Climate, life and the movement of continents: New connections

Planktonic foraminifera, such as these collected in the Gulf of Mexico, form the base of many marine and aquatic food chains. Upon death, their skeletons settle on the seafloor to form sedimentary rock such as limestone and chalk. Pressed together in sufficient quantities, such sedimentary rock could have a lubricating effect on the movement of continental plates.

A new study by The University of Texas at Austin has demonstrated a possible link between life on Earth and the movement of continents. The findings show that sediment, which is often comprised from pieces of dead organisms, could play a key role in determining the speed of continental drift. In addition to challenging existing ideas about how plates interact, the findings are important because they describe potential feedback mechanisms between tectonic movement, climate and life on Earth.

The study, published Nov. 15 in Earth and Planetary Science Letters, describes how sediment moving under or subducting beneath tectonic plates could regulate the movement of the plates and may even play a role in the rapid rise of mountain ranges and growth of continental crust.

The research was led by Thorsten Becker, a professor at the UT Jackson School of Geosciences and research scientist at its Institute for Geophysics (UTIG), and Whitney Behr, a research fellow at the Jackson School and professor at ETH Zurich in Switzerland.

Sediment is created when wind, water and ice erode existing rock or when the shells and skeletons of microscopic organisms like plankton accumulate on the seafloor. Sediment entering subduction zones has long been known to influence geological activity such as the frequency of earthquakes, but until now it was thought to have little influence on continental movement. That's because the speed of subduction was believed to be dependent on the strength of the subducting plate as it bends and slides into the viscous mantle, the semi molten layer of rock beneath the Earth's crust. Continental movement is driven by one plate sinking under another so, in this scenario, the strength of the portion of the plate being pulled into the Earth's mantle (and the energy required to bend it) would be the primary control for the speed of the plate movement, with sediment having little effect.

However, prior research involving UTIG scientists had shown the subducting plates may be weaker and more sensitive to other influences than previously thought. This led researchers to look for other mechanisms that might impact plate velocity. They estimated how different types of rock might affect the plate interface ¬- the boundary where subducting plates meet. Subsequent modelling showed that rock made of sediment can create a lubricating effect between plates, accelerating subduction and increasing plate velocity.

This mechanism could set in motion a complex feedback loop. As plate velocity increases, there would be less time for sediment to accumulate, so the amount of subducting sediment would be reduced. This leads to slower subduction, which may allow for mountains to grow at plate boundaries as the force of the two plates running into each other causes uplift. In turn, erosion of those mountains by wind, water and other forces can produce more sediments which feed back into the subduction zone and restart the cycle by increasing the speed of subduction.

"The feedback mechanisms serve to regulate subduction speeds such that they don't 'runaway' with extremely fast velocities," said Behr.

Behr and Becker's new model also offers a compelling explanation for variations found in plate speed, such as India's dramatic northward acceleration some 70 million years ago. The authors propose that as India moved through equatorial seas teeming with life, an abundance of sedimentary rock formed by organic matter settling on the seafloor created a lubricating effect in the subducting plate. India's march north accelerated from a stately 5 centimeters per year (about 2 inches) to an eye-watering 16 centimeters per year (about 6 inches). As the continent accelerated the amount of sediment being subducted decreased and India slowed before finally colliding with Asia.

Behr and Becker suggest these feedback mechanisms would have been very different in the early Earth before the formation of continents and the emergence of life. Although their model does not examine the origins of these feedback mechanisms, it does raise compelling questions about the interaction between continental movement and life on Earth.

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Overflowing crater lakes carved canyons across Mars

Jezero crater is a paleolake and potential landing site for NASA’s Mars 2020 rover mission to look for past life. The outlet canyon carved by overflow flooding is visible in the upper right side of the crater. Ancient rivers carved the inlets on the right side of the crater.

Today, most of the water on Mars is locked away in frozen ice caps. But billions of years ago it flowed freely across the surface, forming rushing rivers that emptied into craters, forming lakes and seas. New research led by The University of Texas at Austin has found evidence that sometimes the lakes would take on so much water that they overflowed and burst from the sides of their basins, creating catastrophic floods that carved canyons very rapidly, perhaps in a matter of weeks.

The findings suggest that catastrophic geologic processes may have had a major role in shaping the landscape of Mars and other worlds without plate tectonics, said lead author Tim Goudge, a postdoctoral researcher at the UT Jackson School of Geosciences who will be starting as an assistant professor at the school in 2019.

"These breached lakes are fairly common and some of them are quite large, some as large as the Caspian Sea," said Goudge. "So we think this style of catastrophic overflow flooding and rapid incision of outlet canyons was probably quite important on early Mars' surface."

The research was published Nov. 16 in the journal Geology. Co-authors include NASA scientist Caleb Fassett and Jackson School Professor and Associate Dean of Research David Mohrig.

From studying rock formations from satellite images, scientists know that hundreds of craters across the surface of Mars were once filled with water. More than 200 of these "paleolakes" have outlet canyons tens to hundreds of kilometers long and several kilometers wide carved by water flowing from the ancient lakes.

However, until this study, it was unknown whether the canyons were gradually carved over millions of years or carved rapidly by single floods.

Using high-resolution photos taken by NASA's Mars Reconnaissance Orbiter satellite, the researchers examined the topography of the outlets and the crater rims and found a correlation between the size of the outlet and the volume of water expected to be released during a large flooding event. If the outlet had instead been gradually whittled away over time, the relationship between water volume and outlet size likely wouldn't hold, Goudge said.

In total, the researchers examined 24 paleolakes and their outlet canyons across the Red Planet. One of the paleolakes examined in the study, Jezero Crater, is a potential landing site for NASA's Mars 2020 rover mission to look for signs of past life. Goudge and Fassett proposed the crater as a landing site based on prior studies that found it held water for long periods in Mars' past.

While massive floods flowing from Martian craters might sound like a scene in a science fiction novel, a similar process occurs on Earth when lakes dammed by glaciers break through their icy barriers. The researchers found that the similarity is more than superficial. As long as gravity is accounted for, floods create outlets with similar shapes whether on Earth or Mars.

"This tells us that things that are different between the planets are not as important as the basic physics of the overflow process and the size of the basin," Goudge said. "You can learn more about this process by comparing different planets as opposed to just thinking about what's occurring on Earth or what's occurring on Mars."

Although big floods on Mars and Earth are governed by the same mechanics, they fit into different geological paradigms. On Earth, the slow-and-steady motion of tectonic plates dramatically changes the planet's surface over millions of years. In contrast, the lack of plate tectonics on Mars means that cataclysmic events -- like floods and asteroid impacts -- quickly create changes that can amount to near permanent changes in the landscape.

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Kilogram, ampere, kelvin and mole redefined

The International Prototype of the Kilogram (IPK) is held in an underground vault at the International Bureau of Weights and Measures (BIPM), located in Sèvres, near Paris. Following the decision to redefine the SI kilogram starting 20th May 2019, the definition of the kilogram will no longer be based on the physical artefact called the International Prototype but rather on a constant of physics, as are the other seven base units of the SI. The redefinition of the kilogram marks the end of artefacts used to define our measurement units.

Today, in a landmark decision, representatives from 60 countries voted to redefine the International System of Units (SI), changing the world's definition of the kilogram, the ampere, the kelvin and the mole, forever.

The decision, made at the General Conference on Weights and Measures in Versailles, France, which is organised by the International Bureau of Weights and Measures (BIPM), means that all SI units will now be defined in terms of constants that describe the natural world. This will assure the future stability of the SI and open the opportunity for the use of new technologies, including quantum technologies, to implement the definitions.

The changes, which will come into force on 20 May 2019, will bring an end to the use of physical objects to define measurement units.

The definition of the kilogram for more than 130 years, the International Prototype of the Kilogram (IPK), a cylinder of a platinum alloy stored at the BIPM in France, will now be retired. It will be replaced by the Planck constant -- the fundamental constant of quantum physics. While the stability of the IPK could only be confirmed by comparisons with identical copies, a difficult and potentially inaccurate process, the Planck constant is ready for use everywhere and always.

"The SI redefinition is a landmark moment in scientific progress," said Martin Milton, Director, International Bureau of Weights and Measures (BIPM). "Using the fundamental constants we observe in nature as a foundation for important concepts, such as mass and time, means that we have a stable foundation from which to advance our scientific understanding, develop new technologies and address some of society's greatest challenges."

"Today marks the culmination of decades of work by measurement scientists around the world, the significance of which is immense," said Barry Inglis, Director of the International Committee for Weights and Measures. "We will now no longer be bound by the limitations of objects in our measurement of the world, but have universality accessible units that can pave the way to even greater accuracy, and even accelerate scientific advancement."

The new definitions impact four of the seven base units of the SI: the kilogram, ampere, kelvin and mole; and all units derived from them, such as the volt, ohm and joule.

• The kilogram -- will be defined by the Planck constant (h)
• The ampere -- will be defined by the elementary electrical charge (e)
• The kelvin -- will be defined by the Boltzmann constant (k)
• The mole -- will be defined by the Avogadro constant (NA)

Although the size of these units will not change (a kilogram will still be a kilogram), the four redefined units will join the second, the metre and the candela to ensure that the set of SI base units will continue to be both stable and useful. The revised SI will maintain its relevance by facilitating technical innovations. Just as the redefinition of the second in 1967 provided the basis for technology that has transformed how we communicate across the globe, through GPS and the internet, the new changes will have wide-reaching impact in science, technology, trade, health and the environment, among many other sectors.

From Science Daily

Trans-galactic streamers feeding most luminous galaxy in the universe

Artist impression of W2246-0526, the most luminous known galaxy, and three companion galaxies.

The most luminous galaxy in the universe has been caught in the act of stripping away nearly half the mass from at least three of its smaller neighbors, according to a new study published in the journal Science. The light from this galaxy, known as W2246-0526, took 12.4 billion years to reach us, so we are seeing it as it was when our universe was only about a tenth of its present age.

New observations with the Atacama Large Millimeter/submillimeter Array (ALMA) reveal distinct streamers of material being pulled from three smaller galaxies and flowing into the more massive galaxy, which was discovered in 2015 by NASA's space-based Wide-field Infrared Survey Explorer (WISE). It is by no means the largest or most massive galaxy we know of, but it is unrivaled in its brightness, emitting as much infrared light as 350 trillion Suns.

The connecting tendrils between the galaxies contain about as much material as the galaxies themselves. ALMA's amazing resolution and sensitivity allowed the researchers to detect these remarkably faint and distant trans-galactic streamers.

"We knew from previous data that there were three companion galaxies, but there was no evidence of interactions between these neighbors and the central source," said Tanio Díaz-Santos of the Universidad Diego Portales in Santiago, Chile, lead author of the study. "We weren't looking for cannibalistic behavior and weren't expecting it, but this deep dive with the ALMA observatory makes it very clear."

Galactic cannibalism is not uncommon, though this is the most distant galaxy in which such behavior has been observed and the study authors are not aware of any other direct images of a galaxy simultaneously feeding on material from multiple sources at those early cosmic times.

The researchers emphasize that the amount of gas being devoured by W2246-0526 is enough to keep it forming stars and feeding its central black hole for hundreds of millions of years.

This galaxy's startling luminosity is not due to its individual stars. Rather, its brightness is powered by a tiny, yet fantastically energetic disk of gas that is being superheated as it spirals in on the supermassive black hole. The light from this blazingly bright accretion disk is then absorbed by the surrounding dust, which re-emits the energy as infrared light.

This extreme infrared radiation makes this galaxy one of a rare class of quasars known as Hot, Dust-Obscured Galaxies or Hot DOGs. Only about one out of every 3,000 quasars observed by WISE belongs to this class.

Much of the dust and gas being siphoned away from the three smaller galaxies is likely being converted into new stars and feeding the larger galaxy's central black hole. This galaxy's gluttony, however, may lead to its self-destruction. Previous research suggests that the energy of the AGN will ultimately jettison much, if not all of the galaxy's star-forming fuel.

Read more at Science Daily

Solar panels for yeast cell biofactories

The researcher's model of a yeast cell (magenta) with semiconductor nanoparticles (purple) attached to its surface (left) corresponds with their SEM analysis of the completed biohybrid system (right). The semiconductors capture electrons from light and hand them over to the cell where they drive the shikimic acid metabolic pathway.

Genetically engineered microbes such as bacteria and yeasts have long been used as living factories to produce drugs and fine chemicals. More recently, researchers have started to combine bacteria with semiconductor technology that, similar to solar panels on the roof of a house, harvests energy from light and, when coupled to the microbes' surface, can boost their biosynthetic potential.

The first "biological-inorganic hybrid systems" (biohybrids) mostly focused on the fixation of atmospheric carbon dioxide and the production of alternative energies, and although promising, they also revealed key challenges. For example, semiconductors, which are made from toxic metals, thus far are assembled directly on bacterial cells and often harm them in the process. In addition, the initial focus on carbon-fixing microbes has limited the range of products to relatively simple molecules; if biohybrids could be created based on microorganisms equipped with more complex metabolisms, it would open new paths for the production of a much larger range of chemicals useful for many applications.

Now, in a study in Science, a multidisciplinary team led by Core Faculty member Neel Joshi and Postdoctoral Fellows Junling Guo and Miguel Suástegui at Harvard's Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences (SEAS) presents a highly adaptable solution to these challenges.

"While our strategy conceptually builds on earlier bacterial biohybrid systems that were engineered by our collaborator Daniel Nocera and others, we expanded the concept to yeast -- an organism that is already an industrial workhorse and is genetically easy to manipulate -- with a modular semiconductor component that provides biochemical energy to yeast's metabolic machinery without being toxic," said Joshi, Ph.D., who is a Core Faculty member at the Wyss Institute and Associate Professor at SEAS. Co-author Nocera is the Patterson Rockwood Professor of Energy at Harvard University. As a result of the combined manipulations, yeasts' ability to produce shikimic acid, an important precursor of the anti-viral drug Tamiflu, several other medicines, nutraceuticals, and fine chemicals, was significantly enhanced.

The baker's yeast Saccharomyces cerevisiae naturally produces shikimic acid to generate some of its building blocks for the synthesis of proteins and other biomolecules. However, by genetically modifying the yeast's central metabolism, the researchers enabled the cells to funnel more of the carbon atoms that their main nutrient source, the sugar glucose, contains into the pathway that produces shikimic acid and prevent the loss of carbon to alternative pathways by disrupting one of them.

"In principle, the increased 'carbon flux' towards shikimic acid should lead to higher product levels, but in normal yeast cells, the alternative pathway that we disrupted to increase yields, importantly, also provides the energy needed to fuel the final step of shikimic acid production," said co-first author Miguel Suástegui, Ph.D., a chemical engineer and former Postdoctoral Fellow in Joshi's team and now Scientist at Joyn Bio LLC. To boost the more carbon-effective but energy-depleted engineered shikimic acid pathway, "we hypothesized that we could generate the relevant energy-carrying molecule NADPH instead in a biohybrid approach with light-harvesting semiconductors."

Toward this goal, Suástegui collaborated with Junling Guo, Ph.D., the study's other co-corresponding and co-first author and presently a Postdoctoral Fellow with experience in chemistry and materials science in Joshi's lab. They designed a strategy that uses indium phosphide as a semiconductor material. "To make the semiconductor component truly modular and non-toxic, we coated indium phosphide nanoparticles with a natural polyphenol-based "glue," which allowed us to attach them to the surface of yeast cells while at the same time insulating the cells from the metal's toxicity," said Guo.

When tethered to the cell surface and illuminated, the semiconductor nanoparticles harvest electrons (energy) from light and hand them over to the yeast cells, which shuttle them across their cell walls into their cytoplasm. There the electrons elevate the levels of NADPH molecules, which now can fuel shikimic acid biosynthesis. "The yeast biohybrid cells, when kept in the dark, mostly produced simpler organic molecules such as glycerol and ethanol; but when exposed to light, they readily switched into shikimic acid production mode with an 11-fold increase in product levels, showing us that the energy transfer from light into the cell works very efficiently," said Joshi.

"This scalable approach creates an entirely new design space for future biohybrid technologies. In future efforts, the nature of semiconductors and the type of genetically engineered yeast cells can be varied in a plug-and-play fashion to expand the type of manufacturing processes and range of bioproducts," said Guo.

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Earth's magnetotail: First-ever views of elusive energy explosion

Artist depiction of the MMS spacecraft that provided the first view of magnetic reconnection.

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection" -- the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion -- in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can have -- sparking auroras and possibly wreaking havoc on power grids in the case of extremely large events -- but they haven't completely understood the details. In a study published in the journal Science, the scientists outline the first views of the critical details of how this energy conversion process works in the Earth's magnetotail.

"This was a remarkable event," said Roy Torbert of the Space Science Center at UNH and deputy principal investigator for NASA's Magnetospheric Multiscale mission, or MMS. "We have long known that it occurs in two types of regimes: asymmetric and symmetric but this is the first time we have seen a symmetric process."

Magnetic reconnection occurs around Earth every day due to magnetic field lines twisting and reconnecting. It happens in different ways in different places, with different effects. Particles in highly ionized gases, called plasmas, can be converted and cause a single powerful explosion, just a fraction of a second long, that can lead to strong streams of electrons flying away at supersonic speeds. The view, which was detected as part of the scientists' work on the MMS mission, had enough resolution to reveal its differences from other reconnection regimes around the planet like the asymmetric process found in the magnetopause around Earth which is closer to the sun.

"This is important because the more we know and understand about these reconnections," said Torbert, "the more we can prepare for extreme events that are possible from reconnections around the Earth or anywhere in the universe."

Magnetic reconnection also happens on the sun and across the universe -- in all cases forcefully shooting out particles and driving much of the change we see in dynamic space environments -- so learning about it around Earth also helps us understand reconnection in other places in the universe which cannot be reached by spacecraft. The more we understand about different types of magnetic reconnection, the more we can piece together what such explosions might look like elsewhere.

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Deep-time evolution of animal life on islands

A reconstruction of the Eocene of Turkey, where the small marsupial was found. Besides the marsupials, the fauna includes embrithopods (the rhino-like animals of the background, more related to elephants and sea cows), pleuraspidotheriids (primitive ungulates with a deer/dog look), a group of primates called omomyids, bats, tortoises and crocodiles.

Islands have been vital laboratories for advancing evolutionary theory since the pioneering work of Charles Darwin and Alfred Russel Wallace in the 19th century.

Now, a new paper appearing in PLOS ONE from an international team of investigators describes two new fossil relatives of marsupials that shed light on how a unique island ecosystem evolved some 43 million years ago during the Eocene.

"Evolution in many ways is easier to study in an island context than on a large continent like North America because it's a simpler ecosystem," said coauthor K. Christopher Beard, Distinguished Foundation Professor of Ecology and Evolutionary Biology at the University of Kansas and senior curator with KU's Biodiversity Institute and Natural History Museum. "Evolutionary biologists have been focusing on islands ever since Darwin and Wallace independently formulated their ideas about evolution based on their observations of plants and animals living on the Galapagos and the Malay archipelago, which is modern Indonesia."

However, Beard said a poor fossil record for animals living on islands through "deep time," or across a multimillion-year time frame, has hampered our understanding of exactly how island ecosystems are assembled. The new paper describes two new fossil species, identified from their teeth, that inhabited the Pontide region of modern-day north-central Turkey.

During the Eocene the Pontide region was an island in a larger version of the modern Mediterranean Sea called Tethys. At that time, Africa and Eurasia were not connected as they are today in the Middle East, but Africa was drifting northward due to plate tectonics and would eventually collide with Eurasia millions of years later. The Pontide region was sandwiched between these converging continents. This geological setting makes the Pontide region similar to the island of Sulawesi in the Indonesian archipelago, which is similarly sandwiched between the converging continents of Asia and Australia.

"No other ecosystem on the face of the planet from any time period matches what we're finding in the Eocene of Turkey -- it's a completely unique mammalian ecosystem much like Madagascar is today," he said. "But how did this island biota develop over time? You need fossils and time depth to see that. We're able here to study in great detail how this ancient island evolved -- where the different animals came from, how they got there and when they got there. Once they got there, some of these mammals, including one of the new marsupial lineages we've discovered, were able to diversify on the island. Most of the Eocene mammals on the Pontide island seem to have gotten there by swimming or rafting across parts of the Tethys Sea, instead of getting stranded on the island when it got separated from adjacent parts of Eurasia."

Beard's collaborators in the research were Grégoire Métais of the Museum national d'Histoire naturelle in Paris, John R. Kappelman of the University of Texas, Alexis Licht of the University of Washington, Faruk Ocakog?lu of Eskis?ehir Osmangazi University in Turkey, and KU's Pauline M.C. Coster and Michael H. Taylor.

In the Pontide marsupial fossils -- which have no living descendants -- the team found evidence that distinctive forms of life that develop on islands are ill-fated in general, given enough time.

"One thing we know for sure is that the incredibly interesting and unique Eocene biota that occurred on this island in what is now Turkey at some point was totally eradicated," Beard said. "It was eradicated when the island was reconnected to mainland Eurasia and more cosmopolitan animals were able to access it for the first time, driving the weird island biota to extinction. The message for conservation biology today is that island ecosystems are inherently ephemeral on the grand scale of macroevolutionary time. Today, conservation biologists are concerned about many endangered taxa on islands. The ugly truth that paleontology provides is that, given enough time, most island faunas are doomed to extinction. They're cul-de-sacs of evolution -- even though they're wonderful places to study processes of evolution."

Beard said the two newly described fossil marsupials -- Galatiadelphys minor and Orhaniyeia nauta -- lived near the top of the food chain on the Pontide of the Eocene, because mammalian carnivores were unable to reach the small island.

"One of weirdest things about the island fauna from the Pontides is that there are no true mammalian carnivores," he stated. "There was nothing related to cats, dogs, bears or weasels -- no modern mammalian predators. They couldn't get to the Pontide terrain because it was a little island. So, these marsupials ecologically are taking their place at the top of the food chain."

According to the KU researcher, the newly discovered fossils demonstrate geological context has a huge influence on how ecosystems are assembled on any given island.

"Current ideas about island evolution are based on some fairly simplistic, yet fairly effective, models," Beard stated. "These models propose that organisms colonize islands based on two main factors -- how big is the island and how far away is it from nearby continental landmasses? A bigger island makes a bigger target and hosts a greater diversity of habitats, making it easier for organisms to colonize the island and once they get there they have a better chance of surviving and maybe even diversifying."

Based on his team's findings from the Pontide region, Beard said that geological context was at least as important as an island's size or distance from colonizing animals' source territory.

"All men may have been created equal, but all islands were not. The geological context of the island -- here it's in a region of active tectonic convergence -- we think is swamping these other factors, size and distance to mainland," he said. "The oddest thing about the Pontide mammal fauna is that it contains a unique mixture of animals coming from Europe, Africa and Asia. Even our two new marsupials show different evolutionary roots in the north and the south. This makes sense because the Pontide island was being sandwiched between Eurasia and Africa, and animals were arriving there from multiple directions. We can make an interesting analogy with the modern island of Sulawesi in Indonesia, which like the Pontide terrain has a mixed fauna. It mainly hosts animals like tarsiers, pigs and shrews that are clearly related to Asian species, but you also have on Sulawesi species that are obviously related to mammals from New Guinea. If you look at plate tectonics today, Sulawesi is getting sandwiched between Australia and Asia in much the same way the Pontide was being sandwiched between Africa and Asia in the Eocene."

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Climate change likely caused migration, demise of ancient Indus Valley civilization

The Indus civilization was the largest—but least known—of the first great urban cultures that also included Egypt and Mesopotamia. Named for one of their largest cities, the Harappans relied on river floods to fuel their agricultural surpluses. Today, numerous remains of the Harappan settlements are located in a vast desert region far from any flowing river.

More than 4,000 years ago, the Harappa culture thrived in the Indus River Valley of what is now modern Pakistan and northwestern India, where they built sophisticated cities, invented sewage systems that predated ancient Rome's, and engaged in long-distance trade with settlements in Mesopotamia. Yet by 1800 BCE, this advanced culture had abandoned their cities, moving instead to smaller villages in the Himalayan foothills. A new study from the Woods Hole Oceanographic Institution (WHOI) found evidence that climate change likely drove the Harappans to resettle far away from the floodplains of the Indus.

Beginning in roughly 2500 BCE, a shift in temperatures and weather patterns over the Indus valley caused summer monsoon rains to gradually dry up, making agriculture difficult or impossible near Harappan cities, says Liviu Giosan, a geologist at WHOI and lead author on the paper that published Nov. 13, 2018, in the journal Climate of the Past.

"Although fickle summer monsoons made agriculture difficult along the Indus, up in the foothills, moisture and rain would come more regularly," Giosan says. "As winter storms from the Mediterranean hit the Himalayas, they created rain on the Pakistan side, and fed little streams there. Compared to the floods from monsoons that the Harappans were used to seeing in the Indus, it would have been relatively little water, but at least it would have been reliable."

Evidence for this shift in seasonal rainfall -- and the Harapans' switch from relying on Indus floods to rains near the Himalaya in order to water crops -- is difficult to find in soil samples. That's why Giosan and his team focused on sediments from the ocean floor off Pakistan's coast. After taking core samples at several sites in the Arabian Sea, he and his group examined the shells of single-celled plankton called foraminifera (or "forams") that they found in the sediments, helping them understand which ones thrived in the summer, and which in winter.

Once he and the team identified the season based on the forams' fossil remains, they were able to then focus on deeper clues to the region's climate: paleo-DNA, fragments of ancient genetic material preserved in the sediments.

"The seafloor near the mouth of the Indus is a very low-oxygen environment, so whatever grows and dies in the water is very well preserved in the sediment," says Giosan. "You can basically get fragments of DNA of nearly anything that's lived there."

During winter monsoons, he notes, strong winds bring nutrients from the deeper ocean to the surface, feeding a surge in plant and animal life. Likewise, weaker winds other times of year provide fewer nutrients, causing slightly less productivity in the waters offshore.

"The value of this approach is that it gives you a picture of the past biodiversity that you'd miss by relying on skeletal remains or a fossil record. And because we can sequence billions of DNA molecules in parallel, it gives a very high-resolution picture of how the ecosystem changed over time," adds William Orsi, paleontologist and geobiologist at Ludwig Maximilian University of Munich, who collaborated with Giosan on the work.

Sure enough, based on evidence from the DNA, the pair found that winter monsoons seemed to become stronger -- and summer monsoons weaker -- towards the later years of the Harappan civilization, corresponding with the move from cities to villages.

"We don't know whether Harappan caravans moved toward the foothills in a matter of months or this massive migration took place over centuries. What we do know is that when it concluded, their urban way of life ended," Giosan says.

The rains in the foothills seem to have been enough to hold the rural Harapans over for the next millennium, but even those would eventually dry up, likely contributing to their ultimate demise.

"We can't say that they disappeared entirely due to climate -- at the same time, the Indo-Aryan culture was arriving in the region with Iron Age tools and horses and carts. But it's very likely that the winter monsoon played a role," Giosan says.

The big surprise of the research, Giosan notes, is how far-flung the roots of that climate change may have been. At the time, a "new ice age" was settling in, forcing colder air down from the Arctic into the Atlantic and northern Europe. That in turn pushed storms down into the Mediterranean, leading to an upswing in winter monsoons over the Indus valley.

"It's remarkable, and there's a powerful lesson for today," he notes. "If you look at Syria and Africa, the migration out of those areas has some roots in climate change. This is just the beginning -- sea level rise due to climate change can lead to huge migrations from low lying regions like Bangladesh, or from hurricane-prone regions in the southern U.S. Back then, the Harappans could cope with change by moving, but today, you'll run into all sorts of borders. Political and social convulsions can then follow."

Read more at Science Daily

Massive impact crater from a kilometer-wide iron meteorite discovered in Greenland

Map of the bedrock topography beneath the ice sheet and the ice-free land surrounding the Hiawatha impact crater. The structure is 31 km wide, with a prominent rim surrounding the structure. In the central part of the impact structure, an area with elevated terrain is seen, which is typical for larger impact craters. Calculations shows that in order to generate an impact crater of this size, the earth was struck by a meteorite more than 1 km wide.

An international team lead by researchers from the Centre for GeoGenetics at the Natural History Museum of Denmark, University of Copenhagen have discovered a 31-km wide meteorite impact crater buried beneath the ice-sheet in the northern Greenland. This is the first time that a crater of any size has been found under one of Earth's continental ice sheets. The researchers worked for last three years to verify their discovery, initially made in the 2015. The research is described in a new study just published in the internationally recognized journal Science Advances.

The crater measures more than 31 km in diameter, corresponding to an area bigger than Paris, and placing it among the 25 largest impact craters on Earth. The crater formed when a kilometre-wide iron meteorite smashed into northern Greenland, but has since been hidden under nearly a kilometre of ice.

"The crater is exceptionally well-preserved, and that is surprising, because glacier ice is an incredibly efficient erosive agent that would have quickly removed traces of the impact. But that means the crater must be rather young from a geological perspective. So far, it has not been possible to date the crater directly, but its condition strongly suggests that it formed after ice began to cover Greenland, so younger than 3 million years old and possibly as recently as 12,000 years ago -- toward the end of the last ice age" says Professor Kurt H. Kjær from the Center for GeoGenetics at the Natural History Museum of Denmark.

Giant circular depression

The crater was first discovered in July 2015 as the researchers inspected a new map of the topography beneath Greenland's ice-sheet. They noticed an enormous, but previously undetected circular depression under Hiawatha Glacier, sitting at the very edge of the ice sheet in northern Greenland.

"We immediately knew this was something special but at the same time it became clear that it would be difficult to confirm the origin of the depression," says Professor Kjær.

In the courtyard at the Geological Museum in Copenhagen just outside the windows of the Center for GeoGenetics sits a 20-tonne iron meteorite found in North Greenland not far from the Hiawatha Glacier.

"It was therefore not such a leap to infer that the depression could be a previously undescribed meterorite crater, but initially we lacked the evidence," reflects Associate Professor Nicolaj K. Larsen from Aarhus University.

The crucial evidence

Their suspicion that the giant depression was a meteorite crater was reinforced when the team sent a German research plane from the Alfred Wegener Institute to fly over the Hiawatha Glacier and map the crater and the overlying ice with a new powerful ice radar. Joseph MacGregor, a glaciologist at NASA, who participated in the study and is an expert in ice radar measurements adds:

"Previous radar measurements of Hiawatha Glacier were part of a long-term NASA effort to map Greenland's changing ice cover. What we really needed to test our hypothesis was a dense and focused radar survey there. Our colleagues at the Alfred Wegener Institute and University of Kansas did exactly that with a next-generation radar system that exceeded all expectations and imaged the depression in stunning detail. A distinctly circular rim, central uplift, disturbed and undisturbed ice layering, and basal debris. It's all there."

In the summers of 2016 and 2017, the research team returned to the site to map tectonic structures in the rock near the foot of the glacier and collect samples of sediments washed out from the depression through a meltwater channel.

"Some of the quartz sand washed from the crater had planar deformation features indicative of a violent impact, and this is conclusive evidence that the depression beneath the Hiawatha Glacier is a meteorite crater, " says Professor Larsen.

The consequences of the impact on the Earth's climate and life

Earlier studies have shown that large impacts can profoundly affect Earth's climate, with major consequences for life on Earth at the time. It is therefore very resonable to ask when and how and this meteorite impact at the Hiawatha Glacier affected the planet.

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Cold Super-Earth found orbiting closest single star to Sun

The nearest single star to the Sun hosts an exoplanet at least 3.2 times as massive as Earth -- a so-called super-Earth. Data from a worldwide array of telescopes, including ESO's planet-hunting HARPS instrument, have revealed this frozen, dimly lit world. The newly discovered planet is the second-closest known exoplanet to the Earth and orbits the fastest moving star in the night sky. This image shows an artist's impression of the planet's surface.

A planet has been detected orbiting Barnard's Star , a mere 6 light-years away. This breakthrough -- announced in a paper published today in the journal Nature -- is a result of the Red Dots and CARMENES projects, whose search for local rocky planets has already uncovered a new world orbiting our nearest neighbour, Proxima Centauri.

The planet, designated Barnard's Star b, now steps in as the second-closest known exoplanet to Earth. The gathered data indicate that the planet could be a super-Earth, having a mass at least 3.2 times that of the Earth, which orbits its host star in roughly 233 days. Barnard's Star, the planet's host star, is a red dwarf, a cool, low-mass star, which only dimly illuminates this newly-discovered world. Light from Barnard's Star provides its planet with only 2% of the energy the Earth receives from the Sun.

Despite being relatively close to its parent star -- at a distance only 0.4 times that between Earth and the Sun -- the exoplanet lies close to the snow line, the region where volatile compounds such as water can condense into solid ice. This freezing, shadowy world could have a temperature of -170℃, making it inhospitable for life as we know it.

Named for astronomer E. E. Barnard, Barnard's Star is the closest single star to the Sun. While the star itself is ancient -- probably twice the age of our Sun -- and relatively inactive, it also has the fastest apparent motion of any star in the night sky. Super-Earths are the most common type of planet to form around low-mass stars such as Barnard's Star, lending credibility to this newly discovered planetary candidate. Furthermore, current theories of planetary formation predict that the snow line is the ideal location for such planets to form.

Previous searches for a planet around Barnard's Star have had disappointing results -- this recent breakthrough was possible only by combining measurements from several high-precision instruments mounted on telescopes all over the world.

"After a very careful analysis, we are 99% confident that the planet is there," stated the team's lead scientist, Ignasi Ribas (Institute of Space Studies of Catalonia and the Institute of Space Sciences, CSIC in Spain). "However, we'll continue to observe this fast-moving star to exclude possible, but improbable, natural variations of the stellar brightness which could masquerade as a planet."

Among the instruments used were ESO's famous planet-hunting HARPS and UVES spectrographs. "HARPS played a vital part in this project. We combined archival data from other teams with new, overlapping, measurements of Barnard's star from different facilities," commented Guillem Anglada Escudé (Queen Mary University of London), co-lead scientist of the team behind this result. "The combination of instruments was key to allowing us to cross-check our result."

The astronomers used the Doppler effect to find the exoplanet candidate. While the planet orbits the star, its gravitational pull causes the star to wobble. When the star moves away from the Earth, its spectrum redshifts; that is, it moves towards longer wavelengths. Similarly, starlight is shifted towards shorter, bluer, wavelengths when the star moves towards Earth.

Astronomers take advantage of this effect to measure the changes in a star's velocity due to an orbiting exoplanet -- with astounding accuracy. HARPS can detect changes in the star's velocity as small as 3.5 km/h -- about walking pace. This approach to exoplanet hunting is known as the radial velocity method, and has never before been used to detect a similar super-Earth type exoplanet in such a large orbit around its star.

"We used observations from seven different instruments, spanning 20 years of measurements, making this one of the largest and most extensive datasets ever used for precise radial velocity studies." explained Ribas. "The combination of all data led to a total of 771 measurements -- a huge amount of information!"

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Weightlifting is good for your heart and it doesn't take much

Lifting weights for less than an hour a week may reduce your risk for a heart attack or stroke by 40 to 70 percent, according to a new Iowa State University study. Spending more than an hour in the weight room did not yield any additional benefit, the researchers found.

"People may think they need to spend a lot of time lifting weights, but just two sets of bench presses that take less than 5 minutes could be effective," said DC (Duck-chul) Lee, associate professor of kinesiology.

The results -- some of the first to look at resistance exercise and cardiovascular disease -- show benefits of strength training are independent of running, walking or other aerobic activity. In other words, you do not have to meet the recommended guidelines for aerobic physical activity to lower your risk; weight training alone is enough. The study is published in Medicine and Science in Sports and Exercise.

Lee and his colleagues analyzed data of nearly 13,000 adults in the Aerobics Center Longitudinal Study. They measured three health outcomes: cardiovascular events such as heart attack and stroke that did not result in death, all cardiovascular events including death and any type of death. Lee says resistance exercise reduced the risk for all three.

"The results are encouraging, but will people make weightlifting part of their lifestyle? Will they do it and stick with it? That's the million-dollar question," Lee said.

Barriers to resistance training

The researchers recognize that unlike aerobic activity, resistance exercise is not as easy to incorporate into our daily routine. Lee says people can move more by walking or biking to the office or taking the steps, but there are few natural activities associated with lifting. And while people may have a treadmill or stationary bike at home, they likely do not have access to a variety of weight machines.

For these reasons, Lee says a gym membership may be beneficial. Not only does it offer more options for resistance exercise, but in a previous study Lee found people with a gym membership exercised more. While this latest study looked specifically at use of free weights and weight machines, Lee says people will still benefit from other resistance exercises or any muscle-strengthening activities.

"Lifting any weight that increases resistance on your muscles is the key," Lee said. "My muscle doesn't know the difference if I'm digging in the yard, carrying heavy shopping bags or lifting a dumbbell."

Other benefits of strength training

Much of the research on strength training has focused on bone health, physical function and quality of life in older adults. When it comes to reducing the risk for cardiovascular disease, most people think of running or other cardio activity. Lee says weight lifting is just as good for your heart, and there are other benefits.

Using the same dataset, Lee and his colleagues looked at the relationship between resistance exercise and diabetes as well as hypercholesterolemia, or high cholesterol. The two studies, published in Mayo Clinic Proceedings, found resistance exercise lowered the risk for both.

Less than an hour of weekly resistance exercise (compared with no resistance exercise) was associated with a 29 percent lower risk of developing metabolic syndrome, which increases risk of heart disease, stroke and diabetes. The risk of hypercholesterolemia was 32 percent lower. The results for both studies also were independent of aerobic exercise.

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Purple bacteria 'batteries' turn sewage into clean energy

Wastewater treatment plant.

You've flushed something valuable down the toilet today.

Organic compounds in household sewage and industrial wastewater are a rich potential source of energy, bioplastics and even proteins for animal feed -- but with no efficient extraction method, treatment plants discard them as contaminants. Now researchers have found an environmentally-friendly and cost-effective solution.

Published in Frontiers in Energy Research, their study is the first to show that purple phototrophic bacteria -- which can store energy from light -- when supplied with an electric current can recover near to 100% of carbon from any type of organic waste, while generating hydrogen gas for electricity production.

"One of the most important problems of current wastewater treatment plants is high carbon emissions," says co-author Dr Daniel Puyol of King Juan Carlos University, Spain. "Our light-based biorefinery process could provide a means to harvest green energy from wastewater, with zero carbon footprint."

Purple photosynthetic bacteria

When it comes to photosynthesis, green hogs the limelight. But as chlorophyll retreats from autumn foliage, it leaves behind its yellow, orange and red cousins. In fact, photosynthetic pigments come in all sorts of colors -- and all sorts of organisms.

Cue purple phototrophic bacteria. They capture energy from sunlight using a variety of pigments, which turn them shades of orange, red or brown -- as well as purple. But it is the versatility of their metabolism, not their color, which makes them so interesting to scientists.

"Purple phototrophic bacteria make an ideal tool for resource recovery from organic waste, thanks to their highly diverse metabolism," explains Puyol.

The bacteria can use organic molecules and nitrogen gas -- instead of CO2 and H2O -- to provide carbon, electrons and nitrogen for photosynthesis. This means that they grow faster than alternative phototrophic bacteria and algae, and can generate hydrogen gas, proteins or a type of biodegradable polyester as byproducts of metabolism.

Tuning metabolic output with electricity

Which metabolic product predominates depends on the bacteria's environmental conditions -- like light intensity, temperature, and the types of organics and nutrients available.

"Our group manipulates these conditions to tune the metabolism of purple bacteria to different applications, depending on the organic waste source and market requirements," says co-author Professor Abraham Esteve-Núñez of University of Alcalá, Spain.

"But what is unique about our approach is the use of an external electric current to optimize the productive output of purple bacteria."

This concept, known as a "bioelectrochemical system," works because the diverse metabolic pathways in purple bacteria are connected by a common currency: electrons. For example, a supply of electrons is required for capturing light energy, while turning nitrogen into ammonia releases excess electrons, which must be dissipated. By optimizing electron flow within the bacteria, an electric current -- provided via positive and negative electrodes, as in a battery -- can delimit these processes and maximize the rate of synthesis.

Maximum biofuel, minimum carbon footprint

In their latest study, the group analyzed the optimum conditions for maximizing hydrogen production by a mixture of purple phototrophic bacteria species. They also tested the effect of a negative current -- that is, electrons supplied by metal electrodes in the growth medium -- on the metabolic behavior of the bacteria.

Their first key finding was that the nutrient blend that fed the highest rate of hydrogen production also minimized the production of CO2.

"This demonstrates that purple bacteria can be used to recover valuable biofuel from organics typically found in wastewater -- malic acid and sodium glutamate -- with a low carbon footprint," reports Esteve-Núñez.

Even more striking were the results using electrodes, which demonstrated for the first time that purple bacteria are capable of using electrons from a negative electrode or "cathode" to capture CO2 via photosynthesis.

"Recordings from our bioelectrochemical system showed a clear interaction between the purple bacteria and the electrodes: negative polarization of the electrode caused a detectable consumption of electrons, associated with a reduction in carbon dioxide production.

"This indicates that the purple bacteria were using electrons from the cathode to capture more carbon from organic compounds via photosynthesis, so less is released as CO2."

Towards bioelectrochemical systems for hydrogen production

According to the authors, this was the first reported use of mixed cultures of purple bacteria in a bioelectrochemical system -- and the first demonstration of any phototroph shifting metabolism due to interaction with a cathode.

Capturing excess CO2 produced by purple bacteria could be useful not only for reducing carbon emissions, but also for refining biogas from organic waste for use as fuel.

However, Puyol admits that the group's true goal lies further ahead.

"One of the original aims of the study was to increase biohydrogen production by donating electrons from the cathode to purple bacteria metabolism. However, it seems that the PPB bacteria prefer to use these electrons for fixing CO2 instead of creating H2.

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Fish recognize their prey by electric colors

The elephantnose fish produces brief electric pulses which it uses to perceive its environment. Different objects have different 'electrical colors'. In this artistic illustration, aquatic plants are for instance shown red, fish blue, members of the same species and other weakly electric fish yellow and insect larvae green. The mosquito larvae in the soil (orange) -- the favorite food of the elephantnose fish -- stand out from the background and other insect larvae due to their individual electric color.

The African elephantnose fish generates weak electrical pulses to navigate its environment. This localization sense apparently shows an astonishing similarity to vision, as a study by the University of Bonn now shows. The study demonstrates that different objects have different electrical "colors." Fish use these colors for instance to distinguish their favorite food -- mosquito larvae -- from other small animals or plants. The study is published in the journal Current Biology.

Elephantnose fish are nocturnal, which means they cannot rely on their eyes when hunting for prey. But they don't need to: They carry a kind of "electric flashlight" in their tail, which they use to generate short electrical pulses up to 80 times per second. Their skin, especially their trunk-like chin, is covered with electroreceptors: small sensors with which they can measure how these pulses are reflected by the environment.

And in this they have become champions: With their electro-sense they can estimate distances, distinguish forms and materials, differentiate between dead and living objects. And more than that: Within fractions of a second, they can recognize whether mosquito larvae, their favorite food, are hiding in the gravel or sand at the bottom of their habitat. They can do this with considerable accuracy, largely ignoring the larvae of other insects.

How they do this was uncertain for a long time. Objects certainly change the intensity of the electrical signal in a characteristic way -- some reduce it significantly, others reflect it better. "However, this is not enough to clearly identify prey animals," explains Martin Gottwald of the Institute of Zoology at the University of Bonn. "For example, the signal strength also decreases as the distance increases." But there is another characteristic of living organisms: They also modify the shape of the electric pulses. But even this signal change depends on distance, size and position.

The combination of the two signal characteristics could solve these problems. The human eye works in a similar fashion: Its retina contains receptors for red, green and blue light. Our brain then uses the "mixing ratio" to calculate the color of the object we see. And this remains largely constant, no matter how large or far away the object in question is.

Two different receptor types

However, until now there was no proof that a similar process occurs in elephantnose fish. Nevertheless, it is clear that the animals have two different types of electric receptors. One only measures the intensity of the signal, the other additionally measures its shape. "We have now been able to demonstrate that the fish uses the relation between these two measurements to identify their prey," explains Prof. Dr. Gerhard von der Emde, who led the study.

At first, the scientists determined how intensity and shape of the localization signal behave in relation to each other depending on the type of object. "We found that this ratio is always constant for the same objects," says von der Emde. "And this applies regardless of their distance or other environmental parameters." "A mosquito larva therefore actually has a constant 'electrical color', which is clearly different from that of other larvae, plant parts, members of the same species or other fish," adds Gottwald.

The researchers now examined the extent to which their laboratory animals used this information. They presented them with various electronic "mini chips" with a diameter of only one millimeter. Some chips produced different electrical colors; for example, they glowed like a mosquito larva or like other insect larvae. Other chips were electrically 'colorless', similar to a pebble.

Hungry for chips

The effect was astonishing: If the chips were colored like their favorite food, the elephantnose fish chomped down reflexively. They let themselves be fooled in this way in 70 percent of all cases, even though the fake meals did not smell at all like typical prey. Even after numerous experiments, the animals did not learn to avoid the chips. They largely spurned differently colored chips, and even completely ignored electrically colorless ones. "This may suggest that the prey color is hardwired in the brains of the fish," speculates von der Emde.

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Deepwater Horizon oil spill's dramatic effect on stingrays' sensory abilities

The Atlantic stingray, Hypanus sabinus, an elasmobranch fish, is renowned for its well-developed sensory systems, which are critical to alert them of the presence of predators, prey, mates, and unfavorable environmental conditions. Any impairment of these sensory systems could have a damaging effect on their survival and fitness.

It has been almost a decade since the Deepwater Horizon Oil spill. Described as the worst environmental disaster in the United States, nearly 5 million barrels of crude oil oozed into the Gulf of Mexico, severely degrading the marine ecosystem immediately surrounding the spill site and directly impacting coastal habitats along 1,773 kilometers of shoreline. About 10 million gallons remain in the sediment at the bottom of the Gulf and may continue to cause severe physiological damages to marine life, including impairment of sensory systems.

Marine fishes rely on the effective functioning of their sensory systems to survive. Despite the obvious importance of their olfactory (sense of smell) system, the impact of crude oil exposure on sensory function remains largely unexplored.

Researchers at Florida Atlantic University are the first to quantify the physiological effects of whole crude oil on the olfactory function of a marine vertebrate -- the Atlantic stingray, Hypanus sabinus, an elasmobranch fish. Results of the study, published in Scientific Reports, confirm that exposure to crude oil, at concentrations mimicking those measured in coastal areas following the Deepwater Horizon oil spill, significantly impaired olfactory function in the Atlantic stingray after just 48 hours of exposure. These findings suggest that exposure to crude oil could detrimentally impact fitness, lead to premature death, and cause additional cascading effects through lower trophic levels.

"Elasmobranchs are renowned for their well-developed sensory systems, which are critical to alert them of the presence of predators, prey, mates, and unfavorable environmental conditions. Any impairment of these sensory systems could have a damaging effect on their survival and fitness," said Stephen M. Kajiura, Ph.D., co- author, a professor of biological sciences in FAU's Charles E. Schmidt College of Science and director of the Elasmobranch Research Laboratory at FAU.

The work was conducted by Eloise J. Cave, as part of her master's degree in Kajiura's lab. Cave, who is now a Ph.D. student at the Florida Institute of Technology, employed an electro-physiological assay to test olfactory responses from stingrays held under clean water and oil-treated water. She found the oil exposed animals exhibited a smaller response, with a slower onset and longer duration.

"Unlike other sensory systems in which the receptor cells are not in immediate contact with the environment such as the eye, inner ear, lateral line, and electroreceptors, the chemo-sensory cells of the olfactory organ are directly exposed, through the mucus, to the seawater," said Kajiura. "As a result, environmental pollutants have the ability to directly damage the receptor cells and affect olfactory function."

Although this study focused on a shallow water, coastal species, deep-water elasmobranch species may be highly susceptible to crude oil exposure. The researchers caution that deep-sea benthic species like skates -- a type of cartilaginous fish that develop for prolonged periods in egg cases on the seafloor -- in particular, could be continuously exposed to high concentrations of crude oil in the sediment throughout sensitive developmental periods. Also, because the metabolic rate of marine organisms declines significantly with temperature, and hence depth, deep-sea elasmobranch species have a much slower metabolic rate than shallow water species and therefore might metabolize crude oil much more slowly. This prolonged exposure could manifest as different or more severe results.

"Under field conditions, animals are likely to encounter variable exposure concentrations, which may be higher or lower than the concentration used in our study," said Kajiura. "This acute exposure has the potential to induce other physiological responses, potentially compounding the adverse effects of the altered olfactory function. Even if the oil does not cause immediate or direct death, sub-lethal effects could still reduce fitness or contribute to premature death."

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How plants evolved to make ants their servants

A plant that evolved hollow thorns for ants to shelter in. In exchange, the ants defend the plant from attacks from other insects and mammals.

Plants are boring. They just sit there photosynthesizing while animals have all the fun. Right? Not so much. Take a look at the interactions between ants and plants -- plants have evolved features specifically to make them enticing to ants, like juicy nectar for the insects to eat and hollow thorns for them to take shelter in. In exchange, plants use ants to spread their seeds and even act as bodyguards. A new study in the Proceedings of the National Academy of Sciences breaks down the genetic history of 1,700 species of ants and 10,000 plant genera, and the researchers found that the long history of ant and plant co-evolution started with ants foraging on plants and plants later responding by evolving ant-friendly traits.

"My main interest is in studying how interactions between organisms have evolved, and how these interactions shape their evolutionary history. When did ants start using plants, and when did plants start making structures for ants to use?" says Matt Nelsen, a Field Museum post-doctoral researcher and the lead author of the PNAS study.

"There are a number of different structures plants make that are specific for ant use," explains Nelsen, who led the study with his fellow Field Museum researchers and co-authors Rick Ree and Corrie Moreau. "Some plants have evolved features that persuade ants into defending them from attack from other insects and even mammals. These include hollow thorns that ants will live inside, or extra nectar on leaves or stems for the ants to eat. Some ants will just cheat and take the nectar and run, but some will stick around and attack anything that tries to hurt the plant," explains Nelsen. Other plants get ants to help them move their seeds around, by bribing them with rich food packets attached to seeds called elaiosomes. "The ant will pick up the seed and carry it away, eat the food packet, and discard the seed -- often in a nutrient-rich area where it'll grow better, and since it's farther away from its parent, they won't have to compete for resources."

But scientists weren't sure how the evolutionary relationship between ants and plants got started. If evolution is an arms race between species developing ways to profit off of their neighbors, then scientists wanted to know whether plants or ants fired the first shot. "It was a chicken-and-egg question, whether things started with ants developing behaviors to take advantage of plants, or plants evolving structures to take advantage of ants," says Ree, curator of plants at the Field Museum.

The history of ants and plants evolving together goes back to the time of the dinosaurs, and it's not easy to tell from fossils how the organisms interacted. "There are very few fossil records of these structures in plants, and they don't extend very far back in time. And there are tons of ant fossils, but they typically don't show these ant behaviors -- we don't necessarily see an ant preserved in amber carrying a seed," says Nelsen.

So, to determine the early evolutionary history of ant-plant interactions, Nelsen and his colleagues turned to large amounts of DNA data and ecological databases. "In our study, we linked these behavioral and physical features with family trees of ants and plants to determine when ants started eating and living on plants, and when plants developed the capacity to produce structures that ants use," explains Moreau, the Field's curator of ants.

The team mapped the history of plant's ant-friendly traits and of ants' plant use onto these family trees -- a process called ancestral state reconstruction. They were able to determine when plants began relying on ants for defense and seed distribution -- and it looks like ants have relied on plants for longer than plants have directly relied on ants, since plants didn't evolve these specialized structures until long after ants had been relying on them for food and habitat.

"Some ants don't directly use plants for much, while others rely on them for food, foraging habitat, and nesting. We found that to become fully invested in plant-use, ants first began foraging arboreally, then incorporated plants into their diet, and then from there, they started nesting arboreally. While this stepwise shift towards an increased reliance on plants is intuitive, it still surprised us," says Nelsen.

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New finding of particle physics may help to explain the absence of antimatter

Sketch of dimensional reduction.

In the Standard Model of particle physics, there is almost no difference between matter and antimatter. But there is an abundance of evidence that our observable universe is made up only of matter -- if there was any antimatter, it would annihilate with nearby matter to produce very high intensity gamma radiation, which has not been observed. Therefore, figuring out how we ended up with an abundance of only matter is one of the biggest open questions in particle physics.

Because of this and other gaps in the Standard Model, physicists are considering theories which add a few extra particles in ways that will help to solve the problem. One of these models is called the Two Higgs Doublet Model, which, despite the name, actually adds four extra particles. This model can be made to agree with all particle physics observations made so far, including ones from the Large Hadron Collider at CERN, but it was unclear whether it could also solve the problem of the matter-antimatter imbalance. The research group, led by a University of Helsinki team, set out to tackle the problem from a different angle. Their findings have now been published in a paper in the Physical Review Letters.

About ten picoseconds after the Big Bang -- right about the time the Higgs boson was turning on -- the universe was a hot plasma of particles.

"The technique of dimensional reduction lets us replace the theory which describes this hot plasma with a simpler quantum theory with a set of rules that all the particles must follow," explains Dr. David Weir, the corresponding author of the article.

"It turns out that the heavier, slower-moving particles don't matter very much when these new rules are imposed, so we end up with a much less complicated theory."

This theory can then be studied with computer simulations, which provide a clear picture of what happened. In particular, they can tell us how violently out of equilibrium the universe was when the Higgs boson turned on. This is important for determining whether there was scope for producing the matter-antimatter asymmetry at this time in the history of the universe using the Two Higgs Doublet Model.

"Our results showed that it is indeed possible to explain the absence of antimatter and remain in agreement with existing observations," Dr. Weir remarks. Importantly, by making use of dimensional reduction, the new approach was completely independent of any previous work in this model.

Read more at Science Daily

Rare fossil bird deepens mystery of avian extinctions

Fossilized wishbone or furcula of Mirarce eatoni. The V shape is more like the wishbones of today's birds, which are agile, strong fliers, than the U-shaped wishbones of theropod dinosaurs.

During the late Cretaceous period, more than 65 million years ago, birds belonging to hundreds of different species flitted around the dinosaurs and through the forests as abundantly as they flit about our woods and fields today.

But after the cataclysm that wiped out most of the dinosaurs, only one group of birds remained: the ancestors of the birds we see today. Why did only one family survive the mass extinction?

A newly described fossil from one of those extinct bird groups, cousins of today's birds, deepens that mystery.

The 75-million-year-old fossil, from a bird about the size of a turkey vulture, is the most complete skeleton discovered in North America of what are called enantiornithines (pronounced en-an-tea-or'-neth-eens), or opposite birds. Discovered in the Grand Staircase-Escalante area of Utah in 1992 by University of California, Berkeley, paleontologist Howard Hutchison, the fossil lay relatively untouched in University of California Museum of Paleontology at Berkeley until doctoral student Jessie Atterholt learned about it in 2009 and asked to study it.

Atterholt and Hutchison collaborated with Jingmai O'Conner, the leading expert on enantiornithines, to perform a detailed analysis of the fossil. Based on their study, enantiornithines in the late Cretaceous were the aerodynamic equals of the ancestors of today's birds, able to fly strongly and agilely.

"We know that birds in the early Cretaceous, about 115 to 130 million years ago, were capable of flight but probably not as well adapted for it as modern birds," said Atterholt, who is now an assistant professor and human anatomy instructor at the Western University of Health Sciences in Pomona, California. "What this new fossil shows is that enantiornithines, though totally separate from modern birds, evolved some of the same adaptations for highly refined, advanced flight styles."

The fossil's breast bone or sternum, where flight muscles attach, is more deeply keeled than other enantiornithines, implying a larger muscle and stronger flight more similar to modern birds. The wishbone is more V-shaped, like the wishbone of modern birds and unlike the U-shaped wishbone of earlier avians and their dinosaur ancestors. The wishbone or furcula is flexible and stores energy released during the wing stroke.

If enantiornithines in the late Cretaceous were just as advanced as modern birds, however, why did they die out with the dinosaurs while the ancestors of modern birds did not?

"This particular bird is about 75 million years old, about 10 million years before the die-off," Atterholt said. "One of the really interesting and mysterious things about enantiornithines is that we find them throughout the Cretaceous, for roughly 100 million years of existence, and they were very successful. We find their fossils on every continent, all over the world, and their fossils are very, very common, in a lot of areas more common than the group that led to modern birds. And yet modern birds survived the extinction while enantiornithines go extinct."

One recently proposed hypothesis argues that the enantiornithines were primarily forest dwellers, so that when forests went up in smoke after the asteroid strike that signaled the end of the Cretaceous -- and the end of non-avian dinosaurs -- the enantiornithines disappeared as well. Many enantiornithines have strong recurved claws ideal for perching and perhaps climbing, she said.

"I think it is a really interesting hypothesis and the best explanation I have heard so far," Atterholt said. "But we need to do really rigorous studies of enantiornithines' ecology, because right now that part of the puzzle is a little hand-wavey."

Atterholt, Hutchison and O'Connor, who is at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China, published an analysis of the fossil today in the open-access journal PeerJ.

Theropod dinosaurs evolved into birds

All birds evolved from feathered theropods -- the two-legged dinosaurs like T. rex -- beginning about 150 million years ago, and developed into many lineages in the Cretaceous, between 146 and 65 million years ago.

Hutchison said that he came across the fossil eroding out of the ground in the rugged badlands of the Kaiparowits formation in the Grand Staircase-Escalante National Monument in Garfield County, Utah, just inside the boundary of the recently reduced monument. Having found bird fossils before, he recognized it as a late Cretaceous enantiornithine, and a rare one at that. Most birds from the Americas are from the late Cretaceous (100-66 million years ago) and known only from a single foot bone, often the metatarsus. This fossil was almost complete, missing only its head.

"In 1992, I was looking primarily for turtles," Hutchison said. "But I pick up everything because I am interested in the total fauna. The other animals they occur with tells me more about the habitat."

According to Hutchison, the area where the fossil was found dates from between 77 and 75 million years ago and was probably a major delta, like the Mississippi River delta, tropical and forested with lots of dinosaurs but also crocodiles, alligators, turtles and fish.

Unlike most bird fossils found outside America, in particular those from China, the fossil was not smashed flat. The classic early Cretaceous bird, Archaeopteryx, was flattened in sandstone, which preserved a beautiful panoply of feathers and the skeletal layout. Chinese enantiornithines, mostly from the early Cretaceous, are equally beautiful and smashed flatter than a pancake.

"On one hand, it's great -- you get the full skeleton most of the time, you get soft tissue preservation, including feathers. But it also means everything is crushed and deformed," she said. "Not that our fossils have zero deformation, but overall most of the bones have really beautiful three-dimensional preservation, and just really, really great detail. We see places where muscles and tendons were attaching, all kinds of interesting stuff to anatomists."

Once Hutchison prepared the fossils and placed them in the UC Museum of Paleontology collection, they drew the attention of a few budding and established paleontologists, but no one completed an analysis.

"The stuff is legendary. People in the vertebrate paleontology community have known about this thing forever and ever, and it just happened that everyone who was supposedly working on it got too busy and it fell by the wayside and just never happened," Atterholt said. "I was honored and incredibly excited when Howard said that I could take on the project. I was over the moon."

Her analysis showed that by the late Cretaceous, enantiornithines had evolved advanced adaptations for flying independent of today's birds. In fact, they looked quite similar to modern birds: they were fully feathered and flew by flapping their wings like modern birds. The fossilized bird probably had teeth in the front of its beak and claws on its wings as well as feet. Some enantiornithines had prominent tail feathers that may have differed between male and female and been used for sexual display.

"It is quite likely that, if you saw one in real life and just glanced at it, you wouldn't be able to distinguish it from a modern bird," Atterholt said.

This fossil bird is also among the largest North American birds from the Cretaceous; most were the size of chickadees or crows.

"What is most exciting, however, are large patches on the forearm bones. These rough patches are quill knobs, and in modern birds they anchor the wing feathers to the skeleton to help strengthen them for active flight. This is the first discovery of quill knobs in any enantiornithine bird, which tells us that it was a very strong flier."

Atterholt and her colleagues named the species Mirarce eatoni (meer-ark'-ee ee-tow'-nee). Mirarce combines the Latin word for wonderful, which pays homage to "the incredible, detailed, three-dimensional preservation of the fossil," she said, with the mythical Greek character Arce, the winged messenger of the Titans. The species name honors Jeffrey Eaton, a paleontologist who for decades has worked on fossils from the Kaiparowits Formation. Eaton first enticed Hutchison to the area in search of turtles, and they were the first to report fossils from the area some 30 years ago.

Thousands of such fossils from the rocks of the Kaiparowits Formation, many of them dinosaurs, contributed to the establishment of the Grand Staircase-Escalante National Monument in 1996.

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Primates of the Caribbean: Ancient DNA reveals history of mystery monkey

Xenothrix's close relative, the red titi monkey (Callicebus cupreus).

Analysis of ancient DNA of a mysterious extinct monkey named Xenothrix -- which displays bizarre body characteristics very different to any living monkey -- has revealed that it was in fact most closely related to South America's titi monkeys (Callicebinae). Having made their way overwater to Jamaica, probably on floating vegetation, their bones reveal they subsequently underwent remarkable evolutionary change.

The research published today in Proceedings of the National Academy of Sciences (12 November 2018) and carried out by a team of experts from international conservation charity ZSL (Zoological Society of London), London's Natural History Museum (NHM), and the American Museum of Natural History in New York, also reveals that monkeys must have colonised the Caribbean islands more than once. The study reports an incredible discovery of how the unusual ecology of islands can dramatically influence animal evolution.

Xenothrix, unlike any other monkey in the world, was a slow-moving tree-dweller with relatively few teeth, and leg bones somewhat like a rodent's. Its unusual appearance has made it difficult for scientists to work out what it was related to and how it evolved. However, the scientific team have successfully extracted the first ever ancient DNA from an extinct Caribbean primate -- uncovered from bones excavated in a Jamaican cave and providing important new evolutionary insights.

Professor Samuel Turvey from ZSL, a co-author on the paper, said: "This new understanding of the evolutionary history of Xenothrix shows that evolution can take unexpected paths when animals colonise islands and are exposed to new environments. However, the extinction of Xenothrix, which evolved on an island without any native mammal predators, highlights the great vulnerability of unique island biodiversity in the face of human impacts."

Professor Ian Barnes, whom runs the NHM's ancient DNA lab, and co-author said: "Recovering DNA from the bones of extinct animals has become increasingly commonplace in the last few years. However, it's still difficult with tropical specimens, where the temperature and humidity destroy DNA very quickly. I'm delighted that we've been able to extract DNA from these samples and resolve the complex history of the primates of the Caribbean."

It is likely that Xenothrix's ancestors colonised Jamaica from South America around 11 million years ago, probably after being stranded on natural rafts of vegetation that were washed out of the mouths of large South American rivers. Many other animals, such as large rodents called hutias (Capromyidae) that still survive on some Caribbean islands today, probably colonised the region in the same way.

Ross MacPhee of the American Museum of Natural History's Mammalogy Department, a co-author of the study, said: "Ancient DNA indicates that the Jamaican monkey is really just a titi monkey with some unusual morphological features, not a wholly distinct branch of New World monkey. Evolution can act in unexpected ways in island environments, producing miniature elephants, gigantic birds, and sloth-like primates. Such examples put a very different spin on the old cliché that 'anatomy is destiny.'"

What Xenothrix may have looked like has been greatly debated, with suggestions that it looked like a kinkajou (Potos) or a night monkey (Aotus). Living titi monkeys are small tree-dwelling monkeys found across tropical South America, with long soft red, brown, grey or black fur. They are active during the day, extremely territorial and vocal, and live up to 12 years in the wild, with the father often caring for the young.

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Defective DNA damage repair leads to chaos in the genome

Scientists at the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) have now found a cause for the frequent catastrophic events in the genetic material of cancer cells that have only been known for a few years: If an important DNA repair system of the cells has failed, this promotes fragmentation and defective assembly of the genetic material. Cancer cells with such a repair defect can now possibly be treated by a specific group of drugs.

Only a few years ago, scientists at the German Cancer Research Center (DKFZ), among others, described a new damage pattern in the genetic material of cancer cells: In a particularly aggressive type of childhood brain tumors, they discovered an unprecedented chaos in the cell nucleus: Sections of individual chromosomes were broken at innumerable points and reassembled incorrectly, so that whole parts were missing, while others were duplicated or incorporated in a wrong orientation. This chromosome catastrophe differed from all previously known genetic defects in tumors.

Scientists use the term chromothripsis to describe such a genetic disaster, which occurs in about twenty to thirty percent of all cancers. The trigger for this has so far been largely unknown. Aurelie Ernst and her team at the German Cancer Research Center have now been able to show that the failure of certain genetic repair systems is one of the causes of chromosomal chaos.

Many environmental influences, such as UV rays, damage the DNA. Cells have an arsenal of mechanisms in place to repair such defects. What happens if one of these repair systems fails? Aurelie Ernst's team tested this on genetically modified mice. In these animals, the tools used by the cell to repair broken DNA double strands were genetically switched off -- specifically only in the neural precursor cells.

These mice developed malignant brain tumors (medulloblastomas and high-grade gliomas), which exhibited chromothripsis at a high frequency. The researchers noticed that this is almost always accompanied by extra copies of the Myc oncogene, which is known to be a strong driver of cell growth. "If the DNA repair is defective and Myc nevertheless stimulates the division of these damaged cells, the risk of chaos in the genome is particularly high," explains the DKFZ researcher.

Does this connection between defective genome repair and chromosome chaos also apply to human cancers? Aurelie Ernst and her team can confirm this for brain tumors, melanomas and breast cancer. The researchers also found the involvement of the cancer-promoting Myc in human tumors.

"The chromosome chaos caused by repair defects is frightening at first sight," explains Aurelie Ernst. "However, there are ways to specifically combat cancer cells harboring such defects: We can use drugs to switch off additionally another important DNA repair system. This leads to so much genetic damage that the cell is unable to survive. Healthy cells, on the other hand, which have all their repair systems, don't mind these drugs."

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