Feb 4, 2017

Myth busted: No link between gigantic asteroid break-up, rise in biodiversity

Some 470 million years ago, during the middle part of the geological period known as the Ordovician, an asteroid collision took place somewhere between Mars and Jupiter. The collision caused an explosion that sent a cascade of meteorites towards Earth. The heavy bombardment of Earth continued for millions of years, and even today some 20% of all meteorites that reach Earth originate from this asteroid break-up. At the same time Earth witnessed the greatest rise in marine biodiversity since the origin of multicellular life. So, the question is: was there a connection between these two fundamental events in Earth history, as has been proposed? A new study now demonstrates that the rise in biodiversity commenced long before the asteroid collision.

The link between these two fundamental events -- the so-called Ordovician radiation and the sustained meteorite bombardment -- has, for many years, presented a paradox in science. We are used to hearing the story of meteorite impacts that leads to the loss of species richness, such as when the dinosaurs went extinct 65 million years ago. But could the opposite scenario be a possibility as well? asks Assistant Professor Christian M. Ø. Rasmussen from the Natural History Museum of Denmark rhetorically. He is co-authoring the study in which an incidental finding of the rare mineral zircon within the meteorite-bearing rock layers led to an answer to the paradox.

Plus, minus 6 million years

Researchers have long known that the fossil meteorites are lying in rock layers that also witness the great increase in biodiversity, but could only date the asteroid break-up to occur within a time frame of 12 million years. This interval exactly overlaps the initiation of the great biodiversity increase. But, with the lucky finding of zircons in rock layers also containing fossil meteorites, the researchers suddenly had the opportunity to precisely determine when the asteroid collision took place, and thus, whether there was a link to the radiation event, or not.

-Zircons are special as they can be used to date rocks. They come from magma chambers in the crust but are extruded onto Earth's surface through volcanic eruptions. Thus, if you find zircons in the rock record you can date these zircons and thus get an age for when this eruption took place. In this case, this date would also define a precise age for the fossil meteorites, explains Anders Lindskog from the Geological Department, Lund University, who is the lead-author on the study. He was the one who recovered the zircons when studying the rock layers containing the fossil meteorites and subsequently sent them to the Natural History Museum of Denmark, which has the facilities and experience to conduct high-precision dating of rocks.

Calculating the age of the zircons

In Copenhagen, the zircons were handed over to postdoc Mafalda Costa from Centre for Star and planet Formation (StarPlan) at the Natural History Museum of Denmark, who processed and analyzed the minerals in the radiogenic isotope laboratory at the Geological Museum.

Mafalda Costa explains:

Zircons occur in a wide variety of rocks, including in ash layers associated with volcanic eruptions. The determination of the age of these crystals is based on the natural radioactivity of uranium, which is incorporated in the mineral upon crystallization, and that from that moment until today, at a known rate, has been spontaneously decaying to lead. We measure the amount of uranium and lead present in the zircons and from that it is possible to calculate an age that pinpoints the time when they erupted on the surface. In this case, on the same surface that also contained meteorites originating from the asteroid break-up. In this way, we could precisely define the age of the fossil meteorites, explains Mafalda Costa, and adds:

From other isotope analyses of minerals found in the fossil meteorites it had been previously estimated how much time the meteorites spent in space before reaching Earth. Hitherto it was not precisely known when this happened. With our new zircon age, we can determine that the rise in biodiversity occurred ~2.5 million years prior to the asteroid break-up took place.

Read more at Science Daily

Baltic hunter-gatherers began farming without influence of migration, ancient DNA suggests

Levantine farmers did not contribute to hunter-gatherers in the Baltic as they did in Central and Western Europe.
New research indicates that Baltic hunter-gatherers were not swamped by migrations of early agriculturalists from the Middle East, as was the case for the rest of central and western Europe. Instead, these people probably acquired knowledge of farming and ceramics by sharing cultures and ideas -- rather than genes -- with outside communities.

Scientists extracted ancient DNA from a number of archaeological remains discovered in Latvia and the Ukraine, which were between 5,000 and 8,000 years old. These samples spanned the Neolithic period, which was the dawn of agriculture in Europe, when people moved from a mobile hunter-gatherer lifestyle to a settled way of life based on food production.

We know through previous research that large numbers of early farmers from the Levant (the Near East) -- driven by the success of their technological innovations such as crops and pottery -- had expanded to the peripheral parts of Europe by the end of the Neolithic and largely replaced hunter-gatherer populations.

However, the new study, published in the journal Current Biology, shows that the Levantine farmers did not contribute to hunter-gatherers in the Baltic as they did in Central and Western Europe.

The research team, which includes scientists from Trinity College Dublin, the University of Cambridge, and University College Dublin, says their findings instead suggest that the Baltic hunter-gatherers learned these skills through communication and cultural exchange with outsiders.

The findings feed into debates around the 'Neolithic package,' -- the cluster of technologies such as domesticated livestock, cultivated cereals and ceramics, which revolutionised human existence across Europe during the late Stone Age.

Advances in ancient DNA work have revealed that this 'package' was spread through Central and Western Europe by migration and interbreeding: the Levant and later Anatolian farmers mixing with and essentially replacing the hunter-gatherers.

But the new work suggests migration was not a 'universal driver' across Europe for this way of life. In the Baltic region, archaeology shows that the technologies of the 'package' did develop -- albeit less rapidly -- even though the analyses show that the genetics of these populations remained the same as those of the hunter-gatherers throughout the Neolithic.

Andrea Manica, one of the study's senior authors from the University of Cambridge, said: "Almost all ancient DNA research up to now has suggested that technologies such as agriculture spread through people migrating and settling in new areas."

"However, in the Baltic, we find a very different picture, as there are no genetic traces of the farmers from the Levant and Anatolia who transmitted agriculture across the rest of Europe."

"The findings suggest that indigenous hunter-gatherers adopted Neolithic ways of life through trade and contact, rather than being settled by external communities. Migrations are not the only model for technology acquisition in European prehistory."

While the sequenced genomes showed no trace of the Levant farmer influence, one of the Latvian samples did reveal genetic influence from a different external source -- one that the scientists say could be a migration from the Pontic Steppe in the east. The timing (5-7,000 years ago) fits with previous research estimating the earliest Slavic languages.

Researcher Eppie Jones, from Trinity College Dublin and the University of Cambridge, was the lead author of the study. She said: "There are two major theories on the spread of Indo-European languages, the most widely spoken language family in the world. One is that they came from the Anatolia with the agriculturalists; another that they developed in the Steppes and spread at the start of the Bronze Age."

"That we see no farmer-related genetic input, yet we do find this Steppe-related component, suggests that at least the Balto-Slavic branch of the Indo-European language family originated in the Steppe grasslands of the East, which would bring later migrations of Bronze Age horse riders."

The researchers point out that the time scales seen in Baltic archaeology are also very distinct to the rest of Europe, with a much more drawn-out and piecemeal uptake of Neolithic technologies, rather than the complete 'package' that arrives with migrations to take most of Europe by storm.

Andrea Manica added: "Our evidence of genetic continuity in the Baltic, coupled with the archaeological record showing a prolonged adoption of Neolithic technologies, would suggest the existence of trade networks with farming communities largely independent of interbreeding."

"It seems the hunter-gatherers of the Baltic likely acquired bits of the Neolithic package slowly over time through a 'cultural diffusion' of communication and trade, as there is no sign of the migratory wave that brought farming to the rest of Europe during this time.

"The Baltic hunter-gatherer genome remains remarkably untouched until the great migrations of the Bronze Age sweep in from the East."

Read more at Science Daily

Feb 3, 2017

Sleep deprivation handicaps the brain's ability to form new memories, mouse study shows

Sleep is crucial for learning.
Studying mice, scientists at Johns Hopkins have fortified evidence that a key purpose of sleep is to recalibrate the brain cells responsible for learning and memory so the animals can "solidify" lessons learned and use them when they awaken -- in the case of nocturnal mice, the next evening.

The researchers, all of the Johns Hopkins University School of Medicine, also report they have discovered several important molecules that govern the recalibration process, as well as evidence that sleep deprivation, sleep disorders and sleeping pills can interfere with the process.

"Our findings solidly advance the idea that the mouse and presumably the human brain can only store so much information before it needs to recalibrate," says Graham Diering, Ph.D., the postdoctoral fellow who led the study. "Without sleep and the recalibration that goes on during sleep, memories are in danger of being lost."

A summary of their study appears online in the journal Science on Feb. 3.

Diering explains that current scientific understanding of learning suggests that information is "contained" in synapses, the connections among neurons through which they communicate.

On the "sending side" of a synapse, signaling molecules called neurotransmitters are released by a brain cell as it "fires"; on the "receiving side," those molecules are captured by receptor proteins, which pass the "message" along. If a cell receives enough input through its synapses, it fires off its own neurotransmitters.

More specifically, experiments in animals have shown that the synapses on the receiving neuron can be toggled by adding or removing receptor proteins, thereby strengthening or weakening them and allowing the receiving neuron to receive more or less input from nearby signaling neurons.

Scientists believe memories are encoded through these synaptic changes. But there's a hitch in this thinking, Diering says, because while mice and other mammals are awake, the synapses throughout its brain tend to be strengthened, not weakened, pushing the system toward its maximum load. When neurons are "maxed out" and constantly firing, they lose their capacity to convey information, stymying learning and memory.

One possible reason that neurons don't usually max out is a process that has been well-studied in lab-grown neurons but not in living animals, asleep or awake. Known as homeostatic scaling down, it is a process that uniformly weakens synapses in a neural network by a small percentage, leaving their relative strengths intact and allowing learning and memory formation to continue.

To find out if the process does occur in sleeping mammals, Diering focused on the areas of the mouse brain responsible for learning and memory: the hippocampus and the cortex. He purified proteins from receiving synapses in sleeping and awake mice, looking for the same changes seen in lab-grown cells during scaling down.

Results showed a 20 percent drop in receptor protein levels in sleeping mice, indicating an overall weakening of their synapses, compared to mice that were awake.

"That was the first evidence of homeostatic scaling down in live animals," says Richard Huganir, Ph.D., professor of neuroscience, director of the Department of Neuroscience and lead author of the study. "It suggests that synapses are restructured throughout the mouse brain every 12 hours or so, which is quite remarkable."

To learn specifically which molecules were responsible for the phenomenon, the team turned to a protein called Homer1a, discovered in 1997 by Paul Worley, M.D., professor of neuroscience, who was also part of the team conducting the new study. Studies showed that Homer1a -- named for the ancient Greek author and the scientific "odyssey" required to identify it -- is important for the regulation of sleep and wakefulness, and for homeostatic scaling down in lab-grown neurons.

Repeating his previous analysis of synaptic proteins, Diering indeed found much higher levels of Homer1a -- 250 percent more -- in the synapses of sleeping mice than awake mice. And in genetically engineered mice missing Homer1a, the previous decrease of synaptic receptor proteins associated with sleep was no longer present.

To sort out how Homer1a senses when the mice are sleeping or awake, the researchers looked to the neurotransmitter noradrenaline, which drives the brain to arousal and wakefulness. By blocking or enhancing noradrenaline levels, both in lab-grown neurons and in mice, the researchers confirmed that when noradrenaline levels were high, Homer1a stayed away from synapses; when it was low, it collected there.

To directly test whether the location of Homer1a was related to sleep, the team kept mice awake for four extra hours by placing them in an unfamiliar cage. Some then got two and a half hours of "recovery sleep." As predicted, levels of Homer1a in the receiving synapses were much higher in the sleep-deprived mice than in those that got recovery sleep. That suggests, says Diering, that Homer1a is sensitive to an animal's "sleep need," not just what time of day it is.

Diering emphasizes that sleep need is controlled by adenosine, a chemical that accumulates in the brain as an animal stays awake, provoking sleepiness. (Caffeine, the world's most widely consumed psychoactive drug, directly interferes with adenosine.) When mice were given a drug during sleep deprivation that blocks adenosine, Homer1a levels no longer increased in their synapses.

"We think that Homer1a is a traffic cop of sorts," says Huganir. "It evaluates the levels of noradrenaline and adenosine to determine when the brain is sufficiently quiet to begin scaling down."

As the final test of their hypothesis that scaling down during sleep is crucial for learning and memory, the researchers tested the mice's ability to learn without scaling down. Individual mice were placed in an unfamiliar arena and given a mild electrical shock, either as they woke up or right before they went to sleep. Some mice then received a drug known to prevent scaling down.

When an undrugged mouse received a shock just before sleep, its brain went through the scaling-down process and formed an association between that arena and the shock. When placed in that same arena, those mice spent about 25 percent of their time motionless, in fear of another shock. When placed in a different unfamiliar arena, they froze sometimes, but only about 9 percent of their time there, probably because they were relatively good a telling the difference between the two unfamiliar arenas.

Expecting that drugged mice that couldn't scale down during sleep would have weaker memories and therefore freeze less than undrugged mice, Diering was surprised that they were motionless longer (40 percent of their time) when returned to the arena where they were shocked. But the drugged mice were also motionless longer (13 percent of their time) when in a new arena. When the shock was given after the mice woke up, the drug made no difference in how long the mice froze in either arena, confirming that scaling down only occurs during sleep.

"We think that the memory of the shock was stronger in the drugged mice because their synapses couldn't undergo scaling down, but all kinds of other memories also remained strong, so the mice were confused and couldn't easily distinguish the two arenas," says Diering. "This demonstrates why 'sleeping on it' can actually clarify your ideas."

"The bottom line," he says, "is that sleep is not really downtime for the brain. It has important work to do then, and we in the developed world are shortchanging ourselves by skimping on it."

Huganir says that sleep is still a big mystery. "In this study, we only examined what goes on in two areas of the brain during sleep. There are probably equally important processes happening in other areas, and throughout the body, for that matter," he adds.

Read more at Science Daily

Here's What Mars' Amazing Polar Ice Cap Swirls Look Like From Above

This image could be the photographed close-up of a macchiato — foamy bright milk swirling at the top of a cup with the rich undercurrent of aromatic coffee steaming below. In actuality, this is Mars' frozen north pole, created with observational data from the European Space Agency's long-lived orbiter, Mars Express — where swirling ice looks like foam and the ruddy iron oxide-rich dust appears as rich coffee.

Assembled from observations taken during 32 overflights of the north pole between 2004 and 2010 and covering a whopping one million square kilometers, a newly released mosaic (below) highlights the Red Planet's magnificently-structured ice cap that is shaped by climatic cycles and molded by the planet's perpetual winds.

By combining this mosaic with data from the Mars Orbiter Laser Altimeter (MOLA) on board NASA's Mars Global Surveyor spacecraft (which studied Mars from 1997 to 2006), ESA scientists were able to create a "perspective" or "oblique" view of the ice cap, adding depth to the canyons (pictured top). If you looked out of the window from a high-altitude aircraft (or spacecraft in low-Mars orbit) flying over the north pole, this is what you'd see.

Mars Express is no stranger to Mars' north polar ice cap and the mission has added a wealth of information to our understanding of how the region is shaped.

This color moasic was generated from 32 individual orbit 'strips' captured between 2004 and 2010 by the High Resolution Stereo Camera onboard ESA's Mars Express
One major finding after years of study is that the ice cap becomes a key carbon dioxide "sink" during the winter, when it is estimated that 30 percent of Mars' atmospheric CO2 "freezes out," adding a seasonal layer of CO2 ice (commonly known as "dry ice") up to a meter thick. As the northern hemisphere begins to warm up through Martian spring and summer, this CO2 layer sublimates, returning as a gas into the atmosphere, leaving the permanent water ice layers behind.

Recent ice cap research has revealed that there are many layers of water ice and dust, providing a record of how Mars' climate has changed over tens of thousands of years as the planet's tilt has precessed. It is thought that the cap's hurricane-like shape is formed by the action of surface winds swirling with the planet's Coriolis force.

Read more at Discovery News

3D Locations of 23,000 Individual Atoms Seen for the First Time

For the first time, scientists have seen the exact locations of more than 23,000 atoms in a particle that's small enough to fit inside the wall of a single cell.

A team led by Peter Ercius of Lawrence Berkeley National Laboratory and Jianwei Miao of UCLA used a scanning electron microscope to examine a particle that was made of iron (Fe) and platinum (Pt) that was only 8.4 nanometers across, they reported yesterday in the journal Nature. (A nanometer is a billionth of a meter, or 3.9 one-hundred-millionths of an inch.)

Why would anyone care about the location of each little atom? "At the nanoscale, every atom counts," Michael Farle, a physicist at the University of Duisburg-Essen in Germany, wrote in an accompanying News and Views article in Nature. "For example, changing the relative positions of a few Fe and Pt atoms in a FePt nanoparticle dramatically alters the particle's properties, such as its response to a magnetic field."

Electron Beam

Using a scanning electron microscope, a beam of electrons is passed over the surface of an object to create an image. That allows researchers to see even small details of tiny bits of material like crystals and protein molecules. "There are very powerful techniques for figuring out the structure of crystals," he said. "But those have to be perfect crystals."

Ordinarily, when this kind of electron microscope is used to look at a crystal or other large molecule, the electrons are beamed at the sample and they scatter as they hit it, rather like a stream of bullets fired from a machine gun would scatter off Superman's chest. After they bounce off the atoms, the electrons hit a detector, and from there, the researcher can look at where the electrons land to get a look at the arrangement of the atoms in the crystal or molecule.

The problem, Ercius said, is that the image is built from an average that's obtained using many atoms or molecules. That is, the researchers will see a pattern, but it can only tell that person what the bulk arrangement of the atoms is, not where each one is actually located.

The iron-platinum nanoparticles are a kind of irregular crystal. But the ordinary scanning method wouldn't work as well for them, because the atoms are arranged in unique and slightly irregular ways, the researchers said. So they had to find a new way to use the electron microscope: They decided to look at the sample iron-platinum particle from many different sides.

Locating Individual Atoms

To do that, they altered the way the sample was prepared. Instead of leaving it in place, they put it on a special base that let them rotate and tilt their particle of iron and platinum, changing its orientation slightly after each "snapshot" with the electron beam. Otherwise, the process the researchers used was the same as usual.

That simple change was powerful: The varying orientations produced different patterns of scattering. The different patterns, which were picked up on a detector that's similar to the ones in digital cameras, could be used to calculate the exact positions of the 6,569 iron and 16,627 platinum atoms in the nanoparticle. It's not unlike making a 3D model of an object by taking pictures from many angles, which animators do routinely. Their results for the atoms' locations reached a resolution of about one-tenth the diameter of a single atom, according to Farle.

In the future, getting such an accurate picture could aid materials scientists in creating nanometer-size structures for applications such as hard drives. Makers of hard drives want to fabricate tiny, near-perfect crystals so that they can be easily magnetized and will hold a magnetic field for a long time, Ercius noted.

"All crystals have defects," Ercius said. "The problem is when they get nanoparticles that have these weird defects in them. This means they can look at those and how they affect how things work."

Read more at Discovery News

Deadly Snake Lures Frogs With Its Forked Tongue

Africa's deadly puff adder is a serious ambush predator, with fierce fangs and powerful venom. However, it turns out the striking reptile has another weapon. Its tongue is a forked instrument of deception, if you're a frog.

That was the discovery made by a pair of University of the Witwatersrand (Wits) researchers, who recorded and then pored over thousands of hours of video of puff adders hunting. The footage revealed a bit of trickery the snakes were using to draw frogs closer to them – just close enough to strike and snare the poor amphibians.

In a process called "lingual luring," the snakes were essentially fooling frogs into thinking their tongues were something the frog would like to eat - a tasty invertebrate such as a worm. Curious, and hungry, the frogs hopped too close, and then it was too late for them to beat a retreat.

"We know that snakes use their tongues to pick up scent cues in their environment," explained Wits researcher Xavier Glaudas, in a statement. "But these snakes were extending their tongues out of their mouths for up to 30 seconds, which is dramatically longer to what they do when they are just using their tongues to 'smell' their environment."

Although other animals – some wading birds, aquatic snakes and alligator snapping turtles – use tongue luring, "this is the first time that it is reported in a terrestrial snake," Glaudas said.

What's more, only frogs got the lingual luring treatment. Glaudas and research partner Graham Alexander never caught the snakes using the hunting maneuver on other kinds of prey, such as small mammals. That told the scientists that the snakes were making foraging decisions based on the type of potential food within view, which indicated that snakes might have more going on upstairs than typically thought.

"Our study reveals the diverse predatory strategies and complex decision-making process used by 'sit-and-wait' predators, such as ambush-foraging snakes, to catch prey, and indicates that snakes may have higher cognitive abilities than those usually afforded to them," Glaudas and Alexander wrote, in a paper on their findings published in the journal Behavioral Ecology and Social Biology.

Read more at Discovery News

Feb 2, 2017

Bird lovers help scientists discover secrets of beak evolution

European robin (Erithacus rubecula) with scan.
Citizen scientists and bird lovers across the world have helped researchers to uncover new secrets about the evolution of bird's beaks over time in a ground-breaking study.

Researchers at the University of Sheffield asked the public to help measure beak shapes from more than 2000 bird species which have been 3D scanned from specimens at the Natural History Museum and the Manchester Museum.

Using the crowdsourced data, the team were able show that the diversity of bird beaks expanded early in their evolutionary history. The most unusual beak shapes often involved periods of exceptionally fast evolutionary change.

However, once extremes are reached, the changes to bird beaks over time became much smaller as birds filled ever-narrower evolutionary niches.

There are some examples -- such as birds who have evolved in comparative isolation on remote islands such as the Galapagos and the Hawaiian archipelago -- who have continued to evolve rapidly.

Gavin Thomas, the project lead from the Department of Animal and Plant Sciences at the University of Sheffield, said: "The shape of a bird's beak is an important indicator of the food it eats and the way it forages -- its ecological niche.

"This project has given us key insight into how evolutionary processes play out over millions of years -- with major bursts of evolution as new groups emerge, and more fine scale changes thereafter.

"With the efforts of our volunteers from across the world, the study has given us a unique new data set for the study of bird ecology and evolution."

Dr Chris Cooney, from the Department of Animal and Plant Sciences, said: "The great diversity of bird beak shapes has long fascinated biologists and naturalists alike, including Darwin himself. It is wonderful to be able to use the information stored in natural history collections to shed light on how variation in this important ecological trait evolved."

Taking measurements from animals in the wild would have been impossible but 3D models taken from specimens in natural history museums provided new scope for this detailed study.

Members of the public logged onto the website, www.markmybird.org (created by the Digital Humanities Institute, Sheffield) which allowed anyone to access 3D models of the beaks and help create this new resource of bill shapes.

Dr Jen Bright, from the University of South Florida, said: "It's striking how much the speed of evolution changes between different birds. It's a really dynamic process, and it means there are still lots of questions left to answer about how birds managed to come up with the range of beak shapes that they have."

Read more at Science Daily

Low level of oxygen in Earth's middle ages delayed evolution for two billion years

New research explains how atmospheric oxygen was trapped at low levels following the Great Oxidation.
A low level of atmospheric oxygen in Earth's middle ages held back evolution for 2 billion years, raising fresh questions about the origins of life on this planet.

New research by the University of Exeter explains how oxygen was trapped at such low levels.

Professor Tim Lenton and Dr Stuart Daines of the University of Exeter Geography department, created a computer model to explain how oxygen stabilised at low levels and failed to rise any further, despite oxygen already being produced by early photosynthesis. Their research helps explain why the 'great oxidation event', which introduced oxygen into the atmosphere around 2.4 billion years ago, did not generate modern levels of oxygen.

In their paper, published in Nature Communications, Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon, the University of Exeter scientists explain how organic material -- the dead bodies of simple lifeforms -- accumulated in the earth's sedimentary rocks. After the Great Oxidation, and once plate tectonics pushed these sediments to the surface, they reacted with oxygen in the atmosphere for the first time.

The more oxygen in the atmosphere, the faster it reacted with this organic material, creating a regulatory mechanism whereby the oxygen was consumed by the sediments at the same rate at which it was produced.

This mechanism broke down with the rise of land plants and a resultant doubling of global photosynthesis. The increasing concentration of oxygen in the atmosphere eventually overwhelmed the control on oxygen and meant it could finally rise to the levels we are used to today.

This helped animals colonise the land, leading eventually to the evolution of humankind.

The model suggests atmospheric oxygen was likely at around 10% of present day levels during the two billion years following the Great Oxidation Event, and no lower than 1% of the oxygen levels we know today.

Professor Lenton said: "This time in Earth's history was a bit of a catch-22 situation. It wasn't possible to evolve complex life forms because there was not enough oxygen in the atmosphere, and there wasn't enough oxygen because complex plants hadn't evolved -- It was only when land plants came about did we see a more significant rise in atmospheric oxygen.

"The history of life on Earth is closely intertwined with the physical and chemical mechanisms of our planet. It is clear that life has had a profound role in creating the world we are used to, and the planet has similarly affected the trajectory of life. I think it's important people acknowledge the miracle of their own existence and recognise what an amazing planet this is."

Read more at Science Daily

NASA Spacecraft to Hunt for Earth's Asteroid 'Ghosts'

A robotic spacecraft launched in September to return samples from an asteroid will spend about 10 days this month on a side job hunting for asteroids that may be accompanying Earth as it orbits the sun.

So far, scientists know of only one so-called Earth Trojan asteroid, which was discovered in 2010 by NASA's infrared WISE telescope. The 1,000-foot object, known as 2010 TK-7, orbits roughly 60 degrees ahead of Earth.

Osiris-Rex will pick up the hunt on Feb. 9, searching 60 degrees ahead and 60 degrees behind Earth's present position. These regions, known as Lagrange points, are among several locations where the gravitational tug-of-war between Earth and the sun balances out, making for potentially stable orbits for asteroids or other objects. NASA, for example, plans to position the James Webb Space Telescope, its follow-on to Hubble, at a Lagrange point about 1 million miles from Earth.

Jupiter has a large group of Trojans in tow, bodies that scientists say are key to understanding how the solar system formed.

Could similar primordial asteroids be circling Earth?

"That would be the most fascinating thing we could discover," Osiris-Rex lead scientist Dante Lauretta, with the University of Arizona's Lunar and Planetary Laboratory told a NASA science advisory group last month.

Compelling as the science may be, Lauretta authorized the moonlighting job because it provides an excellent dress rehearsal for some key sleuthing Osiris-Rex will do to help ensure its safe arrival at the asteroid Bennu in 2018.

Astronomers don't know if Bennu has any small moons in orbit. Ground-based telescopes can only spot objects larger than about 65 feet.

"That's a substantial object and we'd obviously want to know that it's there and plan our operations accordingly," Lauretta said.

Osiris-Rex is due to put itself into orbit around Bennu for a two-year study and sampling mission.

For target practice, as Osiris-Rex hunts for Earth Trojans it will attempt to locate several known objects in the main asteroid belt.

Read more at Discovery News

Our Supermassive Black Hole Could Be 'Supercharging' Stars' Magnetism

For a supermassive black hole that's so close to us, we still have a lot to learn about Sagittarius A* (Sgr A*), the singularity in the center of the Milky Way.

As astronomers work to learn more about the environment it, a new paper in Astrophysical Journal Letters makes predictions about what would happen to young, highly magnetized stars in Sgr A*'s vicinity. It's the first time a star's magnetic field has been included in simulations where a black hole tidally disrupted a star, meaning the star is pulled apart and stretched.

"Magnetic fields are a bit tricky numerically to simulate," James Guillochon, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, told Seeker. In the past, it's been hard to put magnetic fields in context with other influences on a star, such as gas pressure and gravity. This is especially true towards the boundary or atmosphere of the star.

The simulations show that if a star gets a "glancing blow" from a black hole, it can survive the encounter and its magnetic field amplifies strongly, by a factor of about 30. But if the star gets very close to the black hole, the star is tidally destroyed and the magnetic field maintains its strength.

A Hubble Space Telescope infrared view of the center of the Milky Way galaxy. The inset shows X-rays in the region around Sagittarius A*, the supermassive black hole in the galaxy's heart
"One of the immediate impacts is that we might see highly magnetized stars in the centers of galaxies, and that includes our own galactic center," Guillochon added. "We also would expect this to affect the resulting flare that arises from the disruption of the star by the supermassive black hole. Half the matter of the star falls on to the black hole and feeds it, and that generates a luminous flare of a billion or 10 billion solar luminosities."

A star disruption should theoretically be visible in our own galactic center, but Guillochon says that only happens about once every 10,000 years or so. Luckily, the stream of the disrupted star can persist for centuries, feeding the black hole.

Guillochon co-wrote a paper a couple of years ago about G2, a gas cloud falling into the galactic center in 2014 that produced far less activity than expected. It suggests that G2 could have been produced by the disruption of a red giant star, and its gas envelope is still feeding the black hole today.

He suggested that G2-like clouds would form by "clumping up" due to cooling instabilities, which would put regular deliveries of a G2-type cloud once every decade. When the material is highly magnetized, co-author Michael McCourt has previously suggested that the fields can help stabilize the clouds and prevent them from breaking apart. If the pattern holds true, highly magnetized clouds would continue to pass near the black hole over the next several decades.

That said, the challenge of learning about stars that survive disruption in the galactic center is they tend to be lower mass and hard to see. How many of them are magnetized, and how strongly, remains an open question, Guillochon said. Below is a short animation simulating a star's magnetic field being torn apart by a black hole.

From Discovery News

Ancient Egyptian's Baboon Obsession Laid Hidden Within Luxor Tomb

For Jiro Kondo and his team from Waseda University, it began as just another day of excavating at Luxor, an Egyptian city famous for its temples and other ancient monuments. The researchers were taking care of mundane tasks at an area to the east of the forecourt of the known tomb of Userhat, who was a royal scribe.

"While cleaning the area above the 'rump' to the forecourt, we found a hole," Kondo told Seeker. After entering the hole, he and his team were stunned by what they found: a previously unknown separate chamber.

"The tomb is beautifully decorated and probably dates to the Ramesside period," he said, referring to the span from 1292 to 1069 B.C. "The owner of the tomb is Khonsu, who has the title of 'the royal scribe.'" The ancient Egyptian's name is clearly written in hieroglyphics in the tomb.

Various scenes in the chamber depict Khonsu, his wife, the gods Osiris and Isis, and the ram-headed deities which are thought to be Khnum or Khnum-Re. One detailed painting, however, is perhaps most telling about Khonsu and his likely muse.

"On the north wall of the entrance doorway, we found a scene showing the solar boat of the god Ra-Atum being worshiped by four baboons showing the pose of adoration," Kondo said.

Image of baboons worshipping the early Egyptian god Ra-Atum. The depictions are in the tomb of the royal scribe Konsu at Luxor, Egypt.
Painting of the royal scribe Khonsu, left, shown with his wife in his tomb at Luxor, Egypt.
Ra-Atum was a central ancient Egyptian deity, a sun god through which everything else was created. As for the baboons, they are also sometimes depicted as gods, but are linked to Ra-Atum and were believed to be the spiritual muses of scribes, directing their writing.

Baboons vocalize loudly when the sun rises. They also like to warm themselves in the morning sun, perhaps explaining their mythical connection to Ra-Atum. One may wonder, though, why baboons were depicted at all, since they are not native to Egypt.

Historians suspect that the primates were brought to Egypt from Nubia, which was a region that then encompassed part of Sudan. Based on this latest tomb find, and other ancient Egyptian depictions of baboons, these animals were popular in Egypt and many other parts of Africa.

The world's first known baboon, discovered at a site called Malapa in South Africa, even hails from a region that's often referred to as the Cradle of Humankind.

Read more at Discovery News

Feb 1, 2017

Researchers confirm the existence of a 'lost continent' under Mauritius

This is Indian Ocean topography showing the location of Mauritius as part of a chain of progressively older volcanoes extending from the presently active hot-spot of Réunion toward the 65-million-year-old Deccan traps of northwest India.
Scientists have confirmed the existence of a "lost continent" under the Indian Ocean island of Mauritius that was left-over by the break-up of the supercontinent, Gondwana, which started about 200 million years ago. The piece of crust, which was subsequently covered by young lava during volcanic eruptions on the island, seems to be a tiny piece of ancient continent, which broke off from the island of Madagascar, when Africa, India, Australia and Antarctica split up and formed the Indian Ocean. "We are studying the break-up process of the continents, in order to understand the geological history of the planet," says Wits geologist, Professor Lewis Ashwal, lead author on the paper "Archaean zircons in Miocene oceanic hotspot rocks establish ancient continental crust beneath Mauritius," published in the journal Nature Communications.

By studying the mineral, zircon, found in rocks spewed up by lava during volcanic eruptions, Ashwal and his colleagues Michael Wiedenbeck from the German Research Centre for Geosciences (GFZ) and Trond Torsvik from the University of Oslo, guest scientist at GFZ, have found that remnants of this mineral were far too old to belong on the island of Mauritius.

"Earth is made up of two parts -- continents, which are old, and oceans, which are "young." On the continents you find rocks that are over four billion years old, but you find nothing like that in the oceans, as this is where new rocks are formed," explains Ashwal. "Mauritius is an island, and there is no rock older than 9 million years old on the island. However, by studying the rocks on the island, we have found zircons that are as old as 3 billion years."

Zircons are minerals that occur mainly in granites from the continents. They contain trace amounts of uranium, thorium and lead, and due to the fact that they survive geological process very well, they contain a rich record of geological processes and can be dated extremely accurately.

"The fact that we have found zircons of this age proves that there are much older crustal materials under Mauritius that could only have originated from a continent," says Ashwal.

This is not the first time that zircons that are billions of years old have been found on the island. A study done in 2013 has found traces of the mineral in beach sand. However, this study received some criticism, including that the mineral could have been either blown in by the wind, or carried in on vehicle tyres or scientists' shoes.

"The fact that we found the ancient zircons in rock (6-million-year-old trachyte), corroborates the previous study and refutes any suggestion of wind-blown, wave-transported or pumice-rafted zircons for explaining the earlier results," says Ashwal.

Ashwal suggests that there are many pieces of various sizes of "undiscovered continent," collectively called "Mauritia," spread over the Indian Ocean, left over by the breakup of Gondwanaland.

Read more at Science Daily

Deep-Sea Dragonfish Predators Have a Freakishly Wide Bite

Deep-sea dragonfishes, also known barbeled dragonfishes, open their mouths wider than any other fish, researchers now believe after studying the animal's very unique head joint.

The fish can open their mouths at least 120 degrees (a straight line measures 180 degrees) allowing them to eat extremely large prey relative to the size of these predators. Dragonfishes, described in the journal PLOS ONE, grow up to about one feet, six inches long.

"In the dark, deep sea food is very scarce," co-author G. David Johnson of the Smithsonian's National Museum of Natural History told Seeker.

"The barbeled dragonfishes are ambush lie-and-wait predators, advantageous because less energy is used searching for food. Because prey items are scarce, it is also advantageous to be able to swallow a wider size range of encountered prey and the head joint facilitates engulfing larger items," explained lead author Nalani Schnell of the French Muséum national d'Histoire naturelle.

The researchers, who have studied a myriad of fish anatomy over the years, have never seen anything like the head joint of the deep-sea dragonfishes.

The joint comprises the back of the head and a flexible rod running to the top of the fish's vertebral column. The researchers determined that, when the fish is in a resting position and not elevating its head, the rod has an additional sheath that embraces the back of the head like a socket. When the fish opens its mouth, the sheath gets stretched out and the bottom part of this rod is exposed.

The process is illustrated in the below video:

While the fish clearly has many sharp teeth, they don't actually break food up into bits.

Barbeled dragonfish "swallow their prey whole," Schnell explained. "The teeth are not for chewing; they instead hold onto prey and pass it into the stomach. Some dagger-like teeth even act as a cage, so that swallowed prey won't be able to escape anymore."

Once the fish has swallowed prey, such as another fish, its stomach can expand, causing the predator to look somewhat like a snake that has just swallowed a big victim.

X-ray of a barbeled dragonfish that has eaten a whole lanternfish.
Barbeled dragonfishes inhabit depths between 1640 and about 5000 feet below the water's surface, so they pose no threat to humans. The researchers said that in nets, most of these fish "come up dead due to the difference in pressure, temperature and more."

Read more at Discovery News

Meteorite Reveals Mars Had Active Volcanoes Two Billion Years Ago

A new analysis of a half-pound meteorite from Mars shows that the Red Planet was volcanically active as far back as two billion years ago, making Mars home to not only the biggest volcanoes in the solar system, but the most long-lived ones as well.

The meteorite, known as Northwest Africa (NWA) 7635, was found in 2012 in Algeria (pictured above). A new isotopic analysis, headed by University of Houston geologist Tom Lapen, ties NWA 7635 with 10 other Martian meteorites that likely were blasted out from the same volcano or lava plain by an impacting asteroid or comet about 1.1 million years ago.

"We don't know exactly where these stones were launched from, but it is likely that they are from the volcanic plains and shield volcanoes of the Tharsis or Elysium regions on Mars," Lapen told Seeker.

The study also showed that NWA 7635's solidified lava dates back 2.4 billion years, far older than similar meteorites (known by their scientific designation as incompatible trace element (ITE) depleted shergottites.)

The previously analyzed meteorites range in age from 327 million years old to 600 million years old, the study shows.

"The discovery of a single Mars ejection site with over 2 billion years of stacked lava flows is critical for understanding the volcanic history of Mars," Lapen said. "These data are exciting because this is the first direct evidence for the absolute timing, mantle source characteristics, and spatial associations of volcanism on Mars."

The research also "sets a template for further testable hypotheses regarding the periodicity of magmatism, timing of volcanic gas fluxes into the atmosphere, and the nature of mantle dynamics over most of Mars' history," he added.

The analysis confirms that some of the oldest volcanoes in the solar system are located on Mars.

Mars already was known to host the largest known volcano in the solar system, Olympus Mons, which is as wide as the state of Arizona and about 16 miles high, according to NASA.

NWA 7635 is among about 124 meteorites from Mars that have been recovered on Earth, NASA's Mars Meteorite website shows.

Lapen's research appears in this week's Science Advances.

From Discovery News

Looking Into the 'Eye of the Storm' to Spy on a Brown Dwarf Hugging Its Star

When a hurricane rips across the ocean, a peculiar region of calm appears in its core — called the "eye of the storm." This surprising region of comparative calm is almost as dramatic as the powerful winds that whip around its perimeter. Now, astronomers have developed a method that is analogous to the eye of the storm to create their own region of calm, not within a violent weather system, but in astronomical observations of star systems.

The biggest difficulty facing astronomers looking for worlds orbiting distant stars is the obscuring glare of starlight that can completely hide the dimmer light bouncing off orbiting exoplanets. The glare can be millions of times brighter than the reflected light, requiring astronomers to devise ingenious techniques to reduce that glare. Oftentimes, "occulters" are used within instrumentation — basically tiny disks that physically block the intense starlight from view (a bit like holding your hand up to the sun to block the sun's glare), allowing features around the star to be detected.

Occulters, however, have their limitations. The biggest problem is that, though this method allows the detection of exoplanets orbiting far from their stars, too much glare still bleeds through, obscuring the signal of exoplanets orbiting near to their stars. Entire systems of planets can be blocked from view if their orbits are compact, particularly for more distant stars where planetary systems will appear smaller.

By manipulating the properties of light, however, a new device called a vortex coronagraph installed at the W.M. Keck Observatory in Hawaii has revealed the presence of a brown dwarf closely orbiting the star HIP 79124 (pictured top) and highlighted a planet-forming cloud of dust around the young star HD 141569. Neither objects would have been spotted if the astronomers used more conventional methods of direct imaging.

"The vortex coronagraph allows us to peer into the regions around stars where giant planets like Jupiter and Saturn supposedly form," said research scientist Dmitri Mawet, at NASA's Jet Propulsion Laboratory and Caltech in Pasadena. "Before now, we were only able to image gas giants that are born much farther out. With the vortex, we will be able to see planets orbiting as close to their stars as Jupiter is to our sun, or about two to three times closer than what was possible before."

The vortex coronagraph works by manipulating the starlight coming directly from the star. A filter with microscopic concentric rings act to direct the star's glare away from the instrument's optics. As light is electromagnetic waves, in the center of the coronagraph these waves are directed to cancel each other out (a physical mechanism known as destructive interference). This canceled light creates a dark region in the center, called an "optical singularity," effectively blocking the glare of the star. This method therefore allows the reflected light of worlds orbiting very close to their star to be resolved.

Appearing like a miniature CD, the vortex coronagraph mask is made out of synthetic diamond. A microscopic view of its concentric rings are shown to the right
"Hurricanes have a singularity at their centers where the wind speeds drop to zero — the eye of the storm," added Mawet. "Our vortex coronagraph is basically the eye of an optical storm where we send the starlight."

In the case of HIP 79124, a brown dwarf was discovered orbiting the star at a distance of 23 AU (astronomical units, where 1AU is the average distance at which the Earth orbits the sun). Brown dwarfs are commonly known as "failed stars" — they form a bridge between the most massive planets and the least massive stars and possess qualities of both.

In another vortex study, the innermost ring of planet-forming material around the star HD 141569 was studied. On combining the vortex data with infrared observations from NASA's Spitzer and WISE missions, plus the European Space Agency's Herschel mission, researchers were able to deduce that the material consists of silicate pebbles known as olivine, which is abundant in the Earth's mantle. The temperature of material was measured to be around 100 Kelvin (280 degrees Fahrenheit), a little warmer than the solar system's asteroid belt.

This image shows the dusty disk of planetary material surrounding the young star HD 141569, located 380 light-years away from Earth
"The three rings around this young star are nested like Russian dolls and undergoing dramatic changes reminiscent of planetary formation," said Mawet. "We have shown that silicate grains have agglomerated into pebbles, which are the building blocks of planet embryos."

Both studies were published in the January 2017 issue of The Astrophysical Journal.

Read more at Discovery News

Jan 30, 2017

Bursts of Methane May Have Prepped Ancient Mars for Life

Scientists have a new theory for how early Mars managed to stay warm enough for liquid surface water, a condition that is believed to be essential for life.

An armada of orbiters, landers and rovers studying Mars have returned overwhelming evidence that the dry, cold planet of today was far different three- to four billion years ago when rivers and lakes periodically flowed across its surface.

But at that time, Mars should have been too cold for water to remain liquid.

Newly published research shows Mars' atmosphere may have had periods of warming due to greenhouse gases spurred largely by the release of methane.

"The early Mars climate problem has been around for a long time," lead researcher Robin Wordsworth, with Harvard University's School of Engineering and Applied Science, told Seeker. "All the previously proposed explanations just didn't work. We couldn't get the climate warm enough or wet enough for long."

The new study, published in last week's Geophysical Research Letters, shows that interactions between methane, carbon dioxide and hydrogen in Mars' atmosphere could have absorbed enough solar radiation to spike surface temperatures high enough for water to stay liquid.

Blankets of greenhouse gases could have kept Mars warm for spans of time lasting tens of thousands of years, but not hundreds of millions of years, Wordsworth noted, a finding that matches the evidence of the periodic presence of water coming from NASA's Curiosity rover and other spacecraft at Mars.

Wordsworth said he got the idea about methane bursts from looking at Titan, the largest moon of Saturn and the only body in the solar system besides Earth that has a substantial atmosphere. Titan is loaded with methane, as well as other hydrocarbons.

"It's an analog for how Mars might have been," Wordsworth said.

The scientists expect data from NASA's ongoing MAVEN mission, which is monitoring how Mars' atmosphere is bleeding away into space, will flesh out their models of the planet's past climate.

Read more at Discovery News

Hybrid Lion-Tiger Born in Russia

An extremely rare cross between a tiger and a lion has been born in a travelling zoo in southern Russia, one of only a few dozen of the animals believed to exist.

Named Tsar, the two-month-old "liger" cub is the offspring of a tigress Princess and lion Caesar, zoo director Erik Airapetyan told AFP.

"They have lived together for a long time and know each other well. When the tigress was on heat, she didn't have any other choice," he said.

The cub has the beige fur of a lion and the stripes of a tiger and is currently being fed on milk from one of the zoo's goats.

Ligers can grow to be the biggest cat in the animal kingdom, weighing more than 400 kilograms (882 pounds).

A liger called Hercules in the United States is currently listed in the Guinness Book of World Records as the biggest feline in the world, at a weight of 418 kilograms (922 pounds) and length of 3.33 meters (11 feet).

U.S. zoos do not generally cross-breed big cats, as there is thought to be no purpose to breeding an animal that does not exist in the wild. Instead, they put their energies toward conservation of existing species.

"In terms of conservation," a U.S. lion expert told National Geographic in 2012, "it's so far away from anything, it's kind of pointless to even say it's irrelevant."

In the case with Tsar: "The mother [tiger] was in heat but there were no tigers, and we saw that she was suffering [without a male tiger] so we decided to put her together with a lion. Because they lived next to each other for a long time before, it worked," Airapetyan told Deutsche Welle.

Earlier notions that all ligers are sterile have not proved accurate, as shown by the birth in 2012 of "liliger" Kiara - born to a liger mother and a lion father.

AFP contributed to this report.

From Discovery News

This Bag-Like Sea Creature Was Our Earliest Ancestor

A microscopic bag-like sea creature dating to 540 million years ago is the earliest known ancestor of humans, research on the newly discovered species finds.

The ultra-tiny animal, named Saccorhytus coronarius, is now thought to be the first known "deuterostome" and is described in the journal Nature. Deuterostome refers to a broad biological group of animals that encompasses a number of sub-groups, including vertebrates, which are all animals with a backbone or spinal column.

"Humans are deuterostomes and so too are other vertebrates, as well as animals like sea-squirts and starfish," co-author Simon Conway Morris of the University of Cambridge told Seeker. "What we want to know is what the common ancestor of all these animals looked like. In our opinion, Saccorhytus is the best candidate."

To the naked eye, the creature resembles a black speck of dust. When magnified, however, "the preservation of detail in this (and the other) microscopic fossils is extraordinary," he said.

Conway Morris, lead author Jian Han and their international team of researchers analyzed the remains of Saccorhytus. They believe it lived in a shallow sea ecosystem with primitive mollusks, early representatives of arrow worms (nearly transparent worm-like marine predators) and other water-dwelling species.

There was not much to the animal, by the looks of it. The body was a rounded sack covered with a thin and flexible skin. A relatively large mouth was at the top, with small openings called "body cones" around the primary orifice.

"It could have slithered between the sediment grains, and the mouth seems to have been capable of considerable dilation and so, for its size, (it could) have swallowed relatively large prey with the excess water being discharged via the openings," Conway Morris said.

"We have not observed an anus," he added, explaining that waste material could have left through the mouth.

The openings that are on the body were likely the precursors of gill slits that later evolved in fish and other marine life, the researchers believe. Gills were lost once the ancestors of humans and other related animals became terrestrial.

Read more at Discovery News

On Mars, Life Could Be Hiding Under the Rocks

Living on Mars would be tough by any measure — so tough, that there's considerable debate about whether even the hardiest of microbes could survive. The atmosphere is thin, the surface is baked with radiation and the planet itself is mostly arid, dusty and wind-swept.

But there could be niches where life thrived in the distant past, when Mars had a thicker atmosphere and a wetter surface. So when Red Planet scientist Janice Bishop was invited to look at carbonate rocks in the Mojave Desert a few years ago, she immediately saw implications for Mars.

Bishop had already published a 2006 International Journal of Astrobiology paper calling iron oxides an "ultraviolet sunscreen" for ancient photosynthesis on Earth. The result of the newer study, published in 2011 in the same journal showed that the Mojave rocks collected also had iron oxide coatings, under which carbonates were hiding.

"They were all hiding under this red mineral at the top, called hematite," Bishop told Seeker in an interview. Hematite is also a common element on Mars.

Besides being senior research scientist and chair of the astrobiology group at the SETI Institute, Bishop is known for her work creating an instrument on the Mars Reconnaissance Orbiter called CRISM (Compact Reconnaissance Imaging Spectrometer). The spacecraft has been taking high-resolution pictures and spectroscopic images of Mars for more than a decade, providing reams of information on how the surface looks like today and how it may have evolved.

And Bishop is one of several scientists working on the "sunscreen" idea. The University of Maryland's Gozen Ertem, for example, is looking at how well biomolecules can hide from ultraviolet radiation in different mixtures. She will present on her research at the American Association for the Advancement of Science Conference next month. (Ertem did not respond to requests for an interview.)

It's unclear how well Martian microbes (if they existed) would have fared in their environment, but at the least the studies on iron oxides are yielding valuable information about how life evolved on Earth. This could help scientists better understand the possibility of life in other environments across the solar system, or even exoplanetary systems.

Banded iron formations (such as the one pictured at ceter at Karijini National Park, Western Australia) may come in part from iron metabolized by microorganisms
Some people in this field are trying to figure out how microbes could have evolved when the Earth had no protective ozone layer, similar to what is on Mars today. A 2015 Geology paper led by Tina Gauger at the University of Tubingen suggests that some strains of bacteria could have created iron oxide layers in their environment for protection.

Read more at Discovery News

Jan 29, 2017

Climate change helped kill off super-sized Ice Age animals in Australia

Kangaroo silhouette against sky
During the last Ice Age, Australia, Tasmania and New Guinea formed a single landmass, called Sahul. It was a strange and often hostile place populated by a bizarre cast of giant animals.

There were 500-pound kangaroos, marsupial tapirs the size of horses and wombat-like creatures the size of hippos. There were flightless birds that weighed twice as much as modern emu, 33-foot snakes, 20-foot crocodiles, 8-foot turtles with horned heads and spiked tails, and giant monitor lizards that measured greater than 6 feet from tip to tail and were likely venomous.

By about 30,000 years ago, however, most of these 'megafauna' had disappeared from the Sahul as part of a global mass extinction that saw the end of nearly all of the super-sized animals that had evolved to survive in extreme Ice Age climates. The factors that forced the Australian megafauna into extinction remain a matter of considerable controversy. Many experts argue that the ancestors of the Australian aborigines, who made an appearance approximately 50,000 years ago, either hunted them into extinction or gradually destroyed the habitat they required by practices such as fire-stick burning. Others argue that the gradual drying out of Australia and weakening of the Australian monsoon played a major role in their demise.

A new study has compared the diet of a variety of Australian megafaunal herbivores from the period when they were widespread (350,000 to 570,000 years ago) to a period when they were in decline (30,000 to 40,000 years ago) by studying their fossil teeth. The analysis suggests that climate change had a significant impact on their diets and may well have been a primary factor in their extinction.

"We have found evidence that, as the climate was changing and getting drier, animal diets were shifting dramatically," said Larisa DeSantis, assistant professor of earth and environmental studies at Vanderbilt University, who directed the study. "If climate change was a primary or contributing factor in their demise, as it appears, we need to pay more attention to how current levels of climate change are affecting animals today."

The results of the study are described in a paper titled "Dietary responses of Sahul (Pleistocene Australia-New Guinea) megafauna to climate and environmental change" published on Jan. 25 by the journal Paleobiology. Co-authors on the paper are Judith Field and John Dodson from the University of New South Wales and Stephen Wroe from the University of New England.

Michael Archer, a leading Australian paleontologist at the University of New South Wales who was not involved in the study, commented, "This new study, based on hard evidence, makes it clear that changes in late Pleistocene climate had a major impact on the late Pleistocene megafauna of Australia, adding even more evidence to challenge the imaginative a priori assumption that 'blitzkrieg' by early humans caused the extinction of this continent's lost megafauna.Climate change clearly has been in the past and will continue to be a major cause of extinction into the future."

The teeth that were analyzed came from the Cuddie Springs site in southeastern Australia. It is located on a prehistoric ephemeral lake and it is the only site on mainland Australia that has produced fossil evidence of the co-existence of humans and megafauna. "Unfortunately, many of the advocates of the human predation hypothesis have discounted Cuddie Springs because it does not support the popular 'blitzkrieg' theory that maintains the megafauna went extinct in the 1,000-year period after humans arrived on the scene," said DeSantis.

It's amazing how much information about the prehistoric environment paleontologists can extract from fossil teeth using a dental drill, dental impression material and some sophisticated instruments. The ratios of oxygen and carbon isotopes locked in the enamel provide clues about the animals' diet and the average temperature and humidity of the environment at the time the teeth formed. Differences within individual teeth mirror climate variability. Analysis of the microscopic scratches on the surface of the teeth provides evidence of what the animal was eating in the last few weeks of its life. Differences in wear-patterns can differentiate between animals that were grazing on grass and browsing on bushes.

"For example, we know from the analysis of modern day kangaroos that oxygen isotope ratios in their teeth are highly correlated with the relative humidity and amount of precipitation in their environment," DeSantis said. "This makes them ideally suited for tracking changes in aridity over time."

During the megafaunal heyday around 500,000 years ago, the dental analysis revealed that the climate was semi-arid. In addition, the animals' diets were highly variable, implying that there were a number of ecological niches available to them.

That contrasts markedly with the period from 30,000 to 40,000 years ago. Here, the analysis indicates that the climate was substantially drier and the diet of the giant herbivores was considerably more restricted.

Read more at Science Daily

Anthropologists uncover art by (really) old masters

An international team of anthropologists has uncovered a 38,000-year-old engraved image in a southwestern French rockshelter -- a finding that marks some of the earliest known graphic imagery found in Western Eurasia and offers insights into the nature of modern humans during this period.

"The discovery sheds new light on regional patterning of art and ornamentation across Europe at a time when the first modern humans to enter Europe dispersed westward and northward across the continent," explains NYU anthropologist Randall White, who led the excavation in France's Vézère Valley.

The findings, which appear in the journal Quaternary International, center on the early modern humans' Aurignacian culture, which existed from approximately 43,000 to 33,000 years ago.

Abri Blanchard, the French site of the recently uncovered engraving, a slab bearing a complex image of an aurochs, or wild cow, surrounded by rows of dots, was previously excavated in the early 20th century. White and his team members began their methodical exploration of remaining deposits at the site in 2011, with the discovery occurring in 2012.

White contends that Aurignacian art offers a window into the lives and minds of its makers -- and into the societies they created.

"Following their arrival from Africa, groups of modern humans settled into western and Central Europe, showing a broad commonality in graphic expression against which more regionalized characteristics stand out," he explains. "This pattern fits well with social geography models that see art and personal ornamentation as markers of social identity at regional, group, and individual levels."

Abri Blanchard and its sister site, Abri Castanet, previously excavated by White's team, have long been recognized as being among the oldest sites in Eurasia bearing artifacts of human symbolism. Over time, hundreds of personal ornaments have been discovered, including pierced animal teeth, pierced shells, ivory and soapstone beads, engravings, and paintings on limestone slabs.

From Science Daily