Oct 21, 2017
This fear can even develop into anxiety which limits a person's daily life. Such people are always on edge and cannot enter a room before it is declared "spider free" or cannot venture out into nature for sheer fear that they may encounter a snake. In developed countries one to five per cent of the population are affected by a real phobia of these creatures.
Until now, it was not clear where this widespread aversion or anxiety stems from. While some scientists assume that we learn this fear from our surroundings when we are a child, others suppose that it is innate. The drawback of most previous studies on this topic was that they were conducted with adults or older children -- making it hard to distinguish which behaviour was learnt and which was inborn. Such studies with children only tested whether they spot spiders and snakes faster than harmless animals or objects, not whether they show a direct physiological fear reaction.
Scientists at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig and the Uppsala University, Sweden, recently made a crucial observation: Even in infants a stress reaction is evoked when they see a spider or a snake. And this already at the age of six months, when they are still very immobile and have had little opportunity to learn that these animals can be dangerous.
"When we showed pictures of a snake or a spider to the babies instead of a flower or a fish of the same size and colour, they reacted with significantly bigger pupils," says Stefanie Hoehl, lead investigator of the underlying study and neuroscientist at MPI CBS and the University of Vienna. "In constant light conditions this change in size of the pupils is an important signal for the activation of the noradrenergic system in the brain, which is responsible for stress reactions. Accordingly, even the youngest babies seem to be stressed by these groups of animals."
"We conclude that fear of snakes and spiders is of evolutionary origin. Similar to primates, mechanisms in our brains enable us to identify objects as 'spider' or 'snake' and to react to them very fast. This obviously inherited stress reaction in turn predisposes us to learn these animals as dangerous or disgusting. When this accompanies further factors it can develop into a real fear or even phobia. "A strong panicky aversion exhibited by the parents or a genetic predisposition for a hyperactive amygdala, which is important for estimating hazards, can mean that increased attention towards these creatures becomes an anxiety disorder."
Interestingly, it is known from other studies that babies do not associate pictures of rhinos, bears or other theoretically dangerous animals with fear. "We assume that the reason for this particular reaction upon seeing spiders and snakes is due to the coexistence of these potentially dangerous animals with humans and their ancestors for more than 40 to 60 million years -- and therefore much longer than with today's dangerous mammals. The reaction which is induced by animal groups feared from birth could have been embedded in the brain for an evolutionarily long time.
Read more at Science Daily
|This is s dead staghorn Coral.|
An international team of scientists, including Dr Alex Dunhill from the University of Leeds, has found that although the mass extinction in the Late Triassic period wiped out the vast proportion of species, there appears to be no drastic changes to the way marine ecosystems functioned.
Lead author Dr Dunhill, from the School of Earth and Environment at Leeds, said: "While the Late Triassic mass extinction had a big impact on the overall number of marine species, there was still enough diversity among the remaining species that the marine ecosystem was able to function in the same way it had before."
"We're not saying nothing happened," said co-author Dr William Foster, a palaeontologist from the Jackson School of Geosciences at the University of Texas at Austin. "Rather, global oceans in the extinction's aftermath were a bit like a ship manned by a skeleton crew -- all stations were operational, but manned by relatively few species."
The Late Triassic mass extinction occurred 201 million years ago. Nearly 50 per cent of life on Earth died out as a result of huge volcanic eruptions. The volcanic activity caused high levels of greenhouse gases in the atmosphere which led to rapid global warming. The eruptions are also associated with the break-up of the supercontinent Pangaea and the opening of the Atlantic Ocean
The team compared marine ecosystem across the Late Triassic mass extinction event by examining fossils from the Middle Triassic to Middle Jurassic -- a 70 million-year span. They classified the lifestyle of different ocean-dwelling animals by how they moved, where they lived and how they fed.
They were then able to determine that none of these lifestyles had completely disappeared due to the extinction event, which preserved the marine ecosystem.
Their results, published today in Palaeontology, showed that while the extinction did not result in a global marine ecological shift, it had profound regional and environmental effects and had an extreme impact on specific ocean ecosystems.
Dr Dunhill said: "One of the great marine casualties of the Late Triassic were stationary reef-dwelling animals, such as corals. When we examined the fossil record we saw that while the marine ecosystem continued to function as a whole, it took over 20 million years for tropical reef ecosystems to recover from this environmental cataclysm.
"Reef ecosystems are the most vulnerable to rapid environmental change. The effect of the Late Triassic greenhouse gases on marine ecosystems is not so different from what you see happening to coral reefs suffering from increasing ocean temperatures today."
Co-author, Professor Richard Twitchett, from the Natural History Museum in London said: "Understanding the extent of reef collapse during past extinctions may help us predict what is in store for our modern marine ecosystems.
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Oct 20, 2017
|This is a plot of what the sea ice distribution could look like on a synchronously rotating ocean world. The star is off to the right, blue is where there is open ocean, and white is where there is sea ice.|
"Using a model that more realistically simulates atmospheric conditions, we discovered a new process that controls the habitability of exoplanets and will guide us in identifying candidates for further study," said Yuka Fujii of NASA's Goddard Institute for Space Studies (GISS), New York, New York and the Earth-Life Science Institute at the Tokyo Institute of Technology, Japan, lead author of a paper on the research published in the Astrophysical Journal Oct. 17.
Previous models simulated atmospheric conditions along one dimension, the vertical. Like some other recent habitability studies, the new research used a model that calculates conditions in all three dimensions, allowing the team to simulate the circulation of the atmosphere and the special features of that circulation, which one-dimensional models cannot do. The new work will help astronomers allocate scarce observing time to the most promising candidates for habitability.
Liquid water is necessary for life as we know it, so the surface of an alien world (e.g. an exoplanet) is considered potentially habitable if its temperature allows liquid water to be present for sufficient time (billions of years) to allow life to thrive. If the exoplanet is too far from its parent star, it will be too cold, and its oceans will freeze. If the exoplanet is too close, light from the star will be too intense, and its oceans will eventually evaporate and be lost to space. This happens when water vapor rises to a layer in the upper atmosphere called the stratosphere and gets broken into its elemental components (hydrogen and oxygen) by ultraviolet light from the star. The extremely light hydrogen atoms can then escape to space. Planets in the process of losing their oceans this way are said to have entered a "moist greenhouse" state because of their humid stratospheres.
In order for water vapor to rise to the stratosphere, previous models predicted that long-term surface temperatures had to be greater than anything experienced on Earth -- over 150 degrees Fahrenheit (66 degrees Celsius). These temperatures would power intense convective storms; however, it turns out that these storms aren't the reason water reaches the stratosphere for slowly rotating planets entering a moist greenhouse state.
"We found an important role for the type of radiation a star emits and the effect it has on the atmospheric circulation of an exoplanet in making the moist greenhouse state," said Fujii. For exoplanets orbiting close to their parent stars, a star's gravity will be strong enough to slow a planet's rotation. This may cause it to become tidally locked, with one side always facing the star -- giving it eternal day -- and one side always facing away -giving it eternal night.
When this happens, thick clouds form on the dayside of the planet and act like a sun umbrella to shield the surface from much of the starlight. While this could keep the planet cool and prevent water vapor from rising, the team found that the amount of near-Infrared radiation (NIR) from a star could provide the heat needed to cause a planet to enter the moist greenhouse state. NIR is a type of light invisible to the human eye. Water as vapor in air and water droplets or ice crystals in clouds strongly absorbs NIR light, warming the air. As the air warms, it rises, carrying the water up into the stratosphere where it creates the moist greenhouse.
This process is especially relevant for planets around low-mass stars that are cooler and much dimmer than the Sun. To be habitable, planets must be much closer to these stars than our Earth is to the Sun. At such close range, these planets likely experience strong tides from their star, making them rotate slowly. Also, the cooler a star is, the more NIR it emits. The new model demonstrated that since these stars emit the bulk of their light at NIR wavelengths, a moist greenhouse state will result even in conditions comparable to or somewhat warmer than Earth's tropics. For exoplanets closer to their stars, the team found that the NIR-driven process increased moisture in the stratosphere gradually. So, it's possible, contrary to old model predictions, that an exoplanet closer to its parent star could remain habitable.
This is an important observation for astronomers searching for habitable worlds, since low-mass stars are the most common in the galaxy. Their sheer numbers increase the odds that a habitable world may be found among them, and their small size increases the chance to detect planetary signals.
The new work will help astronomers screen the most promising candidates in the search for planets that could support life. "As long as we know the temperature of the star, we can estimate whether planets close to their stars have the potential to be in the moist greenhouse state," said Anthony Del Genio of GISS, a co-author of the paper. "Current technology will be pushed to the limit to detect small amounts of water vapor in an exoplanet's atmosphere. If there is enough water to be detected, it probably means that planet is in the moist greenhouse state."
In this study, researchers assumed a planet with an atmosphere like Earth, but entirely covered by oceans. These assumptions allowed the team to clearly see how changing the orbital distance and type of stellar radiation affected the amount of water vapor in the stratosphere. In the future, the team plans to vary planetary characteristics such as gravity, size, atmospheric composition, and surface pressure to see how they affect water vapor circulation and habitability.
Read more at Science Daily
NASA's Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft is in orbit around Mars gathering data on how the Red Planet lost much of its atmosphere and water, transforming from a world that could have supported life billions of years ago into a cold and inhospitable place today. The process that creates the twisted tail could also allow some of Mars' already thin atmosphere to escape to space, according to the research team.
"We found that Mars' magnetic tail, or magnetotail, is unique in the solar system," said Gina DiBraccio of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "It's not like the magnetotail found at Venus, a planet with no magnetic field of its own, nor is it like Earth's, which is surrounded by its own internally generated magnetic field. Instead, it is a hybrid between the two." DiBraccio is project scientist for MAVEN and is presenting this research at a press briefing Thursday, Oct. 19 at 12:15pm MDT during the 49th annual meeting of the American Astronomical Society's Division for Planetary Sciences in Provo, Utah.
The team found that a process called "magnetic reconnection" must have a big role in creating the Martian magnetotail because, if reconnection were occurring, it would put the twist in the tail.
"Our model predicted that magnetic reconnection will cause the Martian magnetotail to twist 45 degrees from what's expected based on the direction of the magnetic field carried by the solar wind," said DiBraccio. "When we compared those predictions to MAVEN data on the directions of the Martian and solar wind magnetic fields, they were in very good agreement."
Mars lost its global magnetic field billions of years ago and now just has remnant "fossil" magnetic fields embedded in certain regions of its surface. According to the new work, Mars' magnetotail is formed when magnetic fields carried by the solar wind join with the magnetic fields embedded in the Martian surface in a process called magnetic reconnection. The solar wind is a stream of electrically conducting gas continuously blowing from the Sun's surface into space at about one million miles (1.6 million kilometers) per hour. It carries magnetic fields from the Sun with it. If the solar wind field happens to be oriented in the opposite direction to a field in the Martian surface, the two fields join together in magnetic reconnection.
The magnetic reconnection process also might propel some of Mars' atmosphere into space. Mars' upper atmosphere has electrically charged particles (ions). Ions respond to electric and magnetic forces and flow along magnetic field lines. Since the Martian magnetotail is formed by linking surface magnetic fields to solar wind fields, ions in the Martian upper atmosphere have a pathway to space if they flow down the magnetotail. Like a stretched rubber band suddenly snapping to a new shape, magnetic reconnection also releases energy, which could actively propel ions in the Martian atmosphere down the magnetotail into space.
Since Mars has a patchwork of surface magnetic fields, scientists had suspected that the Martian magnetotail would be a complex hybrid between that of a planet with no magnetic field at all and that found behind a planet with a global magnetic field. Extensive MAVEN data on the Martian magnetic field allowed the team to be the first to confirm this. MAVEN's orbit continually changes its orientation with respect to the Sun, allowing measurements to be made covering all of the regions surrounding Mars and building up a map of the magnetotail and its interaction with the solar wind.
Magnetic fields are invisible but their direction and strength can be measured by the magnetometer instrument on MAVEN, which the team used to make the observations. They plan to examine data from other instruments on MAVEN to see if escaping particles map to the same regions where they see reconnected magnetic fields to confirm that reconnection is contributing to Martian atmospheric loss and determine how significant it is. They also will gather more magnetometer data over the next few years to see how the various surface magnetic fields affect the tail as Mars rotates. This rotation, coupled with an ever-changing solar wind magnetic field, creates an extremely dynamic Martian magnetotail. "Mars is really complicated but really interesting at the same time," said DiBraccio.
Read more at Science Daily
It turns out that the answer — or part of the answer, anyway — appears to be volcanoes.
An international team of historians and climate scientists published research this week in the journal Nature Communications suggesting ancient volcanic eruptions changed the course of history in Africa and the Middle East. It's a twisty tale, concerning class revolt, ancient papyrus records, ice core samples, tropical volcanoes, and the annual flooding of the river Nile.
It helps to have a little background: The Ptolemaic dynasty in Egypt (305-30 BC) relied heavily on the seasonal flooding of the Nile for agriculture. But the Nile was famously unreliable, and when the river didn't flood, crops died, triggering famines, plagues, and social unrest.
Historians know this thanks to various artifacts that show both the history of the Nile's water levels and the history of major political crises and uprisings.
One of those historians is Joseph Manning of Yale University, who co-authored the new study with Francis Ludlow, a climate historian at Trinity College Dublin. While Manning's work focuses on Egyptian history, Ludlow's specialty is tracking major volcanic eruptions throughout history.
The idea for their unique collaboration was to compare timelines of Egyptian unrest with geological records that reveal the timing of major volcanic eruptions. Their conclusion: It's likely that violent volcanic eruptions triggered climate changes that directly impacted the Nile — which in turn may have led to the social upheaval that doomed Cleopatra and the Ptolemaic dynasty.
“My specialty, as a climate historian, is to concentrate upon how we can extract information on past climate conditions from both natural and human archives,” Ludlow told Seeker. “Natural archives might include tree rings or ice cores, and human archives would include written records and even archaeological evidence.”
Digging even deeper into the historical record, Manning was able to determine that volcanic eruptions preceded several major political and economic events during the Ptolemaic period. For instance, a major eruption in 247 BC was followed by a revolt that caused the army of Ptolemy III to withdraw from a Middle Eastern campaign and return home. The revolt was likely due to crop failure, which was almost certainly caused by the Nile failing to flood.
A similar scenario occurred in 44 BC, which led to an outbreak of famine and disease that weakened the rule of Cleopatra.
The researchers are quick to note that much of the cause-and-effect linkage is supposition, and that climate changes are just one of many factors that can contribute to major events in history.
“Connecting climatic changes to complex social and political events like the collapse of a dynasty needs to be done cautiously and with a full recognition of the historical context in which many other factors will also inevitably have played an important role,” Ludlow said.
Still, the concurrence of volcanic activity with Nile river failures — and subsequent civil unrest — is remarkably precise and very unlikely to be simple coincidence, researchers said. The trick is in noticing them in the first place. All the clues were there in the historical record, Manning said, but it took a team of scholars to piece them together.
“It's important to work in this truly interdisciplinary way in order to make progress,” Manning said.
Read more at Seeker
Once a writhing alligator is hauled aboard — large, adult males range between 11 and 16 feet in length — Nifong and his fellow researchers strap it to a board, prop its mouth open with a wide circle of plastic or steel pipe, feed a hose down its throat, fill its stomach with water, and then “jiggle” the animal’s belly around until it pukes up its lunch.
Nifong’s research specialty is the eating habits of the American alligator (Alligator mississippiensis), the toothy alpha predator that inhabits much of the southeastern United States along the Atlantic and Gulf Coasts. While coastal-dwelling alligators are known to chow down on small fish, crustaceans, and unsuspecting birds, they’re also opportunistic eaters. Over the past few years, Nifong’s been trying to figure out if one particular rumor is true: Do alligators really eat sharks?
Stories have circulated for ages about deadly encounters between gators and sharks. A magazine article from 1877 in The Fishing Gazette describes an epic battle between roughly 500 alligators and untold hundreds of sharks along the coast of Jupiter, Florida. The gators gorged themselves on a school of fish trapped by a flood tide and nearby sharks were attracted by the carnage. An eyewitness described the scene: “…[the] sharks and alligators rise on the crest of the waves and fight like dogs.”
But apart from these anecdotal accounts, there was no solid proof — photos or video with exact dates and times of an event — that alligators indeed ate sharks, or vice versa.
So Nifong set out to find some.
Searching through alligator puke wasn’t likely to uncover many clues, since alligators fully digest their prey in one to three days. And even if alligators did eat sharks, it was probably a rare enough occurrence that it would take extremely good luck to capture a gator and pump its stomach within a day of eating a shark.
So Nifong cast his net wider, asking colleagues, friends, and friends of friends if they’d ever personally witnessed an alligator eating a shark or ray, both members of the Elasmobranchii family. He found a sea turtle researcher who had twice documented alligators (1997 and 1999) feeding on sharks on Wassaw Island, Georgia — but there weren’t any pictures. Darn.
But then he hit paydirt. In 2003, a US Fish and Wildlife Service staffer working in the Ding Darling National Wildlife Refuge in Sanibel, Florida, had actually photographed an eight-foot alligator attacking and engulfing a three-foot nurse shark. Here was the proof!
In a recent article in the journal Southeastern Naturalist, Nifong and co-author Russell Lowers, a wildlife biologist at the Kennedy Space Center, documented four separate encounters, recorded and in some cases photographed by field researchers, where an alligator had indeed eaten a shark or ray.
Why was this so important to prove? Because many species of sharks and rays use protected coastal estuaries and tidal rivers as nurseries for their young. And those are exactly the types of brackish environments where the four alligator attacks were documented.
“It’s really important to figure out if the juvenile sharks and rays are getting nailed by these predators and to account for that in population models,” Nifong told Seeker.
It’s no surprise that alligators, sharks, and rays would find themselves in the same waters. Even though alligators primarily stick to freshwater and Elasmobranchii are ocean dwellers, both can handle waters ranging in salinity from 10 to 15 parts per thousand up to full strength seawater (36 ppt). The attack in Georgia, for example, happened right off the beach in pure ocean water.
Alligators lack salt glands to help regulate their body’s salinity, so long-term exposure to high-salinity waters will cause them to dehydrate, but Nifong said that he’s tracked alligators with GPS who regularly “commute” into ocean water for a “seafood buffet” before heading home to freshwater. Alligators will also drink freshwater during a rainstorm to stay hydrated in salty water.
“I’ve seen them standing with their mouth open in the marsh in the rain drinking the rainwater,” Nifong said, “as well as sipping off the top of the water column after it rained.”
Read more at Seeker
Oct 19, 2017
|It's a small world after all.|
A study conducted by the University of Leicester and KU Leuven, Belgium, examined how small worlds emerge spontaneously in all kinds of networks, including neuronal and social networks, giving rise to the well-known phenomenon of "six degrees of separation."
Many systems show complex structures, of which a distinctive feature is small-world network organization. They arise in society as well as ecological and protein networks, the networks of the mammalian brain, and even human-built networks such as the Boston subway and the World Wide Web.
The researchers set out to examine whether this is a coincidence that such structures are so wide-spread or is there a common mechanism driving their emergence?
A study recently published in Scientific Reports by an international team of academics from the University of Leicester and KU Leuven showed that these remarkable structures are reached and maintained by the network diffusion, i.e. the traffic flow or information transfer occurring on the network.
The research presents a solution to the long-standing question of why the vast majority of networks around us (WWW, brain, roads, power grid infrastructure) might have a peculiar yet common structure: small-world topology.
The study showed that these structures emerge naturally in systems in which the information flow is accounted for in their evolution.
Nicholas Jarman, who recently completed his PhD degree at the Department of Mathematics, and is first author of the study, said: "Algorithms that lead to small-world networks have been known in scientific community for many decades. The Watts-Strogatz algorithm is a good example. The Watts-Strogatz algorithm, however, was never meant to address the problem of how small-world structure emerges through self-organisation. The algorithm just modifies a network that is already highly organised."
Professor Cees van Leeuwen, who led the research at KU Leuven said: "The network diffusion steers network evolution towards emergence of complex network structures. The emergence is effectuated through adaptive rewiring: progressive adaptation of structure to use, creating short-cuts where network diffusion is intensive while annihilating underused connections. The product of diffusion and adaptive rewiring is universally a small-world structure. The overall diffusion rate controls the system's adaptation, biasing local or global connectivity patterns, the latter providing a preferential attachment regime to adaptive rewiring. The resulting small-world structures shift accordingly between decentralised (modular) and centralised ones. At their critical transition, network structure is hierarchical, balancing modularity and centrality -- a characteristic feature found in, for instance, the human brain."
Dr Ivan Tyukin from the University of Leicester added: "The fact that diffusion over network graph plays crucial role in keeping the system at a somewhat homeostatic equilibrium is particularly interesting. Here we were able to show that it is the diffusion process, however small or big gives rise to small-world network configurations that remain in this peculiar state over long intervals of time. At least as long as we were able to monitor the network development and continuous evolution."
Alexander Gorban, Professor in Applied Mathematics, University of Leicester commented: "Small-world networks, in which most nodes are not neighbours of one another, but most nodes can be reached from every other node by a small number of steps, were described in mathematics and discovered in nature and human society long ago, in the middle of the previous century. The question, how these networks are developing by nature and society remained not completely solved despite of many efforts applied during last twenty years. The work of N. Jarman with co-authors discovers a new and realistic mechanism of emergence of such networks. The answer to the old question became much clearer! I am glad that the University of Leicester is a part of this exciting research."
From Science Daily
|Toe bones, the upper jaw and snout of the fossilized remains of a tyrannosaur skeleton found in Grand Staircase-Escalante National Monument. The skeleton is the most complete of its kind found in the Southwest United States.|
"With at least 75 percent of its bones preserved, this is the most complete skeleton of a tyrannosaur ever discovered in the southwestern US," said Dr. Randall Irmis, curator of paleontology at the Museum and associate professor in the Department of Geology and Geophysics at the University of Utah. "We are eager to get a closer look at this fossil to learn more about the southern tyrannosaur's anatomy, biology, and evolution."
GSENM Paleontologist Dr. Alan Titus discovered the fossil in July 2015 in the Kaiparowits Formation, part of the central plateau region of the monument. Particularly notable is that the fossil includes a nearly complete skull. Scientists hypothesize that this tyrannosaur was buried either in a river channel or by a flooding event on the floodplain, keeping the skeleton intact.
"The monument is a complex mix of topography -- from high desert to badlands -- and most of the surface area is exposed rock, making it rich grounds for new discoveries, said Titus. "And we're not just finding dinosaurs, but also crocodiles, turtles, mammals, amphibians, fish, invertebrates, and plant fossils -- remains of a unique ecosystem not found anywhere else in the world," said Titus.
Although many tyrannosaur fossils have been found over the last one hundred years in the northern Great Plains region of the northern US and Canada, until relatively recently, little was known about them in the southern US. This discovery, and the resulting research, will continue to cement the monument as a key place for understanding the group's southern history, which appears to have followed a different path than that of their northern counterparts.
This southern tyrannosaur fossil is thought to be a sub-adult individual, 12-15 years old, 17-20 feet long, and with a relatively short head, unlike the typically longer-snouted look of northern tyrannosaurs.
Collecting such fossils from the monument can be unusually challenging. "Many areas are so remote that often we need to have supplies dropped in and the crew hikes in," said Irmis. For this particular field site, Museum and monument crews back-packed in, carrying all of the supplies they needed to excavate the fossil, such as plaster, water and tools to work at the site for several weeks. The crews conducted a three-week excavation in early May 2017, and continued work during the past two weeks until the specimen was ready to be airlifted out.
Irmis said with the help of dedicated volunteers, it took approximately 2,000-3,000 people hours to excavate the site and estimates at least 10,000 hours of work remain to prepare the specimen for research. "Without our volunteer team members, we wouldn't be able to accomplish this work. We absolutely rely on them throughout the entire process," said Irmis.
Irmis says that this new fossil find is extremely significant. Whether it is a new species or an individual of Teratophoneus, the new research will provide important context as to how this animal lived. "We'll look at the size of this new fossil, it's growth pattern, biology, reconstruct muscles to see how the animal moved, how fast could it run, and how it fed with its jaws. The possibilities are endless and exciting," said Irmis.
Read more at Science Daily
Their evolutionary history has been shrouded in mystery, but a new genetic analysis published in the journal Current Biology reveals many surprising finds. One is the link between these stealthy carnivores and animals that are now residing in many households the world over.
“The two saber-toothed cat mitochondrial lineages we investigated — Smilodon and Homotherium — diverged from all living cat-like species around 20 million years ago,” lead author Johanna Paijmans told Seeker, clarifying that the big, ancient cats were indeed related to today’s common domesticated cats.
Paijmans, a researcher at the University of Potsdam’s Institute for Biochemistry and Biology, has always been interested in extinct mammal lineages. When she was asked to perform DNA analysis on saber-tooth cat remains starting about 5 years ago, she jumped at the chance.
The story behind this particular study began long before then, however.
“It all started with the recovery of a 28,000-year-old Homotherium fossil from the North Sea by Jelle Reumer and colleagues in 2000,” Paijmans explained.
Paijmans, senior author Michael Hofreiter, and their team analyzed this big cat’s complete mitochondrial genome and compared it to that of Smilodon, the world’s best-known saber-toothed cat that became extinct around 10,000 years ago.
“Our results prove that Homotherium did exist in Europe around 28,000 years ago,” Paijmans said.
“With the current knowledge,” she continued, “it’s not clear whether Homotherium did exist (in Europe) between 300,000 and 30,000 years ago at very low population densities, or if Homotherium re-dispersed from North America during the Late Pleistocene after the earlier populations had already gone extinct.”
The date of Homotherium’s presence in Europe opens up yet another intriguing mystery.
“When the first anatomically modern humans migrated to Europe, there may have been a saber-toothed cat waiting for them,” she said.
There is no question that Neanderthals and other early hominids in Europe and Asia lived in regions where saber-toothed cats lurked.
A few years ago, a team of archaeologists working at the Schöningen site in north-central Germany found saber-toothed cat remains next to an ancient stash of weapons. They included several wooden spears, a lance, a double-pointed stick and another stick that was burnt.
It is then possible that early humans waged battles with saber-toothed cats, attempting to either kill or scare them off with torches and their weapons. Since both humans and these predators were drawn to caves, their paths could easily have crossed often, with each group going after similar prey — not to mention each other.
Saber-toothed cats might have even affected early human migration routes, but more evidence is needed to clarify how our human ancestors could have interacted with these fierce felines.
Paijmans said we need to re-think how and where Homotherium lived during the Late Pleistocene, as it occurred in Europe much later than we previously thought. “This,” she said, “can open up new questions about its extinction that can be addressed in future studies.”
In short, it is now possible that anatomically modern humans migrating from Africa could have killed off this species of saber-toothed cat, and possibly others.
“In terms of their mitochondrial DNA, these two saber-toothed cats are more distant from each other than tigers are from housecats,” Paijmans said.
After the cats diverged from their common ancestor, they traveled and evolved into distinct forms. Nonetheless, they shared the similar, very toothy dentition that was lost when they went extinct.
Read more at Seeker
Dog owners might do well to watch out for this powerful look, because new research suggests that canines tailor their facial expressions for human viewers, and may even intentionally manipulate us with them.
“There is quite a bit of research showing that human attention affects dog behavior. Our study is one of them,” lead author Juliane Kaminski of the University of Portsmouth told Seeker.
Kaminski, along with colleagues Jennifer Hynds, Paul Morris and senior author Bridget Waller, came to their conclusions after studying 24 beloved family dogs: 13 males and 11 females of various breeds and ages. Before testing started, each dog was allowed to familiarize itself with the human experimenter and the quiet room in which the testing was conducted.
The dogs were next individually brought to the room to a predetermined spot. Each dog was attached to a lead while a female experimenter positioned herself in front of the canine and behaved according to certain conditions. In some instances, she was attentive and holding up food treats that all of the dogs loved. In others, she was attentive, but had no food, or she simply ignored the dog altogether.
As all of these conditions were enacted, a video camera recorded the dogs’ faces. Their facial movements were then analyzed via the Facial Action Coding System (FACS), which was first developed for humans. It identifies observable facial changes associated with underlying muscle movements, permitting an objective, reliable, and standardized measurement of facial movements.
Kaminski and her team found that the dogs produced significantly more facial movements when the experimenter was facing them than when not. Surprisingly, the presence of food had no effect.
Dogs therefore are not only sensitive to a human’s attention when producing facial expressions, but they also appear to be intentionally using these subtle — and sometimes not so subtle — movements to communicate with the viewer.
The findings, published in the journal Scientific Reports, provide evidence that facial expressions of dogs are not always inflexible and involuntary displays reflecting their emotions. Instead, they also often appear to be used for communication, and likely manipulation, too.
“Humans also have the ability to move facial muscles both voluntarily and spontaneously,” Waller said. “So, in some situations we can control our muscles very carefully, and in others, perhaps when we are overcome with emotion, it can be very difficult.”
She added, “In dogs, it is possible that voluntary movement of facial muscles evolved later and in response to selection pressures during domestication.”
Most mammals have a fairly similar set of facial muscles, she explained, but humans and dogs have a particularly complex network of muscles that are capable of producing very slight, as well as very specific, movements. Dogs have some movements that are uncannily similar to those of humans — and their babies.
“But they also have different movements, like ear movements, that humans don’t have,” Waller said. “Other apes, like chimpanzees, also don’t have many ear movements, but numerous monkey species do.”
In some cases, the expressions might have been learned from humans. In others, the expressions could hold meanings that are more dog-centric, as for visual cues using additional parts of their body. For example, dogs often lower their front two paws in an unmistakable bow when they want to play.
It could be that dogs use different facial expressions when communicating with other dogs, but the authors are not sure.
“We do not have a lot of research looking at the sensitivity of dogs to other dogs’ attention,” Kaminski said. “We know dogs follow other dogs’ gazes, so they seem to be sensitive to other dogs’ line of sight.”
The researchers suggest it’s possible that horses and goats also attempt to communicate with humans using facial expressions, given that these animals tend to be sensitive to human gazes and levels of attention.
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