Supergene is key to copycat butterflies

Supergene is key to copycat butterflies

  6:14:00 PM    Science Lover

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Since Charles Darwin, biologists have pondered the mystery of "mimicry butterflies", which survive by copying the wing patterns of other butterflies that taste horrible to their predators, birds.

This undated handout photo released by the CNRS shows butterflies, Melinaea mneme (top) and Heliconius numata. The mystery of how a butterfly has changed its wing patterns to mimic neighbouring species and avoid being eaten by birds has been solved by a team of European scientists.

The answer, according to a study released on Friday, lies in an astonishing cluster of about 30 genes in a single chromosome.

"We were blown away by what we found," said Mathieu Joron of France's National Museum of Natural History, who led the probe into what is being called a "supergene".

"These butterflies are the 'transformers' of the insect world," said Joron.

"But instead of being able to turn from a car into a robot with the flick of a switch, a single genetic switch allows these insects to morph into several different mimetic forms.

"It is amazing, and the stuff of science fiction. Now we are starting to understand how this switch can have such a pervasive effect."



The trick, known as Muellerian mimicry, was investigated by French and British scientists, who focussed on a species of Amazonian rainforest butterfly, Heliconius numata.

It is able to copy the colour patterns of several species of the Melinaea butterfly which are unpalatable to birds.

The "supergene" comprises a tightly packed region of genes on a single chromosome which control different elements of the wing pattern.

"By changing just one gene, the butterfly is able to fool its predators," explained Richard ffrench-Constant of the University of Exeter, southwestern England.

Even more astonishing is that three versions of the chromosome exist within this species, with each version controlling distinct wing-pattern forms.

Even though the butterflies look quite different from each other, they have the same DNA.

The supergene apparently transmits in a block from generation to generation, rather than go through recombination -- the mingling of genes from both parents.

The "supergene" also appears important in other species, say the authors.

One such species, the peppered moth, developped black wings in 19th-century Britain as a means of gaining camouflage in the sooty industrial environment.

"It's a gene that really packs an evolutionary punch," said ffrench-Constant. The paper is published online by the British science journal Nature.

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Emotional Signals Are Chemically Encoded in Tears, Researchers Find

Emotional Signals Are Chemically Encoded in Tears, Researchers Find

  9:47:00 AM    Science Lover

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Emotional crying is a universal, uniquely human behavior. When we cry, we clearly send all sorts of emotional signals. In a paper published online January 6 in Science Express, scientists at the Weizmann Institute have demonstrated that some of these signals are chemically encoded in the tears themselves. Specifically, they found that merely sniffing a woman's tears -- even when the crying woman is not present -- reduces sexual arousal in men.

Scientists have found that certain emotional signals are chemically encoded in tears. (Credit: iStockphoto/Arpad Nagy-Bagoly)

Humans, like most animals, expel various compounds in body fluids that give off subtle messages to other members of the species. A number of studies in recent years, for instance, have found that substances in human sweat can carry a surprising range of emotional and other signals to those who smell them.

But tears are odorless. In fact, in a first experiment led by Shani Gelstein, Yaara Yeshurun and their colleagues in the lab of Prof. Noam Sobel in the Weizmann Institute's Neurobiology Department, the researchers first obtained emotional tears from female volunteers watching sad movies in a secluded room and then tested whether men could discriminate the smell of these tears from that of saline. The men could not.

In a second experiment, male volunteers sniffed either tears or a control saline solution, and then had these applied under their nostrils on a pad while they made various judgments regarding images of women's faces on a computer screen. The next day, the test was repeated -- the men who were previously exposed to tears getting saline and vice versa. The tests were double blinded, meaning neither the men nor the researchers performing the trials knew what was on the pads. The researchers found that sniffing tears did not influence the men's estimates of sadness or empathy expressed in the faces. To their surprise, however, sniffing tears negatively affected the sex appeal attributed to the faces.

To further explore the finding, male volunteers watched emotional movies after similarly sniffing tears or saline. Throughout the movies, participants were asked to provide self-ratings of mood as they were being monitored for such physiological measures of arousal as skin temperature, heart rate, etc. Self-ratings showed that the subjects' emotional responses to sad movies were no more negative when exposed to women's tears, and the men "smelling" tears showed no more empathy. They did, however, rate their sexual arousal a bit lower. The physiological measures, however, told a clearer story. These revealed a pronounced tear-induced drop in physiological measures of arousal, including a significant dip in testosterone -- a hormone related to sexual arousal.

Finally, in a fourth trial, Sobel and his team repeated the previous experiment within an fMRI machine that allowed them to measure brain activity. The scans revealed a significant reduction in activity levels in brain areas associated with sexual arousal after the subjects had sniffed tears.

Sobel said, "This study raises many interesting questions. What is the chemical involved? Do different kinds of emotional situations send different tear-encoded signals? Are women's tears different from, say, men's tears? Children's tears? This study reinforces the idea that human chemical signals -- even ones we're not conscious of -- affect the behavior of others."

Human emotional crying was especially puzzling to Charles Darwin, who identified functional antecedents to most emotional displays -- for example, the tightening of the mouth in disgust, which he thought originated as a response to tasting spoiled food. But the original purpose of emotional tears eluded him. The current study has offered an answer to this riddle: Tears may serve as a chemosignal. Sobel points out that some rodent tears are known to contain such chemical signals. "The uniquely human behavior of emotional tearing may not be so uniquely human after all," he says.

The work was authored by Shani Gelstein, Yaara Yeshurun, Liron Rozenkrantz, Sagit Shushan, Idan Frumin, Yehudah Roth and Noam Sobel, was conducted in collaboration with the Edith Wolfson Medical Center, Holon.

Prof. Noam Sobel's research is supported by the James S. McDonnell Foundation 21st Century Science Scholar in Understanding Human Cognition Program; the Minerva Foundation; the European Research Council; and Regina Wachter, NY.

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Bridge to the Quantum World: Darwinian Concept of Natural Selection Figures Into Theory About Core of Physical Reality

Bridge to the Quantum World: Darwinian Concept of Natural Selection Figures Into Theory About Core of Physical Reality

  9:11:00 PM    Science Lover

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Science fiction has nothing over quantum physics when it comes to presenting us with a labyrinthine world that can twist your mind into knots when you try to make sense of it.

Researchers believe they've opened a door to a clearer 
view of how the common, everyday world we experience 
through our senses emerges from the ethereal 
quantum world. (Credit: iStockphoto)

A team of Arizona State University researchers, however, believes they've opened a door to a clearer view of how the common, everyday world we experience through our senses emerges from the ethereal quantum world.

Physicists call our familiar everyday environment the classical world. That's the world in which we and the things around us appear to have measurable characteristics such as mass, height, color, weight, texture and shape.

The quantum world is the world of the elemental building block of matter -- atoms. Atoms are combinations of neutrons and protons and electrons bound to a nucleus by electrical attraction.

But most of an atom -- more than 99 percent of it -- is empty space filled with invisible energy.

So from a quantum-world view, we and the things around us are mostly empty space. The way we experience ourselves and other things in the classical world is really just "a figment of our imaginations shaped by our senses," explains ASU Regents' Professor David Ferry.

For more than a century, scientists and engineers have struggled to come to a satisfactory conclusion about the missing link that bridges the classical and quantum worlds and enables a transition from that world of mostly empty space to the familiar environment we experience through our senses.

One proposed scenario based on these questions was investigated in a dissertation written by Adam Burke to earn his doctorate in electrical engineering in 2009 from ASU's Ira A. Fulton Schools of Engineering.

To try working out an answer to some of the questions, Burke teamed with Ferry, a professor in the School of Electrical, Computer and Energy Engineering, Tim Day, who recently earned his doctorate in electrical engineering from the school, physicist Richard Akis, an associate research professor in the school, Gil Speyer, an assistant research scientist for the engineering schools' High Performance Computing Initiative, and Brian Bennett, a materials scientist with the Naval Research Laboratory.

The result is an article published recently in the research journal Physical Review Letters. It describes the transition from quantum to classical world as a "decoherence" process that involves a kind of evolutionary progression somewhat analogous to Charles Darwin's concept of natural selection.

The authors built on two theories called decoherence and quantum Darwinism, both proposed by Los Alamos National Laboratory researcher Wojciech Zurek.

The decoherence concept holds that many quantum states "collapse" into a "broad diaspora," or dispersion, while interacting with the environment. Through a selection process, other quantum states arrive at a final stable state, called a pointer state, which is "fit enough" (think "survival of the fittest" in Darwinian terms) to be transmitted through the environment without collapsing.

These single states with the lowest energy can then make high-energy copies of themselves that can be described by the Darwinian process and observed on the macroscopic scale in the classical world.

The experiments arose from using advanced scanning gate microscopy to obtain images of what are called quantum dots.

Burke, now doing research in a post-doctoral program at the University of New South Wales in Sydney, Australia, explains it like this:

Imagine the quantum dot as a billiard table in which the quantum point contacts are the two openings through which a ball could enter or leave the dot, and the interior walls of the dot act as bumpers.

If there were no friction on the table, a billiard ball with an initial trajectory would bounce off of these walls until eventually finding an exit and leaving the dot (this is the decoherence part).

Or it might find a trajectory that does not couple to the openings and would therefore be a surviving pointer state, what is called a diamond state.

One difference between the classical physics of billiard balls and the quantum physics of electrons is that an electron can tunnel through "forbidden phase space" to enter this diamond state, whereas a billiard ball entering from outside the dot would not find itself able to reach this diamond trajectory.

It is this isolated classical trajectory, and the buildup of an electron wave functions' amplitude along that trajectory, that is referred to as a scarred wave function.

To experimentally measure these scars, imagine that we can't see inside the walls of our billiard table, but we can count the billiard balls exiting the table. This is what is normally measured with the conductance of the quantum dot and its environment.

"We measure the current through the dot, the numbers of 'billiard balls' passing through it per second, to try to see how this changes when we move our probe around the 'billiard table,' " Ferry says.

Furthermore, there is the probe of the scanning gate microscope, which applies a small electric field. This can be pictured as a small circular bumper on the billiard table that can be moved around within the dot.

This small "bumper" is rastered left to right, top to bottom over the area of interest. If a ball is traveling along this diamond pattern it is perturbed by the bumper when it rasters into the trajectory.

Think of rastering like the way a television image works, with a pattern of scanning lines that cover the area on which the image is projected, or a set or horizontal lines composed of individual pixels that are used to form an image on a computer screen.

When this happens, the ball bounces off the perturbation, and takes a new course within the dot until finally coupling out one of the openings to be measured. The change in the ball's motion appears as a change in the conductance -- the number of balls going through the openings in a given time.

Ferry explains: "With scanning gate microscopy, we monitor where these changes occur within the scans, and hopefully this gives us a map of the scarred wave functions corresponding to the pointer states."

Quantum mechanically, he says, a new electron will tunnel right into the diamond state, so the measurement can continue until the whole area is mapped.

The data that came from the team's experiment supports Zurek's theories of decoherence and quantum Darwinism, Burke says.

Ferry says these findings are just one step in a process that is open to conjecture, but they point toward a "smoking gun" for the existence of this quantum Darwinism and a new view in the search for evidence of how the quantum-to-classical world transition actually occurs.

If you can wrap your mind around all this, he says, "You open the door to a deeper understanding of what is really going on" at the core of physical reality.

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Rise in Certain Disorders can be Explain by Human Evolution

Rise in Certain Disorders can be Explain by Human Evolution

  12:09:00 AM    Science Lover

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The subtle but ongoing pressures of human evolution could explain the seeming rise of disorders such as autism, autoimmune diseases, and reproductive cancers, researchers write in the Proceedings of the National Academy of Sciences. Certain adaptations that once benefited humans may now be helping such ailments persist in spite of -- or perhaps because of -- advancements in modern culture and medicine.

New research suggests that certain adaptations that once benefited humans may now be helping such ailments persist in spite of -- or perhaps because of -- advancements in modern culture and medicine. (Credit: iStockphoto/Mads Abildgaard)

"This work points out linkages within the plethora of new information in human genetics and the implications for human biology and public health, and also illustrates how one could teach these perspectives in medical and premedical curricula," says author Peter Ellison, John Cowles Professor of Anthropology at Harvard University.

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Charles Darwin facing accusations of plagiarism

Charles Darwin facing accusations of plagiarism

  9:54:00 PM    Science Lover

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Experts have criticised Charles Darwin for plagiarism and unjustly claiming credit as the father of evolutionary theory.

As the scientific world prepares to mark bicentenary of the author of 'On the Origin of Species', a group of critics has commissioned computer experts with specialized anti-plagiarism software to scour Darwin's book, published in 1859, for similarities to a paper released the year before by Alfred Russel Wallace, a naturalist who worked for eight years in modern Indonesia.

Initial indications are that the analysis will reveal that some of the ideas in On the Origin of Species were taken from Wallace, particularly, the idea that species with variations helping them to survive would thrive and pass on these features to their offspring.

As far as the dispute over who deserves the credit is concerned, it is as old as evolutionary theory itself, with Darwin's defenders claiming the two came up with similar ideas independently at the same time, reports TimesOnline.

According to James Moore, a biographer and professor of the history of science at the Open University, the new plagiarism claim is "manufactured."

He added that those pursuing it were under qualified to do so.

"You wouldn't go to a plumber to do your tax return," he said.

The adulation has shocked critics, including lawyer David Hallmark, a trustee of the Wallace Foundation of Indonesia.

"The descent of Wallace from equality to relative invisibility is the direct result of the unlawful conduct of Charles Darwin by suppressing the true worth of Wallace as the author of the theory," Hallmark said.

The software used by Hallmark's copyright experts can detect where phrasing is identical and also signs of an author's style being copied.

Hallmark plans to submit his findings to the International Association of Forensic Linguists in Amsterdam in July.

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