Ancient genomes trace the origin and decline of the Scythians

 Because of their interactions and conflicts with the major contemporaneous civilizations of Eurasia, the Scythians enjoy a legendary status in historiography and popular culture. The Scythians had major influences on the cultures of their powerful neighbors, spreading new technologies such as saddles and other improvements for horse riding. The ancient Greek, Roman, Persian and Chinese empires all left a multitude of sources describing, from their perspectives, the customs and practices of the feared horse warriors that came from the interior lands of Eurasia.

Still, despite evidence from external sources, little is known about Scythian history. Without a written language or direct sources, the language or languages they spoke, where they came from and the extent to which the various cultures spread across such a huge area were in fact related to one another, remain unclear.

The Iron Age transition and the formation of the genetic profile of the Scythians

A new study published in Science Advances by an international team of geneticists, anthropologists and archeologists lead by scientists from the Archaeogenetics Department of the Max Planck Institute for the Science of Human History in Jena, Germany, helps illuminate the history of the Scythians with 111 ancient genomes from key Scythian and non-Scythian archaeological cultures of the Central Asian steppe. The results of this study reveal that substantial genetic turnovers were associated with the decline of the long-lasting Bronze Age sedentary groups and the rise of Scythian nomad cultures in the Iron Age. Their findings show that, following the relatively homogenous ancestry of the late Bronze Age herders, at the turn of the first millennium BCE, influxes from the east, west and south into the steppe formed new admixed gene pools.

The diverse peoples of the Central Asian Steppe

The study goes even further, identifying at least two main sources of origin for the nomadic Iron Age groups. An eastern source likely originated from populations in the Altai Mountains that, during the course of the Iron Age, spread west and south, admixing as they moved. These genetic results match with the timing and locations found in the archeological record and suggest an expansion of populations from the Altai area, where the earliest Scythian burials are found, connecting different renowned cultures such as the Saka, the Tasmola and the Pazyryk found in southern, central and eastern Kazakhstan respectively. Surprisingly, the groups located in the western Ural Mountains descend from a second separate, but simultaneous source. Contrary to the eastern case, this western gene pool, characteristic of the early Sauromatian-Sarmatian cultures, remained largely consistent through the westward spread of the Sarmatian cultures from the Urals into the Pontic-Caspian steppe.

The decline of the Scythian cultures associated with new genetic turnovers

The study also covers the transition period after the Iron Age, revealing new genetic turnovers and admixture events. These events intensified at the turn of the first millennium CE, concurrent with the decline and then disappearance of the Scythian cultures in the Central Steppe. In this case, the new far eastern Eurasian influx is plausibly associated with the spread of the nomad empires of the Eastern steppe in the first centuries CE, such as the Xiongnu and Xianbei confederations, as well as minor influxes from Iranian sources likely linked to the expansion of Persian-related civilization from the south.

Although many of the open questions on the history of the Scythians cannot be solved by ancient DNA alone, this study demonstrates how much the populations of Eurasia have changed and intermixed through time. Future studies should continue to explore the dynamics of these trans-Eurasian connections by covering different periods and geographic regions, revealing the history of connections between west, central and east Eurasia in the remote past and their genetic legacy in present day Eurasian populations.

From Science Daily

Measurable changes in brain activity during first few months of studying a new language

 A study with first-time learners of Japanese has measured how brain activity changes after just a few months of studying a new language. The results show that acquiring a new language initially boosts brain activity, which then reduces as language skills improve.

"In the first few months, you can quantitatively measure language-skill improvement by tracking brain activations," said Professor Kuniyoshi L. Sakai, a neuroscientist at the University of Tokyo and first author of the research recently published in Frontiers in Behavioral Neuroscience.

Researchers followed 15 volunteers as they moved to Tokyo and completed introductory Japanese classes for at least three hours each day. All volunteers were native speakers of European languages in their 20s who had previously studied English as children or teenagers, but had no prior experience studying Japanese or traveling to Japan.

Volunteers took multiple choice reading and listening tests after at least eight weeks of lessons and again six to fourteen weeks later. Researchers chose to assess only the "passive" language skills of reading and listening because those can be more objectively scored than the "active" skills of writing and speaking. Volunteers were inside a magnetic resonance imaging (MRI) scanner while taking the tests so that researchers could measure local blood flow around their brain regions, an indicator of neuronal activity.

"In simple terms, there are four brain regions specialized for language . Even in a native, second or third language, the same regions are responsible," said Sakai.

Those four regions are the grammar center and comprehension area in the left frontal lobe as well as the auditory processing and vocabulary areas in the temporo-parietal lobe. Additionally, the memory areas of the hippocampus and the vision areas of the brain, the occipital lobes, also become active to support the four language-related regions while taking the tests.

During the initial reading and listening tests, those areas of volunteers' brains showed significant increases in blood flow, revealing that the volunteers were thinking hard to recognize the characters and sounds of the unfamiliar language. Volunteers scored about 45% accuracy on the reading tests and 75% accuracy on the listening tests (random guessing on the multiple choice tests would produce 25% accuracy).

Researchers were able to distinguish between two subregions of the hippocampus during the listening tests. The observed activation pattern fits previously described roles for the anterior hippocampus in encoding new memories and for the posterior hippocampus in recalling stored information.

At the second test several weeks later, volunteers' reading test scores improved to an average of 55%. Their accuracy on the listening tests was unchanged, but they were faster to choose an answer, which researchers interpret as improved comprehension.

Comparing results from the first tests to the second tests, after additional weeks of study, researchers found decreased brain activation in the grammar center and comprehension area during listening tests, as well as in the visual areas of the occipital lobes during the reading tests.

"We expect that brain activation goes down after successfully learning a language because it doesn't require so much energy to understand," said Sakai.

Notably during the second listening test, volunteers had slightly increased activation of the auditory processing area of their temporal lobes, likely due to an improved "mind's voice" while hearing.

"Beginners have not mastered the sound patterns of the new language, so cannot hold in memory and imagine them well. They are still expending a lot of energy to recognize the speech in contrast to letters or grammar rules," said Sakai.

This pattern of brain activation changes -- a dramatic initial rise during the learning phase and a decline as the new language is successfully acquired and consolidated -- can give experts in the neurobiology of language a biometric tool to assess curricula for language learners or potentially for people regaining language skills lost after a stroke or other brain injury.

"In the future, we can measure brain activations to objectively compare different methods to learn a language and select a more effective technique," said Sakai.

Until an ideal method can be identified, researchers at UTokyo recommend acquiring a language in an immersion-style natural environment like studying abroad, or any way that simultaneously activates the brain's four language regions.

This pattern of brain activation over time in individual volunteers' brains mirrors results from previous research where Sakai and his collaborators worked with native Japanese-speaking 13- and 19-year-olds who learned English in standard Tokyo public school lessons. Six years of study seemed to allow the 19-year-olds to understand the second language well enough that brain activation levels reduced to levels similar to those of their native language.

The recent study confirmed this same pattern of brain activation changes over just a few months, not years, potentially providing encouragement for anyone looking to learn a new language as an adult.

Read more at Science Daily

Warm water has overlooked importance for cold-water fish, like salmon and trout

 Warm river habitats appear to play a larger than expected role supporting the survival of cold-water fish, such as salmon and trout, a new Oregon State University-led study published today found.

The research has important implications for fish conservation strategies. A common goal among scientists and policymakers is to identify and prioritize habitat for cold-water fish that remains suitably cool during the summer, especially as the climate warms.

This implicitly devalues areas that are seasonally warm, even if they are suitable for fish most of the year, said Jonny Armstrong, lead author of the paper and an ecologist at Oregon State. He called this a "potentially severe blind spot for climate change adaptation."

"Coldwater fish like trout and salmon are the polar bears of river ecosystems -- iconic species that are among the most vulnerable to climate change," Armstrong said. "A huge challenge for conservation is to figure out how to help these fish survive a warmer future. The conclusion is that we should not waste money on warm habitats and instead focus on saving the coldest places, such as high mountain streams, which are already the most pristine parts of basins. Most people agree we should give up on places that are warm in summer, but forget that these places are actually optimal for much of the year."

In the new paper, published in Nature Climate Change, Armstrong and collaborators at Oregon State and several federal agencies, show that warm river habitats, typically lower in basins, provide pulses of growth potential during the spring and fall, so-called shoulder seasons, when the rivers are not at peak summer temperatures. Foraging in these warm habitats can provide fish the needed energy to travel to cooler parts of the river during the summer and to reproduce.

"The synergy between cold water and warm water is really important," said Armstrong, an assistant professor in the Department of Fisheries and Wildlife in the College of Agricultural Sciences. "We're not saying cold water is not important. We're saying that warm portions of basins are also important because they grow fish during the shoulder seasons. Conserving this habitat is critical for unlocking the full potential of rivers to support fisheries.

"In a warmer future, many fish will need fish to take a summer vacation and move to cold places to survive the hottest months of the year. Their ability to do that could often depend on how much energy they can get in the spring and how well they can feed in the fall to bounce back. The places that are stressfully warm in summer are just right in spring and fall, and there is growing evidence that they can fuel fisheries"

For the study, the researchers used data from another team of scientists that used remote sensing technology to obtain river water temperature data across entire landscapes throughout the year. That team compiled data for 14 river basins in Oregon, Washington and Idaho.

The OSU-led team plugged these temperature data into a "bioenergetics model" that predicts fish growth potential based on equations derived from lab studies. This provided new insights into how growth opportunities shift across river basins throughout the year, and how a large fraction of total growth potential can accrue during the spring and autumn in places that are too hot during summer.

To explore how these warm habitats could contribute to fisheries, the team created a simulation model in which virtual rainbow trout were given simple behavior rules and allowed to forage throughout the year in a basin with cold tributaries and a warm, productive main-stem river. Their simulations showed the majority of fish moved into cooler waters in the summer and exhibited meager growth rates. However, outside summer, the simulation showed the fish resided primarily in seasonally warm downstream habitats, which fueled the vast majority of their growth.

"In conservation, we often judge streams by their summer conditions; this is when we traditionally do field work, and this is the season we focus on when planning for climate change," Armstrong said. "We place value on places that hold fish during summer and devalue those that don't. Our simulation showed why this can be a problem -- the portions of rivers that contribute most to growth may not be the places where fish are found during summer, so they get written off."

The simulations reveal the synergy between seasonally warm and perennially cool habitats and that fish that lived in these two types of habitats grew much more than fish that were restricted to either habitat alone, Armstrong said.

"We think of things in this binary way -- it's either warm-water habitat or its cold-water habitat," Armstrong said. "And we have definitions for fish -- it's either a warm-water fish or a cold-water fish. But the places we think of as warm are, in fact, cold way more than they are warm."

He then mentioned an example using rivers in Oregon, including the Willamette, a tributary of the Columbia River that runs nearly 200 miles from Eugene to Portland.

"When it's warm enough for humans to swim, it's bad for cold-water fish. But there's only like six weeks of the year where it is comfortable to go swimming in Oregon," Armstrong said. "That speaks to the fact that we write off places because they get too hot through the lens of August. They're actually pretty nice for most of the year if you're a cold-water fish. And fish don't necessarily have to live there in August, just like you don't have to go swimming in the Willamette in December."

This research is continuing in the field at Upper Klamath Lake in Southern Oregon, where Armstrong and a team of researchers are tracking the movement and feeding behavior of redband trout as water temperature changes.

Read more at Science Daily

Dogs (not) gone wild: DNA tests show most 'wild dogs' in Australia are pure dingoes

 Almost all wild canines in Australia are genetically more than half dingo, a new study led by UNSW Sydney shows -- suggesting that lethal measures to control 'wild dog' populations are primarily targeting dingoes.

The study, published today in Australian Mammalogy, collates the results from over 5000 DNA samples of wild canines across the country, making it the largest and most comprehensive dingo data set to date.

The team found that 99 per cent of wild canines tested were pure dingoes or dingo-dominant hybrids (that is, a hybrid canine with more than 50 per cent dingo genes).

Of the remaining one per cent, roughly half were dog-dominant hybrids and the other half feral dogs.

"We don't have a feral dog problem in Australia," says Dr Kylie Cairns, a conservation biologist from UNSW Science and lead author of the study. "They just aren't established in the wild.

"There are rare times when a dog might go bush, but it isn't contributing significantly to the dingo population."

The study builds on a 2019 paper by the team that found most wild canines in NSW are pure dingoes or dingo-dominant hybrids. The newer paper looked at DNA samples from past studies across Australia, including more than 600 previously unpublished data samples.

Pure dingoes -- dingoes with no detectable dog ancestry -- made up 64 per cent of the wild canines tested, while an additional 20 per cent were at least three-quarters dingo.

The findings challenge the view that pure dingoes are virtually extinct in the wild -- and call to question the widespread use of the term 'wild dog'.

"'Wild dog' isn't a scientific term -- it's a euphemism," says Dr Cairns.

"Dingoes are a native Australian animal, and many people don't like the idea of using lethal control on native animals.

"The term 'wild dog' is often used in government legislation when talking about lethal control of dingo populations."

The terminology used to refer to a species can influence our underlying attitudes about them, especially when it comes to native and culturally significant animals.

This language can contribute to other misunderstandings about dingoes, like being able to judge a dingo's ancestry by the colour of its coat -- which can naturally be sandy, black, white, brindle, tan, patchy, or black and tan.

"There is an urgent need to stop using the term 'wild dog' and go back to calling them dingoes," says Mr Brad Nesbitt, an Adjunct Research Fellow at the University of New England and a co-author on the study.

"Only then can we have an open public discussion about finding a balance between dingo control and dingo conservation in the Australian bush."

Tracing the cause of hybridisation

While the study found dingo-dog hybridisation isn't widespread in Australia, it also identified areas across the country with higher traces of dog DNA than the national average.

Most hybridisation is taking place in southeast Australia -- and particularly in areas that use long-term lethal control, like aerial baiting. This landscape-wide form of lethal control involves dropping meat baits filled with the pesticide sodium fluoroacetate (commonly known as 1080) into forests via helicopter or airplane.

"The pattern of hybridisation is really stark now that we have the whole country to look at," says Dr Cairns.

"Dingo populations are more stable and intact in areas that use less lethal control, like western and northern Australia. In fact, 98 per cent of the animals tested here are pure dingoes.

"But areas of the country that used long-term lethal control, like NSW, Victoria and southern Queensland, have higher rates of dog ancestry."

The researchers suggest that higher human densities (and in turn, higher domestic dog populations) in southeast Australia are likely playing a key part in this hybridisation.

But the contributing role of aerial baiting -- which fractures the dingo pack structure and allows dogs to integrate into the breeding packs -- is something that can be addressed.

"If we're going to aerial bait the dingo population, we should be thinking more carefully about where and when we use this lethal control," she says.

"Avoiding baiting in national parks, and during dingoes' annual breeding season, will help protect the population from future hybridisation."

Protecting the ecosystem

Professor Mike Letnic, senior author of the study and professor of conservation biology, has been researching dingoes and their interaction with the ecosystem for 25 years.

He says they play an important role in maintaining the biodiversity and health of the ecosystem.

"As apex predators, dingoes play a fundamental role in shaping ecosystems by keeping number of herbivores and smaller predators in check," says Prof. Letnic.

"Apex predators' effects can trickle all the way through ecosystems and even extend to plants and soils."

Prof. Letnic's previous research has shown that suppressing dingo populations can lead to a growth in kangaroo numbers, which has repercussions for the rest of the ecosystem.

For example, high kangaroo populations can lead to overgrazing, which in turn damages the soil, changes the face of the landscape and can jeopardise land conservation.

A study published last month found the long-term impacts of these changes are so pronounced they are visible from space.

But despite the valuable role they play in the ecosystem, dingoes are not being conserved across Australia -- unlike many other native species.

"Dingoes are a listed threatened species in Victoria, so they're protected in national parks," says Dr Cairns. "They're not protected in NSW and many other states."

The need for consultation

Dr Cairns, who is also a scientific advisor to the Australian Dingo Foundation, says the timing of this paper is important.

"There is a large amount of funding currently going towards aerial baiting inside national parks," she says. "This funding is to aid bushfire recovery, but aerial wild dog baiting doesn't target invasive animals or 'wild dogs' -- it targets dingoes.

"We need to have a discussion about whether killing a native animal -- which has been shown to have benefits for the ecosystem -- is the best way to go about ecosystem recovery."

Dingoes are known to negatively impact farming by preying on livestock, especially sheep.

The researchers say it's important that these impacts are minimised, but how we manage these issues is deserving of wider consultation -- including discussing non-lethal methods to protect livestock.

"There needs to be a public consultation about how we balance dingo management and conservation," says Dr Cairns. "The first step in having these clear and meaningful conversations is to start calling dingoes what they are.

Read more at Science Daily

The very first structures in the Universe

The very first moments of the Universe can be reconstructed mathematically even though they cannot be observed directly. Physicists from the Universities of Göttingen and Auckland (New Zealand) have greatly improved the ability of complex computer simulations to describe this early epoch. They discovered that a complex network of structures can form in the first trillionth of a second after the Big Bang. The behaviour of these objects mimics the distribution of galaxies in today's Universe. In contrast to today, however, these primordial structures are microscopically small. Typical clumps have masses of only a few grams and fit into volumes much smaller than present-day elementary particles. The results of the study have been published in the journal Physical Review D.

The researchers were able to observe the development of regions of higher density that are held together by their own gravity. "The physical space represented by our simulation would fit into a single proton a million times over," says Professor Jens Niemeyer, head of the Astrophysical Cosmology Group at the University of Göttingen. "It is probably the largest simulation of the smallest area of the Universe that has been carried out so far." These simulations make it possible to calculate more precise predictions for the properties of these vestiges from the very beginnings of the Universe.

Although the computer-simulated structures would be very short-lived and eventually "vaporise" into standard elementary particles, traces of this extreme early phase may be detectable in future experiments. "The formation of such structures, as well as their movements and interactions, must have generated a background noise of gravitational waves," says Benedikt Eggemeier, a PhD student in Niemeyer's group and first author of the study. "With the help of our simulations, we can calculate the strength of this gravitational wave signal, which might be measurable in the future."

It is also conceivable that tiny black holes could form if these structures undergo runaway collapse. If this happens they could have observable consequences today, or form part of the mysterious dark matter in the Universe. "On the other hand," says Professor Easther, "If the simulations predict black holes form, and we don't see them, then we will have found a new way to test models of the infant Universe."

From Science Daily

Controlled scar formation in the brain

When the brain suffers injury or infection, glial cells surrounding the affected site act to preserve the brain's sensitive nerve cells and prevent excessive damage. A team of researchers from Charité -- Universitätsmedizin Berlin have been able to demonstrate the important role played by the reorganization of the structural and membrane elements of glial cells. The researchers' findings, which have been published in Nature Communications, shed light on a new neuroprotective mechanism which the brain could use to actively control damage following neurological injury or disease.

The nervous system lacks the ability to regenerate nerve cells and is therefore particularly vulnerable to injury. Following brain injury or infection, various cells have to work together in a coordinated manner in order to limit damage and enable recovery. 'Astrocytes', the most common type of glial cell found in the central nervous system, play a key role in the protection of surrounding tissues. They form part of a defense mechanism known as 'reactive astrogliosis', which facilitates scar formation, thereby helping to contain inflammation and control tissue damage. Astrocytes can also ensure the survival of nerve cells located immediately adjacent to a site of tissue injury, thereby preserving the function of neuronal networks. The researchers were able to elucidate a new mechanism which explains what processes happen inside the astrocytes and how these are coordinated.

"We were able to show for the first time that the protein 'drebrin' controls astrogliosis," says study lead Prof. Dr. Britta Eickholt, Director of Charité's Institute of Biochemistry and Molecular Biology. "Astrocytes need drebrin in order to form scars and protect the surrounding tissue." By switching off the production of drebrin inside astrocytes, the researchers were able to study its role in brain injury in an animal model. They used electron microscopy and high-resolution light microscopy to investigate cellular changes in the brain, in addition to undertaking real-time investigations using isolated astrocytes in cell culture. "Loss of drebrin results in the suppression of normal astrocyte activation," explains Prof. Eickholt. She adds: "Instead of engaging in defensive reactions, these astrocytes suffer complete loss of function and abandon their cellular identity." Without protective scar formation, normally harmless injuries will spread, and more and more nerve cells will die.

To enable scar formation, drebrin controls the reorganization of the actin cytoskeleton, an internal scaffold responsible for maintaining astrocyte mechanical stability. By doing so, drebrin also induces the formation of long cylindrical membrane structures known as tubular endosomes, which are used in the uptake, sorting and redistribution of surface receptors and are needed for the defensive measures of astrocytes. Summing up the researchers' findings, Prof. Eickholt says: "Our findings also show how drebrin uses the dynamic and versatile cytoskeleton as well as membrane structures to control astrocyte functions which are fundamental to the defense mechanism against injury." She continues: "In particular, the membrane tubules which are formed during this process have not previously been described in this manner, neither in cultured astrocytes nor in the brain."

Read more at Science Daily

New images reveal magnetic structures near supermassive black hole

 A new view of the region closest to the supermassive black hole at the center of the galaxy Messier 87 (M87) has shown important details of the magnetic fields close to the black hole and hints about how powerful jets of material can originate in that region.

A worldwide team of astronomers using the Event Horizon Telescope, a collection of eight telescopes, including the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, measured a signature of magnetic fields -- called polarization -- around the black hole. Polarization is the orientation of the electric fields in light and radio waves and it can indicate the presence and alignment of magnetic fields.

"We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets," said Monika Mo?cibrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University in the Netherlands.

New images with the EHT and ALMA allowed scientists to map magnetic field lines near the edge of M87's black hole. That same black hole is the first ever to be imaged -- by the EHT in 2019. That image revealed a bright ring-like structure with a dark central region -- the black hole's shadow. The newest images are a key to explaining how M87, 50 million light-years from Earth, can launch energetic jets from its core.

The black hole at M87's center is more than 6 billion times more massive than the Sun. Material drawn inward forms a rotating disk -- called an accretion disk -- closely orbiting the black hole. Most of the material in the disk falls into the black hole, but some surrounding particles escape and are ejected far out into space in jets moving at nearly the speed of light.

"The newly published polarized images are key to understanding how the magnetic field allows the black hole to 'eat' matter and launch powerful jets," said Andrew Chael, a NASA Hubble Fellow at the Princeton Center for Theoretical Science and the Princeton Gravity Initiative in the U.S.

The scientists compared the new images that showed the magnetic field structure just outside the black hole with computer simulations based on different theoretical models. They found that only models featuring strongly magnetized gas can explain what they are seeing at the event horizon.

"The observations suggest that the magnetic fields at the black hole's edge are strong enough to push back on the hot gas and help it resist gravity's pull. Only the gas that slips through the field can spiral inwards to the event horizon," explained Jason Dexter, Assistant Professor at the University of Colorado Boulder and Coordinator of the EHT Theory Working Group.

To make the new observations, the scientists linked eight telescopes around the world -- including ALMA -- to create a virtual Earth-sized telescope, the EHT. The impressive resolution obtained with the EHT is equivalent to that needed to measure the length of a credit card on the surface of the Moon.

This resolution allowed the team to directly observe the black hole shadow and the ring of light around it, with the new image clearly showing that the ring is magnetized. The results are published in two papers in the Astrophysical Journal Letters by the EHT collaboration. The research involved more than 300 researchers from multiple organizations and universities worldwide.

A third paper also was published in the same volume of the Astrophysical Journal Letters, based on data from ALMA, lead by Ciriaco Goddi, a scientist at Radboud University and Leiden Observatory, the Netherlands.

"The combined information from the EHT and ALMA allowed scientists to investigate the role of magnetic fields from the vicinity of the event horizon to far beyond the core of the galaxy, along its powerful jets extending thousands of light-years," Goddi said.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever obtained by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems -- creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

The individual telescopes involved are: ALMA, APEX, the Institut de Radioastronomie Millimetrique (IRAM) 30-meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), the South Pole Telescope (SPT), the Kitt Peak Telescope, and the Greenland Telescope (GLT).

The EHT consortium consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.

Read more at Science Daily

New study finds false memories can be reversed

 Rich false memories of autobiographical events can be planted -- and then reversed, a new paper has found.

The study highlights -- for the first time -- techniques that can correct false recollections without damaging true memories. It is published by researchers from the University of Portsmouth, UK, and the Universities of Hagen and Mainz, Germany.

There is plenty of psychological research which shows that memories are often reconstructed and therefore fallible and malleable. However, this is the first time research has shown that false memories of autobiographical events can be undone.

Studying how memories are created, identified and reversed could be a game changer in police and legal settings, where false memories given as evidence in a courtroom can lead to wrongful convictions.

According to Dr Hartmut Blank, co-author of the research from the University of Portsmouth's Department of Psychology, "believing, or even remembering something that never happened may have severe consequences. In police interrogations or legal proceedings, for instance, it may lead to false confessions or false allegations, and it would be highly desirable, therefore, to reduce the risk of false memories in such settings.

"In this study, we made an important step in this direction by identifying interview techniques that can empower people to retract their false memories."

The researchers recruited 52 participants for a study on 'childhood memories' and with the help of parents, they implanted two false negative memories that definitely didn't happen, but were plausible. For example getting lost, running away or being involved in a car accident.

Along with two true events, which had actually happened, participants were persuaded by their parents that all four events were part of their autobiographical memory.

The participants were then asked to recall each event in multiple interview sessions. By the third session, most believed the false events had happened and -- similar to previous research -- about 40 per cent had developed actual false memories of them.

The researchers then attempted to undo the false memories by using two strategies.

The first involved reminding participants that memories may not always be based on people's own experience, but also on other sources such as a photograph or a family member's narrative. They were then asked about the source of each of the four events.

The second strategy involved explaining to them that being asked to repeatedly recall something can elicit false memories. They were asked to revisit their event memories with this in mind.

The result, according to Dr Blank, was that "by raising participants' awareness of the possibility of false memories, urging them to critically reflect on their recollections and strengthening their trust in their own perspective, we were able to significantly reduce their false memories. Moreover, and importantly, this did not affect their ability to remember true events.

Read more at Science Daily

Penguin hemoglobin evolved to meet oxygen demands of diving

 Call it the evolutionary march of the penguins.

More than 50 million years ago, the lovable tuxedoed birds began leaving their avian relatives at the shoreline by waddling to the water's edge and taking a dive in the pursuit of seafood.

Webbed feet, flipper-like wings and unique feathers all helped penguins adapt to their underwater excursions. But new research from the University of Nebraska-Lincoln has shown that the evolution of diving is also in their blood, which optimized its capture and release of oxygen to ensure that penguins wouldn't waste their breath while holding it.

Relative to land-dwelling birds, penguin blood is known to contain more hemoglobin: the protein that picks up oxygen from the lungs and transports it through the bloodstream before dropping it off at various tissues. That abundance could partly explain the underwater proficiency of, say, the emperor penguin, which dives deeper than any bird and has been documented holding its breath for more than 30 minutes while preying on krill, fish and squid.

Still, the particulars of their hemoglobin -- and how much it actually evolved to help penguins become fish-gobbling torpedoes that spend up to half of their lives underwater -- remained open questions. So Nebraska biologists Jay Storz and Anthony Signore, who often study the hemoglobin of birds that survive miles above sea level, decided to investigate the birds most adept at diving beneath it.

"There just wasn't a lot of comparative work on blood-oxygen transport as it relates to diving physiology in penguins and their non-diving relatives," said Signore, a postdoctoral researcher in Storz's lab.

Answering those questions meant sketching in the genetic blueprints of two ancient hemoglobins. One belonged to the common ancestor of all penguin species, which began branching from that ancestor about 20 million years ago. The other, dating back roughly 60 million years, resided in the common ancestor of penguins and their closest non-diving relatives -- albatrosses, shearwaters and other flying seabirds. The thinking was simple: Because one hemoglobin originated before the emergence of diving in the lineage, and the other after, any major differences between the two would implicate them as important to the evolution of diving in penguins.

Actually comparing the two was less simple. To start, the researchers literally resurrected both proteins by relying on models that factored in the gene sequences of modern hemoglobins to estimate the sequences of their two ancient counterparts. Signore spliced those resulting sequences into E. coli bacteria, which churned out the two ancient proteins. The researchers then ran experiments to evaluate the performance of each.

They found that the hemoglobin from the common ancestor of penguins captured oxygen more readily than did the version present in the blood of the older, non-diving ancestor. That stronger affinity for oxygen would mean less chance of leaving behind traces in the lungs, an especially vital issue among semi-aquatic birds needing to make the most of a single breath while hunting or traveling underwater.

Unfortunately, the very strength of that affinity can present difficulties when hemoglobin arrives at tissues starved for the oxygen it's carrying.

"Having a greater hemoglobin-oxygen affinity sort of acts like a stronger magnet to pull more oxygen from the lungs," Signore said. "It's great in that context. But then you're at a loss when it's time to let go."

Any breath-holding benefits gained by picking up extra oxygen, in other words, can be undone if the hemoglobin struggles to relax its iron-clad grip and release its prized cargo. The probability that it will is dictated in part by acidity and carbon dioxide in the blood. Higher levels of either make hemoglobins more likely to loosen up.

As Storz and Signore expected, the hemoglobin of the recent penguin ancestor was more sensitive to its surrounding pH, with its biochemical grip on oxygen loosening more in response to elevated acidity. And that, Signore said, made the hemoglobin more biochemically attuned to the exertion and oxygen needs of the tissues it served.

"It really is a beautiful system, because tissues that are working hard are becoming acidic," he said. "They need more oxygen, and hemoglobin's oxygen affinity is able to shift in response to that acidity to provide more oxygen.

"If pH drops by, say, 0.2 units, the oxygen affinity of penguin hemoglobin is going to decrease by more than would the hemoglobin of their non-diving relatives."

Together, the findings indicate that as penguins took to the seas, their hemoglobin evolved to maximize both the pick-up and drop-off of available oxygen -- especially when it was last inhaled five, or 10, or even 20 minutes earlier. They also illustrate the value of resurrecting proteins that last existed 20, or 40, or even 60 million years ago.

"These results demonstrate how the experimental analysis of ancestral proteins can reveal the mechanisms of biochemical adaptation," Storz said, "and also shed light on how organismal physiology evolved in response to new environmental challenges."

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Older than expected: Teeth reveal the origin of the tiger shark

With a total length of up to 5.5m, the tiger shark is one of the largest predatory sharks known today. This shark is a cosmopolitan species occurring in all oceans worldwide. It is characterized by a striped pattern on its back, which is well marked in juveniles but usually fades in adults.

An international team of researchers led by Julia Türtscher from the University of Vienna examined the fossil record of these apex predators and found out that modern tiger sharks are older than previously thought and that several tiger shark species existed in past compared to the single species living today. The results of this study are published in the journal Paleobiology.

The fossil history of modern sharks reaches back to the Permian, about 295 million years ago. Complete fossil shark skeletons are very rare -- the skeleton, which consists almost entirely of cartilage, is only preserved under very special circumstances during the fossilization processes. Due to the lifelong continuous tooth replacement, most extinct sharks are therefore only known by their well-mineralized teeth, which, nonetheless, can provide deep insights into their evolutionary history.

The teeth of the modern tiger shark are unique: they have a broad, double-serrated cutting edge which even allows them to cut through sea turtle shells with ease. Tiger shark teeth are known in the fossil record since about 56 million years. Based on these fossil teeth, over 22 extinct tiger shark species have been described.

An international team of researchers led by Julia Türtscher from the University of Vienna has now examined the fossil history of the tiger shark and its extinct relatives. With the help of geometric morphometrics, the scientists were able to show that only 5 of the 22 known fossil tiger sharks actually represent valid species. Nevertheless, tiger sharks were more diverse in the past and only a single species survived until today.

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