Computational model links family members using genealogical and law-enforcement databases

Genetic sequences

The notion of using genetic ancestry databases to solve crimes recently crossed from hypothetical into credible when police used an online genealogical database to track down the alleged Golden State Killer, a serial criminal who terrorized much of California in the 1970s and 1980s. Now, in a study published October 11 in Cell, researchers are reporting ways in which that type of inquiry could potentially be expanded.

Specifically, they have published a computational method for linking individuals in ancestry databases to those in law-enforcement databases. These two databases use completely different systems of genetic markers. The investigators report in a proof of principle with 872 people that for close relatives -- either sibling or parent-offspring pairs -- more than 30% can be accurately matched with the correct relative using nonoverlapping genetic markers from the two different databases.

"There's a legacy problem in that so many DNA profiles have been collected with this older genetic marker system that's been used by law enforcement since the 1990s. The system is not designed for the more challenging queries that are currently of interest, such as identifying people represented in a DNA mixture or identifying relatives of the contributor of a DNA sample," says senior author Noah Rosenberg, a biology professor at Stanford University. "In this study, we were trying to pose the question of whether a newer, more modern system of genetic markers could be tested against the old system and still get matches and find relatives."

The database used by the FBI and other law-enforcement agencies is known as the Combined DNA Index System (CODIS). It relies on short tandem repeat (STR) markers, a type of copy-number variation, in noncoding regions of the DNA. (The system originally used 13 markers; it recently was updated and now includes 20.) By contrast, ancestry databases look for differences in single-nucleotide polymorphisms (SNPs) across hundreds of thousands of sites in the genome.

In a study published last year, Rosenberg's team reported that software could match individuals who appeared in both databases even with genotype datasets that had no shared markers. They matched more than 90% of people using the 13-marker version of CODIS and up to 99% with 20 markers. The key idea is that each STR marker is surrounded by SNPs that are typically inherited together with the STR. As a result, a person's genotypes for those SNPs can partially predict the genotype of the neighboring STR and vice versa. When these subtle correlations are accumulated across many STRs, it becomes possible to match an SNP profile with an STR profile.

The new paper built on that research by looking at whether the same approach would work in connecting close family members. They found that when one individual had been analyzed for STR markers and the other for SNP markers, about 30%-32% of parent-offspring pairs and 35%-36% of sibling pairs could be linked.

In the Golden State Killer case, law enforcement submitted DNA collected from one of the crime scenes for SNP genotyping, then used an open-source ancestry database to link that profile with other individuals who were present in the database. But the technique reported in the new paper suggests that familial searches might be possible to perform linking people in CODIS to relatives in an ancestry database or vice versa.

The study was intended to provide data for discussing many of the issues surrounding forensic genetics and genomic privacy, Rosenberg explains. "We wanted to examine to what extent these different types of databases can communicate with each other," he says. "It's important for the public to be aware that information between these two types of genetic data can be connected, often in unexpected ways."

When current policies surrounding DNA evidence were established, it wasn't possible to make this connection. "We have shown that the investigative reach of forensic STR profiles might be possible to expand beyond what was previously believed to be the limit," he adds.

In the paper, the researchers note other policy-relevant issues surrounding this expanded capability. For example, certain populations are overrepresented in law-enforcement STR databases. Expanding the use of database searches could change the calculation about who is accessible to investigators from the profiles in those databases. "There has already been a lot of legal analysis on how STR databases are used," Rosenberg says. "With this study, we suggest that SNP databases and their links to STR databases should also be considered in that analysis."

The new findings have applications for other areas of study beyond law enforcement. For example, ecologists studying organisms in the field could use this approach to determine whether animals living in a particular geographic site descended from animals whose DNA had been collected on a previous sampling trip even if only STR data is available from the older samples. The linkage tools also could potentially be used to link DNA fragments from ancient humans with each other -- for example, when multiple samples are tested from an ancient burial site.

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Did mosasaurs hunt like killer whales?

A plaster cast of mosasaur jaws show how sharp and ferocious their teeth were.

Did prehistoric sea creatures called mosasaurs subdue prey by ramming them with their bony snouts like killer whales do today?

It's a theory that University of Cincinnati biology professor Takuya Konishi proposed after taking a closer look at a newborn fossil specimen for his latest research study. Konishi will present his findings at October's Society of Vertebrate Paleontology conference in Albuquerque, New Mexico.

"Killer whales don't hunt big prey by biting. They hunt by ramming and tearing them apart after the prey is weak," Konishi said. "They are chasing fast-moving animals so they use inertia. If they were swimming full speed at you, they would generate a lot of force. And their snout is conspicuously protruding."

Mosasaur, the unlikely hero of the movie "Jurassic World," was an enormous marine reptile that lived in the time of Tyrannosaurus rex during the Cretaceous Period more than 65 million years ago. They had a similar body shape as today's orcas, with flippers, powerful tails and sharp teeth. Some grew bigger than orcas to nearly the size of a school bus.

Like orcas, they were the apex predators of the seas. The only thing mosasaurs had to fear were bigger mosasaurs.

In a study published this month in the Journal of Vertebrate Paleontology, Konishi re-examined fossils of a newborn mosasaur he first studied in Kansas while working on his master's degree in 2004. About 20 small fragments of skull were unearthed in 1991 by paleontologist Michael Everhart in a rock formation called the Kansas Chalk renowned for marine fossils.

Initially, the specimen was identified as a mosasaur called Platecarpus, a species commonly found in that area during the same period 85 million years ago. The family Mosasauridae features more than 30 genera of species, so identifying a particular specimen from a handful of fossil fragments can be daunting.

"A colleague of mine told me mosasaurs are boring because they all look the same. That's sort of true," he said. "But once you know more about them you can begin to tell them apart."

Some mosasaurs had short, powerful jaws capable of crushing the shells of sea turtles. Others had pointy teeth that suggested they feed mostly on fish.

Konishi was inspired to take a second look after a fellow researcher demonstrated how particular bones called quadrates were not as reliable in identifying species as researchers once thought. The telltale fossils of adults of different species look very similar in juveniles.

In the many years since Konishi first examined the baby mosasaur, he has become an expert on these seagoing lizards, including the largest of them called Tylosaurus. This was the creature that inspired "Jurassic World," a meat-eating monster capable of hunting other mosasaurs and marine reptiles.

In re-examining the skull fragments from the newborn mosasaur, Konishi found it did not resemble other specimens of Platecarpus. While Platecarpus and other mosasaurs have teeth that begin virtually at the tip of their snouts, Tylosaurus has a bony protrusion called a rostrum that extends out from its face like an orca that might have served to protect its front teeth when they slammed into prey.

"It's a subtle feature perhaps by horned dinosaur standards, but for us it really signifies what kind of mosasaur you're looking at," Konishi said. "If you have this protruding snout in this part of western Kansas, you're a Tylosaurus."

Like many other kinds of baby animals today, the baby mosasaur had not yet developed certain telltale features found in adults, Konishi said.

"The degree of snout development was nowhere near that of an adult, which made me look elsewhere such as the braincase to call it Tylosaurus in the end. It was the ugly duckling that hadn't yet become the graceful swan," Konishi said.

Unlike other mosasaur species, Konishi said the tylosaur had broader and more robust facial bones connected to a sturdy cranial vault that would have provided support as a battering ram.

Konishi pulled up a dramatic photo showing a breaching orca pummeling a large dolphin with its snout. The dolphin, a species called a false killer whale, was struck so hard that its body was contorted at a painful-looking angle.

"When orcas hunt dolphins and small whales, they subdue them by ramming them. And when you look at them, you see they have a protruding snout as well," Konishi said.

The fossils represent the youngest and smallest specimen of Tylosaurus ever found. Everhart confirmed to Konishi that the baby mosasaur was found alone with no associated fossils. Mosasaurs didn't lay eggs but gave birth to live young. That suggests the specimen was a free-swimming newborn rather than an embryo when it died, he said.

Just how the baby mosasaur perished is a matter of speculation. Only its skull was found. Konishi said the mosasaur could have succumbed to countless mishaps from predation to accident to disease.

It took a miracle of improbability that the baby mosasaur was found in the first place, he said.

Finding any baby dinosaur, or marine reptile in this case, is extremely rare for the simple reason that baby animals often end up as someone else's dinner. The bones of baby animals are lighter and more likely to scatter. But in this case, bones that weren't chewed up reached the ocean floor where they were covered in sediment and remained for millions of years until the seas receded and the former ocean floor became the wheat fields and farmlands of today's Kansas.

"And luckily an expert on mosasaurs was searching in exactly that spot and had sharp enough eyes to find it -- all separated by about 85 million years," Konishi said.

"Most fossils are fragmentary. You almost never find an entirely articulated fossil in the ground. That's near fantasy," Konishi said. "Luckily, the remaining bones were buried and became fossilized."

Konishi's theory strikes a chord with orca experts such as Ken Balcomb, senior scientist with the nonprofit Center for Whale Research outside Seattle, Washington. Balcomb has been studying orcas for 43 years. He has seen firsthand the myriad clever methods they employ to hunt different prey.

"They pummel their prey quite a bit. They will throw their body against a gray whale. They'll ram great white sharks, too," Balcomb said.

But Balcomb said they're choosy about what and how they attack, often using their flukes or whole body rather than their heads. They even distinguish between different types of prey.

"They know which kinds of seals will fight back," Balcomb said. "So they're cautious. They don't want to get hurt."

Contributing to Konishi's study were Paulina Jiménez-Huidobro and Michael Caldwell, both of the University of Alberta. The study was funded in part by the Natural Sciences and Engineering Research Council of Canada.

Konishi said this better understanding of the development of baby mosasaurs could help scientists learn more about fossils of other baby dinosaurs and marine reptiles that look markedly different from their parents.

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'Vampire burial' reveals efforts to prevent child's return from grave

A rock was inserted into the mouth of a 10-year-old to keep the deceased child from rising from the grave and spreading malaria, researchers believe.

The discovery of a 10-year-old's body at an ancient Roman site in Italy suggests measures were taken to prevent the child, possibly infected with malaria, from rising from the dead and spreading disease to the living.

The skeletal remains, uncovered by archaeologists from the University of Arizona and Stanford University, along with archaeologists from Italy, included a skull with a rock intentionally inserted into the mouth. Researchers believe the stone may have been placed there as part of a funeral ritual designed to contain disease -- and the body itself.

The discovery of this unusual, so-called "vampire burial" was made over the summer in the commune of Lugnano in Teverina in the Italian region of Umbria, where UA archaeologist David Soren has overseen archaeological excavations since 1987.

"I've never seen anything like it. It's extremely eerie and weird," said Soren, a Regents' Professor in the UA School of Anthropology and Department of Religious Studies and Classics. "Locally, they're calling it the 'Vampire of Lugnano.'"

The discovery was made at La Necropoli dei Bambini, or the Cemetery of the Babies, which dates to the mid-fifth century when a deadly malaria outbreak swept the area, killing many vulnerable babies and small children. The bodies of the young victims were buried at the site of an abandoned Roman villa that was originally constructed at the end of the first century B.C.

Until now, archaeologists believed the cemetery was designated specifically for infants, toddlers and unborn fetuses; in previous excavations of more than 50 burials, a 3-year-old girl was the oldest child found.

The discovery of the 10-year-old, whose age was determined based on dental development but whose sex is unknown, suggests that the cemetery may have been used for older children as well, said bioarcheologist Jordan Wilson, a UA doctoral student in anthropology who analyzed the skeletal remains in Italy.

"There are still sections of the cemetery that we haven't excavated yet, so we don't know if we'll find other older kids," Wilson said.

Excavation director David Pickel, who has a master's degree in classical archaeology from the UA and is now a doctoral student at Stanford, said the discovery has the potential to tell researchers much more about the devastating malaria epidemic that hit Umbria nearly 1,500 years ago, as well as the community's response to it.

"Given the age of this child and its unique deposition, with the stone placed within his or her mouth, it represents, at the moment, an anomaly within an already abnormal cemetery," Pickel said. "This just further highlights how unique the infant -- or now, rather, child -- cemetery at Lugnano is."

Witchcraft as disease control

In previous excavations at the Cemetery of the Babies, archaeologists found infant and toddler bones alongside items like raven talons, toad bones, bronze cauldrons filled with ash and the remains of puppies that appear to have been sacrificed -- all objects commonly associated with witchcraft and magic. In addition, the body of the 3-year-old girl had stones weighing down her hands and feet -- a practice used by different cultures throughout history to keep the deceased in their graves.

"We know that the Romans were very much concerned with this and would even go to the extent of employing witchcraft to keep the evil -- whatever is contaminating the body -- from coming out," Soren said.

The "evil," in the case of the babies and toddlers uncovered in Lugnano, was malaria, Soren believed. DNA testing of several of the excavated bones supported his theory.

Although the 10-year-old's remains have not yet undergone DNA testing, the child had an abscessed tooth -- a side effect of malaria -- that suggests he or she may also have fallen victim to the disease, Wilson said.

The child was one of five new burials uncovered at the cemetery over the summer. The body was found lying on its left side in a makeshift tomb created by two large roof tiles propped against a wall -- an alla cappuccina-style burial typical of Roman Italy.

"Knowing that two large roof tiles were used for this burial, I was expecting something unique to be found inside, perhaps a 'double-inhumation' -- not uncommon for this cemetery -- where a single burial contains two individuals," Pickel said. "After removing the roof tiles, however, it became immediately clear to us that we were dealing with an older individual."

The open position of the child's jaw, which would not have opened naturally during decomposition with the body positioned on its side, suggests that the rock was intentionally inserted in the mouth after death, Wilson said. Teeth marks on the surface of the stone provide further evidence that it was placed purposefully.

The 10-year old was the first at the cemetery to be found with a stone in its mouth. Similar burials have been documented in other locations, including in Venice, where an elderly 16th-century woman dubbed the "Vampire of Venice" was found with a brick in her mouth in 2009. In Northamptonshire, England, in 2017, an adult male from the third or fourth century was found buried facedown with his tongue removed and replaced with a stone.

These types of burials are often referred to as vampire burials, since they are associated with a belief that the dead could rise again. Other examples of vampire burials throughout history include bodies being staked to the ground through the heart or dismembered prior to interment.

"This is a very unusual mortuary treatment that you see in various forms in different cultures, especially in the Roman world, that could indicate there was a fear that this person might come back from the dead and try to spread disease to the living," Wilson said.

Archaeologists will return to Lugnano next summer to complete excavations of the cemetery and learn more about a dark time in history.

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Mouse pups with same-sex parents born in China using stem cells and gene editing

This image shows a healthy adult bimaternal mouse (born to two mothers) with offspring of her own.

Researchers at the Chinese Academy of Sciences were able to produce healthy mice with two mothers that went on to have normal offspring of their own. Mice from two dads were also born but only survived for a couple of days. The work, presented October 11 in the journal Cell Stem Cell, looks at what makes it so challenging for animals of the same sex to produce offspring and suggests that some of these barriers can be overcome using stem cells and targeted gene editing.

"We were interested in the question of why mammals can only undergo sexual reproduction. We have made several findings in the past by combining reproduction and regeneration, so we tried to find out whether more normal mice with two female parents, or even mice with two male parents, could be produced using haploid embryonic stem cells with gene deletions," says co-senior author Qi Zhou.

While some reptiles, amphibians, and fish can reproduce with one parent of the same sex, it's challenging for mammals to do the same even with the help of fertilization technology. In mammals, because certain maternal or paternal genes are shut off during germline development by a mechanism called genomic imprinting, offspring that don't receive genetic material from both a mother and a father might experience developmental abnormalities or might not be viable. By deleting these imprinted genes from immature eggs, researchers have produced bimaternal mice -- mice with two mothers -- in the past. "However, the generated mice still showed defective features, and the method itself is very impractical and hard to use," says Zhou.

To produce their healthy bimaternal mice, Zhou, co-senior author Baoyang Hu, co-senior author Wei Li, and their colleagues used haploid embryonic stem cells (ESCs), which contain half the normal number of chromosomes and DNA from only one parent and which the researchers believe were the key to their success. The researchers created the mice with two mothers by deleting three imprinting regions of the genome from haploid ESCs containing a female parent's DNA and injected them into eggs from another female mouse. They produced 29 live mice from 210 embryos. The mice were normal, lived to adulthood, and had babies of their own.

One advantage of using haploid ESCs is that even before the problematic genes are knocked out, they contain less of the imprinting programming that ultimately causes maternal- or paternal-specific genes to be expressed. "We found in this study that haploid ESCs were more similar to primordial germ cells, the precursors of eggs and sperm. The genomic imprinting that's found in gametes was 'erased,'" says Hu.

Twelve live, full-term mice with two genetic fathers were produced using a similar but more complicated procedure. Haploid ESCs containing only a male parent's DNA were modified to delete seven key imprinted regions. The edited haploid ESCs were then injected -- along with sperm from another male mouse -- into an egg cell that had its nucleus, and therefore its female genetic material, removed. This created an embryo containing only genomic DNA from the two male parents. These embryos were transferred along with placental material to surrogate mothers, who carried them to term.

These pups survived 48 hours after birth, but the researchers are planning to improve the process so that the bipaternal mice live to adulthood. Similar results were achieved in 2011 but using a method that relied on a female intermediary produced from the first father's stem cells to mate with the second father. That method sidestepped the problem of genomic imprinting but presents ethical and practical hurdles if this technology were to ever be considered for humans.

Li notes that there are still obstacles to using these methods in other mammals, including the need to identify problematic imprinted genes that are unique to each species and concerns for the offspring that don't survive or that experience severe abnormalities. They do hope, however, to explore these techniques in other research animals in the future.

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Death of a massive star and birth of compact neutron star binary

The three panels represent moments before, during, and after the faint supernova iPTF14gqr, visible in the middle panel, appeared in the outskirts of a spiral galaxy located 920 million light years away. The massive star that died in the supernova left behind a neutron star in a very tight binary system. These dense stellar remnants will ultimately spiral into each other and merge in a spectacular explosion, giving off gravitational and electromagnetic waves.

A Caltech-led team of researchers has observed the peculiar death of a massive star that exploded in a surprisingly faint and rapidly fading supernova. These observations suggest that the star has an unseen companion, gravitationally siphoning away the star's mass to leave behind a stripped star that exploded in a quick supernova. The explosion is believed to have resulted in a dead neutron star orbiting around its dense and compact companion, suggesting that, for the first time, scientists have witnessed the birth of a compact neutron star binary system.

The research was led by graduate student Kishalay De and is described in a paper appearing in the October 12 issue of the journal Science. The work was done primarily in the laboratory of Mansi Kasliwal (MS '07, PhD '11), assistant professor of astronomy. Kasliwal is the principal investigator of the Caltech-led Global Relay of Observatories Watching Transients Happen (GROWTH) project.

When a massive star -- at least eight times the mass of the sun -- runs out of fuel to burn in its core, the core collapses inwards upon itself and then rebounds outward in a powerful explosion called a supernova. After the explosion, all of the star's outer layers have been blasted away, leaving behind a dense neutron star -- about the size of a small city but containing more mass than the sun. A teaspoon of a neutron star would weigh as much as a mountain.

During a supernova, the dying star blasts away all of the material in its outer layers. Usually, this is a few times the mass of the sun. However, the event that Kasliwal and her colleagues observed, dubbed iPTF 14gqr, ejected matter only one fifth of the mass of the sun.

"We saw this massive star's core collapse, but we saw remarkably little mass ejected," Kasliwal says. "We call this an ultra-stripped envelope supernova and it has long been predicted that they exist. This is the first time we have convincingly seen core collapse of a massive star that is so devoid of matter."

The fact that the star exploded at all implies that it must have previously been enveloped in lots of material, or its core would never have become heavy enough to collapse. But where, then, was the missing mass?

The researchers inferred that the mass must have been stolen -- the star must have some kind of dense, compact companion, either a white dwarf, neutron star, or black hole -- close enough to gravitationally siphon away its mass before it exploded. The neutron star that was left behind from the supernova must have then been born into orbit with that dense companion. Observing iPTF 14gqr was actually observing the birth of a compact neutron star binary. Because this new neutron star and its companion are so close together, they will eventually merge in a collision similar to the 2017 event that produced both gravitational waves and electromagnetic waves.

Not only is iPTF 14gqr a notable event, the fact that it was observed at all was fortuitous since these phenomena are both rare and short-lived. Indeed, it was only through the observations of the supernova's early phases that the researchers could deduce the explosion's origins as a massive star.

"You need fast transient surveys and a well-coordinated network of astronomers worldwide to really capture the early phase of a supernova," says De. "Without data in its infancy, we could not have concluded that the explosion must have originated in the collapsing core of a massive star with an envelope about 500 times the radius of the sun."

The event was first seen at Palomar Observatory as part of the intermediate Palomar Transient Factory (iPTF), a nightly survey of the sky to look for transient, or short-lived, cosmic events like supernovae. Because the iPTF survey keeps such a close eye on the sky, iPTF 14gqr was observed in the very first hours after it had exploded. As the earth rotated and the Palomar telescope moved out of range, astronomers around the world collaborated to monitor iPTF 14gqr, continuously observing its evolution with a number of telescopes that today form the GROWTH network of observatories.

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A break from the buzz: Bees go silent during total solar eclipse

Honey bee.

While millions of Americans took a break from their daily routines on August 21, 2017, to witness a total solar eclipse, they might not have noticed a similar phenomenon happening nearby: In the path of totality, bees took a break from their daily routines, too.

In an unprecedented study of a solar eclipse's influence on bee behavior, researchers at the University of Missouri organized a cadre of citizen scientists and elementary school classrooms in setting up acoustic monitoring stations to listen in on bees' buzzing -- or lack thereof -- as the 2017 eclipse passed over. The results, published October 10 in the Annals of the Entomological Society of America, were clear and consistent at locations across the country: Bees stopped flying during the period of total solar eclipse.

"We anticipated, based on the smattering of reports in the literature, that bee activity would drop as light dimmed during the eclipse and would reach a minimum at totality," says Candace Galen, Ph.D., professor of biological sciences at the University of Missouri and lead researcher on the study. "But, we had not expected that the change would be so abrupt, that bees would continue flying up until totality and only then stop, completely. It was like 'lights out' at summer camp! That surprised us."

As anticipation mounted for the eclipse, "it seemed as if everyone and their dog was asking me what animals would do during a total eclipse," Galen says. However, few formal studies had ever examined the behavior of insects, specifically, during a solar eclipse, and none had looked at bees. Galen and colleagues, meanwhile, had recently field-tested a system to track bee pollination remotely by listening for their flight buzzes in soundscape recordings.

"It seemed like the perfect fit," Galen says. "The tiny microphones and temperature sensors could be placed near flowers hours before the eclipse, leaving us free to put on our fancy glasses and enjoy the show."

Supported by a grant from the American Astronomical Society, the project engaged more than 400 participants -- including scientists, members of the public, and elementary school teachers and students -- in setting up 16 monitoring stations in the path of totality in Oregon, Idaho, and Missouri. At each location, small USB microphones were hung on lanyards near bee-pollinated flowers in areas away from foot and vehicle traffic. In some of the locations, light and temperature data were also captured. Participants then sent the devices to Galen's lab, where the recordings were matched up with the eclipse periods from each location and analyzed for the number and duration of bee flight buzzes. The recordings didn't allow for differentiation between bee species, but participant observations indicated most bees monitored were bumble bees (genus Bombus) or honey bees (Apis mellifera).

The data showed that bees remained active during the partial-eclipse phases both before and after totality, but they essentially ceased flying during the period of totality. (Just one buzz was recorded during totality in all of the 16 monitoring locations.) However, shortly before and shortly after totality, bee flights tended to be longer in duration than at times early in the pre-totality phase and late in post-totality. Galen and colleagues interpret these longer flight durations as an indicator of slower flight under reduced light or possibly as the bees returning to their nests.

Bees commonly fly more slowly at dusk and return to their colonies at night, and so the same behavior triggered by a solar eclipse offers evidence about how they respond to environmental cues when those cues occur unexpectedly.

"The eclipse gave us an opportunity to ask whether the novel environmental context -- mid-day, open skies -- would alter the bees' behavioral response to dim light and darkness. As we found, complete darkness elicits the same behavior in bees, regardless of timing or context. And that's new information about bee cognition," Galen says.

Another total solar eclipse for North America is not far away: April 8, 2024. Galen says her team is working to enhance its audio-analysis software to distinguish the flights that foraging bees make when they leave or return to their colonies. Thus prepared, she hopes to answer the question of whether bees return home when the "lights go out" at totality in 2024.

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Rapid, widespread changes may be coming to Antarctica's Dry Valleys

A member of the research team inspects buried ice melting out from beneath a thin soil cover.

Antarctica's sandy polar desert, the McMurdo Dry Valleys, has undergone changes over the past decade and the recent discovery of thawing permafrost, thinning glaciers and melting ground ice by a Portland State University-led research team are signs that rapid and widespread change could be on the horizon.

Led by Andrew Fountain, a geology professor in PSU's College of Liberal Arts and Sciences, a team of researchers used an airborne laser scanner, or lidar, to measure the surface elevations of glaciers, soils and ice-covered lakes in Antarctica's largest exposed land region. The team then compared the elevations to similar measurements made in 2001 by a different project.

The work was support by the National Science Foundation, which manages the U.S. Antarctic Program, the nation's research endeavor on the southernmost continent.

The findings were reported Sept. 13 in the journal Geomorphology.

"Millions of cubic meters of buried ice have melted in the last decade," said Joseph Levy, the paper's lead author and an assistant professor of geology at Colgate University. "It's unprecedented change over the historic period of Antarctica and perhaps since the end of the last ice age. If it keeps up, it could remove the last ice deposits from some valleys in about five hundred years."

Levy said they believe the culprit is meltwater. When soils thaw and become wet from melting the buried ice below, their insulating capacity is reduced and they conduct much more heat.

"The valleys have been considered almost timeless, yet here we see some changes that would be considered rapid even in more temperate climates," Fountain said.

These rapid changes over the past 14 years come at a time when the Antarctic climate may be turning a corner. While the Dry Valleys region was cooling locally during the 1990s and early 2000s, warmer summers followed. A major melt episode in the Antarctic summer of 2001-2002 set the stage for widespread melting in this polar desert landscape.

"The melting mirrors the kind of melting scientists expect to see in the coming decades if climate warming catches up with the more isolated corners of Antarctica," Levy said.

Fountain added that the Dry Valleys may be on the threshold of a major reorganization.

Levy and Fountain said the melting of ground ice and thinning of glaciers threatens to disrupt delicate polar desert ecosystems and wash away clues to past climate change.

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Oldest fossil of a flying squirrel sheds new light on its evolutionary tree

An artistic reconstruction of the extinct flying squirrel Miopetaurista neogrivensis.

The oldest flying squirrel fossil ever found has unearthed new insight on the origin and evolution of these airborne animals.

Writing in the open-access journal eLife, researchers from the Institut Català de Paleontologia Miquel Crusafont (ICP) in Barcelona, Spain, described the 11.6-million-year-old fossil, which was discovered in Can Mata landfill, approximately 40 kilometers outside the city.

"Due to the large size of the tail and thigh bones, we initially thought the remains belonged to a primate," says first author Isaac Casanovas-Vilar, researcher at the ICP. In fact, and much to the disappointment of paleoprimatologists, further excavation revealed that it was a large rodent skeleton with minuscule specialised wrist bones, identifying it as Miopetaurista neogrivensis -- an extinct flying squirrel.

Combining molecular and paleontological data to carry out evolutionary analyses of the fossil, Casanovas-Vilar and the team demonstrated that flying squirrels evolved from tree squirrels as far back as 31 to 25 million years ago, and possibly even earlier.

In addition, their results showed that Miopetaurista is closely related to an existing group of giant flying squirrels called Petaurista. Their skeletons are in fact so similar that the large species that currently inhabits the tropical and subtropical forests of Asia could be considered living fossils.

With 52 species scattered across the northern hemisphere, flying squirrels are the most successful group of mammals that adopted the ability to glide. To drift between trees in distances of up to 150 metres, these small animals pack their own 'parachute': a membrane draping between their lower limbs and the long cartilage rods that extend from their wrists. Their tiny, specialised wrist bones, which are unique to flying squirrels, help support the cartilaginous extensions.

But the origin of these animals is highly debated. While most genetic studies point towards the group splitting from tree squirrels about 23 million years ago, some 36-million-year-old remains that could belong to flying squirrels have previously been found. "The problem is that these ancient remains are mainly teeth," Casanovas-Vilar explains. "As the dental features used to distinguish between gliding and non-gliding squirrels may actually be shared by the two groups, it is difficult to attribute the ancient teeth undoubtedly to a flying squirrel. In our study, we estimate that the split took place around 31 and 25 million years ago, earlier than previously thought, suggesting the oldest fossils may not belong to flying squirrels.

"Molecular and paleontological data are often at odds, but this fossil shows that they can be reconciled and combined to retrace history," he adds. "Discovering even older fossils could help to retrace how flying squirrels diverged from the rest of their evolutionary tree."

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New telescope almost doubles known number of mysterious 'fast radio bursts'

These are antennas of CSIRO's Australian SKA Pathfinder with the Milky Way overhead.

Australian researchers using a CSIRO radio telescope in Western Australia have nearly doubled the known number of 'fast radio bursts' -- powerful flashes of radio waves from deep space.

The team's discoveries include the closest and brightest fast radio bursts ever detected.

Their findings were reported today in the journal Nature.

Fast radio bursts come from all over the sky and last for just milliseconds.

Scientists don't know what causes them but it must involve incredible energy -- equivalent to the amount released by the Sun in 80 years.

"We've found 20 fast radio bursts in a year, almost doubling the number detected worldwide since they were discovered in 2007," said lead author Dr Ryan Shannon, from Swinburne University of Technology and the OzGrav ARC Centre of Excellence.

"Using the new technology of the Australia Square Kilometre Array Pathfinder (ASKAP), we've also proved that fast radio bursts are coming from the other side of the Universe rather than from our own galactic neighbourhood."

Co-author Dr Jean-Pierre Macquart, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said bursts travel for billions of years and occasionally pass through clouds of gas.

"Each time this happens, the different wavelengths that make up a burst are slowed by different amounts," he said.

"Eventually, the burst reaches Earth with its spread of wavelengths arriving at the telescope at slightly different times, like swimmers at a finish line.

"Timing the arrival of the different wavelengths tells us how much material the burst has travelled through on its journey.

"And because we've shown that fast radio bursts come from far away, we can use them to detect all the missing matter located in the space between galaxies -- which is a really exciting discovery."

CSIRO's Dr Keith Bannister, who engineered the systems that detected the bursts, said ASKAP's phenomenal discovery rate is down to two things.

"The telescope has a whopping field of view of 30 square degrees, 100 times larger than the full Moon," he said.

"And, by using the telescope's dish antennas in a radical way, with each pointing at a different part of the sky, we observed 240 square degrees all at once -- about a thousand times the area of the full Moon.

"ASKAP is astoundingly good for this work."

Dr Shannon said we now know that fast radio bursts originate from about halfway across the Universe but we still don't know what causes them or which galaxies they come from.

The team's next challenge is to pinpoint the locations of bursts on the sky.

"We'll be able to localise the bursts to better than a thousandth of a degree," Dr Shannon said.

"That's about the width of a human hair seen ten metres away, and good enough to tie each burst to a particular galaxy."

ASKAP is located at CSIRO's Murchison Radio-astronomy Observatory (MRO) in Western Australia and is a precursor for the future Square Kilometre Array (SKA) telescope.

The SKA could observe large numbers of fast radio bursts, giving astronomers a way to study the early Universe in detail.

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Clues from a Somalian cavefish about modern mammals' dark past

This image shows a Somalian blind cavefish that, after evolving for millions of years in darkness, has lost the capacity to harness light for repairing DNA.

After millions of years living in constant darkness, a species of blind cavefish found only in Somalia has lost an ancient system of DNA repair. That DNA repair system, found in organisms including bacteria, fungi, plants, and most other animals, harnesses energy from visible light to repair DNA damage induced by ultraviolet (UV) light.

The findings reported in journal Current Biology on October 11 are intriguing in part because only placental mammals, the group including people, were previously known to lack this system. Researchers say that the discovery supports the "nocturnal bottleneck" theory, which holds that the ancestors of modern mammals lived a subterranean or exclusively nocturnal existence as a strategy to avoid being eaten by dinosaurs.

"We have revealed in a species of blind cavefish the loss of an ancient DNA repair system that is highly conserved," says Nicholas Foulkes of Karlsruhe Institute of Technology, Germany. "Curiously, the only other animals previously known to lack photoreactivation DNA repair are placental mammals. So, what we see in this species of cavefish may be the first stages in a process that happened before in our ancestors in the Mesozoic era."

Foulkes's team, including first author Haiyu Zhao, in collaboration with Cristiano Bertolucci at the University of Ferrara, Italy, is interested in understanding evolution in extreme environmental conditions and especially changes in DNA repair systems. The cavefish known as Phreatichthys andruzzii represented an ideal model for their studies because it has lived without any exposure to UV or visible light from the sun for more than 3 million years.

The researchers found that P. andruzzii carries mutations that disrupt the function of essential DNA repair genes. It also lacks a regulatory enhancer element, which coordinates and enhances DNA repair in response to sunlight in other species by turning other genes "on."

Foulkes says that other cavefish species that have not been isolated in their cave environments for as long as P. andruzzii show normal, or even enhanced, photoreactivation mechanisms. Therefore, the new findings "highlight a more extreme level of adaptation in P. andruzzii compared with other cavefish species."

The findings add to evidence that modern mammals once lived in darkness.

"Many features of modern mammals, such as the anatomy and function of the eye, show tell-tale features of a nocturnal life style," Foulkes says. "It means we can now more confidently predict that mammalian ancestors experienced a prolonged period of evolution in complete darkness."

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Time-traveling illusion tricks the brain

The Rabbit Illusion (see video: https://youtu.be/yCpsQ8LZOco).

We experience the world through our senses, a constant torrent of sights, sounds, smells, and more. Our brains take these signals and process them, giving rise to our individual perceptions of the world. But sometimes our senses play tricks on us, notably in the case of perceptual illusions.

Now, Caltech researchers have developed two new illusions that reveal how the senses can influence each other -- in particular, how sound can give rise to visual illusions. These illusions occur so quickly that they illustrate a phenomenon called postdiction (as opposed to prediction) in which a stimulus that occurs later can retroactively affect our perceptions of an earlier event.

The Caltech work is among the first to show this kind of time-traveling illusion across multiple senses.

The work was done in the laboratory of Shinsuke Shimojo, Gertrude Baltimore Professor of Experimental Psychology and affiliated faculty member of the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech. A paper describing the research appears in the October 3 issue of the journal PLOS ONE.

"Illusions are a really interesting window into the brain," says first author Noelle Stiles (PhD '15), a visitor in biology and biological engineering and a postdoctoral scholar-research associate at USC. "By investigating illusions, we can study the brain's decision-making process. For example, how does the brain determine reality with information from multiple senses that is at times noisy and conflicting? The brain uses assumptions about the environment to solve this problem. When these assumptions happen to be wrong, illusions can occur as the brain tries to make the best sense of a confusing situation. We can use these illusions to unveil the underlying inferences that the brain makes."

The two illusions in this study were developed to illustrate how stimuli that occur later can affect the perception of stimuli that have already occurred. Postdictive processing has been demonstrated within individual senses, but this work focuses on how the phenomenon can bridge multiple senses. The key to both of the new illusions is that the audio and visual stimuli occur rapidly, in under 200 milliseconds (one-fifth of a second). The brain, trying to make sense of this barrage of information, synthesizes the stimuli from both senses to determine the experience, using postdiction to do so.

The first illusion is called the Illusory Rabbit. To produce the illusion, first a short beep and a quick flash are played nearly simultaneously on a computer, with the flash appearing at the left side of the screen. Next, 58 milliseconds after the first beep, a lone beep is played. Finally, 58 milliseconds after the second beep, a second nearly simultaneous beep-flash pair occurs, but with the flash appearing on the right side of the screen. The beep location is always central and does not move. Though only two flashes are played, most people viewing the illusion perceive three flashes, with an illusory flash coinciding with the second beep and appearing to be located in the center of the screen.

The fact that the illusory flash is perceived in between the left and right flashes is the key evidence that the brain is using postdictive processing.

"When the final beep-flash pair is later presented, the brain assumes that it must have missed the flash associated with the unpaired beep and quite literally makes up the fact that there must have been a second flash that it missed," explains Stiles. "This already implies a postdictive mechanism at work. But even more importantly, the only way that you could perceive the shifted illusory flash would be if the information that comes later in time -- the final beep-flash combination -- is being used to reconstruct the most likely location of the illusory flash as well."

The second illusion is called the Invisible Rabbit. In this related illusion, three flashes are shown on the screen, the first on the left, the second in the middle, and finally the third on the right, with only the first and third flashes coinciding with beeps. In this case, most people do not see the second flash -- the one without a corresponding sound -- at all. The absence of the second beep leads the brain to decide after the fact that there actually was no flash, even though it was in fact present.

By showing that a sound can excite a visual illusion, the researchers have uncovered new clues as to how the brain combines the senses over space and time to generate an integrated sense of perception.

"The significance of this study is twofold," says Shimojo. "First, it generalizes postdiction as a key process in perceptual processing for both a single sense and multiple senses. Postdiction may sound mysterious, but it is not -- one must consider how long it takes the brain to process earlier visual stimuli, during which time subsequent stimuli from a different sense can affect or modulate the first. The second significance is that these illusions are among the very rare cases where sound affects vision, not vice versa, indicating dynamic aspects of neural processing that occur across space and time. These new illusions will enable researchers to identify optimal parameters for multisensory integration, which is necessary for both the design of ideal sensory aids and optimal training for low-vision individuals."

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Wild chimpanzees share food with their friends

Chimpanzees share food with their friends.

Sharing meat after hunting and exchanging other valued food items is considered key in the evolution of cooperation in human societies. One prominent idea is that humans share valuable foods to gain future favors, such that those we chose to share with are more likely to cooperate with us in the future. Despite regularly occurring in humans, sharing food outside of kinship or mating relationships is rare in non-human animals. Our two closest living relatives, chimpanzees and bonobos, are two of the rare exceptions, and because of the important role of food sharing in human evolution, examining the sharing patterns of chimpanzees can help to answer questions on how sharing food amongst adults evolved and how it may have shaped human cooperation.

Researchers from the MPI-EVA observed natural food sharing behavior of the chimpanzees of the Tai National Park, Ivory Coast, and found that chimpanzees are very selective in who they share desirable food items, like meat, honey or large fruits, with. They show that chimpanzees were more likely to share food with their friends, and that neither high dominance status nor harassment by beggars influenced their decision. This complements results from another study by the same team published last month that examined meat sharing after group hunting of monkeys. There they found that chimpanzees in possession of meat after successful hunts were likely to reward other hunters by sharing with them. "Collectively our research shows that the chimpanzees decide when to share food based on the likelihood that this favor will be returned in the future," says Liran Samuni, first author of both studies. "Or, in case of sharing after group hunts, sharing of meat is returning the favor for helping out."

Previous studies in another subspecies of chimpanzees have suggested that food sharing in chimpanzees mainly occurs because of harassment pressure from beggars. "This was not the case for the Tai chimpanzees," Catherine Crockford, senior author on the studies, points out, "emphasizing the high variation in cooperation across chimpanzee populations." Human populations also vary in how cooperative they are and research is ongoing in both humans and non-human animals assessing what might make some populations more cooperative than others. "The need to stay in a cohesive unit, because of high predation pressure, or the capability to exhibit strong cohesion, because of rich food sources, are two possible scenarios to promote the expression of cooperative acts," suggests Roman Wittig, the second senior author of the studies.

Additionally, the researchers collected urine samples from chimpanzees after hunting and food sharing events and measured the hormone oxytocin. "We know that oxytocin plays a strong role in lactation, which you could look at as an example of food sharing between mother and infant, and is generally involved in social behavior and bonding," Liran Samuni explains. The researchers found high levels of oxytocin after chimpanzees shared meat and other valued foods, and after chimpanzee participated in hunting with others. "That we found higher oxytocin levels after both hunting and sharing adds to the idea that oxytocin is a key hormone involved in cooperation in general," Liran Samuni points out.

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Mystery at the center of the Milky Way solved

Stars at the center of the Milky Way.

Astronomers from Lund University in Sweden have now found the explanation to a recent mystery at the centre of the Milky Way galaxy: the high levels of scandium discovered last spring near the galaxy's giant black hole were in fact an optical illusion.

Last spring, researchers published a study about the apparent presence of astonishing and dramatically high levels of three different elements in red giant stars, located less than three light years away from the big black hole at the centre of our galaxy. Various possible explanations were presented, for example that the high levels were a result of earlier stars being disrupted as they fall into the black hole, or a result of debris from the collisions of neutron stars.

Now another group of astronomers from Lund University among others, in collaboration with UCLA in California, have found an explanation for the high levels of scandium, vanadium and yttrium. They argue that the so-called spectral lines presented last spring were actually an optical illusion. Spectral lines are used to find out which elements a star contains -- by using its own light.

"These giant red stars have used up most of their hydrogen fuel and their temperatures are therefore only half of the sun's," says Brian Thorsbro, lead author of the study and doctoral student in astronomy at Lund University.

According to the new study, the lower temperatures of the giant stars helped to create the optical illusion that appeared in the measurements of spectral lines. Specifically, it means that the electrons in the elements behave differently at different temperatures, which in turn can be misleading when measuring the spectral lines of elements in different stars. The conclusion is the result of a close collaboration between astronomers and atomic physicists.

Brian Thorsbro and his colleagues have had the world's largest telescope, at the W. M. Keck Observatory on Mauna Kea, Hawaii, at their disposal, thanks to their collaboration with R. Michael Rich at UCLA. Using this telescope and others, the research team is currently conducting a comprehensive mapping of the central areas of the Milky Way, exploring the spectral lines in the light from different stars to find out which elements they contain. The purpose is to gain an understanding of the events that have occurred in the history of the Milky Way, but also to understand how galaxies in general have formed.

"Our research collaboration is world-leading in terms of systematically mapping the elements contained in the huge central star cluster -- the star cluster that surrounds the black hole," says research leader and astronomer Nils Ryde at Lund University.

The spectral lines for different elements are recorded in a high-resolution spectrometer -- an advanced camera that generates a rainbow of the starlight. The research team has studied the part of the spectrum consisting of near-infrared light, i.e. the heat radiation emitted by the stars. The reason for this is that infrared light can penetrate the dust that obstructs the line-of-sight between us and the centre of the Milky Way, approximately 25,000 light years away. The technology for recording this light is very advanced, and has only recently become available to astronomers.

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The stuff that planets are made of

Possible model of exoplanets with a rocky core and gaseous atmosphere (artist's impression).

Is there a second Earth out there in space? Our knowledge of planetary systems far, far away is increasing constantly, as new technologies continue to sharpen our gaze into space. To date, 3,700 planets have already been discovered outside our solar system. The planetary masses and radii of these exoplanets can be used to infer their mean density, but not their exact chemical composition and structure. The intriguing question about what these planets could look like is thus still open.

"Theoretically, we can assume various compositions, such as a world of pure water, a world of pure rock, and planets that have hydrogen-helium atmospheres and explore what radii are expected" explains Michael Lozovsky, a doctoral candidate in the group of Prof. Ravit Helled at the Institute for Computational Science at the University of Zurich.

Thresholds for planetary composition

Lozovsky and collaborators have used databases and statistical tools to characterize exoplanets and their atmospheres. These are fairly common and surrounded by a volatile layer of hydrogen and helium. However, the directly measured data previously didn't allow the researchers to determine the exact structure, since different compositions may lead to the same mass and radius. In addition to the accuracy of the data relating to mass and radius, the research team thus also investigated the assumed internal structure, temperature and reflected radiation in 83 of the 3,700 known planets, for which the masses and radii are well-determined.

"We used a statistical analysis to set limits on possible compositions. Using a database of detected exoplanets, we found that every theoretical planetary structure has a 'threshold radius', a planetary radius above which no planets of this composition exist," explains Michael Lozovsky. The amount of elements in the gaseous layer that are heavier than helium, the percentage of hydrogen and helium, as well as the distribution of elements in the atmosphere are important factors in determining the threshold radius.

Super-Earths and mini-Neptunes

The researchers from the Institute for Computational Science found that planets with a radius of up to 1.4 times that of Earth (6,371 kilometers) can be earth-like, i.e. they have a composition similar to Earth. Planets with radii above this threshold have a higher share of silicates or other light materials. Most of the planets with a radius above 1.6 radii of the Earth must have a layer of hydrogen-helium gas or water in addition to their rocky core, while those larger than 2.6 Earth radii can't be water worlds and therefore might be surrounded by an atmosphere. Planets with radii larger than 4 Earth radii are expected to be very gaseous and consist of at least 10 percent hydrogen and helium, similarly to Uranus and Neptune.

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Cleaning, but safely! Cocoons protect sensitive ant brood during toxic disinfection

Ants clean their nest box with formic acid. Special paper that turns pink on contact with acids was used to see when and how much formic acid the ants spray.

Ants are neat: when they move into a new nest box, they spend the first days cleaning it thoroughly, like us humans getting out the cleaning bucket when moving into a new home. Despite keeping the nest clean, using poison within the nest is dangerous and can kill unprotected brood. However, the silk cocoon that surrounds the ant's sensitive pupae protects them from any harmful effects, as Sylvia Cremer from the Institute of Science and Technology Austria (IST Austria), and her team, including first author doctoral student Christopher Pull -- now a postdoc at the Royal Holloway University London (RHUL) -- show in today's edition of Current Biology.

Many ants produce highly acidic chemicals from specialized glands in their body. For a long time, researchers assumed that ants only spray this poison, which is made mostly of formic acid, to fight other ants and would-be predators. But in two studies published in 2013 and 2018, Sylvia Cremer and her team showed that ants use acidic chemicals to disinfect nest-mates contaminated and infected with pathogens. In the current study, published by Pull et al., Cremer's research team show that Lasius neglectus ants also spray their nests prophylactically with their acidic poison, likely ensuring that the nest is clean for first-time occupancy. But, given the poison doubles-up as a chemical weapon, the use of the poison within the nest raises further questions, as Sylvia Cremer explains: "How can ants spray this aggressive acid in their nest, whilst leaving their sensitive brood in the acidic fog?" Whilst adult ants are protected from the poison by a thick skin (the cuticle) and eggs by a protective "shell" (the corion), the cuticle of the pupae is thin and fragile, and so very susceptible to damage. However, pupae of the Lasius neglectus species are also covered in a silk cocoon, which Pull et al hypothesized may offer them protection.

Through a series of experiments, the research team searched for the answer. First, they removed the protective silk cocoon from some pupae and found that these nude pupae survived just as well alone as pupae wrapped in a cocoon. But when they placed nude pupae and worker ants into a nest together, more nude pupae died than cocooned pupae. Is the increased death a result of the acidic poison? To test this, the researchers glued shut the poison glands of the worker ants with superglue. "We created a 'functional knock-out' ant by creating animals that could not spray formic acid," explains Cremer. In a nest with ants unable to spray their acid, nude and wrapped pupae had the same chance of survival. "So it is the formic acid that kills nude pupae, but pupae in a cocoon are protected from it," Cremer concludes -- and we behave similarly: "When we use harmful cleaning products, we protect ourselves with gloves. The cocoon has a similar function to protective gloves."

The current study provides the first example at colony level of so-called immunopathology, a phenomenon also known from the human immune system. The immune system often fights pathogens with toxic substances, but at the same time, it must limit damage to its own body cells. The immune system, therefore, faces the challenge of fighting pathogens as aggressively as possible, while protecting the body's own cells and organs from collateral damage. The same happens in ants on the colony level: they protect the most sensitive parts of their colony from the harmful side effects of cleaning with a caustic poison.

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Nobel Prize in Economics 2018

Technological Earth concept

The Royal Swedish Academy of Sciences has decided to award the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2018 to William D. Nordhaus, Yale University, New Haven, USA "for integrating climate change into long-run macroeconomic analysis" and Paul M. Romer, NYU Stern School of Business, New York, USA "for integrating technological innovations into long-run macroeconomic analysis."

Integrating innovation and climate with economic growth

William D. Nordhaus and Paul M. Romer have designed methods for addressing some of our time's most basic and pressing questions about how we create long-term sustained and sustainable economic growth.

At its heart, economics deals with the management of scarce resources. Nature dictates the main constraints on economic growth and our knowledge determines how well we deal with these constraints. This year's Laureates William Nordhaus and Paul Romer have significantly broadened the scope of economic analysis by constructing models that explain how the market economy interacts with nature and knowledge.

Technological change

Romer demonstrates how knowledge can function as a driver of long-term economic growth. When annual economic growth of a few per cent accumulates over decades, it transforms people's lives. Previous macroeconomic research had emphasised technological innovation as the primary driver of economic growth, but had not modelled how economic decisions and market conditions determine the creation of new technologies. Paul Romer solved this problem by demonstrating how economic forces govern the willingness of firms to produce new ideas and innovations.

Romer's solution, which was published in 1990, laid the foundation of what is now called endogenous growth theory. The theory is both conceptual and practical, as it explains how ideas are different to other goods and require specific conditions to thrive in a market. Romer's theory has generated vast amounts of new research into the regulations and policies that encourage new ideas and long-term prosperity.

Climate change

Nordhaus' findings deal with interactions between society and nature. Nordhaus decided to work on this topic in the 1970s, as scientists had become increasingly worried about the combustion of fossil fuel resulting in a warmer climate. In the mid-1990s, he became the first person to create an integrated assessment model, i.e. a quantitative model that describes the global interplay between the economy and the climate. His model integrates theories and empirical results from physics, chemistry and economics. Nordhaus' model is now widely spread and is used to simulate how the economy and the climate co-evolve. It is used to examine the consequences of climate policy interventions, for example carbon taxes.

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Land-locked Atlantic salmon also use magnetic field to navigate

Atlantic salmon.

A new study shows that Atlantic salmon use the Earth's magnetic field as a navigational tool -- much like their cousins, Pacific salmon -- and don't lose that ability through several generations of fish even after they have been transplanted into a land-locked lake.

The findings suggest that Atlantic salmon, which are widely used in aquaculture, may have greater potential to navigate and thus invade novel habitats if they escape their pens, researchers say.

Results of the study are being published this week in the journal Proceedings of the National Academy of Sciences.

This is the first time in which scientists have documented that another genus of salmon use the magnetic field as a map for navigation. A landmark 2014 study by Oregon State University researchers show that Chinook salmon use the magnetic field to orient themselves as they migrate over hundreds, even thousands of miles through the Pacific Ocean to target their oceanic foraging grounds.

The researchers constructed a testing apparatus at the Oregon Hatchery Research Center with several "arenas" surrounded by wooden coils wrapped in copper wire to mimic Earth's magnetic field, and tested 1,150 juvenile Atlantic salmon transported from Oregon's Hosmer Lake.

Atlantic salmon had first been brought to the land-locked lake from Maine some 60 years ago, and the researchers were curious to see if they had navigational abilities similar to ocean-going salmon, according to lead author Michelle Scanlan, faculty research assistant in OSU's College of Agricultural Sciences and lead author on the PNAS article.

"We wanted to see how Atlantic salmon would respond if we put them into different magnetic fields at the boundaries of Pacific salmon oceanic range," Scanlan said. "If we put them into an extreme northern field, would they 'course-correct' and align themselves in a southerly direction, and vice-versa? And the answer was yes. They clearly aligned themselves in the tank to adjust to an appropriate magnetic field signal."

This ability to use the magnetic field to navigate by land-locked Atlantic salmon is of particular concern because of an incident in August of 2017, when 200,000 to 300,000 Atlantic salmon escaped an aquaculture pen in Washington's Puget Sound. Eight months later, one of the fish was reportedly caught 40 miles up the Skagit River, raising concerns about the impact on native salmon and the ecosystem.

The state of Washington has since banned Atlantic salmon farms.

The study also raises some interesting questions about how long fish in general, and salmon in particular, retain skills they no longer need, said Nathan Putman, a senior scientist with LGL Ecological Research Associates in Bryan, Texas, who led the 2014 Pacific salmon navigation study as a post-doctoral scholar at OSU.

"Why didn't the Hosmer Lake fish lose their ability to navigate?" Putman said. "It apparently isn't a 'use it or lose it' skill. It may be possible that they have some finer-scale navigation tools at their disposal to use in a lake. Even at small-scales, fish are confronted by a variety of spatial tasks that might benefit from use of magnetic cues -- from traveling in a straight line to maneuvering through the water column. More research is needed to answer those questions."

A study by the same researchers published in February in Biology Letters found that larval salmon use the magnetic field when emerging from "redds" or nests and into the water column -- suggesting salmon do have some fine-scale magnetic tools that may not have been fully identified.

On a broad scale, however, the use of the magnetic field explains, in part, how salmon can find the way to their river of origin.

"The magnetic field is kind of like having a GPS system in your car," said Amanda Pollock, a graduate student in OSU's Department of Fisheries and Wildlife and co-author on the study. "That gets them close to their river and then their olfactory senses kick in."

Read more at Science Daily

Drier, less predictable environment may have spurred human evolution

During the dry season, evaporating water leaves behind trona crystals growing on the Lake Magadi lakebed. The drilling rig used in this study towers above the dry lakebed in the background.

A progressively drying climate punctuated by variable wetter episodes may have precipitated the transition from our hominin ancestors to anatomically modern humans, according to research published on Oct. 8 in the online edition of the Proceedings of the National Academy of Science (PNAS).

Since the discovery of a rich assemblage of human fossils as well as stone tools and other archeological evidence in the rift valley of East Africa, a region often referred to as the cradle of humanity, scientists have attempted to piece together the complex puzzle that is the history of our human origins, including the environmental context of that history.

The study, based on lake sediment cores, is the first to provide a continuous environmental context for the diverse archeological evidence recovered from nearby localities in the rift valley basins of southern Kenya. The cores were sampled from Lake Magadi as part of the Hominin Sites and Paleolakes Drilling Project, or HSPDP, which is directed by University of Arizona professor Andrew Cohen.

Lake Magadi, a shallow, periodically dry lake, is close to the Olorgesailie basin in Kenya, one of the most productive sites for archaeological evidence of human evolution in Africa. The authors suggest that the profound climatic changes may have been driving forces behind hominin evolution, the origins of modern Homo sapiens and the onset of the Middle Stone Age.

While previous hypotheses have related hominin evolution to climate change, most prior studies lack regional-scale evidence for a link between environment and hominin evolution, the authors write in the paper, "Progressive aridification in East Africa over the last half million years and implications for human evolution." According to the study, a trend toward intense aridification in the area began 575,000 years ago. The change, not previously documented in continuous continental cores from East Africa, corresponds with faunal extinctions and a major transformation in stone tool technology documented in the Olorgesailie region.

"Much evidence for human evolution has been gathered from the area, but linking those records to detailed environmental records was missing until now," said the study's lead author, Richard Owen, of Hong Kong Baptist University. "There is a big gap in the records between the last Early Stone Age tools 500,000 years ago and the appearance of Middle Stone Age tools about 320,000 years ago. Our results plugged that gap with a continuous environmental record."

A critical transition occurred sometime during this gap, a period for which archeologists have unearthed evidence of a leap in early humans' abilities to make, use and trade stone tools.

The cores from Lake Magadi provide the first detailed link between climate change and events known from the region's archeological record.

"We have known for a while that the climate at the time was very varied, but the key here is that the records are in proximity to the archeological evidence for this transition," says Cohen, a professor in the University of Arizona's Department of Geosciences. "The older stone tools found at Olorgesailie did not change much between 1.2 million and a half-million years ago. And suddenly, after 500,000 and before 320,000 years ago -- we don't know exactly when, but in that timespan -- there was a critical transition in archeology when tools became more sophisticated and were transported over longer distances."

At the same time the lake core records point to the climate becoming drier and more variable, there is evidence elsewhere in Africa of the appearance of modern Homo sapiens, prompting much speculation whether the two are connected, Cohen said.

"Whether the evolution of bigger brains goes hand in hand with new toolkits is not entirely clear," he said. "But the earliest modern Homo sapiens fossils from Morocco date back 325,000 years, the same time we see this transition of tools. And both happened around the same time that our core record indicates severe drying very close to the archeological sites."

The deepest core drilled at Lake Magadi reached 200 meters (650 feet), penetrating all sedimentary layers down to the volcanic bedrock of the lake. The core samples, each about 10 feet long and 2 1/2 inches in diameter, are cut into manageable 5-foot segments, packaged and air-freighted to the National Lake Core Facility at the University of Minnesota for curation, analysis and storage.

According to the hypothesis of variability selection, a rapidly changing environment creates selective pressure that forces species to adapt to rapid change, Owen said. Under that scenario, the larger brains of anatomically modern humans would have allowed our ancestors to adapt quickly to an increasingly less predictable world.

"Now we have evidence that at the same time the toolkits were changing, the mammal fauna changed and the climate became more arid," Owen said. "So you have a series of coincidences that makes you think, 'This could be real.' Now we can say when the environment changed and then compare that to the archeological evidence of the region."

Drilling at other nearby sites by HSPDP has been completed as researchers gather more of the region's climate data to continue studying the importance of environmental variability in the course of human evolution.

Read more at Science Daily

Out like a light: Researchers ID brain's 'sleep switch'

Two decades ago, Clifford B. Saper, MD/PhD, Chairman of the Department of Neurology at Beth Israel Deaconess Medical Center (BIDMC), and colleagues discovered a set of nerve cells they thought might be the switch that turns the brain off, allowing it to sleep. In a new study published in Nature Communications today, Saper and colleagues demonstrate in mice that that these cells -- located in a region of the hypothalamus called the ventrolateral preoptic nucleus (VLPO) -- are in fact essential to normal sleep.

"Our paper is the first test of what happens when you activate the VLPO neurons," said Saper, who is also James Jackson Putnam Professor of Neurology and Neuroscience at Harvard Medical School. "The findings support our original observation that the VLPO cells are essential to normal sleep."

Working with genetically engineered mice, Saper's team artificially activated the VLPO neurons using several different tools. In one set of experiments, the scientists activated the neuron cells using a laser light beam to make them fire, a process called optogentics. In another test, the team used a chemical to selectively activate the VLPO neurons. In both cases, activating these cells profoundly drove sleep.

The results confirmed Saper and colleagues' earlier findings that these neurons are active during sleep and that damage to them causes insomnia -- as seen in Saper's subsequent work with laboratory animals and, in 2014, in older people who have lost cells of the VLPO as part of the natural aging process.

Based on that previous body of work, it came as a surprise when another team of researchers reported just the opposite. In a 2017 publication, experiments stimulating the VLPO neurons woke laboratory animals up. In their current paper, Saper's team cleared up the seeming contradiction.

"We found that when the VLPO cells are stimulated one to four times per second, they fire each time they are stimulated, resulting in sleep," Saper said. "But if you stimulate them faster than that, they begin to fail to fire and eventually stop firing altogether. We learned our colleagues in the other lab were stimulating the cells 10 times per second, which was actually shutting them off."

Additionally, Saper's team also found that activating the VLPO cells caused a fall in body temperature. Scientists already knew that warm temperatures activate VLPO cells, and that body temperature dips slightly during sleep, when the VLPO neurons are firing.

"We thought that this is why people need to curl up under a warm blanket to get to sleep," Saper added.

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When is a nova not a nova? When a white dwarf and a brown dwarf collide

This object is possibly the oldest of its kind ever catalogued: the hourglass-shaped remnant named CK Vulpeculae.

Researchers from Keele University have worked with an international team of astronomers to find for the first time that a white dwarf and a brown dwarf collided in a 'blaze of glory' that was witnessed on Earth in 1670.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the international team of astronomers, including workers from the Universities of Keele, Manchester, South Wales, Arizona State, Minnesota, Ohio State, Warmia & Mazury, and the South African Astronomical Observatory, found evidence that a white dwarf (the remains of a star like the Sun at the end of its life) and a brown dwarf (a 'failed' star without sufficient mass to sustain thermonuclear fusion) collided in a short-lived blaze of glory that was witnessed on Earth in 1670 as Nova Cygni -- 'a new star below the head of the Swan.' The brown dwarf star was 'shredded' and dumped on the surface of a white dwarf star, leading to the 1670 eruption and the hourglass we see today.

In July of 1670, observers on Earth witnessed a 'new star', or nova, in the constellation Cygnus -- the Swan. Where previously there was no obvious star, there abruptly appeared a star as bright as those in the Plough, that gradually faded, reappeared, and finally disappeared from view.

Modern astronomers studying the remains of this cosmic event initially thought it was triggered by the merging of two main-sequence stars -- stars on the same evolutionary path as our Sun. This so-called 'new star' was long referred to as 'Nova Vulpeculae 1670', and later became known as CK Vulpeculae.

However, we now know that CK Vulpeculae was not what we would today describe as a 'nova', but is in fact the merger of two stars -- a white dwarf and a brown dwarf.

By studying the debris from this explosion -- which takes the form of dual rings of dust and gas, resembling an hourglass with a compact central object -- the research team concluded that a brown dwarf, a so-called failed star without the mass to sustain nuclear fusion, had merged with a white dwarf.

Professor Nye Evans, Professor of Astrophysics at Keele University and co-author on the paper appearing in the Monthly Notices of the Royal Astronomical Society explains:

"CK Vulpeculae has in the past been regarded as the oldest 'old nova'. However, the observations of CK Vulpeculae I have made over the years, using telescopes on the ground and in space, convinced me more and more that this was no nova. Everyone knew what it wasn't -- but nobody knew what it was! But a stellar merger of some sort seemed the best bet. With our ALMA observations of the exquisite dusty hourglass and the warped disc, plus the presence of lithium and peculiar isotope abundances, the jig-saw all fitted together: in 1670 a brown dwarf star was 'shredded' and dumped on the surface of a white dwarf star, leading to the 1670 eruption and the hourglass we see today."

The team of European, American and South African astronomers used the Atacama Large Millimeter/submillimeter Array to examine the remains of the merger, with some interesting findings. By studying the light from two, more distant, stars as they shine through the dusty remains of the merger, the researchers were able to detect the tell-tale signature of the element lithium, which is easily destroyed in stellar interiors.

Dr Stewart Eyres, Deputy Dean of the Faculty of Computing, Engineering and Science at the University of South Wales and lead author on the paper explains:

"The material in the hourglass contains the element lithium, normally easily destroyed in stellar interiors. The presence of lithium, together with unusual isotopic ratios of the elements C, N, O, indicate that an (astronomically!) small amount of material, in the form of a brown dwarf star, crashed onto the surface of a white dwarf in 1670, leading to thermonuclear 'burning', an eruption that led to the brightening seen by the Carthusian monk Anthelme and the astronomer Hevelius, and in the hourglass we see today."

Professor Albert Zijlstra, from The University of Manchester's School of Physics & Astronomy, co-author of the study, says:

"Stellar collisions are the most violent events in the Universe. Most attention is given to collisions between neutrons stars, between two white dwarfs -- which can give a supernova -- and star-planet collisions.

"But it is very rare to actually see a collision, and where we believe one occurred, it is difficult to know what kind of stars collided. The type we believe that happened here is a new one, not previously considered or ever seen before. This is an extremely exciting discovery."

Professor Sumner Starrfield, Regents' Professor of Astrophysics at Arizona State University comments:

"The white dwarf would have been about 10 times more massive than the brown dwarf, so as the brown dwarf spiralled into the white dwarf it would have been ripped apart by the intense tidal forces exerted by the white dwarf. When these two objects collided, they spilled out a cocktail of molecules and unusual element isotopes.

"These organic molecules, which we could not only detect with ALMA, but also measure how they were expanding into the surrounding environment, provide compelling evidence of the true origin of this blast. This is the first time such an event has been conclusively identified.

"Intriguingly, the hourglass is also rich in organic molecules such as formaldehyde (H2CO), methanol (CH3OH) and methanamide (NH2CHO). These molecules would not survive in an environment undergoing nuclear fusion and must have been produced in the debris from the explosion. This lends further support to the conclusion that a brown dwarf met its demise in a star-on-star collision with a white dwarf."

Since most star systems in the Milky Way are binary, stellar collisions are not that rare, the astronomers note.

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Mystery of Saturn's moon Titan's atmospheric haze

The atmospheric haze of Titan, Saturn's largest moon (pictured here along Saturn's midsection), is captured in this natural-color image (box at left). A new study, which involved experiments at Berkeley Lab's Advanced Light Source, has provided new clues about the chemical steps that may have produced this haze.

Saturn's largest moon, Titan, is unique among all moons in our solar system for its dense and nitrogen-rich atmosphere that also contains hydrocarbons and other compounds, and the story behind the formation of this rich chemical mix has been the source of some scientific debate.

Now, a research collaboration involving scientists in the Chemical Sciences Division at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has zeroed in on a low-temperature chemical mechanism that may have driven the formation of multiple-ringed molecules -- the precursors to more complex chemistry now found in the moon's brown-orange haze layer.

The study, co-led by Ralf Kaiser at the University of Hawaii at Manoa and published in the Oct. 8 edition of the journal Nature Astronomy, runs counter to theories that high-temperature reaction mechanisms are required to produce the chemical makeup that satellite missions have observed in Titan's atmosphere.

The team also included other researchers at Berkeley Lab, the University of Hawaii at Manoa, Samara University in Russia, and Florida International University. The team used vacuum ultraviolet light experiments at Berkeley Lab's Advanced Light Source (ALS), together with computer simulations and modeling work to demonstrate the chemical reactions that contribute to Titan's modern-day atmospheric chemistry.

"We provide evidence here for a low-temperature reaction pathway that people have not thought about," said Musahid Ahmed, a scientist in Berkeley Lab's Chemical Sciences Division and co-leader of the study at the ALS. "This gives rise to a missing link in Titan's chemistry."

Titan may yield clues to the development of complex chemistry on other moons and planets, including Earth, he explained. "People use Titan to think about a 'pre-biotic' Earth -- when nitrogen was more prevalent in the early Earth's atmosphere."

Benzene, a simple hydrocarbon with a six-carbon single-ring molecular structure, has been detected on Titan and is believed to be a building block for larger hydrocarbon molecules with two- and three-ring structures that, in turn, formed other hydrocarbons and aerosol particles that now make up Titan's atmosphere. These multiple-ring hydrocarbon molecules are known as polycyclic aromatic hydrocarbons (PAHs).

In the latest study, researchers mixed two gases -- a short-lived two-ring PAH known as a naphthyl radical (C10H7) and a hydrocarbon called vinylacetylene (C4H4) -- at the ALS, and produced three-ring PAHs in the process. Both of the chemicals used to drive the reaction are inferred to exist on Titan based on what is known about the chemical makeup of its atmosphere.

The ALS experiments jetted away the end products of the reactions from a small reaction chamber. Researchers used a detector known as a reflectron time-of-flight mass spectrometer to measure the mass of molecular fragments produced in the reaction of the two gases. Those measurements supplied details about the chemistry of the three-ring PAHs (phenanthrene and anthracene).

While the ALS experiments used a chemical reactor to simulate the chemical reaction and a beam of vacuum ultraviolet light to detect the products of the reaction, supporting calculations and simulations showed how the chemicals formed in the ALS experiments do not require high temperatures.

PAHs like the chemicals studied at the ALS have properties that make them particularly difficult to identify in deep space, Kaiser said. "In fact, not a single, individual PAH has been detected in the gas phase of the interstellar medium," which is the material that fills the space between stars.

He added, "Our study demonstrates that PAHs are more widely spread than anticipated, since they do not require the high temperatures that are present around carbon stars. This mechanism we explored is predicted to be versatile and is expected to lead to the formation of even more complex PAHs."

And because PAHs are considered as precursors to forming molecular clouds -- the so-called "molecular factories" of more complex organic molecules that can include the precursors to life as we know it -- "This could open up theories and new models of how carbon-containing material in deep space and in the rich atmospheres of planets and their moons in our solar system evolve and originate," he said.

Alexander M. Mebel, a chemistry professor at Florida International University and co-leader of the study, carried out calculations that showed how the reactants can naturally come together and form new compounds at very low temperatures.

"Our calculations revealed the reaction mechanism," Mebel said. "We showed that you don't need any energy to drive the reaction of naphthyl and vinylacetylene, so the reaction should be efficient even in the low-temperature and low-pressure atmospheric conditions on Titan."

A key to the study was in the detailed modeling of the reactor cell where the gases were mixed.

Mebel noted that modeling of the energies and simulations of the gas-flow dynamics in play within the reactor help to monitor reaction progress inside the reactor, and allowed researchers to tie theoretical results closely with experimental observations.

The modeling work, which helped to predict the chemicals produced in the reactions based on the initial gases and the temperature and pressure of the heated chamber where the gases were mixed and struck with the vacuum ultraviolet beam, was led by the research team at Samara University.

"This verification of the model, by comparing it with experiments, can also be helpful in predicting how the reaction would proceed in different conditions -- from Titan's atmosphere to combustion flames on Earth."

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