In brain evolution, size matters, most of the time

An African sedge warbler, a species with a simple song that is also adapted to eating insects.

Which came first, overall bigger brains or larger brain regions that control specialized behaviors? Neuroscientists have debated this question for decades, but a new Cornell University study settles the score.

The study reports that though vertebrate brains differ in size, composition and abilities, evolution of overall brain size accounts for most of these differences, with larger brains leading to greater capabilities.

The study of 58 species of songbirds also found that once a species evolved a larger brain, brain regions that control the beak and mouth, and the area for song, developed additional complex neural networks.

The paper, co-authored by Jordan Moore Ph.D., currently a postdoctoral fellow at Columbia University, and Timothy DeVoogd, a Cornell professor of psychology, was published May 10 in the Proceedings of the Royal Society B.

The findings suggest that this principle may also help explain human evolution; we may have first evolved larger brains, which then allowed for adaptations that enhanced brain regions that control specific abilities, such as language.

"Most neuroscientists believe there is nothing special about the way that our brains have evolved, that what we need to do is understand the principles that underlie brain evolution in general, which is what this study involves," said DeVoogd. "The way you build a bigger brain is not just making everything bigger but rather slowing down or lengthening late pieces of development."

In this way, bigger brains have a more developed cortex (which plays key roles in memory, attention, perception, awareness, thought, language and consciousness) that is the last region to develop in animals and humans.

The study is the first to compare -- and resolve -- two competing theories of brain evolution. One theory holds that natural selection drove progressive changes in particular areas of the brain, which then led to larger overall brains in species that needed them to survive.

The other theory contends that some species acquired a bigger brain in general, and its larger basic parts could then be recruited for specific complex behaviors.

To test these theories, Moore and DeVoogd measured the sizes of overall brains and 30 discrete areas that control behaviors in 58 songbirds spanning 20 families.

"One of the advantages of looking in the brains of birds is that it's relatively easy to get samples from lots of different species, and there's a lot of data on what the different species do. And specific areas devoted to these functions can be easily seen in the brain," DeVoogd said.

Most of the variation in brain regions was accounted for by differences in the brain's overall size. But in two specific systems there was a significant amount of variation beyond what could be explained by brain size. Areas that controlled song were much larger in species that produce more varied and complex songs. Also, brain areas controlling the face and mouth were especially large in species with short, fat beaks that eat seeds, and they were small in species with long, thin beaks that eat insects.

"If you've ever watched a bird deal with a sunflower seed, it pushes the seed around with its tongue and grasps it with different points in its beak. And then it is able to break it open and get the inside out," DeVoogd explained.

Read more at Science Daily

Saying goodbye to glaciers

Twila Moon is pictured during field work to study ice-ocean interaction at the LeConte Glacier, Alaska.

Glaciers around the world are disappearing before our eyes, and the implications for people are wide-ranging and troubling, Twila Moon, a glacier expert at the University of Colorado Boulder, concludes in a Perspectives piece in the journal Science today.

The melting of glacial ice contributes to sea-level rise, which threatens to "displace millions of people within the lifetime of many of today's children," Moon writes. Glaciers also serve up fresh water to communities around the world, are integral to the planet's weather and climate systems, and they are "unique landscapes for contemplation or exploration."

And they're shrinking, fast, writes Moon, who returned to the National Snow and Ice Data Center this month after two years away. Her analysis, "Saying goodbye to glaciers," is published in the May 12 issue of Science.

Moon admits she was pretty giddy when an editor at Science reached out to her to write a perspective piece on the state of the world's glaciers, because of her research knowledge and extensive publication record. "There was some serious jumping up and down," Moon says. "I thought, 'I've made it!' Their invitation was an exciting recognition of my hard work and expertise."

But the topic, itself, is far from a happy one. Moon describes the many ways researchers study glacier dynamics, from in-place measurements on the ice to satellite-based monitoring campaigns to models. And she describes sobering trends: The projection that Switzerland will lose more than half of its small glaciers in the next 25 years; the substantial retreat of glaciers from the Antarctic, Patagonia, the Himalayas, Greenland and the Arctic; the disappearance of iconic glaciers in Glacier National Park, Montana, or reduction to chunks of ice that no longer move (by definition, a glacier must be massive enough to move).

In her piece, Moon calls for continued diligence by the scientific community, where ice research is already becoming a priority.

Moon says she got hooked on glaciers as an undergraduate in geological and environmental sciences at Stanford University, when she spent a semester abroad in Nepal. "For the first time I saw a big valley glacier, flowing through the Himalaya," she said, "and I thought it was about the coolest thing ever. After studying geology, the movement and sound of the ice, right now, made it feel almost alive.'"

That experience kicked off a research career that has taken Moon to Greenland, Alaska, Norway, and to conferences around the world. She began her work "merely" as a geologist and glaciologist, interested in ice itself, Moon said. Only later did the influence of climate change come to play in her work.

"I think I'm about as young as you can get for being a person who started in glaciology at a time when climate change was not a primary part of the conversation," says Moon, who is 35.

She is consistently sought out by journalists hoping to understand Earth's ice, and she's sought out in the scientific community as well, recognized as someone who likes to collaborate across disciplinary boundaries. She recently worked with a biologist in Washington, for example, on a paper about how narwhals use glacial fronts in summertime -- the tusked marine mammals appear to be attracted to glaciers with thick ice fronts and freshwater melt that's low in silt, though it's not yet clear why.

After a couple of post-doctoral research years, at the National Snow and Ice Data Center and then the University of Oregon, Moon and her husband headed to Bristol, England, where she took a faculty position at the University of Bristol's School of Geographical Sciences. When it became clear that her husband's work wouldn't transfer, the two determined to head back to the Rocky Mountains.

Read more at Science Daily

Different places warm at different paces

Temperature change per decade in the air (left) and the surface of the ocean (right) between 2005 and 2100, as projected by the Norwegian Earth System model under a strong emission scenario (RCP8.5). Notice the rapid ocean warming at around 40S, 40N, and in the Arctic, in contrast to the surface atmospheric warming mainly in the Arctic.

One of the robust features of global warming under increasing greenhouse gas concentrations is that different places warm at different paces. It turns out that the fast warming in each region has its own cause. Ocean heat transport links subpolar and Arctic warming, but that is not the whole story.

Ocean heat transport links subpolar and Arctic warming, but that is not the whole story, writes Aleksi Nummelin. Read his account of how he, Camille Li and Paul Hezel worked to solve a climate riddle.

Ocean heat transport links together the subpolar and Arctic warming -- but it's not the whole story. About a year ago Camille, Paul and I realized that something was missing in our understanding of the ocean's role for Arctic warming, and it was time to find out! Here is our story:

One of the robust features of global warming under increasing greenhouse gas concentrations is that different places warm at different paces.

Observations had already shown that Earth's surface warms fastest in the polar regions and slowest in the tropics. On the other hand, observations and model results had revealed that the ocean warms fastest over midlatitudes and the Arctic (Levitus et al. 2012, Wu et al. 2012, Armour et al. 2016).

Indeed, the pattern of ocean warming is not quite the same as the pattern of atmospheric warming. What is causing the ocean warming to follow a different pattern than the atmospheric warming, and how are the two linked?

We set out to answer these questions by exploring climate model simulations over the ongoing century. We started out by constructing a heat budget for the global ocean in the Norwegian Earth System model (NorESM), a fully coupled ocean-atmosphere model used in Norway. The model results clearly agreed with the observational data; the ocean was warming fastest in the midlatitudes and in the Arctic.

So why such a pattern? The next step was to look into the exchange of energy through the ocean surface in NorESM and in other climate models.

It turns out that the fast warming in each region had its own cause.

In the northern midlatitudes, the ocean warms quickly because more sunlight reaches the surface ocean. This happens because the subtropical high pressure region to the south expands northward and pushes away the cloudy skies.

This northward expansion of the subtropical high pressure region is really another somewhat complex story, but a short version goes roughly like this: Normally air rises in the tropics and descends in the subtropics, but global warming generally forces air upward (warm air is light) and acts against the descending motion in the subtropics. Since the air has to descend somewhere the descending branch of the circulation simply moves further north. NorESM simulations also revealed that, as a response to the circulation changes in the atmosphere, the whole subtropical ocean gyre moves slightly northward as well.

The Arctic Ocean is warming because it receives more heat from the subpolar oceans, which are warming because they are losing less heat to the warming atmosphere above. This was one of the important results of our study as we noted that the Arctic ocean warming was linked to the subpolar atmospheric warming, and not to the mid-latitude ocean warming.

In order to understand the subpolar to Arctic linkage in detail it helps to first consider the annual mean picture of ocean-atmosphere interaction at these northern latitudes. In the mean the relatively warm ocean loses heat to the relatively cold atmosphere above. However, under global warming, the atmosphere warms much faster than the ocean surface and as a result the ocean heat loss weakens. In a way the atmosphere does not need as much heat from the ocean as it did before and the ocean is happy to keep the heat. The extra heat does not remain in the subpolar oceans, but it is delivered to the Arctic by ocean circulation, not unlike the way the rapidly warming midlatitude Southern Ocean has been gaining its extra heat.

Indeed, last year Armour et al. showed that an atmospheric warming signal in the subpolar Southern Ocean moves to the rapidly warming southern midlatitudes with the equatorward ocean circulation. Our analysis of the climate model results show that locally in the rapidly warming southern midlatitudes, the atmosphere even acts against the ocean warming as the surface ocean loses an increasing amount of heat to the atmosphere.

With these results at hand we got excited. There was an oceanic linkage from the subpolar region to the Arctic that could potentially also link the atmospheric warming in these two regions.

As noted in the very beginning, one of the robust features of global warming is the relatively slow warming in the tropics and relatively fast warming in the Arctic. This phenomenon is known as Arctic amplification, and it is caused by several rather well understood mechanisms, although their relative importance is still discussed.

What is less well understood, however, is why models disagree on the amount of Arctic amplification that occurs under global warming. The most recent climate model estimates span a range between 2 to 5 times more warming in the Arctic than in the tropics.

Since one of the causes of Arctic amplification is the reduction in sea ice cover, we hypothesized that the mechanism connecting the subpolar region and the Arctic could be the following: As the ocean loses less heat to the atmosphere in the subpolar region, it remains relatively warm as the waters flow to the Arctic. The warmer waters flow northward and consequently the ocean also freezes up much further north, pushing the sea ice edge northward.

Because the atmosphere receives more heat from open water than from ice covered ocean, the atmospheric warming is amplified in the areas of sea ice loss. With this possibility in mind we went back to the climate model results and noticed that a reduced subpolar heat loss was indicative of an increase in the ocean heat loss in the Arctic, leading to strong Arctic amplification.

The ocean connected the Arctic to the subpolar region! After this realization, the pieces of the story started to fall in place.

As the atmosphere warms over the subpolar region more heat is left for the ocean to carry to the Arctic. Part of the extra heat carried by the ocean is released back to the atmosphere within the Arctic, explaining some of the differences in Arctic amplification between the models.

Read more at Science Daily

Jurassic drop in ocean oxygen lasted a million years

Pacific Ocean.

Dramatic drops in oceanic oxygen, which cause mass extinctions of sea life, come to a natural end -- but it takes about a million years.

The depletion of oxygen in the oceans is known as "anoxia," and scientists from the University of Exeter have been studying how periods of anoxia end.

They found that the drop in oxygen causes more organic carbon to be buried in sediment on the ocean floor, eventually leading to rising oxygen in the atmosphere which ultimately re-oxygenates the ocean.

Scientists believe the modern ocean is "on the edge of anoxia" -- and the Exeter researchers say it is "critical" to limit carbon emissions to prevent this.

"Once you get into a major event like anoxia, it takes a long time for the Earth's system to rebalance," said lead researcher Sarah Baker, a geographer at the University of Exeter.

"This shows the vital importance of limiting disruption to the carbon cycle to regulate the Earth system and keep it within habitable bounds."

The researchers, who also include Professor Stephen Hesselbo from the Camborne School of Mines, studied the Toarcian Oceanic Anoxic Event, which took place 183 million years ago and was characterized by a major disturbance to the global carbon cycle, depleted oxygen in Earth's oceans and mass extinction of marine life.

Numerical models predicted that increased burial of organic carbon -- due to less decomposition and more plant and marine productivity in the warmer, carbon-rich environment -- should drive a rise in atmospheric oxygen, causing the end of an anoxic event after one million years.

To test the theory, the scientists examined fossil charcoal samples to see evidence of wildfires -- as such fires would be more common in oxygen-rich times.

They found a period of increased wildfire activity started one million years after the onset of the anoxic event, and lasted for about 800,000 years.

"We argue that this major increase in fire activity was primarily driven by increased atmospheric oxygen," said Baker.

"Our study provides the first fossil-based evidence that such a change in atmospheric oxygen levels could occur in a period of one million years."

The increase in fire activity may have also helped end ocean anoxia by burning and reducing the amount of plants on land.

This is because plants can help to erode rocks on the land that contain nutrients needed for marine life -- therefore with fewer plants, fewer nutrients are available to be carried to the sea and used to support marine life in the oceans.

Less marine life -- that would use oxygen to breathe -- would mean less oxygen being used in the oceans, and could therefore help the oceans to build up a higher oxygen content, ending anoxia.

It may therefore be essential to maintain the natural functioning of wildfire activity to help regulate the Earth system in the long-term, the researchers say.

Read more at Science Daily

Ancient Mars impacts created tornado-like winds that scoured surface

An infrared image reveals strange bright streaks extending from Santa Fe crater on Mars. Researchers suggest the streaks were caused by tornado-force winds created by the impact that formed the crater.

In looking at NASA images of Mars a few years ago, Brown University geologist Peter Schultz noticed sets of strange bright streaks emanating from a few large-impact craters on the planet's surface. The streaks are odd in that they extend much farther from the craters than normal ejecta patterns, and they are only visible in thermal infrared images taken during the Martian night.

Using geological observation, laboratory impact experiments and computer modeling, Schultz and Brown graduate student Stephanie Quintana have offered a new explanation for how those streaks were formed. They show that tornado-like wind vortices -- generated by crater-forming impacts and swirling at 500 miles per hour or more -- scoured the surface and blasted away dust and small rocks to expose the blockier surfaces beneath.

"This would be like an F8 tornado sweeping across the surface," Schultz said. "These are winds on Mars that will never be seen again unless another impact."

The research is published online in the journal Icarus.

Schultz says he first saw the streaks during one of his "tours of Mars." In his downtime between projects, he pulls up random images from NASA's orbital spacecraft just to see if he might spot something interesting. In this case, he was looking at infrared images taken during the Martian nighttime by the THEMIS instrument, which flies aboard the Mars Odyssey orbiter.

The infrared images capture contrasts in heat retention on the surface. Brighter regions at night indicate surfaces that retain more heat from the previous day than surrounding surfaces, just as grassy fields cool off at night while buildings in the city remain warmer.

"You couldn't see these things at all in visible wavelength images, but in the nighttime infrared they're very bright," Schultz said. "Brightness in the infrared indicates blocky surfaces, which retain more heat than surfaces covered by powder and debris. That tells us that something came along and scoured those surfaces bare."

And Schultz had an idea what that something might be. He has been studying impacts and impact processes for years using NASA's Vertical Gun Range, a high-powered cannon that can fire projectiles at speeds up to 15,000 miles per hour.

"We had been seeing some things in experiments we thought might cause these streaks," he said.

When an asteroid or other body strikes a planet at high speed, tons of material from both the impactor and the target surface are instantly vaporized. Schultz's experiments showed that vapor plumes travel outward from an impact point, just above the impact surface, at incredible speeds. Scaling laboratory impacts to the size of those on Mars, a vapor plume's speed would be supersonic. And it would interact with the Martian atmosphere to generate powerful winds.

The plume and its associated winds on their own didn't cause the strange streaks, however. The plumes generally travel just above the surface, which prevents the kind of deep scouring seen in the streaked areas. But Schultz and Quintana showed that when the plume strikes a raised surface feature, it disturbs the flow and causes powerful tornadic vortices to form and drop to the surface. And those vortices, the researchers say, are responsible for scouring the narrow streaks.

Schultz and Quintana showed that the streaks are nearly always seen in conjunction with raised surface features. Very often, for example, they are associated with the raised ridges of smaller impact craters that were already in place when the larger impact occurred. As the plume raced outward from the larger impact, it encountered the small crater rim, leaving bright twin streaks on the downwind side.

"Where these vortices encounter the surface, they sweep away the small particles that sit loose on the surface, exposing the bigger blocky material underneath, and that's what gives us these streaks," Schultz said.

Schultz says the streaks could prove useful in establishing rates of erosion and dust deposition in areas where the streaks are found.

"We know these formed at the same time as these large craters, and we can date the age of the craters," Schultz said. "So now we have a template for looking at erosion."

But with more research, the streaks could eventually reveal much more than that. From a preliminary survey of the planet, the researchers say the streaks appear to form around craters in the ballpark of 20 kilometers across. But they don't appear in all such craters. Why they form in some places and not others could provide information about the Martian surface at the time of the impact.

Read more at Science Daily

Mars May Have Been Born in the Asteroid Belt

Mars and Earth have very different histories. A simple example: Earth is mostly covered with water, while Mars lost its water in the distant past. But scientists have also known that the elements on Mars have different isotopes, or atomic masses, particularly for chromium, titanium, and oxygen.

A new paper published in the journal Earth and Planetary Science Letters argues these compositional differences arose because Mars formed in a different part of the solar system than where it is now located. Instead of being between the sun and the asteroid belt, the paper argues Mars formed within the asteroid belt before migrating somewhat closer to the sun to where it is now. The migration occurred, the paper says, due to Mars gravitationally interacting with planetesimals – small bodies such as asteroids – within the belt.

"Since Mars is more massive than the planetesimals, it tends to lose energy when it scatters these planetesimals because it passes them to Jupiter, which then ejects them from the solar system," Ramon Brasser, lead author and associate professor at the Tokyo Institute of Technology's Earth-Life Science Institute, wrote in an e-mail.

The prevailing theory of the solar system's formation suggests that the sun and its planets formed after a cloud of gas and dust was gravitationally compressed, perhaps from a passing star. Over time, small gas and dust particles stuck together, forming the sun and the modern-day planets.

There is still some debate about whether planets migrated during this process. Previously, scientists theorized that the rocky planets of Mercury, Venus, Earth and Mars collected less gas than the gas giants of Jupiter, Uranus, Saturn and Neptune because the rocky planets were closer to the sun. It was thought that the sun's radiation blew most of the gas into the outer solar system. However, scientists have spotted several Jupiter-sized exoplanets very close to their host stars, which could imply a different formation process that included migration.

In this case, the team tested their hypothesis about Mars' formation by running simplified computer scenarios of the formation of the terrestrial, or rocky, planets, and also looked at samples from Earth, Mars, the moon, and Vesta, which is an asteroid. "We looked for Mars analogs that accreted material in a portion of the disc which Earth did not, and we concluded that the only way to do this is to form Mars far from the Sun, in the inner asteroid belt," Brasser wrote.

Based on previous work from the University of Chicago's Nicolas Dauphas and colleagues, the simulations used by Brasser's team started with sub-Mars planetary embryos. The simulations suggest that Mars grew quickly, then lost access to most of the material, such as gas and dust, to grow within 5-10 million years after the solar system formed. It settled into its current orbit about 120 million years after the solar system's birth, at which point its liquid surface hardened into a crust.

Mars likely had liquid water running on its surface in the ancient past, but over time its atmosphere thinned and made it impossible for water to exist in liquid form on the surface. Brasser said, however, that the origins of Mars would not influence that process. While Mars was formed in a colder environment (since the asteroid belt is further from the sun), it was only there for a few million years before migrating to its current location.

Read more at Discovery News

Baleen whales' ancestors were toothy suction feeders

This photo shows members of the excavation team digging around the skeleton of Mystacodon selenensis at the Media Luna locality in the Pisco Basin, Peru.

Modern whales' ancestors probably hunted and chased down prey, but somehow, those fish-eating hunters evolved into filter-feeding leviathans. An analysis of a 36.4-million-year-old whale fossil suggests that before baleen whales lost their teeth, they were suction feeders that most likely dove down and sucked prey into their large mouths. The study published on May 11 in Current Biology also shows that whales most likely lost the hind limbs that stuck out from their bodies more recently than previously estimated.

The specimen, which researchers unearthed in the Pisco Basin in southern Peru, is the oldest known member of the mysticete group, which includes the blue whale, the humpback whale, and the right whale. At 3.75-4 meters long, this late Eocene animal was smaller than any of its living relatives, but the most important difference was in the skull. Modern mysticetes have keratin fibers -- called baleen -- in place of teeth that allow them to trap and feed on tiny marine animals such as shrimp. However, the newly described whale has teeth, so the paleontologists dubbed it Mystacodon, meaning "toothed mysticete."

"This find by our Peruvian colleague Mario Urbina fills a major gap in the history of the group, and it provides clues about the ecology of early mysticetes," says paleontologist and study co-author Olivier Lambert of the Royal Belgian Institute of Natural Sciences. "For example, this early mysticete retains teeth, and from what we observed of its skull, we think that it displays an early specialization for suction feeding and maybe for bottom feeding."

Mystacodon's teeth exhibit a pattern of wear that differs from more archaic whales, the basilosaurids. Many basilosaurids were probably active hunters, similar to modern orcas, with mouths that were suited for biting and attacking, but Mystacodon has a mouth more suited for sucking in smaller animals, leading the researchers to conclude that Mystacodon most likely represents an intermediate step between raptorial and filter feeding and between the ancient basilosaurids and modern mysticetes.

"For a long time, Creationists took the evolution of whales as a favorite target to say that, 'Well, you say that whales come from a terrestrial ancestor, but you can't prove it. You can't show the intermediary steps in this evolution,'" says Lambert. "And that was true, maybe thirty years ago. But now, with more teams working on the subject, we have a far more convincing scenario."

Mystacodon bolsters that argument by displaying features of both basilosaurids and mysticetes. "It perfectly matches what we would have expected as an intermediary step between ancestral basilosaurids and more derived mysticetes,"says Lambert. "This nicely demonstrates the predictive power of the theory of evolution."

Lambert and his colleagues think that Mystacodon may have started suction feeding in response to ecological changes. In illustrated reconstructions, Mystacodon is depicted diving down to the sea floor in a shallow cove, but based on this initial analysis, the researchers aren't sure to which extent Mystacodon was adapted to bottom feeding. "We will look inside the bone to see if we can find some changes that may be correlated with this specialized behavior," says Lambert. "Among marine mammals, when a slow-swimming animal is living close to the sea floor, generally the bone is much more compact, and this is something we want to test with these early mysticetes."

The fossil's pelvis offered another surprise: Mystacodon had fully articulated, tiny vestigial hind limbs that would have stuck out away from the whale's body. Previously, paleontologists had thought that whales lost the hip articulation during the basilosaurid phase of their evolution, before baleen whales and modern toothed whales diverged. Though Mystacodon's hind limbs were already tiny and well down the path toward being vestigial and useless, their articulation with the pelvis suggests that mysticetes and modern toothed whales may have lost this feature independently.

Read more at Science Daily

Millennia-Old Mummies Are Under Threat From Yemen's Civil War

Yemen's war has claimed thousands of lives and pushed millions to the brink of famine. Now the conflict threatens to erase a unique part of the country's ancient history.

A collection of millennia-old mummies at Sanaa University Museum in the Yemeni capital could face destruction as a result of the fighting.

With electricity intermittent at best and the country's ports under blockade, experts are fighting to save the 12 mummies in the face of heat, humidity, and a lack of preservative chemicals.

Some of the remains, from pagan kingdoms that ruled the region around 400 BC, still have teeth and strands of hair.

"These mummies are tangible evidence of a nation's history," said Abdulrahman Jarallah, head of the archaeology department at Sanaa University, but "even our mummies are affected by the war."

"Mummies need a suitable, controlled environment and regular care, including sanitization every six months," he told AFP. "Some of them have begun to decay as we cannot secure electricity and the proper preservative chemicals, and we're struggling to control the stench."

"We're concerned both for the conservation of the mummies and for the health of those handling them," Jarallah said.

The mummies are among a host of priceless ancient remains threatened by conflicts across the region.

From Syria's Palmyra to Libya's Leptis Magna, millennia-old historical remains face looting and destruction in various parts of the Middle East.

The Islamic State group systematically demolished pre-Islamic monuments in Syria and Iraq after seizing swathes of both countries in 2014, looting and selling smaller pieces on the black market to fund their rule.

Swiss authorities last year seized cultural relics looted from Yemen, Syria, and Libya that had been stored in Geneva's free ports — highly secured warehouses where valuables can be stashed tax-free with few questions asked.

Supplies, Experts Needed

Old Sanaa, inscribed on UNESCO's World Heritage List since 1986, faces other dangers.

Perched 2,300 meters (7,500 feet) up in Yemen's western mountains, it has been continuously inhabited for over 2,500 years and is home to some of the earliest Islamic architecture.

With more than 100 mosques and 6,000 houses built before the 11th century, the old city is famed for its multi-storied homes of red basalt rock, with arched windows decorated with white latticework.

But months after a Saudi-led coalition intervened against Iran-backed Houthi rebels in March 2015, UNESCO added the ancient city to its List of World Heritage in Danger.

In June that year, a bombing in the old city killed five people and destroyed a section including several houses and an Ottoman fort.

Witnesses blamed an air strike by the Saudi-led coalition on the rebel-held capital.

No party has claimed responsibility for the strike.

The coalition has also imposed an air and naval blockade on Houthi-controlled Red Sea ports that are crucial entry points for food and aid.

The UN estimates 60 percent of Yemen's population is at risk of famine.

Yemeni archaeologists have appealed to both local authorities and international organizations to help preserve Yemen's mummies by easing the flow of supplies and personnel.

"We can already see the mummies suffering the effects of a long period of not having been properly maintained," Sanaa University Museum restoration specialist Fahmi al-Ariqi told AFP.

"We need supplies and experts in this sort of maintenance to work with us to save the 12 mummies here at the university, as well as another dozen at the National Museum in Sanaa."

Read more at Discovery News

The Trail of Antibiotic-Resistant Superbugs Leads Back to the First Land Animals

Early life as it is believed to have looked 335 million years ago, well before the age of the dinosaurs. Ancestors of hospital pathogens are now believed to have lived in the guts of these ancient land animals.

One of today’s biggest biohazards may have its roots in the days before the dinosaurs, when animals first started crawling onto land. 

Enterococcus bacteria are hard-to-kill bugs that flourish in the digestive systems of nearly all land animals. They’re also able to survive long periods without food or water and withstand many of the disinfectants used in hospitals — traits they started to acquire shortly after emerging more than 425 million years ago, researchers at Harvard and the Massachusetts Institute of Technology reported today.

Knowing how they got that tough can help scientists figure out new ways to protect people from the harmful infections they produce, said Ashley Earl, a microbiologist and head of the bacterial genomics group at the Broad Institute, a joint venture of Harvard and MIT.

The fact that enterococcus species are so widespread “suggests an early origin,” Earl said. The researchers then used what geneticists call a molecular clock, a technique used to estimate when an evolutionary change occurred.

“Using genomic data, we can make best guesses for the timing at which different species likely went their separate ways from their last common ancestor and became something new,” she said. And when she and her partners compared those estimates to the fossil record, which shows when other species emerged, “We start to see this really interesting pattern that kind of fits beautifully for the expansion and the reductions of terrestrial animal life.”

“It fits really nicely with the dating we get from the genomic information,” she said. “That sort of lands the timing for the very first emergence of enterococcus lands at right around the time that terrestrialization first began,” Earl said.

The findings were published in the scientific journal Cell. The research team included scientist from Massachusetts Eye and Ear and the Harvard-wide Program on Antibiotic Resistance. 

The rise of drug-resistant bacteria has become a leading worry for doctors and scientists, raising fears that old killers like pneumonia or tuberculosis could make a comeback. Modern enterococci are a common source of hospital illnesses; they can take root in the blood, urinary tract, and the lining of the heart and fight off several common antibiotics.

Bacteria excreted from the guts of marine life find themselves in a “comparatively hospitable” water, where those excreted from land animals “would experience comparative isolation, starvation, desiccation, and possibly extinction.” Those excreted by land animals risk drying out or starving to death — but the ones that could survive those threats passed those traits on to their descendants, producing the hardy microbes that concern doctors today.

Over the course of the study, the scientists compiled what Earl called a “parts list” of genes that might reveal the bacteria’s vulnerabilities.

“We want to take those strengths and turn them into their weaknesses,” she said. She compared the bacteria to a tank — a dangerous, durable piece of military hardware.

Read more at Discovery News

Watery Atmosphere Discovered on Neptune-Like Exoplanet

The atmosphere of the distant “warm Neptune” HAT-P-26b, illustrated here, is unexpectedly primitive, composed primarily of hydrogen and helium. By combining observations from NASA’s Hubble and Spitzer space telescopes, researchers determined that, unlike Neptune and Uranus, the exoplanet has relatively low metallicity, an indication of the how rich the planet is in all elements heavier than hydrogen and helium.

While the number of known exoplanets continues to soar, uncovering specific details about these distant worlds has been more challenging. The delicate task of finding out the specifics of an exoplanet’s atmosphere can provide data about the planet’s potential habitability, as well as clues to how the exoplanet formed.

A new study of a Neptune-size world has revealed a surprisingly “primitive atmosphere” composed almost entirely of hydrogen and helium, with water vapor and possible clouds. Scientists say this finding could provide an important breakthrough in understanding how planets form, and how atmospheres can vary between exoplanets with different masses.

“Astronomers have just begun to investigate the atmospheres of these distant Neptune-mass planets, and almost right away we found an example that goes against the trend in our solar system,” said Hannah Wakeford from NASA’s Goddard Space Flight Center. “This kind of unexpected result is why I really love exploring the atmospheres of alien planets.”

Wakeford, along with David Sing from the University of Exeter and a team of other researchers, looked at the exoplanet HAT-P-26b, which was discovered in 2010 and is located about 430 light years from Earth. It is a “warm” world that orbits relatively close to its star, circling it every 4.23 days.

Using observations from the Hubble Space Telescope and the Spitzer Space Telescope, the researchers found strong indications of water as well as a possible cloud layer with a unique makeup in the atmosphere of HAT-P-26b.

“What we have detected is a strong water absorption feature with some evidence of a cloud layer deep in the atmosphere at the base altitude of the measurements we have made,” Wakeford told Seeker. “This cloud would not be made of water due to the high temperature of the atmosphere but would instead be more exotic and composed most likely of Na2S (di-sodium sulfide). At the altitudes we probed with these observations and the strong water vapor absorption signature, this is a relatively cloudless portion of the atmosphere.”

Measuring the abundance of atmospheric water provides information about the proportion of elements in the atmosphere that are heavier than hydrogen and helium, a value astronomers refer to as the metallicity. Surprisingly, it was lower than expected, only about 4.8 times that of the Sun — less than that of Neptune and Uranus, for example, and closer to the value for Jupiter.

“HAT-P-26b is the first to buck the trend seen with our solar system and other exoplanets, which suggest that lower mass planets have higher metallicities,” Wakeford said via email. “As the first to buck this trend, HAT-P-26b will be an important marker in our understanding of planetary formation scenarios.”

When a distant planet transits, or passes in front its host star, starlight gets filtered through the planet’s atmosphere. Using a spectrometer, astronomers can measure the light to see what elements are present in the planet’s atmosphere.

“This is the strongest water absorption feature that has measured for an exoplanet of this size,” Wakeford said. “Additionally, what is most important is that we have been able to use this detection to approximate the overall metallicity of the atmosphere based on the water abundance, and compared to similar sized planets in our solar system we find that HAT-P-26b has a much lower metallicity.”

This suggests that it formed differently — perhaps closer to the star or late in the lifetime of the disk around the star — compared to Neptune.

In our own solar system, the metallicity in Jupiter, which is five times greater than the Sun, and Saturn (10 times), suggest that these “gas giants” are made almost entirely of hydrogen and helium. Neptune and Uranus, however, are richer in the heavier elements, with metallicities of about 100 times that of the sun.

Read more at Discovery News