Harnessing energy from glass walls

Prototype of a semi-transparent perovskite solar cell with thermal-mirror functionality.

A Korean research team has developed semi-transparent perovskite solar cells that could be great candidates for solar windows.

Scientists are exploring ways to develop transparent or semi-transparent solar cells as a substitute for glass walls in modern buildings with the aim of harnessing solar energy. But this has proven challenging, because transparency in solar cells reduces their efficiency in absorbing the sunlight they need to generate electricity.

Typical solar cells today are made of crystalline silicon, which is difficult to make translucent. By contrast, semi-transparent solar cells use, for example, organic or dye-sensitized materials. But compared to crystalline silicon-based cells, their power-conversion efficiencies are relatively low. Perovskites are hybrid organic-inorganic photovoltaic materials, which are cheap to produce and easy to manufacture. They have recently received much attention, as the efficiency of perovskite solar cells has rapidly increased to the level of silicon technologies in the past few years.

Using perovskites, a Korean research team, led by Professor Seunghyup Yoo of the Korea Advanced Institute of Science and Technology and Professor Nam-Gyu Park of Sungkyunkwan University, has developed a semi-transparent solar cell that is highly efficient and functions very effectively as a thermal mirror.

One key to achieving efficient semitransparent solar cells is to develop a transparent electrode for the cell's uppermost layer that is compatible with the photoactive material. The Korean team developed a 'top transparent electrode' (TTE) that works well with perovskite solar cells. The TTE is based on a multilayer stack consisting of a metal film sandwiched between a high refractive index layer and an interfacial buffer layer. This TTE, placed as a solar cell's top-most layer, can be prepared without damaging ingredients used in the development f perovskite solar cells. Unlike conventional transparent electrodes that only transmit visible light, the team's TTE plays the dual role of allowing visible light to pass through while at the same time reflecting infrared rays.

The semi-transparent solar cells made with the TTEs exhibited an average power conversion efficiency as high as 13.3%, reflecting 85.5% of incoming infrared light. Currently available crystalline silicon solar cells have up to 25% efficiency but are opaque.

Read more at Science Daily

Water forms 'spine of hydration' around DNA, group finds

This is an illustration of what chiral nonlinear spectroscopy reveals: that DNA is surrounded by a chiral water super-structure, forming a 'spine of hydration.'

Water is Earth's most abundant natural resource, but it's also something of a mystery due to its unique solvation characteristics -- that is, how things dissolve in it.

"It's uniquely adapted to biology, and vice versa," said Poul Petersen, assistant professor of chemistry and chemical biology at Cornell University. "It's super-flexible. It dissipates energy and mediates interactions, and that's becoming more recognized in biological systems."

How water relates to and interacts with those systems -- like DNA, the building block of all living things -- is of critical importance, and Petersen's group has used a relatively new form of spectroscopy to observe a previously unknown characteristic of water.

"DNA's chiral spine of hydration," published May 24 in the American Chemical Society journal Central Science, reports the first observation of a chiral water superstructure surrounding a biomolecule. In this case, the water structure follows the iconic helical structure of DNA, which itself is chiral, meaning it is not superimposable on its mirror image. Chirality is a key factor in biology, because most biomolecules and pharmaceuticals are chiral.

"If you want to understand reactivity and biology, then it's not just water on its own," Petersen said. "You want to understand water around stuff, and how it interacts with the stuff. And particularly with biology, you want to understand how it behaves around biological material -- like protein and DNA."

Water plays a major role in DNA's structure and function, and its hydration shell has been the subject of much study. Molecular dynamics simulations have shown a broad range of behaviors of the water structure in DNA's minor groove, the area where the backbones of the helical strand are close together.

The group's work employed chiral sum frequency generation spectroscopy (SFG), a technique Petersen detailed in a 2015 paper in the Journal of Physical Chemistry. SFG is a nonlinear optical method in which two photon beams -- one infrared and one visible -- interact with the sample, producing an SFG beam containing the sum of the two beams' frequencies, or energies. In this case, the sample was a strand of DNA linked to a silicon-coated prism.

More manipulation of the beams and calculation proved the existence of a chiral water superstructure surrounding DNA.

In addition to the novelty of observing a chiral water structure template by a biomolecule, chiral SFG provides a direct way to examine water in biology.

"The techniques we have developed provide a new avenue to study DNA hydration, as well as other supramolecular chiral structures," Petersen said.

The group admits that their finding's biological relevance is unclear, but Petersen thinks the ability to directly examine water and its behavior within biological systems is important.

"Certainly, chemical engineers who are designing biomimetic systems and looking at biology and trying to find applications such as water filtration would care about this," he said.

Read more at Science Daily

'Heat island' effect could double climate change costs for world's cities

Tokyo-Yokohama is the most populous urban area in the world.

Overheated cities face climate change costs at least twice as big as the rest of the world because of the 'urban heat island' effect, new research shows.

The study by an international team of economists of all the world's major cities is the first to quantify the potentially devastating combined impact of global and local climate change on urban economies.

The analysis of 1,692 cities, published in the journal Nature Climate Change, shows that the total economic costs of climate change for cities this century could be 2.6 times higher when heat island effects are taken into account than when they are not.

For the worst-off city, losses could reach 10.9 per cent of GDP by the end of the century, compared with a global average of 5.6 per cent.

The urban heat island occurs when natural surfaces, such as vegetation and water, are replaced by heat-trapping concrete and asphalt, and is exacerbated by heat from cars, air conditioners and so on. This effect is expected to add a further two degrees to global warming estimates for the most populated cities by 2050.

Higher temperatures damage the economy in a number of ways -- more energy is used for cooling, air is more polluted, water quality decreases and workers are less productive, to name a few.

The authors -- from the University of Sussex in the UK, Universidad Nacional Autónoma de México and Vrije University Amsterdam -- say their new research is significant because so much emphasis is placed on tackling global climate change, while they show that local interventions are as, if not more, important.

Professor Richard S.J. Tol MAE, Professor of Economics at the University of Sussex, said: "Any hard-won victories over climate change on a global scale could be wiped out by the effects of uncontrolled urban heat islands.

"We show that city-level adaptation strategies to limit local warming have important economic net benefits for almost all cities around the world."

Although cities cover only around one per cent of Earth's surface, they produce about 80 per cent of Gross World Product, consume about 78 per cent of the world's energy and are home to over half of the world's population.

Measures that could limit the high economic and health costs of rising urban temperatures are therefore a major priority for policy makers.

The research team carried out a cost-benefit analysis of different local policies for combating the urban heat island, such as cool pavements -- designed to reflect more sunlight and absorb less heat -- cool and green roofs and expanding vegetation in cities.

The cheapest measure, according to this modelling, is a moderate-scale installation of cool pavements and roofs. Changing 20 per cent of a city's roofs and half of its pavements to 'cool' forms could save up to 12 times what they cost to install and maintain, and reduce air temperatures by about 0.8 degrees.

Doing this on a larger scale would produce even bigger benefits but the vastly increased costs mean that the cost-benefit ratio is smaller.

The research has important implications for future climate policy decisions -- the positive impacts of such local interventions are amplified when global efforts are also having an effect, the study shows. Professor Tol said: "It is clear that we have until now underestimated the dramatic impact that local policies could make in reducing urban warming.

Read more at Science Daily

A first look at dolphin immune system

While there are a number of studies and reports that suggest a correlation between environmental contaminants, immune disturbances and disease susceptibility in wild dolphins and other marine mammals, scientists and veterinarians need a way to characterize, monitor and evaluate specific immune cells to investigate and confirm this correlation.

For humans, there are hundreds of antibodies available on the market to evaluate immune status in health and diseases. However, for the more than 42 known species of dolphins around the world, commercially available marine-specific antibodies do not exist. With the drastic increase in the number of unusual dolphin strandings and deaths along the southeastern coast of the United States and elsewhere, finding specific antibodies to test, monitor and document their immune health is critical.

Researchers from Florida Atlantic University's Charles E. Schmidt College of Medicine in collaboration with Georgia Aquarium, conducted a study to identify cross-reactive terrestrial-specific antibodies for dolphins, which is the first study to characterize their immune cell subsets using this methodology. The goal of this study was to assess changes in immune cell populations in dolphins in the wild and results are published in the journal BMC Veterinary Research.

"We know that a strong immune system is important for combatting infectious diseases and cancer in both humans and animals," said Mahyar Nouri-Shirazi, DVM., Ph.D., lead author of the study and a professor of integrated medical science in FAU's College of Medicine. "Wild dolphins are impacted by newly characterized infectious disease and cancer, often associated with immunologic disturbances, which are now being better characterized."

While there are a number of studies and reports that suggest a correlation between environmental contaminants, immune disturbances and disease susceptibility in wild dolphins and other marine mammals, scientists and veterinarians need a way to characterize, monitor and evaluate specific immune cells to investigate and confirm this correlation.

The gold standard to monitor immune status and disease progression in humans is flow cytometry, a powerful tool that is used to rapidly measure and isolate immune cells. However, flow cytometry for dolphins requires the use of dolphin specific antibodies that are presently limited for the many different types of immune cells. To address this limitation, Nouri-Shirazi's team identified cross-reactive, terrestrial-specific antibodies to phenotype the immune cells of dolphins under human care and compare them with the immune status of Atlantic bottlenose dolphins in the wild.

"When we compared the samples, we were able to see that the profile of some of the dolphins in the wild had changed significantly," said Nouri-Shirazi. "We saw abnormal distributions and increases in the percentages of the immune cells, which indirectly tells us that there may be a disease present."

Results from this study show that out of 65 terrestrial-specific antibodies tested, 11 were cross-reactive and identified dolphin immune cell populations within their peripheral blood. Using these antibodies, the researchers found significant differences in the absolute number of cells expressing specific markers within their lymphocyte and monocyte fractions. They found that the cross-reactive antibodies not only identified specific changes in the immune cells of dolphins in the wild, but also opened up the possibility to investigate the causal relationship between immune disturbances and morbidity and mortality seen in these dolphins in the wild.

"Georgia Aquarium's collaborative bottlenose dolphin research with FAU has demonstrated the intricate and dynamic interactions that occur between infectious disease, anthropogenic contaminants and immunologic responses. We have found that these interactions highlight the complexity of evaluating health in dolphins," said Gregory Bossart, VMD, Ph.D., co-author of the study and senior vice president and chief veterinary officer, Georgia aquarium. "Additionally, we have demonstrated that the bottlenose dolphin is a valuable sentinel species for understanding emerging or re-emerging diseases that may impact environmental and human health."

Findings from this study open up the possibility of utilizing flow cytometry for routine health assessment by monitoring specific changes in immune cells of wild dolphins caused by environmental contaminants or infectious agents with the goal of understanding pathogenesis of diseases.

The researchers anticipate that this new approach could be applicable to dolphins as well as other marine mammals including whales and manatees.

Read more at Science Daily

Magnetic switch turns strange quantum property on and off

These images show the orbital paths of electrons trapped within a circular region within graphene. In the classical orbit (top image), an electron that travels in a complete circuit has the same physical state as when it started on the path. However, when an applied magnetic field reaches a critical value, (bottom image), an electron completing a circuit has a different physical state its original one. The change is called a Berry phase and the magnetic field acts as a switch to turn on the Berry phase. The result is that the electron is raised to a higher energy level.

When a ballerina pirouettes, twirling a full revolution, she looks just as she did when she started. But for electrons and other subatomic particles, which follow the rules of quantum theory, that's not necessarily so. When an electron moves around a closed path, ending up where it began, its physical state may or may not be the same as when it left.

Now, there is a way to control the outcome, thanks to an international research group led by scientists at the National Institute of Standards and Technology (NIST). The team has developed the first switch that turns on and off this mysterious quantum behavior. The discovery promises to provide new insight into the fundamentals of quantum theory and may lead to new quantum electronic devices.

To study this quantum property, NIST physicist and fellow Joseph A. Stroscio and his colleagues studied electrons corralled in special orbits within a nanometer-sized region of graphene -- an ultrastrong, single layer of tightly packed carbon atoms. The corralled electrons orbit the center of the graphene sample just as electrons orbit the center of an atom. The orbiting electrons ordinarily retain the same exact physical properties after traveling a complete circuit in the graphene. But when an applied magnetic field reaches a critical value, it acts as a switch, altering the shape of the orbits and causing the electrons to possess different physical properties after completing a full circuit.

The researchers report their findings in the May 26, 2017, issue of Science.

The newly developed quantum switch relies on a geometric property called the Berry phase, named after English physicist Sir Michael Berry who developed the theory of this quantum phenomenon in 1983. The Berry phase is associated with the wave function of a particle, which in quantum theory describes a particle's physical state. The wave function -- think of an ocean wave -- has both an amplitude (the height of the wave) and a phase -- the location of a peak or trough relative to the start of the wave cycle.

When an electron makes a complete circuit around a closed loop so that it returns to its initial location, the phase of its wave function may shift instead of returning to its original value. This phase shift, the Berry phase, is a kind of memory of a quantum system's travel and does not depend on time, only on the geometry of the system -- the shape of the path. Moreover, the shift has observable consequences in a wide range of quantum systems.

Although the Berry phase is a purely quantum phenomenon, it has an analog in non-quantum systems. Consider the motion of a Foucault pendulum, which was used to demonstrate Earth's rotation in the 19th century. The suspended pendulum simply swings back and forth in the same vertical plane, but appears to slowly rotate during each swing -- a kind of phase shift -- due to the rotation of Earth beneath it.

Since the mid-1980s, experiments have shown that several types of quantum systems have a Berry phase associated with them. But until the current study, no one had constructed a switch that could turn the Berry phase on and off at will. The switch developed by the team, controlled by a tiny change in an applied magnetic field, gives electrons a sudden and large increase in energy.

Several members of the current research team -- based at the Massachusetts Institute of Technology and Harvard University -- developed the theory for the Berry phase switch.

To study the Berry phase and create the switch, NIST team member Fereshte Ghahari built a high-quality graphene device to study the energy levels and the Berry phase of electrons corralled within the graphene.

First, the team confined the electrons to occupy certain orbits and energy levels. To keep the electrons penned in, team member Daniel Walkup created a quantum version of an electric fence by using ionized impurities in the insulating layer beneath the graphene. This enabled a scanning tunneling microscope at NIST's nanotechnology user facility, the Center for Nanoscale Science and Technology, to probe the quantum energy levels and Berry phase of the confined electrons.

The team then applied a weak magnetic field directed into the graphene sheet. For electrons moving in the clockwise direction, the magnetic field created tighter, more compact orbits. But for electrons moving in counterclockwise orbits, the magnetic field had the opposite effect, pulling the electrons into wider orbits. At a critical magnetic field strength, the field acted as a Berry phase switch. It twisted the counterclockwise orbits of the electrons, causing the charged particles to execute clockwise pirouettes near the boundary of the electric fence.

Ordinarily, these pirouettes would have little consequence. However, says team member Christopher Gutiérrez, "the electrons in graphene possess a special Berry phase, which switches on when these magneticallyinduced pirouettes are triggered."

Read more at Science Daily

From blue and black dresses to turbine blades, here's the science of 'fake fake' photographs

Pictured is the Blade in situ, viewed from below.

Whether it's a blue and black dress -- or white and gold depending on your take -- or a pair of legs streaked with white paint, eagle-eyed viewers are always keen to debate a visual illusion when these puzzling images appear online.

A new study published today reveals the science behind another 'trick of the light' that made high-profile photographs of a major piece of public art appear 'faked' to some people despite the pictures being entirely genuine.

Vision science researchers from the University of Lincoln examined photographs of the art installation, Blade, which took pride of place in the centre of Hull earlier this year. Their interest was triggered when some pictures published online of the work -- a 75-metre long, 25-tonne wind turbine blade -- made the object appear to be super-imposed.

The researchers found that this visual illusion was caused by the particular way light reflected from the blade, which then played on pre-conceived notions people have of how objects are lit in natural settings, effectively altering the object's shape to the human eye.

Daylight hitting the object from above produced shading which created the illusion that the blade was cylindrical, and was being lit from the side rather than above. This subtly reinforced the visual impression that the blade was out-of-place, and that the image of the blade and its backdrop must therefore be a composite of two different scenes.

To demonstrate this, researchers created virtual versions of a cylindrical C-shaped profile and a more complex S-shaped profile, and produced two images of each shape, one lit from above and the other lit from the front. The images demonstrated that the S-shape when lit from above and the C-shape when lit from the front both appeared cylindrical.

Professor of Vision Science, George Mather, from the University of Lincoln's School of Psychology, said: "I saw pictures of the installation in the media, and at first sight the photographs seemed to be clumsy fakes. Something else seemed to be at work too, at least to my eyes as a vision scientist.

"The blade appeared to be a cylindrical object, strangely out-of-keeping with the local environment, lit differently, as though it was superimposed on the scene digitally, but it really was there.

"We had an idea about what it was that conveyed this impression -- light and shadow on the blade which is apparently inconsistent with the surroundings. The computer generated images were a way of testing the idea."

The blade was made by turbine manufacturer Siemens and placed in Victoria Square as a major public art installation to mark the start of Hull's year as the UK City of Culture 2017. Artist Nayan Kulkarni created the installation for Look Up, a programme of temporary artworks designed for Hull's public spaces and places. It used one of the first B75 rotor blades manufactured in Hull.

Read more at Science Daily

How do blind cavefish find their way? The answer could be in their bones.

A micro-CT scan shows the differences in bone structure between a surface fish and a blind cavefish.

Cavefish are genetically similar to their symmetrical and keen-sighted cousins, Mexican tetras, found in nearby creeks and rivers on the surface. They're so closely related that they easily interbreed and produce fertile young, even though the two species are believed to have diverged millions of years ago.

Cavefish start their lives with symmetrical features like other fish. But when they mature, their fragmented cranial bones harden in a visibly skewed direction, the study found.

UC's researchers speculate that this adaptation helps the typically left-leaning cavefish navigate by using sensory organs called neuromasts to follow the contours of the cave as they swim in a perpetual counterclockwise pattern. This behavior was observed among captive cavefish, which keep moving around the edges of their tanks while surface fish tend to stay motionless in the shadows of their tank or swim in haphazard ways.

"That was a real big piece of the puzzle for us," said Joshua Gross, a UC biology professor and co-author. "It's a mystery how they've been able to adapt. The amazing thing is that they're not just barely surviving -- they thrive in total darkness."

Gross has been studying cavefish for years at UC. They make an excellent model to examine regressive evolution, the process by which animals lose features over generations, he said.

"The traits they've lost are very conspicuous -- their eyes, their pigmentation," Gross said. "The beauty of studying cave animals is it's a very robust model for understanding why features are lost, and it's a simple, stable set of environmental pressures that cause those features to go away."

Cave-dwelling animals as diverse as salamanders and crayfish have responded similarly by losing pigment and eyesight while gaining or augmenting other sensory structures.

"The fact that they're all moving in the same evolutionary direction is not a coincidence. They're all living in total darkness with a limited food supply," he said.

Cavefish are especially valuable for evolutionary study, Gross said, because of their genetic relationship with readily abundant surface fish. Many antecedents of other cave-dwelling animals have been lost to extinction from natural selection or calamity.

The UC biology lab has dozens of aquariums and breeding tanks full of cave and surface fish, each smaller than a goldfish. Researchers use QR-code stickers to keep track of the family history of the resident fish swimming in slow circles.

The hardy fish are easy to keep because they are not picky eaters. They get a mix of foods including flakes, brine shrimp and blackworms. UC gets its study fish from natural populations maintained by colleagues and reputable breeders.

"Our lab really tries to avoid taking any animals from nature," Gross said.

Mexican cavefish also are raised as a popular aquarium pet.

The skulls of all but a couple cavefish UC studied bend to the left. They seem to be right-finned, swimming in a lazy counterclockwise pattern around their aquariums in the biology lab.

"You could see how asymmetry might be an advantage in navigation," Powers said.

"They tend to swim in a unidirectional, circular motion around their tanks to explore their surroundings," she said. "Having asymmetry in their skull we think is attributed to handedness. If their skull is bent to the left, they could be 'right-handed.' They're feeling the wall to the right with their sensory structures."

This kind of asymmetry is uncommon in nature. Think of the fiddler crab with its outsized claw. Owls have asymmetrical ears -- one canal placed higher on the skull than the other -- perhaps to help the night predators target the faint rustling of a mouse in the dark.

In the biology lab, researchers breed surface fish with cavefish and study the resulting hybrids, co-author and recent UC graduate Shane Kaplan said. He and UC student Erin Davis also contributed to the study.

The interesting genetic combinations occur in the second generation or F2 population of hybridization, he said.

"You can capture the genetic diversity of the entire population," Kaplan said. "Some fish look exactly like surface fish. Others look exactly like cavefish. Then you'll have intermittent phenotypes. Some are pale but have eyes while others will have no eyes but are fully pigmented."

The study was funded by grants from the National Institutes of Health and the National Science Foundation.

Powers traveled with Gross to Mexico in 2013, in 2015 and again this year to study wild cavefish. They wore dust masks to guard against fungal spores associated with the respiratory disease histoplasmosis, which can be found in bat guano. Getting to the fish pools required a little spelunking.

"The group ahead of us disturbed some bats. As we were coming in, bats were going out," she said. "They have incredible echo-location. The bats knew where you were and would fly around you in the darkness, even though it was a very small chamber."

The cave had several distinct pools, each farther from the entrance. The deeper they went, the fewer surface-dwelling fish they found until they found only blind cavefish.

"Whenever you would touch the surface of the water with your finger, a swarm of cavefish would come right up to it," Powers said. "Not many fish would do that. These cavefish have zero predators so they're not afraid. That was a really cool experience."

Kaplan said it would be worthwhile to explore the cavefish's DNA to find out what prompts the asymmetry in adult cavefish.

"We haven't yet delved into why it's happening. I'd love to get more into the genetics and developmental processes that lead to these bizarre phenotypes," Kaplan said.

Read more at Science Daily

Marmoset monkeys learn to call the same way human infants learn to babble

Marmoset monkeys.

A baby's babbles start to sound like speech more quickly if they get frequent vocal feedback from adults. Princeton University researchers have found the same type of feedback speeds the vocal development of infant marmoset monkeys, in the first evidence of such learning in nonhuman primates, researchers report in Current Biology on May 25.

"We wanted to find out whether the idea that monkeys don't do any learning during their vocal development is actually true," says the study's senior co-author Asif Ghazanfar, a professor of psychology and the Princeton Neuroscience Institute. "So we picked a species that we know really relies on vocalizations as its primary social signals. What we found in marmoset vocal development very closely parallels pre-linguistic vocal development in humans."

Although marmoset vocal calls do not approach the complexity of human language systems, vocal development in both species begins with infants making more or less random sounds.

"When an infant blurts out something and the parent responds, that's a contingent response. And the more often a parent provides that contingent response, the faster the human infant will develop its vocalizations," Ghazanfar says.

To find out whether the same principle held true for marmosets, Ghazanfar and his colleagues set up an experiment using pairs of fraternal twin marmosets, small, highly social monkeys from South America. Starting from the day after the marmosets were born, the researchers would separate the infants from the adult marmosets for 40 minutes each day. In the first 10 minutes, they recorded the noises that the infant marmosets made while sitting alone. Then, for the next half hour, the researchers gave the young marmosets contingent feedback in the form of audio playbacks of the parent's calls.

One twin in each pair got consistent feedback, mirroring what a young marmoset would receive from an especially attentive parent; the other twin got less consistent feedback on their vocalizations. They repeated these experiments up until the infants were 2 months old, roughly the equivalent of 2 years old in marmoset years.

Even though these sessions lasted less than an hour each day, infant marmosets that received lots of contingent feedback developed adult-sounding calls more rapidly than their siblings.

"When they're infants, this call is really noisy," Ghazanfar says. "It sounds kind of coarse, and then gradually it becomes very clean and tonal like an adult call."

Previous studies had found a correlation between the amount of feedback marmosets get from parents and the rate of vocal development, but the experimental design in this study more firmly establishes the causality between parental responses and vocal development, the researchers say.

"This system of vocal learning production may be linked to the idea that an infant that more quickly produces adult-sounding calls is more likely to get care from a caregiver in a cooperative breeding environment where multiple individuals could be that caregiver in addition to the parents," Ghazanfar says. "So it's not only this process of learning that's similar to humans; the whole reproductive strategy is similar to humans."

The researchers' next steps will include collecting more detailed data on marmosets' neural activity when they are chattering or calling to neighbors, he says.

Read more at Science Daily

Ancient Hunter-Gatherers and Farmers Made Love, Not War

Facial reconstruction of a hunter-gatherer woman from Chan do Lindeiro, Spain, who lived about 9,000 years ago.

For much of human history, our ancestors were hunter-gatherers, mostly nomadic people who lived by hunting, fishing and harvesting wild food. Around 10,000 years ago, farming developed in Western Asia and quickly spread across Europe and to other parts of the world. The ancient lifestyle shift begs the question: What happened when the farmers first encountered the hunter-gatherers?

New DNA evidence reported in the journal Current Biology helps to provide the answer by showing that, at least in the area now known as Romania, hunter-gatherers and farmers were living side by side, intermixing with each other, and having children.

It was not necessarily love at first sight, though.

“Farmers arrived very suddenly, as a result of a fast expansion,” co-author Andrea Manica of the University of Cambridge said. “It is likely that they lived side by side with local hunter-gatherer populations for a period of time — centuries or even a millennium or two — with increasing contact and mixing among the two communities.”

Manica, lead author Gloria Gonzalez-Fortes, and their international team came to these conclusions after recovering four ancient human genomes from Romania dating to between 8.8–5.4 thousand years ago. For context, they analyzed two hunter-gatherer genomes from Spain, as well as other known early genomes from these European regions.

Co-author Clive Bonsall from the University of Edinburgh explained that indigenous hunter-gatherers can be distinguished archaeologically from immigrant farmers by their material culture, such as artifacts, architecture, burial traditions, art, and body ornamentation. The two groups also differ in subsistence practices, determined by food refuse preserved in the archaeological record and chemical analysis of human remains.

“For example, in our study region, hunter-gatherers did not cultivate or raise livestock, although they did keep domestic dogs," Bonsall said. "They did not use pottery, and buried their dead in a different way.”

The DNA analysis revealed that the early Romanian genomes had significant input from Western hunter-gatherers, but still showed a sizable contribution from Anatolian farmers. This suggests that some hunter-gatherers and farmers were mating and raising children.

The scientists suspect that the challenging climate of the region might have caused the farmers to supplement their diet with food from hunter-gatherer activities, helping to bring the two distinct groups of people together.

Skeleton within a burial at Schela Cladovei, Romania.

Chemical investigation of related human bones demonstrates that the joining of the two cultures broadened the diets of each. Bonsall said early Southeast European farmers cultivated cereals, such as wheat and barley, and legumes, like peas and lentils. They also raised sheep, goats, cattle, and pigs.

They additionally consumed some dairy products, even though all of the individuals examined in the study were lactose intolerant. Co-author Eppie Jones of the University of Cambridge explained that “the mutation, which allowed people to drink milk into adulthood, has not been found in Europe before the Bronze Age (starting around 2300 B.C.).”

The hunter-gatherers, on the other hand, brought plenty of nuts, plant foods, fish, and shellfish to the table. Some hunter-gatherers along the lower Danube River were so good at fishing that they lived in more permanent settlements, known as fishing villages.

Previously it was thought that farmers horned in on the hunter-gatherer territory and outcompeted the native populations, but the DNA evidence indicates that, at least in some cases, the two groups managed to live together despite large cultural differences.

Jones mentioned that the new findings, combined with prior research, reveal that “the amount of mixing between the groups varies in different regions of Europe. In Central and Western Europe, the incoming farmers largely replaced the local populations, while in areas further north, such as the Baltic, farmers didn’t make much of a genetic impact.”

Read more at Discovery News

Early Collapse of Arctic Sea Ice Is Another Ominous Sign of Rapid Warming

This image from 2010 shows the boundary between permanent and seasonal sea ice in the Arctic Ocean, northwest of Greenland.

Earth’s already-beleaguered northern icecap suffered another blow this month with the early collapse of a barrier that kept some of Arctic’s most durable ice in place.

The ice arch across the Nares Strait, which separates Greenland from Ellesmere Island in Canada’s far northeast, gave way two months earlier than usual, said Laurence Dyke, a paleoglaciologist at the Geological Survey of Denmark and Greenland.

“On May 10, this arch disintegrated, leaving the oldest and thickest sea ice in the Arctic vulnerable to being swept south where it will melt away,” Dyke told Seeker. “Over the last two weeks, the area of broken ice has expanded massively to the north, and lots of Arctic sea ice is flowing southwards through the Nares Strait.”

The channel and the Lincoln Sea, at the northern tip of Greenland, are normally covered by a sheet of ice several meters thick until around July, Dyke said. Usually, ice sheets that cover the strait are anchored to land and don’t move, blocking the passage of sea ice through the strait.

But as heat-trapping fossil-fuel emissions like carbon dioxide build up in the atmosphere, the Arctic is warming twice as fast as the rest of the globe. And this year, land-anchored ice in the strait failed to form amid the record warmth and record low sea ice coverage recorded across the Arctic. That left only an arch of ice at the northern end of the strait, where it joined the Lincoln Sea — the structure that gave way earlier this month.

“This is especially important as the Lincoln Sea contains the last bastion of old, thick multi-year sea ice,” Dyke said.

The Nares Strait is the smaller of two passages that can funnel ice from that area toward the Atlantic.

The Fram Strait, on the east side of Greenland, carries “significantly more,” said Twila Moon, a glaciologist at the National Snow and Ice Data Center in Colorado — “But every little bit counts.”

And the loss of multi-year ice is already a chronic problem in the Arctic. It forms the heart of next year’s sea ice and provides habitat for whales, seals, and birds.

“It’s also playing a role to reduce the amount of heat the ocean can take in during the summer,” Moon said. If less ice is floating on the surface of the Arctic ocean, the dark-colored sea will absorb more of the Sun’s energy — “and of course, more heat in the ocean reduces our sea ice further, and we get a runaway effect.”

“Each of these small events adds up, and they’re not good news,” she added.

This year’s event isn’t unprecedented: Something similar happened in 2007. But when that occurred, “that led to the largest flux of Arctic Sea ice through Nares Strait in at least the last 15 years,” Dyke said.

“Multi-year ice has been steadily declining over the last two decades, and this early break-up will surely destroy another large portion of it,” he said.

Since sea ice is floating in water already, its melting doesn’t add to sea-level rise — which a recent study suggests has accelerated dramatically since the 1990s. But the warming of the surrounding oceans is already starting to eat away at the miles of ice that cover Greenland.

Dykes was part of a 2015 expedition to study the Greenland’s massive Petermann Glacier, which overlooks the Nares Strait, and said that the loss of sea ice is starting to affect that structure.

Read more at Discovery News