johns Hopkins Medical Institutions
Scientists Discover How Brain Draws And Re-draws Picture Of World
Children usually spill if trying to drink from a full cup, but adults rarely do. How we learn to almost automatically complete complex movements -- like how to lift a cup and tip it so the liquid is right at the edge when we're ready to drink -- is one of our brain's mysterious abilities.
Now, by conducting experiments with robots and humans, scientists at Johns Hopkins have solved part of this mystery and created a new computer model that accurately reflects how the brain uses experience to improve motor control.
"Now we have a much better idea of how the brain uses information from a variety of sources to create a model of the world around us, and how errors modify that model and change subsequent movements," says Reza Shadmehr, Ph.D., associate professor of biomedical engineering at The Johns Hopkins University School of Medicine. "We don't just know how to control objects around us, we have to learn how."
The researchers' work is described in the November issue of PLoS Biology, a new peer-reviewed journal launched by the Public Library of Science.
In the researchers' experiments, volunteers grasped the end of a robot arm that precisely tracked their attempts to overcome resistance to reach a target, a stopping point 10 centimeters (about four inches) away. While real-life resistance might be a paperweight or a full mug, in these experiments the researchers programmed forces that would hinder movement of the robot arm in predictable ways. To reach the target in the allotted time (half a second), volunteers had to learn to balance those forces.
To provide the spatial information necessary for the brain to create a model, or map, of forces expected in the "world" of the experiment, subjects started from one of three positions -- left, center or right. For different groups of subjects, starting positions were separated by as little as half a centimeter (less than a quarter inch) up to 12 centimeters (about four and three-quarter inches).
In initial trials without resistance, subjects moved the robot arm in a straight line toward the target from each of the starting positions. In the next set of trials, subjects had to overcome resistance when beginning from the left and right starting positions, but not from the center.
At first, the resistance pushed subjects' movements aside. With practice, most groups of subjects were able to reach the target in a more-or-less straight line again, indicating they had learned to account for the forces applied to the robot arm.
However, if the starting positions were too close together, the brain failed to draw appropriate conclusions about where to expect forces, even though visual cues reinforced whether the subject was starting from the left, middle or right, the researchers report.
"When the starting positions were just half a centimeter apart, the brain couldn't create an accurate picture of the forces -- even with practice -- and improve movement," says Shadmehr. "When the starting positions were farther apart, however, subjects more easily adjusted to the resistance and generalized their experiences to anticipate forces likely outside of the tested space."
With information from these experiments, the scientists developed a new computer model of how the brain uses experience to create an impression of the world to apply to similar but new situations. The new computer model matches observations from this and all previous experiments, and Shadmehr says it's the first to show that the brain multiplies, rather than adds, electrical signals from nerve cells that convey the arm's position and velocity.
"We know the brain transforms sensory cues -- the arm's position and velocity, among other things -- into motor commands," says Shadmehr. "Our model suggests that it does so by multiplying signals of position and velocity to create what we call a gain field -- a system that allows the brain to predict appropriate movement for a wide range of new but similar movements."
In subsequent experiments with volunteers, the researchers proved correct two predictions based on the computer model: how people generalize experience in the tests to other starting positions and under what circumstances people most effectively learn to balance the resistance.
Authors on the paper are Shadmehr, graduate student Eun Jung Hwang and postdoctoral fellows Opher Donchin and Maurice Smith, all of Johns Hopkins. Funding for the study was provided by the National Institute of Neurological Diseases and Stroke, and by postdoctoral fellowships from the National Institutes of Health and the Johns Hopkins Department of Biomedical Engineering.
The original news release can be found here.
Send page by E-Mail
Posted: Friday, November 21, 2003
Source: The Leakey Foundation
Baboon Studies Reveal Pressures And Benefits Of Complex Social Societies
SAN FRANCISCO, CA -- Can the complex loves and rivalries of baboons in Botswana's Okavango Delta rival the social dynamics of Shakespeare's Romeo and Juliet?
Two recent studies of African baboons provide new insights into the complexity of monkey social behavior. This research may in turn reveal the conditions that contributed to the evolution of distinctly human traits, such as language and certain strategies for survival. Both studies are to be published in the November 14 issue of the journal Science and received support from The Leakey Foundation.
It is accepted that humans routinely classify others according to their individual attributes, such as status or wealth. We all know that we classify others according to what groups they belong to in society – Republicans, Red Sox fans, the 'Bloods", and so on. The ability to classify others by membership in a group, maybe even more than one group, requires a lot of computing power – brainpower - and may even require language. Until now, we have not known whether such complex group classifications are uniquely human, or whether animals do it too.
To investigate this question, scientists from the University of Pennsylvania have studied a group of more than 80 baboons in Botswana's Okavango Delta since 1992. Baboon groups are organized around a rank hierarchy of matrilineal families. At the top of the rank order is the matriarch of the highest-ranking family, followed in descending rank order by her offspring, then the highest-ranking female in the next family followed by her offspring, and so on. Experiments conducted in 1995 and 1999 showed that baboons recognize both the rank and the kinship relations among others. Now the University of Pennsylvania team wanted to test whether baboons -- like humans -- could combine their knowledge of kinship and rank into a genuine hierarchical structure based on both social rules simultaneously.
To do this, Dorothy Cheney, Robert Seyfarth and their colleagues Thore Bergman and Jacinta Beehner designed an experiment for baboons in Botswana's Okavango Delta in which they played to a wild female a sequence of calls mimicking a fight between two other females. The listening females' reactions showed that they knew not only which individuals were fighting, but which families they belonged to, whether dominant or subordinate.
These experiments have demonstrated for the first time that animals other than humans classify members of their community simultaneously according to both individual attributes and membership of a societal group. The selective pressures imposed by complex societies may therefore have favored cognitive skills that constitute an evolutionary precursor to human cognition, and may inform theories concerned with the evolution of human language.
In a second new study, also of baboons, sixteen years of behavioral data on a well-studied population of baboons in Amboseli, Kenya demonstrates that friendliness pays! Friendly mothers raise their infants more successfully than do unfriendly mothers. The social bonds of adult female baboons -- typically characterized by frequent grooming, close spatial proximity, and occasional acts of coalitionary support -- are an important component of variation in female lifetime fitness. For example, close association with other group members may reduce stress levels of infant and mother alike. Alternatively, close association with other group members may provide mother and infant with direct material benefits, such as protection from harassment or access to valuable resources.
Together, the two studies show that natural selection has favored a sophisticated social intelligence in primates -- social intelligence that improves a baboon female's reproductive success and may help us to understand the evolution of intelligence in humans. The roots of human sociality extend far back into our primate roots.
###
The Leakey Foundation is an international membership committed to research related to human origins, behavior and survival.
The original news release can be found here.
Send page by E-Mail
Most Distant X-Ray Jet Discovered Provides Clues To Big Bang Posted: Tuesday, November 18, 2003
Source: NASA/Marshall Space Flight Center
The most distant jet ever observed was discovered in an image of a quasar made by NASA's Chandra X-ray Observatory.
Extending more than 100,000 light-years from the supermassive black hole powering the quasar, the jet of high-energy particles provides astronomers with information about the intensity of the cosmic microwave background radiation 12 billion years ago.
The discovery of this jet was a surprise to the astronomers, according to team members. Astronomers had previously known the distant quasar GB1508+5714 to be a powerful X-ray source, but there had been no indication in previous images of any complex structure or a jet.
"This jet is especially significant because it allows us to probe the cosmic background radiation 1.4 billion years after the big bang," said Aneta Siemiginowska of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a report on this research in the November 20 Astrophysical Journal Letters. Prior to this discovery, the most distant confirmed X-ray jet corresponded to a time about 3 billion years after the big bang.
Quasars are thought to be galaxies that harbor an active central supermassive black hole fueled by infalling gas and stars. This accretion process is often observed to be accompanied by the generation of powerful high-energy jets.
As the electrons in the jet fly away from the quasar at near the speed of light, they move through the sea of cosmic background radiation left over from the hot early phase of the universe.
When a fast-moving electron collides with one of these background photons, it can boost the photon's energy up into the X-ray band. The X-ray brightness of the jet depends on the power in the electron beam and the intensity of the background radiation.
"Everyone assumes that the background radiation will change in a predictable way with time, but it is important to have this check on the predictions," said Siemiginowska. "This jet is hopefully just the first in a large sample of these distant objects that can be used to tell us how the intensity of the cosmic microwave background changed over time."
"In fact, if this interpretation is correct, then discovery of this jet is consistent with our previous prediction that X-ray jets can be detected at arbitrarily large distances!" said team member Dan Schwartz, also of the Harvard-Smithsonian Center for Astrophysics.
Chandra originally observed GB 1508+5714 with the purpose of studying the X-ray emission from the dust located between the Earth and the far-flung quasar. The jet was found by Siemiginowska and her colleagues when they examined the data once it became available publicly in the Chandra archive.
This led another astronomer to then carefully look at radio observations of the object. Indeed, archived Very Large Array data confirmed the existence of the jet associated with the quasar GB 1508+5714. A paper on the radio observations of GB 1509+5714 has been accepted by Astrophysical Journal Letters from Teddy Cheung of Brandeis University in Waltham, Mass.
Another group of astronomers led by Weimen Yuan of the University of Cambridge, United Kingdom, independently reported the discovery of the extended emission in GB 1508+5714 in X-rays. In a paper to be published in an upcoming issue of the Monthly Notices of the Royal Astronomical Society, the authors note that significant energy is being deposited in the outer regions of the host galaxy at a very early stage. This energy input could have a profound effect on the evolution of the galaxy by triggering the formation of stars, or inhibiting the growth of the galaxy through accretion of matter from intergalactic space.
NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.
Additional information on these results can be found at: http://chandra.harvard.edu and http://chandra.nasa.gov
The original news release can be found here.
Send page by E-Mail
Research Sheds New Light On Process Of Evolution Posted: Tuesday, November 18, 2003
Source: Michigan State University
For more than a century, scientists have concluded that a species evolves or adapts by going through an infinite number of small genetic changes over a long period of time.
However, a team of researchers, including a Michigan State University plant biologist, has provided some new evidence that an alternate theory is actually at work, one in which the process begins with several large mutations before settling down into a series of smaller ones.
The research is published in the Nov. 12 issue of the journal Nature.
"The question is asked, ‘If a population finds itself in some maladaptive state, due perhaps to a change in climate, how will it adapt?’" said Douglas Schemske, MSU Hannah Professor of Plant Biology and a member of the research team. "The evidence that has come to light recently – both in plants and other organisms – is that the initial changes are bigger than we might have expected."
To study the question, Schemske and his colleagues used a common plant called the monkeyflower, changing its genetic make up in a rather dramatic way to see if it would attract new pollinators – hummingbirds instead of bees or vice versa.
By moving a small piece of the genome between two different species of the plants – the pink-flowered M. lewisii and the red-flowered M. cardinalis – the researchers created different colored flowers that attracted new pollinators.
"We discovered that moving this single genetic region caused a dramatic increase in visitation by a ‘new’ pollinator," Schemske said. "Specifically, the orange flowers produced on the previously pink flowered and bee-pollinated M. lewisii were regularly visited by hummingbirds but shunned by bees.
"Also, the pink flowers of the previously hummingbird-pollinated M. cardinalis were attractive to both bees and hummingbirds," he said.
Schemske and H.D. "Toby" Bradshaw, a professor of biology at the University of Washington and the lead author of the paper that appeared in Nature, said altering the genetic region responsible for the flowers’ color is much like what could happen during a naturally occurring mutation.
"Perhaps a single mutation having to do with color changed the pollinator milieu back when there was only a single species," Bradshaw said. "That one big evolutionary step may then have been followed by many smaller steps triggered by pollinator preferences that led ultimately to different species."
Schemske compared the process to the repairing of a finely tuned watch.
"In our model, the first adaptive adjustments might require big changes, similar to banging the broken watch a few times before making the final small tweaks to restore its optimal performance," he said.
The plants used in the work were produced in a campus greenhouse and then transported to an area near the Yosemite National Park where natural populations of both species occur.
"This was a rather unique aspect of the work," Schemske said, "in that it combined molecular genetic techniques and ecological observations to elucidate the process of adaptation in natural populations."
The work was supported by a grant from the National Science Foundation.
The original news release can be found here.
Send page by E-Mail
Nicotine Metabolite May Improve Memory Posted: Wednesday, November 12, 2003
Source: Society For Neuroscience
Nicotine Metabolite May Improve Memory, Protect Against Disease
NEW ORLEANS - Scientists continue to explore the remarkable protective effect of nicotine -- the addictive chemical in tobacco -- on the brain. One recent study has found that one of nicotine's metabolites, cotinine, may improve memory and protect brain cells from diseases such as Alzheimer's and Parkinson's. Another new study shows that nicotine can help improve some of the learning and memory problems associated with hypothyroidism. Such studies suggest that nicotine -- or drugs that mimic nicotine -- may one day prove beneficial in the treatment of neurological disorders.
"These findings don't mean people should smoke," warns neuroscientist Michael Kuhar, PhD, of Emory University. "Any benefits from the nicotine in cigarettes or other tobacco products are far outweighed by the proven harm of using those products. But pure nicotine-like compounds as medications do show promise for treating human disorders."
New studies continue to report on the dangers of smoking. One such study suggests that mothers who smoke during pregnancy may be putting their children at risk of having emotional learning problems that last into adulthood. Another study indicates that when smoking is taken up in adolescence, it also produces long-lasting effects on brain development -- effects that interfere with learning and memory.
The children of women who smoke during pregnancy have been found to be at greater risk for a wide variety of emotional and behavioral disorders, such as attention deficit hyperactivity disorder (ADHD) and conduct disorder. Now, new animal studies from the Yale University School of Medicine demonstrate that the effects of developmental nicotine on emotional learning last into adulthood.
"If we can identify the mechanism for this long-term behavioral change, we may be able to develop new therapies for human emotional disorders that are linked to prenatal nicotine exposure," says Sarah King, PhD.
For their most recent study, King and her colleague, Marina Picciotto, PhD, used an animal model of emotional learning known as passive avoidance. This model measures how long an animal avoids a dark chamber in which it had previously received a mild electric shock. King and Picciotto found that nicotine-treated mice showed a hypersensitive response and avoided the dark compartment longer than non-exposed mice.
This response was identical to one the researchers had reported on previously (Journal of Neuroscience, May 2003) in genetically altered mice that lack high affinity nicotine receptors as a result of a knockout mutation. "We believe that nicotine exposure during development-- the same kind of exposure that occurs in mothers who smoke during pregnancy -- disrupts normal nicotine receptor activity, much like the knockout mutation, and that this leads to altered emotional learning in adulthood," says King.
King and Picciotto have also identified a novel brain circuit -- glutamate neurons, which originate in the cortex and project to the thalamus (corticothalmic neurons) -- as the likely site where changes occur in the brain during early nicotine exposure. They are currently working to identify the molecular changes that developmental exposure to nicotine triggers in the corticothalamic neurons.
Each year, about 2 million teenagers become regular smokers, according to the American Lung Association. Because the brain continues to develop during adolescence -- and beyond -- scientists at George Mason University decided to investigate the effect that exposure to nicotine during adolescence has on later behavioral functioning. The researchers implanted 46 rats with small minipumps that dispensed either 3 or 6 mg of nicotine per kilogram of body weight per day -- or no nicotine at all (controls). When the animals reached adulthood, they were tested for spatial learning and memory.
Nicotine made a significant difference in the animals' performance in the tests. Low and high doses of nicotine altered behavior in opposite directions: The low-dose group tended to learn faster and the high-dose group tended to learn slower than the control animals. "Whether performance improved or declined is probably less important than the demonstration that nicotine does produce long-lasting changes in the animals' performance, presumably reflecting long-lasting effects on brain development," says Robert Smith, PhD.
Although this research was done in rats, the processes of brain development are similar in humans, which leads Smith to believe that teenagers who smoke aren't risking only addiction, but also lasting changes in the development of their brains. Smith and his colleagues are now examining the genetic mechanisms that are involved in producing this lasting change in behavior.
During times of stress, smokers tend to increase the number of cigarettes they light up -- perhaps as a form of self-medication to counteract the harmful effects of stress on the brain. Stress, which may range from mild anxiety to posttraumatic stress disorder, has been shown to impair normal brain function, including learning and memory.
Researchers in the laboratories of Karim Alkadhi, PhD, at the University of Houston College of Pharmacy recently studied the effect of nicotine on stress-induced memory impairment in rats. They found that when stressed animals were given nicotine, they performed significantly better at short-term memory tests than stressed animals not given the chemical. In fact, the nicotine-treated stressed animals performed the same as unstressed (control) animals.
"Our findings are important to the understanding of the mechanism by which nicotine repairs stress-damaged brain function," says Abdulaziz Aleisa, a doctoral student at UH. "This research may eventually help in the designing of new, safe approaches to the treatment of Alzheimer's and Parkinson's diseases -- approaches that mimic the beneficial effect of nicotine on stress."
In other studies, another doctoral student, Karem Al-Zoubi, and his colleagues have found that nicotine may improve some of the learning and memory problems associated with hypothyroidism, a common disorder in which the thyroid gland makes inadequate amounts of thyroid hormones. These findings add to the understanding of the mechanism by which nicotine repairs damaged brain function, and may one day help scientists design new, safe therapeutic agents for hypothyroidism and other conditions that cause brain impairments.
An estimated 5 million Americans have hypothyroidism, which produces a variety of symptoms, including such mental impairments as cloudy thinking, inability to concentrate, and memory problems. The elderly, particularly women, are more likely to develop the disease. Up to 10 percent of women over age 50 and up to 1.25 percent of men over age 60 have a defective thyroid gland that puts out less-than-adequate amounts of thyroid hormone in the blood. The condition can also strike infants and children, where its effects can be very serious. One in 4,000 babies are born with hypothyroidism. In infants, the condition often results in severe developmental problems, including mental retardation, and is referred to as cretinism.
To study the effect of nicotine on hypothyroidism, the researchers surgically removed most of the thyroid gland from a group of rats. They then treated some of those rats twice daily with a dose of nicotine that produced blood nicotine levels equivalent to those seen in the blood of smokers. All the animals were then given a test that has both learning and a memory phase.
The nicotine-treated hypothyroid animals made significantly fewer errors on both phases of the test than the untreated hypothyroid animals. In fact, the treated hypothyroid animals had a similar error rate to an untreated control group with normal thyroid glands and a nicotine-treated group with normal thyroid glands.
"Nicotine appears to repair learning and memory deficits caused by hypothyroidism, although it doesn't appear to improve learning and memory in normal animals," says Al-Zoubi.
The group is now working to uncover the means by which stress and hypothyroidism produce mental deficits and how nicotine corrects these deficits.
Cotinine, the primary breakdown product (metabolite) of nicotine, shows promise for improving memory and for protecting brain cells from diseases such as Alzheimer's and Parkinson's -- but perhaps with less addiction and other side effects of nicotine, report scientists from the Medical College of Georgia. The researchers have also found that, in animal studies, the properties of cotinine may be helpful in treating the debilitating psychotic behavior of people with schizophrenia.
Up to now, cotinine's biggest use has been as a urine marker for tobacco use, although its potential use in curbing smoking also has been explored.
"Many people have thought that cotinine was an essentially inactive metabolite, but we have shown that at appropriate doses, it enhances memory and protects brain cells from dying, as well as having anti-psychotic properties," says Jerry Buccafusco, PhD.
Buccafusco became interested in studying cotinine after observing in studies that monkeys continued to derive memory benefits from nicotine long after the chemical had left the body. Nicotine is rapidly metabolized, and has a half life of about one hour. Cotinine is metabolized at a much lower rate; its half life is about 24 hours.
In one of their current studies, Buccafusco and his colleagues gave both young and old monkeys cotinine, then tested the animals' memory skills. The monkeys that received cotinine did better on the tests than those that didn't receive the metabolite --results similar to those that Buccafusco has found with nicotine.
The researchers also studied cotinine's effect on neuron-like cells in culture. They used a model in which growth factor is taken away from the cells so that they start to die, just as they do in neurodegenerative diseases such as Alzheimer's. "We were surprised to find that cotinine was as effective as nicotine at preventing cell death," says Buccafusco.
In further studies involving rats, Buccafusco and his colleagues discovered that cotinine was as effective as standard anti-schizophrenic drugs in reducing the startle response -- the natural reaction to a loud noise. Normally, rats -- and people -- are startled by loud noises. If a less intense noise consistently precedes the loud one, however, the startle response tends to weaken -- but not in people with schizophrenia or in laboratory animals given schizophrenic-producing drugs.
"Cotinine was nearly as effective as a standard clinically used anti-schizophrenic drug in reversing this response," says Buccafusco. "This finding holds tremendous promise for patients suffering from schizophrenia since the drugs currently being used to treat this illness are often associated with severe long-term neurological side effects, such as parkinsonian-like tremors and memory problems."
Send page by E-Mail
Sex In The Soil Posted: Thursday, November 6, 2003
Source: University Of Alberta
Even in the animal world, mating is so desirable that the nematode worm will change its sex to increase the chances of partners-a groundbreaking discovery of nurture changing nature, says a University of Alberta scientist, part of a that which conducted the research.
"We all know that we can alter our behaviour, depending on the environment in which we are raised," said Dr. David Pilgrim, from the U of A's Faculty of Science. "But it was thought that our basic genetic makeup is unaltered by these effects. What we have now shown is that our nature-our genes-may be altered by our nurture, the environment."
Pilgrim, Dr. Veena Prahlad and Dr. Elizabeth Goodwin have published their results in the prestigious international journal, Science. Prahlad was a post-doctoral student in Pilgrim's lab before moving to the University of Wisconsin, where she completed the work in Goodwin's lab.
Like humans, the female nematode worm bears XX chromosomes but the male nematode has only a single X. The team showed that the sex ratio-percentage of males and females-could be altered depending on the amount of food the animal senses. While the young female is still too young to display any sexual characteristics, it judges how much food will be available once it grows up. If it thinks there will be a lot of food available once it is sexually mature, a significant number of XX animals will lose one of their X chromosomes-making them genetically male. If they think that food will be scarce, they will keep both their XX chromosomes and grow up to be female.
Also, the female--actually a hermaphrodite since it can produce sperm as well as egg-can self-fertilize if she doesn't find a male but the offspring then are only female (XX).
If the population density is high, as it would be near food, then there is a benefit to being a male since the male nematode is rarer and the chances of finding a potential female partner are higher. If it is low, then the worm is safer being a female since she can still have offspring even if she never meets another animal.
"The trick comes in being able to estimate whether the food will be plentiful or not when it is ready to reproduce, because it needs to make the decision to be male or female well before that," said Pilgrim. "This research helps understand how animals adapt to a variable environment, and to a certain extent, why sex exists."
The U of A in Edmonton, Alberta is one of Canada's premier teaching and research universities serving more than 33,000 students with 6,000 faculty and staff. It continues to lead the country with the most 3M Teaching Fellows, Canada's only national award recognizing teaching excellence.
Send page by E-Mail
What is happening to the Sun? Posted: Wednesday, November 5, 2003
By Dr David Whitehouse
BBC News Online science editor
Scientists say they have been amazed by the ferocity of the gigantic flares exploding on the solar surface.
The past 24 hours have seen three major events erupt over our star, hurling billions of tonnes of superhot gas into space - some of it directed at Earth.
Researchers are once more predicting colourful displays of aurorae - polar lights - when the charged particles from the Sun crash into our atmosphere.
The X files
Powerful solar flares are given an "X" designation. There was an X8 and an X3 event on Sunday.
On Monday, there was an X3 flare followed by smaller ones.
Last week there were X7 and X10 events that took place back-to-back.
Flares with an X rating are unusual and, if the gas cloud from them reaches the Earth, are capable of causing a geomagnetic storm.
The Earth's changing magnetic field in such a storm can cause power grid and satellite problems. Japanese engineers believe that one of their satellites failed last week because of one such storm.
Huge energy
Last week's flares came from giant Sunspot 486, as did the first flare on Sunday.
Subsequent flares have emanated from Sunspot 488 which appears to be growing in activity.
Some experts are saying that the Sun is more active than it has been in living memory.
Dr Paal Brekke, deputy project scientist for the Solar Heliospheric Observatory (Soho) Sun-monitoring satellite, told BBC News Online: "It is quite amazing that the flaring regions continue releasing such strong flares.
"I think the last week will go into the history books as one of the most dramatic solar activity periods we have seen in modern times.
"As far as I know there has been nothing like this before."
Skywatchers will be looking out for spectacular lights in the night sky.
These Northern and Southern Lights are generated when fast-moving particles (electrons and protons) ejected from the Sun get trapped in the magnetic field around the Earth, and collide with the gases in the upper atmosphere.
Reproduced from:
http://news.bbc.co.uk/2/hi/science/nature/3238961.stm
Send page by E-Mail
Stone Tool And Bone Find Earliest Ever Excavated Posted: Wednesday, November 5, 2003
Source: Southern Connecticut State University
Michael Rogers, an assistant professor of anthropology at Southern Connecticut State University, has discovered the earliest direct evidence of stone tool manufacture and use in a controlled setting, in an excavation in Gona, Ethiopia. Rogers and his research team date the tools they found to 2.6 million years old. An article reporting their findings was published in the September 2003 issue of the Journal of Human Evolution.
Three years ago, Rogers was in Ethiopia working on a paleoanthropological research project in Gona, in an area that hadn't been looked at before. He found a few flakes-tools that are pieces of stone chipped off of a larger stone-and began digging with a crew of experienced excavators. What they eventually discovered is a significant development in the field of paleoanthropology: the earliest stone tools and animal bones at the same site, clearly associated with each other, indicating early humans' use of tools to provide food for themselves.
"This is the earliest site that really documents the two together," says Rogers, adding, "There's no question that they are associated with each other. Our ancestors were using the artifacts to process animal parts, which probably shows that humans were expanding their diets to include animals and were no longer largely vegetarians-they were becoming at least partly carnivorous."
At the time of the discovery, Rogers was part of an international research team, the Gona Paleoanthropological Research Project, led by Sileshi Semaw, Ph.D., an Ethiopian anthropologist working at CRAFT Research Center, Indiana University. Gona is in Ethiopia's Awash Valley, nearly at sea level. This area was already known to have the earliest stone tools, and is adjacent to Hadar, where "Lucy," probably the most famous hominid fossil yet to be discovered, was found in 1974.
Researchers on the Gona Project have found cutmarked bones before, says Rogers, but not in a controlled setting. The setting where he and his group made their discovery is an excavation area that is four meters wide by one meter deep. Several hundred artifacts were found in this area. "If this was the earliest site in the world, we expected things to be crude, but the tools appear to have been well made," says Rogers. The tools they found "are incredibly fresh for their age," he adds. "The condition of the site, for its age, is shocking."
Rogers says the site is on the bank of a river and at one time was probably covered over when the river flooded and hasn't been touched since. "This site is in pristine condition," he says. "We know it hasn't been moved." The materials the researchers found are being kept at the National Museum of Ethiopia in Addis Ababa.
Rogers and his colleagues found at the site diverse types of stone, indicating that the toolmakers were discriminating about the materials they chose to use. "Our ancestors had to know what kind of rock flakes the best," says Rogers. "They chose only the rarest kinds of cobbles from the ancient stream bed nearby for their ‘flake-ability.' They were being very selective."
Rogers says that the group's find shows the start of something that hasn't yet stopped: human beings' use of technology. "You can trace our technology use way back," he says. "These stone tools show that our human ancestors were capable of creating something completely new and that they had an insight about what they were creating."
In his anthropology classes, Rogers shows his students how flaking works, and then has them give it a try. To do it, one holds the core stone in one hand and a smaller stone in the other, and then hits the smaller stone against the core, with the goal of flaking pieces off. It's not easy to do well, Rogers points out, so the earliest toolmakers must have had some kind of skill. "You have to make a glancing blow, at the right angle and with the right force. It requires good eye-hand coordination. And you have to choose the right kind of stone. All of this was abundantly evident at the site."
In the field of the earliest archaeology, Rogers says, "everything is in Africa-there is nothing older anywhere else. People say it all the time: Africa is the cradle of humankind."
The original news release can be found here.
Send page by E-Mail
Gender Differences In Brain Response To Pain Posted: Wednesday, November 5, 2003
Source: University Of California - Los Angeles
A new UCLA study shows that different parts of the brain are stimulated in reaction to pain depending on gender. The research, which represents the largest gender-comparison study of its kind, focused on people with irritable bowel syndrome (IBS), one of the nation's most common chronic medical conditions. The findings may help develop and target better treatments for IBS and other illnesses.
"We are finding more scientific differences between men and women as we improve research methods and broaden study populations," said study co-author Dr. Emeran Mayer, UCLA professor of bio-behavioral sciences, and medicine, physiology and psychiatry. "This growing base of research will help us develop more effective treatments based on a new criteria: gender."
Dr. Mayer is the director of the new Center for Neurovisceral Sciences & Women's Health (CNS) at UCLA, which conducted the study.
Published in the June 2003 issue of the journal Gastroenterology, the study examined 26 women and 24 men with IBS. UCLA researchers took positron emission tomography (PET) brain scans of patients during mild pain stimuli.
Although researchers found some overlapping areas of brain activation in men and women, several areas of male and female brains reacted differently when given the same pain stimulus. The female brain showed greater activity in limbic regions, which are emotion-based centers. In men, the cognitive regions, or analytical centers, showed greater activity.
"The reason for the two different brain responses may date back to primitive days, when the roles of men and women were more distinct," said study co-author Dr. Bruce Naliboff, UCLA clinical professor of psychiatry and biobehavioral sciences, and co-director of CNS.
According to Naliboff, these gender differences in brain responses to pain may have evolved as part of a more general difference in stress responses between men and women. Men's cognitive areas may be more highly triggered because of the early male role in defending the homestead, where in response to stress and pain, the brain launched a calculated fight-or-flight reaction.
The female limbic regions may be more responsive under threat because of their importance in triggering a nurturing and protecting response for the young, leading to a more emotion-based response in facing pain and stress.
Naliboff noted that both responses have advantages and neither is better. In fact, under conditions of external threat, the different responses may lead to complementary behaviors between men and women.
In addition, researchers found that the anticipation of pain generated the same brain responses from study volunteers as the actual pain stimulus. "The brain is a powerful force in dictating how the body responds to pain and stress," said study co-author Dr. Lin Chang, UCLA associate professor of medicine and co-director of CNS.
The next step, according to Mayer, is to look at how the results of the study may impact treatment for IBS and other disorders. Mayer adds that one current drug for IBS, Lotronex, affects the limbic system and has worked more successfully in women than men.
UCLA's Center for Neurovisceral Sciences and Women's Health studies how the brain, stress and emotions impact the development of disorders that affect mainly women.
Irritable bowel syndrome affects 15 to 20 percent of Americans and causes discomfort in the abdomen, along with diarrhea and/or constipation.
The National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Nursing Research, both part of the National Institutes of Health, funded the study.
Send page by E-Mail
Humans Sped to U.K. After Ice Age, Study Says Posted: Monday, November 3, 2003
James Owen in England
for National Geographic News
November 3, 2003
Humans hotfooted it to Britain after the last ice age, scientists say. The new research, which challenges previous studies, suggests these early settlers advanced rapidly as the glaciers melted away.
A team of European scientists estimated the speed and timing of human resettlement in late glacial Britain by comparing radiocarbon dated remains with ice-core climate records. Their findings, now published in the Journal of Quaternary Science, suggest a wave of migration coincided with a sudden rise in temperature and the northwards spread of herd animals such as wild horse and deer.
Previously, scientists thought repopulation had been a drawn-out affair, preceded by centuries of sporadic forays from mainland Europe.
"The big question has always been how quickly, and in what number, did people return once the glaciers had retreated," said research team leader Nick Barton, from the anthropology department of Oxford Brookes University, Oxford, England. "Now with the benefit of larger numbers of radiocarbon dates corrected against a highly accurate record of global climatic change from the Greenland ice record, it seems reoccupation was an almost instantaneous event across northern and central Europe."
Early modern humans reached Britain by around 30,000 years ago, but within 3,000 years they were driven out by the advance of the last ice age.
The archaeologists looked for evidence of their return in ancient caves in western and northern England. The team radiocarbon dated bits of butchered bone from animals the settlers hunted such as red deer, and wild horse and cattle. The data reveal repopulation began as far back as 16,000 years ago.
Roger Jacobi, from the paleontology department of the Natural History Museum, London, said: "When you compare the pattern of radiocarbon dating against the Greenland ice core, humans get back when the ice cores are showing quite a sharp temperature rise."
Jacobi says the oldest bones came from a cave at Cheddar Gorge, Somerset. He added: "They were a group of neck vertebrae from wild horses that had been butchered and were therefore covered in cut marks. It's very clear humans had been instrumental in dismembering them."
Rapid Advance
The bones are only slightly younger than earliest dated human-modified remains from countries such as Belgium and Germany, suggesting a rapid advance from mainland Europe. Their progress was helped by the fact Britain was a peninsula, not an island.
"Most of the English Channel and southern North Sea would have been dry land," added Jacobi. "So Britain would have been joined eastwards to the northern tip of Denmark. It was a huge land connection."
Jacobi and his colleagues suggest it was the movement of animals across this same land connection that triggered the wave of human migration.
"It seems clear that people were following herds of large animals, like horse, which expanded to occupy the continent," said co-researcher Martin Street, from the Römisch-Germanisches Zentralmuseum, Neuwied, Germany. "Humans can be seen as part of that pulse."
They brought with them a tool kit of projectile points and knives used to kill and dismember their prey. Analysis of flint tools specific to the late glacial period shows these early settlers were highly mobile and covered large distances.
"For instance, we know from flint evidence at Cheddar Gorge that hunters were moving at least 70 kilometers (43 miles) on a regular basis," Jacobi added.
One of the strongest patterns to emerge from the study is the correlation between the location of early settlement sites and the edges of upland areas. Jacobi says this again highlights the importance of prey animals as a catalyst for human repopulation.
Diverse Fauna
"It looks as if there was a whole range of micro-environments at the interface between uplands and lowlands," said Jacobi. "The joy of living on an upland edge is that you are able to exploit a whole range of environments and with it a more diverse fauna. The typography of places like Cheddar Gorge also make them ideal for trapping game against rock walls."
Remains found at Creswell Crags in Derbyshire suggest these early Britons were also partial to Arctic hare. "As well as its meat, they were probably going for the white winter pelts which were thick and look so attractive," Jacobi added.
The recent discovery at Creswell Crags of the world's northernmost ice age cave art lends weight to the study's findings. Though no match for the artistry of examples from caves in France and Spain, one of the animals depicted hints at the speed at which migrants spread from mainland Europe.
Archaeologists made out the outline of an ibex, an animal which is thought to have been absent from Britain.
"It's possible evidence that these people came from an area like Belgium, as ibexes certainly occurred in places like the Ardennes," said Jacobi. "Some researchers have interpreted this as indicating that groups had seen ibex on the continent and were drawing them from memory."
Yet these early colonizers secured only a temporary foothold in Britain, as Jacobi explains. "Interestingly, radiocarbon dating seems to show that humans, having resettled Britain in the late glacial period, then go away again for several hundred years, when it gets very cold again."
So it appears humans were cleaned out of Britain one last time, around 12,000 years ago. But they soon returned, hot on the heels of those deer and wild horses. And this time they were there to stay.
Reproduced from: news.nationalgeographic.com
Send page by E-Mail
Designed and maintained by: Renee, Hendricks, Vashti, Meri & Amon. S.E.L.F.