Jul 1, 2017

Surprisingly exact timing of voluntary movements

Dan-Anders Jirenhed and Anders Rasmussen.
Almost everything we do -- walking, talking, or drinking coffee -- is completely dependent on accurate timing when activating many muscles at once. The prevailing theory has been that the exact timing of this type of movement is not voluntarily controlled, and the timing has therefore been assumed to be fully automated when learning movements. However, researchers at Lund University in Sweden now argue that this may be wrong. A new study shows that people are fully capable of controlling their blinking with a time precision that was previously believed not to be possible.

It has long been known that both animals and humans, through a type of learning known as eyeblink conditioning, can learn to blink in response to a tone with a precision of some tens of milliseconds. Previous studies have shown that eyeblink conditioning is dependent on the cerebellum and, so far, it has been assumed that the precise timing is completely automatic.

When researchers Anders Rasmussen and Dan-Anders Jirenhed performed laboratory studies as part of their teaching at the medical programme at Lund University, they discovered that the theory was incorrect in practice.

Rasmussen and Jirenhed tested 21 medical students at Lund University and could see that the students were able to control the exact timing of their blinking with unexpected accuracy. The researchers' results, now published in Scientific Reports, question whether previous studies on human eyeblink conditioning have, in fact, studied purely automated learning or if the test subjects also voluntarily controlled their their blinking.

"Our results are an important step in understanding how the human brain can control the timing of our movements -- and to what extent we can influence them at will," says Anders Rasmussen.

The fact that the movements can be controlled at will also shows that the cerebral cortex, perhaps through cooperation with the cerebellum, can play an important role in terms of timing.

Read more at Science Daily

Birds become immune to influenza

Pair of mallards.
An influenza infection in birds gives a good protection against other subtypes of the virus, like a natural vaccination, according to a new study.

Water birds, in particular mallards, are often carriers of low-pathogenic influenza A virus. Researchers previously believed that birds infected by one variant of the virus could not benefit from it by building up immunity against other virus subtypes. However, the recent study concludes that mallards infected with a low-pathogenic virus build up significant immunity and resistance to other variants of the same virus.

"It was previously thought that the birds were not particularly good at protecting themselves against subsequent infections, but in fact they manage quite well," says Neus Latorre-Margalef, a biologist at Lund University.

The study conducted by Latorre-Margalef, together with colleagues from the University of Georgia in the US, shows that, after an infection, mallards become partially immune and resistant to influenza infections to which they are later exposed. How high their resistance is depends partly on which viruses are involved, and on how genetically similar they are.

"For future infections, the birds' previous infections are important. Birds which have had influenza could be partially protected against virulent variants such as H5N1 or H5N8," says Neus Latorre-Margalef.

The H5N1 and H5N8 strains are highly pathogenic and those most often associated with avian flu. Just over ten years ago, H5N1 spread around the world from chicken flocks in Southeast Asia. Both domestic poultry flocks and wild bird populations were gravely affected. Humans also became ill, in some cases fatally.

It is unclear why there are more subtypes of influenza among birds than among humans and other mammals. One explanation could be what Neus Latorre-Margalef and her colleagues show in their study: that various viruses compete with one another as birds build up immunity and the duration of infection becomes shorter. The virus then gets a chance to mutate and change.

Read more at Science Daily

Jun 30, 2017

The sharpest laser in the world

This is one of the two silicon resonators.
No one had ever come so close to the ideal laser before: theoretically, laser light has only one single color (also frequency or wavelength). In reality, however, there is always a certain linewidth. With a linewidth of only 10 mHz, the laser that the researchers from the Physikalisch-Technische Bundesanstalt (PTB) have now developed together with US researchers from JILA, a joint institute of the National Institute of Standards and Technology and the University of Colorado Boulder, has established a new world record. This precision is useful for various applications such as optical atomic clocks, precision spectroscopy, radioastronomy and for testing the theory of relativity. The results have been published in the current issue of Physical Review Letters.

Lasers were once deemed a solution without problems -- but that is now history. More than 50 years have passed since the first technical realization of the laser, and we cannot imagine how we could live without them today. Laser light is used in numerous applications in industry, medicine and information technologies. Lasers have brought about a real revolution in many fields of research and in metrology -- or have even made some new fields possible in the first place.

One of a laser's outstanding properties is the excellent coherence of the emitted light. For researchers, this is a measure for the light wave's regular frequency and linewidth. Ideally, laser light has only one fixed wavelength (or frequency). In practice, the spectrum of most types of lasers can, however, reach from a few kHz to a few MHz in width, which is not good enough for numerous experiments requiring high precision.

Research has therefore focused on developing ever better lasers with greater frequency stability and a narrower linewidth. Within the scope of a nearly 10-year-long joint project with the US colleagues from JILA in Boulder, Colorado, a laser has now been developed at PTB whose linewidth is only 10 mHz (0.01 Hz), hereby establishing a new world record. "The smaller the linewidth of the laser, the more accurate the measurement of the atom's frequency in an optical clock. This new laser will enable us to decisively improve the quality of our clocks," PTB physicist Thomas Legero explains.

In addition to the new laser's extremely small linewidth, Legero and his colleagues found out by means of measurements that the emitted laser light's frequency was more precise than what had ever been achieved before. Although the light wave oscillates approx. 200 trillion times per second, it only gets out of sync after 11 seconds. By then, the perfect wave train emitted has already attained a length of approx. 3.3 million kilometers. This length corresponds to nearly ten times the distance between Earth and the moon.

Since there was no other comparably precise laser in the world, the scientists working on this collaboration had to set up two such laser systems straight off. Only by comparing these two lasers was it possible to prove the outstanding properties of the emitted light.

The core piece of each of the lasers is a 21-cm long Fabry-Pérot silicon resonator. The resonator consists of two highly reflecting mirrors which are located opposite each other and are kept at a fixed distance by means of a double cone. Similar to an organ pipe, the resonator length determines the frequency of the wave which begins to oscillate, i.e., the light wave inside the resonator. Special stabilization electronics ensure that the light frequency of the laser constantly follows the natural frequency of the resonator. The laser's frequency stability -- and thus its linewidth -- then depends only on the length stability of the Fabry-Pérot resonator.

The scientists at PTB had to isolate the resonator nearly perfectly from all environmental influences which might change its length. Among these influences are temperature and pressure variations, but also external mechanical perturbations due to seismic waves or sound. They have attained such perfection in doing so that the only influence left was the thermal motion of the atoms in the resonator. This "thermal noise" corresponds to the Brownian motion in all materials at a finite temperature, and it represents a fundamental limit to the length stability of a solid. Its extent depends on the materials used to build the resonator as well as on the resonator's temperature.

For this reason, the scientists of this collaboration manufactured the resonator from single-crystal silicon which was cooled down to a temperature of -150 °C. The thermal noise of the silicon body is so low that the length fluctuations observed only originate from the thermal noise of the dielectric SiO2/Ta2O5 mirror layers. Although the mirror layers are only a few micrometers thick, they dominate the resonator's length stability. In total, the resonator length, however, only fluctuates in the range of 10 attometers. This length corresponds to no more than a ten-millionth of the diameter of a hydrogen atom. The resulting frequency variations of the laser therefore amount to less than 4 × 10-17 of the laser frequency.

The new lasers are now being used both at PTB and at JILA in Boulder to further improve the quality of optical atomic clocks and to carry out new precision measurements on ultracold atoms. At PTB, the ultrastable light from these lasers is already being distributed via optical waveguides and is then used by the optical clocks in Braunschweig.

Read more at Science Daily

Ancient Swiss reptile shows its bizarre scale armor for the first time

Reconstruction of Eusaurosphargis dalsassoi.
Grisons, 241 million years ago -- Instead of amidst high mountains, a small reptile suns itself on an island beach in a warm shallow sea, where many fish and marine reptiles frolic. This is the story told by an excellently preserved new discovery of the reptile Eusaurosphargis dalsassoi studied by paleontologists from the University of Zurich.

About 20 centimeters in length, the Swiss reptile was small and juvenile, but its skin was already strongly armored with variously formed smooth, jagged or even thorny osteoderms. Its skeleton indicates a life on land, even though the animal was found together with fish and marine reptiles in the 241 million year old calcareous deposits of the Prosanto Formation near Ducanfurgga at an altitude of 2,740 meters south of Davos in the canton Grisons, Switzerland. The Swiss-British team of researchers led by Torsten Scheyer, paleontologist at the University of Zurich, and James Neenan from the Oxford University Museum of Natural History therefore assumes that it was washed off a nearby island into the sea basin and became embedded in the finely layered marine sediments after death.

Skeleton and appearance reconstructed

14 years ago, the species Eusaurosphargis dalsassoi was described using a partially preserved, completely disarticulated sample from the vicinity of the Swiss-Italian UNESCO World Heritage Site Monte San Giorgio. The new find from the Grisons Mountains, on the other hand, is very well-preserved, allowing researchers to reconstruct the skeleton and outward appearance of the animal for the first time.

In the process, they discovered something astonishing: Externally, Eusaurosphargis dalsassoi looks very similar to girdled lizards (Cordylidae), a group of small, scaled reptiles (Lepidosauria) that usually live in the dry regions of southern Africa. Some of the more strongly armored girdled lizard species could have served as the basis of mythical dragon legends due to their appearance. "This is a case of convergent development as the extinct species is not closely related to today's African lizards" , Scheyer explains.

Related to Helveticosaurus

An exact examination of the phylogenetic relationships rather confirms that its closest relatives are marine reptiles such as ichthyosaurs (Ichthyosauria or "fish lizards"), sauropterygians (Sauropterygia "lizard flippers") or even Helveticosaurus, a marine reptile that is unique to Switzerland, all of which have been found at Monte San Giorgio. The skeleton of Eusaurosphargis, however, shows neither a streamlined body structure, nor arms and legs that have transformed into flippers, as well as no tail fin, which would indicate a life at sea.

Read more at Science Daily

Why there are so many species of tropical trees and other organisms

This is an exit hole drilled in a black oak acorn by an insect that lays its egg on the developing flowers and hatches inside the acorn. Shot at the Tyson ForestGEO plot in Eureka, Missouri.
If aliens sent an exploratory mission to Earth, one of the first things they'd notice -- after the fluffy white clouds and blue oceans of our water world -- would be the way vegetation grades from exuberance at the equator through moderation at mid-latitudes toward monotony at higher ones. We all learn about this biodiversity gradient in school, but why does it exist?

Even Charles Darwin wondered. Though the pattern is striking, it is difficult to explain. Since it is global in scale, the initial tendency was to suspect long-term or large-scale mechanisms, such as climate stability (no glaciers in the tropics), rates of speciation (higher in the tropics) or rates of extinction (lower in the tropics according to the fossil record).

In 1970 and 1971, two ecologists independently proposed a radically different mechanism, one that operates at scales not of kilometers but of meters. Daniel Janzen and Joseph Connell suggested that host-specific natural enemies which kill seeds and seedlings clumped near parent trees might keep locally common species from dominating a forest and give locally rare species space to flourish.

The Janzen-Connell hypothesis is now nearly 50 years old, but it has been hard to evaluate, especially at the global scale. Few studies have explicitly looked at the connection between self suppression and species diversity, and no study has looked at this relationship across temperate and tropical latitudes.

A year ago, however, Jonathan Myers, an assistant professor of biology at Washington University in St. Louis, and Joe LaManna, a postdoctoral research associate at Washington University's Tyson Research Center, proposed a test of the Janzen-Connell hypothesis to the principal investigators of an international network of long-term forest dynamics research sites called the Smithsonian Center for Tropical Forest Science-Forest Global Earth Observatory (CTFS-ForestGEO).

Over the next year, LaManna analyzed the data from 24 research plots, including one at Washington University's Tyson Research Center. Together these plots are home to more than 3,000 tree species and roughly 2.4 million trees. The analysis provided the first evidence that the Janzen-Connell effect contributes to the biodiversity gradient across tropical and temperate latitudes. The paper, which has 50 authors from 12 countries, was published in the June 30, 2017, issue of the journal Science

"This is the first time we've had the data to do this kind of in-depth analysis and to look across temperate and tropical latitudes," said LaManna, who is the corresponding author on the paper.

The analysis also provided a delicious twist on the hypothesis, namely that the plant predators that kill rare species may also keep them from going extinct. "When species get too rare, their enemies also thin out, and they have what is known as a rare species advantage," Myers said. So the specialized predators ultimately stabilize rare species instead of wiping them out.

"We were able to show for the first time that this stabilizing effect may be stronger for rare species in the tropics; this may explain why rainforests harbor so many rare trees," LaManna said.

What's eating you?

The scientists emphasize that what they see in the data is the signature of the Janzen-Connell mechanism but that the data are agnostic about the mechanism itself. In other words, it doesn't point a finger at particular plant enemies.

The mechanism requires that the enemies be host specific rather than generalists, however. "That means the FBI (fungus, bacteria and invertebrates)," LaManna said, "the very tiny organisms that are evolving rapidly and are more likely to be host-specific."

These pathogens are everywhere even though they usually escape our notice. Scientists at the University of Missouri-Saint Louis who worked at the Tyson Research Center discovered more than 100 different species of insect herbivores that feed just on the adults of white oak, Myers said.

Both scientists mention the work of Scott Mangan, an assistant professor in the department of biology at Washington University and a co-author on the paper. Mangan has done both greenhouse and field experiments (on Panama's Barro Colorado Island) showing that soil pathogens alone -- disregarding nutrients, insects, mammals or above-ground diseases -- suppress the growth of seedlings strongly enough to explain the maintenance of biodiversity.

But other studies have documented suppression by other enemies, so the question of mechanism remains open.

Close relatives make bad neighbors

The key observation on which the Janzen-Connell hypothesis is based is that seedfall is heaviest under a parent tree but the young tend to do better away from their parent.

The effect of pathogens on trees is similar to the effect of pathogens on people. We're more likely to catch and die from a disease such as scarlet fever or typhus if we're packed in tenements than if we're living in rural isolation. So, at least without the benefits of modern medicine, we are also self suppressing.

The new study exposed two key aspects of self suppression. "We find that self suppression is on average stronger in a tropical forest than a temperate one," Myers said, "and that it changes systematically with latitude. This is big result number one."

Two aspects of the CTFS-ForestGEO network gave the data the necessary power, Myers said. One is that the forest plots are large enough that they contain decent numbers of rare species, the other is that all of the trees in the plots have been tagged, mapped, measured and identified down to a small size class. "No other globally coordinated forest plot network combines large plots with censuses that go down to 1-centimeter in diameter," he said.

The second result is that, in the tropics, self suppression is stronger for rare species than for common ones. In the temperate zone rare and common species are equally affected, Myers said, or in some cases self suppression actually flips and is stronger for the common species than the rare ones.

The scientists find this result exciting because it may explain a puzzling characteristic of tropical forests: Their diversity is due not to large numbers of species in general but rather to large numbers of rare species.

"How can you pack more than a thousand species in a 50-hectare plot in the tropics if the rare species are being negatively impacted by these specialized enemies?" Myers asks. "You'd think that if these species are rare they'd be more likely to go extinct, so what maintains them in the system?"

Read more at Science Daily

An Ancient ‘Skull Cult’ in Turkey Practiced Rituals With Bones of the Dead

Anthropomorphic depictions from Göbekli Tepe. (A) Intentionally decapitated human statue (height, 24 inches). Credit: Nico Becker, Göbekli Tepe Archive, DAI. (B) The gift bearer holds in his hands a human head (height, 10 inches). (C) Pillar 43 (building D) with low relief of an ithyphallic headless individual, one arm raised (bottom right).
When the ruins of Göbekli Tepe, meaning “Potbelly Hill,” were first discovered in Turkey in the early 1960s, the artifacts there seemed well matched to a typical hunter-gatherer lifestyle. Stone tools and animal bones for example were unearthed at the site, which also features pillars decorated with carved animal reliefs and other designs.

The mundane image of Göbekli Tepe has just been erased, however, given the recent discovery of three carved human skulls within the ruins. The findings are reported in the journal Science Advances.

“It can be that the individuals were decapitated when still ‘fresh,’” lead author Julia Gresky of the German Archaeological Institute’s Department of Natural Sciences said.

“But,” she added, “it can also be that, like known burial customs of other Neolithic sites, the burials were reopened after some time, the skulls were taken and remnants of soft tissue that were still adhering to the bone were scraped away. Then the carvings were performed and the skulls were displayed.”

In short, the site was likely home to a Neolithic skull cult.

Skull cults refer to groups that practiced rituals involving the heads of the dead. The cults were sometimes peaceful and tied to ancestor veneration. The authors believe that carving “branded” the skulls, marking them as different from other human remains. But branding might instead have informed onlookers that these individuals were dead enemies.

Skull fragments with cut marks.
Another similarly aged site, Tell Qarassa North in Syria dated to 10,700-11,600 years ago, featured deliberately mutilated facial skeletons. They have been interpreted as an expression of post-mortal punishment.

The skulls at Göbekli Tepe lack collagen, Gresky said, but organic residues were found in the mud mortar and wall plaster residues near the remains. These were radiocarbon dated to what are known as the Pre-Pottery Neolithic A period (10,000-11,500 BC) and the Pre-Pottery Neolithic B period that followed and lasted until about 7,000 BC in this region. Göbekli Tepe is located 7 miles northeast of the city of Şanlıurfa, Turkey.

A pillar from Building D at Göbekli Tepe
Analysis of the skulls revealed that one belonged to a female who lived to be 25–40 years old. Another was an individual who died between the ages of 30–45. The sex and age of the third skeleton could not be determined.

The adult ages of the individuals did not surprise the researchers.

“People who survived the critical periods in life, like childhood, and in women, the period of giving birth, had the chance to become quite old,” Gresky explained. “The average age in the Neolithic is low because of high infant mortality.”

Read more at Seeker

Jun 29, 2017

Ancient South Carolina whale yields secrets to filter feeding's origins

This photograph shows Coronodon havensteini teeth.
The blue whale is the largest animal that has ever lived. And yet they feed almost exclusively on tiny crustaceans known as krill. The secret is in the baleen, a complex filter-feeding system that allows the enormous whales to strain huge volumes of saltwater, leaving only krill and other small organisms behind. Now, researchers who have described an extinct relative of baleen whales in Current Biology on June 29 offer new insight into how baleen first evolved.

The findings shed light on a long-standing debate about whether the first baleen whales were toothless suction feeders or toothed whales that used their teeth like a sieve to filter prey out of water, the researchers say. The teeth of the newly discovered species of mysticete, called Coronodon havensteini, lend support to the latter view.

"We know from the fossil record that the ancestors of baleen whales had teeth," says Jonathan Geisler of the New York Institute of Technology College of Osteopathic Medicine. "However, the transition from teeth to baleen is controversial. Our study indicates that early toothed whales used spaces between their large complex teeth for filtering and that baleen gradually replaced teeth over millions of years."

The new whale species was found in the early 2000s by a scuba diver in South Carolina's Wando River. He was looking for shark teeth and found the fossilized whale instead. The whale, which lived some 30 million years ago, was later recognized as a representative of a new transitional species.

"The skull of this species indicates that it split off very early in mysticete whale evolution, and our analyses confirm that evolutionary position," Geisler says.

Geisler and his colleagues realized that meant the whale could offer important clues about the teeth to baleen transition. The whale under study also had other interesting features. It was larger than other toothed mysticetes, with a skull nearly one meter long. Its large molars in comparison to other whales further suggested an unusual feeding behavior.

Closer examination of the shape and wear on the whale's teeth led the researchers to conclude that the whale used its front teeth to snag prey. But the whale's large, back molars were used in filter feeding, by expelling water through open slots between the closed teeth.

"The wear on the molars of this specimen indicates they were not used for shearing food or for biting off chunks of prey," he says. "It took us quite some time to come to the realization that these large teeth were framing narrow slots for filter feeding."

As confirmation, the researchers found wear on the hidden cusps bordering those slots between the teeth.

Read more at Science Daily

Exposure to neonic pesticides results in early death for honeybee workers and queens

A worker honeybee has been fitted with a RFID on its back so researchers can record when it enters and leaves the colony.
Worker and queen honeybees exposed to field realistic levels of neonicotinoids die sooner, reducing the health of the entire colony, a new study led by York University biologists has found.

The researchers were also surprised to find that the neonicotinoid contaminated pollen collected by the honeybees came not from crops grown from neonicotinoid treated seeds, but plants growing in areas adjacent to those crops.

The role of neonicotinoid insecticides in honeybee colony deaths in Ontario and other parts of North America has been controversial. Some critics dismissed studies that found negative effects on worker behavior and colony health as unrealistic, suggesting bees were exposed to higher doses of pesticides for much longer than realistically found in the field.

"This debate about field realistic exposure has been going on for a long time," said York U biology Professor Amro Zayed of the Faculty of Science. "We needed season-long monitoring of neonics in bee colonies to determine the typical exposure scenarios that occur in the field, which we have now done.

The research team studied honey bee colonies in five apiaries close to corn grown from neonicotinoid-treated seeds and six apiaries that were far from agriculture. These colonies were extensively sampled and tested for pesticides from early May to September.

"Honeybee colonies near corn were exposed to neonicotinoids for three to four months. That is most of the active bee season in temperate North America," said York U PhD student Nadia Tsvetkov.

However, the neonicotinoid contaminated pollen the honeybees collected did not belong to corn or soybean plants -- the two primary crops grown from neonicotinoid treated seeds in Ontario and Quebec.

"This indicates that neonicotinoids, which are water soluble, spill over from agricultural fields into the surrounding environment, where they are taken up by other plants that are very attractive to bees," said Tsvetkov.

The researchers then chronically fed colonies with an artificial pollen supplement containing progressively smaller amounts of the most commonly used neonicotinoid in Ontario, clothianidin, over a 12-week period. The experiment mimicked what would occur naturally in the field.

The worker bees exposed to the treated pollen during the first nine days of life had their lifespans cut short by 23 per cent. Colonies that were exposed to treated pollen were unable to maintain a healthy laying queen, and had poor hygiene. "We found that realistic exposure to neonicotinoids near corn fields reduces the health of honey bee colonies," said Tsvetkov.

While chronic exposure to neonicotinoids has negative effects on honeybees, the researchers also discovered that a commonly used fungicide can interact with neonicotinoids to make them more dangerous.

Read more at Science Daily

No detectable limit to how long people can live

New research suggests there is no detectable limit to how long people can live.
Emma Morano passed away last April. At 117 years old, the Italian woman was the oldest known living human being.

Super- centenarians, such as Morano and Jeanne Calment of France, who famously lived to be 122 years old, continue to fascinate scientists and have led them to wonder just how long humans can live. A study published in Nature last October concluded that the upper limit of human age is peaking at around 115 years.

Now, however, a new study in Nature by McGill University biologists Bryan G. Hughes and Siegfried Hekimi comes to a starkly different conclusion. By analyzing the lifespan of the longest-living individuals from the USA, the UK, France and Japan for each year since 1968, Hekimi and Hughes found no evidence for such a limit, and if such a maximum exists, it has yet to be reached or identified, Hekimi says.

Far into the foreseeable future

"We just don't know what the age limit might be. In fact, by extending trend lines, we can show that maximum and average lifespans, could continue to increase far into the foreseeable future," Hekimi says. Many people are aware of what has happened with average lifespans. In 1920, for example, the average newborn Canadian could expect to live 60 years; a Canadian born in 1980 could expect 76 years, and today, life expectancy has jumped to 82 years. Maximum lifespan seems to follow the same trend.

It's impossible to predict what future lifespans in humans might look like, Hekimi says. Some scientists argue that technology, medical interventions, and improvements in living conditions could all push back the upper limit.

"It's hard to guess," Hekimi adds. "Three hundred years ago, many people lived only short lives. If we would have told them that one day most humans might live up to 100, they would have said we were crazy."

From Science Daily

3,000-year-old textiles are earliest evidence of chemical dyeing in the Levant

This is a dyed textile at Timna.
Tel Aviv University archaeologists have revealed that cloth samples found in the Israeli desert present the earliest evidence of plant-based textile dyeing in the region. They were found at a large-scale copper smelting site and a nearby temple in the copper ore district of Timna in Israel's Arava desert and are estimated to date from the 13th-10th centuries BCE.

The wool and linen pieces shed light on a sophisticated textile industry and reveal details about a deeply hierarchical society dependent on long-distance trade to support its infrastructure in the unforgiving desert.

The study was published in PLOS ONE. It was led by Dr. Erez Ben-Yosef of TAU's Department of Archaeology and Near Eastern Cultures and Dr. Naama Sukenik of the Israel Antiquities Authority; and conducted in collaboration with Vanessa Workman of TAU's Department of Archaeology, Dr. Orit Shamir of the Israel Antiquities Authority and Dr. Zohar Amar, Dr. Alexander Varvak and Dr. David Iluz of Bar-Ilan University.

Textiles suggest significant social stratification

"This was clearly a formative period, with local kingdoms emerging and replacing Egyptian hegemony in Canaan," Dr. Ben-Yosef said. "These beautiful masterpieces of weaving and dyeing -- the first evidence of industrial dyeing at the time, of wash-resistant color on textile -- support the idea of a strong, hierarchical Edomite Kingdom in Timna at the time.

"It is apparent that there was a dominant elite in this society that took pains to dress according to their 'class,' and had the means to engage in long-distance trade to transport these textiles -- and other materials and resources -- to the desert."

The research suggests a sophisticated dyeing process involving cooking colorful plants in water, then adding fleece fixed with alum to create a chemical bond between fabrics and dye. The result is a wash-resistant colorful fabric.

The researchers radiocarbon-dated the textile pieces and harnessed gas chromatography to identify the cloth's organic molecules. They found "red" molecules produced from the madder plant and "blue" molecules from the woad plant.

"Both plants were known in antiquity as sources of organic dyes," said Dr. Ben-Yosef. "We know that these plants were used to create elaborate costumes during the Roman period, more than a thousand years later. Now we have evidence in the region of an Edomite society wearing textiles produced the same way, versus an earlier 'primitive' smearing of color on fabric."

"We can make many inferences according to this discovery," Dr. Ben-Yosef continued. "To force a large group of people to work in dangerous mines in the desert, you need a strong ruling party -- an elite that probably wore exquisite clothes to further distinguish themselves. The smelters, working in furnaces, were considered 'magicians' or even priests, and they probably wore fine clothing too. They represented the highest level of society, managing a sensitive and complex process to produce copper from rock."

Read more at Science Daily

Almost All Horses Today Are Descendants of Arabian and Central Asian Stallions

A Lipizzan horse. The Y chromosome sequence that was needed as a template to detect Y variants in any horse was sourced from a stallion of this breed.
Horse lovers admire a wide variety of breeds, each with apparently distinctive characteristics and traits. But it may come as a surprise that nearly all horses alive today descend from stallions that were brought into Europe from the Arabian Peninsula and Central Asia over the past 700 years, according to new genetic research.

The study, published in the journal Current Biology, focused on Y chromosomes, which are passed down from fathers to their male offspring. The findings show how heavily human-controlled breeding has shaped the modern horse.

Lead author Barbara Wallner, an animal scientist at the University of Veterinary Medicine in Vienna who specializes in evolutionary biology, explained that all such breeding is done to achieve specific goals. She said that some of these aims have been to produce horses that “run faster and with more endurance, perform better, and are healthy and beautiful. As breeds were formed, these goals were achieved faster by the introgression of foreign breeding studs.”

Wallner and her team could see the hybridization via their Y chromosome analysis of numerous horse breeds as well as related animals. They included a Connemara pony, South German draft horse, English thoroughbred, Warmblood Trakehner, Arabian, Icelandic horse, Lipizzan, Norwegian fjord horse, Shetland pony, Sorraia horse, Warmblood Oldenburg, Warmblood Swiss, Morgan horse, Standardbred, American Quarter Horse, Warmblood Baden Wurttemberg, Warmblood Holsteiner, Warmblood Hanoverian, Warmblood Bavarian, Warmblood Westphalian, French Montagne, Przewalski’s horse, and a donkey.

The thoroughbred American Pharoah won the Belmont Stakes and the first Triple Crown since 1978 at Belmont Park in 2015.
Wallner explained that mutations to the Y chromosome accumulate over time, such that males originating from a common patrilineal ancestor will share a particular collection of Y chromosome mutations forming what is called a haplogroup. These can be difficult to identify, which has hampered past efforts to reconstruct the history of stallions.

For the new study, the scientists overcame prior challenges by using deep, next-generation DNA sequencing. This allowed them to identify even the smallest changes to the 52 Y chromosomes included in the research.

Combining this chromosome data with written records, the scientists determined that, apart from a few Northern European haplotypes, all modern horse breeds included in the study clustered into a 700-year-old haplogroup. It mostly originated from the Original Arabian lineage of horses from the Arabian Peninsula and the Turkoman horse lineage from the steppes, or grasslands, of Central Asia.

“The purest descendant of the Turkoman horse today is the Akhal-Teke,” Wallner noted.

An Akhal-Teke stallion.
The Akhal-Teke’s coat has a distinctive metallic sheen, so the horse appears to literally shimmer in the sun. This breed also has a reputation for high intelligence, speed, and endurance. The breed remains a national emblem in Turkmenistan, whose early tribes prided themselves on their horse breeding skills.

Horses are valued to this day, but because of their central roles in the societies of earlier times, they were prized more than almost anything else.

“By riding horses, humans were able to travel faster,” Wallner explained. “They could connect huge territories, and the domestication of the horse revolutionized warfare.”

Horse domestication goes back more than 5000 years, so the fact that most horses today descend from lineages dating to just 700 years ago shows how intense breeding from that time onward has greatly affected these majestic mammals.

A similar phenomenon has affected cats and dogs. Like horses, just a few key lineages are at the root of most breeding efforts. These animals, however, bred with local native species, creating the variety of types seen today.

Read more at Seeker

Jun 28, 2017

Analysis of Neanderthal teeth grooves uncovers evidence of prehistoric dentistry

Three views of the four articulated teeth making up KDP 20. a. occlusal view showing lingually placed mesial interproximal wear facet on P4 (arrow) and buccal wear on M3; b. lingual view showing a mesially placed interproximal wear facet on P4 (arrow), chips from lingual faces of all teeth and rotated, partially impacted M3; c. buccal view showing rotated buccal face of M3 (arrow) and hypercementosis on its root.
Neanderthals treating toothaches?

A discovery of multiple toothpick grooves on teeth and signs of other manipulations by a Neanderthal of 130,000 years ago are evidence of a kind of prehistoric dentistry, according to a new study led by a University of Kansas researcher.

"As a package, this fits together as a dental problem that the Neanderthal was having and was trying to presumably treat itself, with the toothpick grooves, the breaks and also with the scratches on the premolar," said David Frayer, professor emeritus of Anthropology. "It was an interesting connection or collection of phenomena that fit together in a way that we would expect a modern human to do. Everybody has had dental pain, and they know what it's like to have a problem with an impacted tooth."

The Bulletin of the International Association for Paleodontology recently published the study. The researchers analyzed four isolated but associated mandibular teeth on the left side of the Neanderthal's mouth. Frayer's co-authors are Joseph Gatti, a Lawrence dentist, Janet Monge, of the University of Pennsylvania; and, Davorka Radovčić, curator at the Croatian Natural History Museum.

The teeth were found at Krapina site in Croatia, and Frayer and Radovčić have made several discoveries about Neanderthal life there, including a widely recognized 2015 study published in PLOS ONE about a set of eagle talons that included cut marks and were fashioned into a piece of jewelry.

The teeth and all the Krapina Neanderthal fossils were discovered more than 100 years ago from the site, which was originally excavated between 1899-1905.

However, Frayer and Radovčić in recent years have reexamined many items collected from the site.

In this case, they analyzed the teeth with a light microscope to document occlusal wear, toothpick groove formation, dentin scratches, and ante mortem, lingual enamel fractures.

Even though the teeth were isolated, previous researchers were able to reconstruct their order and location in the male or female Neanderthal's mouth. Frayer said researchers have not recovered the mandible to look for evidence of periodontal disease, but the scratches and grooves on the teeth indicate they were likely causing irritation and discomfort for some time for this individual.

They found the premolar and M3 molar were pushed out of their normal positions. Associated with that, they found six toothpick grooves among those two teeth and the two molars further behind them.

"The scratches indicate this individual was pushing something into his or her mouth to get at that twisted premolar," Frayer said.

The features of the premolar and third molar are associated with several kinds of dental manipulations, he said. Mostly because the chips of the teeth were on the tongue side of the teeth and at different angles, the researchers ruled out that something happened to the teeth after the Neanderthal died.

Past research in the fossil record has identified toothpick grooves going back almost 2 million years, Frayer said. They did not identify what the Neanderthal would have used to produce the toothpick grooves, but it possibly could have been a bone or stem of grass.

"It's maybe not surprising that a Neanderthal did this, but as far as I know, there's no specimen that combines all of this together into a pattern that would indicate he or she was trying to presumably self-treat this eruption problem," he said.

The evidence from the toothpick marks and dental manipulations is also interesting in light of the discovery of the Krapina Neanderthals' ability to fashion eagle talons fashioned into jewelry because people often think of Neanderthals as having "subhuman" abilities.

Read more at Science Daily

Brooding dinosaurs

Prepared oviraptorosaur egg with preserved embryo skeleton. Scale 1cm.
A new method used to perform geochemical analysis of fossilized eggs from China has shown that oviraptorosaurs incubated their eggs with their bodies within a 35-40° C range, similar to extant birds today. This finding is the result of Franco-Chinese collaboration coordinated by Romain Amiot of the Laboratoire de géologie de Lyon: Terre, planètes et environnement (CNRS/ENS de Lyon/Université Claude Bernard Lyon 1).

Dinosaurs' reproductive strategies, and in particular the way they incubated their eggs, still raise numerous scientific questions. Until now, interpretations have been based on indirect indices such as the morphology of fossilized eggshells or the organization of nests. Researchers from Lyon, working in collaboration with a Chinese team, have developed a method based on the geochemical analysis of fossilized eggs and have calculated for the first time that the oviraptorosaur eggs were incubated within a 35-40° C temperature range.

Oviraptorosaurs were feathered bipedal dinosaurs with a beak, giving them an appearance reminiscent of certain birds. A member of the theropod group,[1] they weighed a few dozen kilos and could measure up to two meters in length. In order to determine the temperature at which these dinosaurs incubated their eggs, the researchers analyzed seven fossilized eggs recovered from southern China. These 70-million-year-old eggs still contain embryos. Both the eggshells and the embryo bones were analyzed in order to determine their oxygen isotope composition.[2] During the formation of the embryo skeletons, oxygen from the egg fluids was transferred to the embryo bones, the isotopic abundance of which would depend on the temperature of the egg. Taking these measurements into account, the researchers -- assisted by a physiologist colleague -- were able to model the different developmental stages integrating the oxygen isotope compositions. In doing so, they were able to ascertain the temperature at which the egg was formed: between 35 and 40° C. By way of comparison, crocodiles, which bury their eggs, incubate their eggs at a temperature of around 30° C, while hen's eggs are incubated at 37.5° C. According to the researchers, the incubation temperature calculated for the oviraptorosaurs eggs is thus coherent with the way these dinosaurs are thought to have incubated their eggs.

This result confirms the discovery made in the 1990s of fossilized oviraptorosaurs stretched across their clutch, suggesting that they incubated their eggs. The work also opens new avenues for research in paleontology: the method employed makes it possible to ascertain the incubation strategies adopted by other dinosaurs. No doubt some dinosaurs, weighing several dozen metric tons, could not lie on their eggs to incubate them, but they may have used other external heat sources, for example by covering their clutch with a mound of plant matter, which would have provided heat as it decomposed. The estimated incubation temperature will be a reflection of the incubation strategy employed, subject to being able access these rare and precious fossils for corroborative purposes.

 Read more at Science Daily

Climate Experts Warn That 2020 Is the Deadline for Avoiding Catastrophe

Humanity must put carbon dioxide emissions on a downward slope by 2020 to have a realistic shot at capping global warming at well under two degrees Celsius, the bedrock goal of the Paris climate accord, experts said Wednesday.

A world that heats up beyond that threshold will face a crescendo of devastating impacts ranging from deadly heatwaves to mass migration caused by rising seas, the experts warned in a commentary published in the science journal Nature.

With 1.0 degree Celsius (1.8 degrees Fahrenheit) of warming so far, ice sheets that could lift oceans by a dozen meters are melting more quickly, coral reefs are dying from heat stress, and ever more damaging storm surges are hammering coastal communities. 

The transition to cleaner energy sources is well underway and is backed by broad consensus on the need to beat back the threat of climate change — with the notable exception of the United States under President Donald Trump.

After rising for decades, global emissions of carbon dioxide driven by the burning of fossil fuels have levelled off during the last two years at about 41 billion tons per year.

But even at this rate the planet's "carbon budget" — the amount of CO2 that can be released into the atmosphere without crossing the 2.0 Celsius (3.6 Fahrenheit) red line — would be used up within a couple of decades, perhaps sooner.

"There is a long way to go to decarbonize the world economy," according to the commentary signed by former UN climate chief Christiana Figueres, three top climate scientists, and two sustainability experts from the business sector.

"When it comes to climate, timing is everything," they wrote.

The authors called on leaders set to gather at the G20 summit in Hamburg, Germany, on July 7-8 to highlight 2020 as a make-or-break point for taking action.

But after Trump's decision to withdraw from the Paris Agreement, which was signed by 196 nations, and his refusal to join a climate consensus at a G7 summit in late May, such an outcome seems doubtful.  

A number of benchmarks should be met by 2020, according to the commentary.

Renewable energy — mainly wind and solar — must make up at least 30 percent of the world's electricity supply, it said. Moreover, no additional coal-fired power plants should be approved after that date.

In the transport sector, electric vehicles — which currently represent one percent of new car sales — should account for 15 percent of the market by that date.

Governments should also require a 20 percent improvement in fuel efficiency for heavy-duty vehicles, and a 20 percent drop in carbon dioxide pollution per kilometer traveled in the aviation sector. Still climbing sharply, CO2 from the aviation industry account for about two percent of all human-generated emissions.

Read more at Seeker

The Search for the Next Large Asteroid That Might Slam Into Earth

An illustration of the asteroid impact over Tunguska, Siberia, on June 30, 1908 — the date on which Asteroid Day is marked.
Throughout its 4.5-billion-year history, Earth has been repeatedly pummeled by space rocks that have caused anything from an innocuous splash in the ocean to species annihilation.

When the next big impact will be, nobody knows.

But the pressure is on to predict — and intercept — its arrival.

"Sooner or later we will get... a minor or major impact," Rolf Densing, who heads the European Space Operations Centre (ESOC) in Darmstadt, Germany, told AFP ahead of International Asteroid Day on Friday.

It may not happen in our lifetime, he said, but "the risk that Earth will get hit in a devastating event one day is very high."

For now, there is little we can do.

And yet, the first-ever mission to crash a probe into a small space rock to alter its trajectory suffered a major setback when European ministers declined in December to fund part of the project.

"We are not ready to defend ourselves" against an Earth-bound object, said Densing. "We have no active planetary defense measures."

Hitherto relegated to the realms of science fiction, tactics could include nuking an incoming asteroid, using lasers to vaporize it, sending a space "tractor" to drag it off course, or bumping it into a new direction.

But first, we need to be able to spot the threat.

Astrophysicists monitoring the risk classify objects into sizes ranging from a few millimeters to behemoths 10 kilometers (6.2 miles) across — the size of rock that wiped out non-avian dinosaurs some 65 million years ago.

The smallest type enter Earth's atmosphere daily, burning up prettily as shooting stars.

End of days

The largest occur once every 100 million years, and the next impact could well ring in the end of human civilization.

But when would it happen?

So far, experts have managed to list more than 90 percent of asteroids in the dino-killing range, and determined that none poses an immediate threat.

A much bigger concern is the whereabouts of millions of asteroids in the 15- to 140-meter (49- to 460-feet) range.

One such object, a 40-meter space rock, caused the largest impact in recent history when it exploded over Tunguska, Siberia, on June 30, 1908 — the date on which Asteroid Day is marked.

The blast flattened some 80 million trees over 2,000 sparsely populated square kilometers (772 square miles) — an area bigger than greater London.

Tunguska-sized events happen, on average, every 300 years or so.

"Imagine that this type of asteroid would fall in a very populated area like... Paris or Germany, I mean this is something that would be really, really a catastrophe," said Nicolas Bobrinsky, program manager of the European Space Agency's Space Situational Awareness project, which surveys asteroids.

At least the ones it knows of.

The Chelyabinsk impact in 2013, for example, caught everyone unawares.

A once-a-decade category rock of about 20m exploded in the atmosphere over central Russia with the kinetic energy of some 27 Hiroshima bombs.

The resulting shockwave blew out the windows of nearly 5,000 buildings and injured more than 1,200 people.

"Now that we have discovered most of the (asteroids) that are about a kilometer in size and larger, the goal is to discover most of the ones which are (up to) about 140 m," said Patrick Michel, an astrophysicist with France's CNRS research institute.

"This is the threshold — if an object of this size impacts the Earth — for regional damage at the scale of a country or a continent."

Another unknown is long-period comets: wanderers of the solar system which can take centuries or millennia to orbit the Sun, and whose passage has never been recorded.

Eye on the sky

Europe is setting up a network of telescopes to provide us with a heads-up.

Scheduled for completion in about two years, it "will scan systematically the sky every night and any asteroid which is coming... would be detected with a warning time of approximately two to three weeks," said Bobrinsky.

This is admittedly "not much, but it's better than what we have now," he added.

At the very least, it would allow for cities to be evacuated, or a shockwave warning to be issued.

"Contrary to all other natural risks that we face on Earth, like tsunamis, earthquakes and things like that, this is the only one that we can predict," Michel said.

Read more at Seeker

Jun 27, 2017

Astronomers detect orbital motion in pair of supermassive black holes

Artist's conception of the pair of supermassive black holes at the center of the galaxy 0402+379, 750 million light-years from Earth.
Using the supersharp radio "vision" of the National Science Foundation's Very Long Baseline Array (VLBA), astronomers have made the first detection of orbital motion in a pair of supermassive black holes in a galaxy some 750 million light-years from Earth.

The two black holes, with a combined mass 15 billion times that of the Sun, are likely separated by only about 24 light-years, extremely close for such a system.

"This is the first pair of black holes to be seen as separate objects that are moving with respect to each other, and thus makes this the first black-hole 'visual binary,'" said Greg Taylor, of the University of New Mexico (UNM).

Supermassive black holes, with millions or billions of times the mass of the Sun, reside at the cores of most galaxies. The presence of two such monsters at the center of a single galaxy means that the galaxy merged with another some time in the past. In such cases, the two black holes themselves may eventually merge in an event that would produce gravitational waves that ripple across the universe.

"We believe that the two supermassive black holes in this galaxy will merge," said Karishma Bansal, a graduate student at UNM, adding that the merger will come at least millions of years in the future.

The galaxy, an elliptical galaxy called 0402+379, after its location in the sky, was first observed in 1995. It was studied in 2003 and 2005 with the VLBA. Based on finding two cores in the galaxy, instead of one, Taylor and his collaborators concluded in 2006 that it contained a pair of supermassive black holes.

The latest research, which Taylor and his colleagues are reporting in the Astrophysical Journal, incorporates new VLBA observations from 2009 and 2015, along with re-analysis of the earlier VLBA data. This work revealed motion of the two cores, confirming that the two black holes are orbiting each other. The scientists' initial calculations indicate that they complete a single orbit in about 30,000 years.

"We need to continue observing this galaxy to improve our understanding of the orbit, and of the masses of the black holes," Taylor said. "This pair of black holes offers us our first chance to study how such systems interact," he added.

The astronomers also hope to discover other such systems. The galaxy mergers that bring two supermassive black holes close together are considered to be a common process in the universe, so astronomers expect that such binary pairs should be common.

"Now that we've been able to measure orbital motion in one such pair, we're encouraged to seek other, similar pairs. We may find others that are easier to study," Bansal said.

The VLBA, part of the Long Baseline Observatory, is a continent-wide radio telescope system using ten, 240-ton dish antennas distributed from Hawaii to St. Croix in the Caribbean. All ten antennas work together as a single telescope with the greatest resolving power available to astronomy. That extraordinary resolving power allows scientists to make extremely fine measurements of objects and motions in the sky, such as those done for the research on 0402+379.

Read more at Science Daily

Odd properties of water and ice explained: Water exists as two different liquids

Pictured is an artist's impression of the two forms of ultra-viscous liquid water with different density. On the background is depicted the x-ray speckle pattern taken from actual data of high-density amorphous ice, which is produced by pressurizing water at very low temperatures.
We normally consider liquid water as disordered with the molecules rearranging on a short time scale around some average structure. Now, however, scientists at Stockholm University have discovered two phases of the liquid with large differences in structure and density. The results are based on experimental studies using X-rays, which are now published in Proceedings of the National Academy of Science.

Most of us know that water is essential for our existence on planet Earth. It is less well-known that water has many strange or anomalous properties and behaves very differently from all other liquids. Some examples are the melting point, the density, the heat capacity, and all-in-all there are more than 70 properties of water that differ from most liquids. These anomalous properties of water are a prerequisite for life as we know it.

"The new remarkable property is that we find that water can exist as two different liquids at low temperatures where ice crystallization is slow," says Anders Nilsson, professor in Chemical Physics at Stockholm University. The breakthrough in the understanding of water has been possible through a combination of studies using X-rays at Argonne National Laboratory near Chicago, where the two different structures were evidenced and at the large X-ray laboratory DESY in Hamburg where the dynamics could be investigated and demonstrated that the two phases indeed both were liquid phases. Water can thus exist as two different liquids.

"It is very exciting to be able to use X-rays to determine the relative positions between the molecules at different times," says Fivos Perakis, postdoc at Stockholm University with a background in ultrafast optical spectroscopy. "We have in particular been able to follow the transformation of the sample at low temperatures between the two phases and demonstrated that there is diffusion as is typical for liquids."

When we think of ice it is most often as an ordered, crystalline phase that you get out of the ice box, but the most common form of ice in our planetary system is amorphous, that is disordered, and there are two forms of amorphous ice with low and high density. The two forms can interconvert and there have been speculations that they can be related to low- and high-density forms of liquid water. To experimentally investigate this hypothesis has been a great challenge that the Stockholm group has now overcome.

"I have studied amorphous ices for a long time with the goal to determine whether they can be considered a glassy state representing a frozen liquid," says Katrin Amann-Winkel, researcher in Chemical Physics at Stockholm University. "It is a dream come true to follow in such detail how a glassy state of water transforms into a viscous liquid which almost immediately transforms to a different, even more viscous, liquid of much lower density."

"The possibility to make new discoveries in water is totally fascinating and a great inspiration for my further studies," says Daniel Mariedahl, PhD student in Chemical Physics at Stockholm University. "It is particularly exciting that the new information has been provided by X-rays since the pioneer of X-ray radiation, Wilhelm Röntgen, himself speculated that water can exist in two different forms and that the interplay between them could give rise to its strange properties."

"The new results give very strong support to a picture where water at room temperature can't decide in which of the two forms it should be, high or low density, which results in local fluctuations between the two," says Lars G.M. Pettersson, professor in Theoretical Chemical Physics at Stockholm University. "In a nutshell: Water is not a complicated liquid, but two simple liquids with a complicated relationship."

Read more at Science Daily

The dust storm microbiome

Dust storm in Timna Park is shown.
Israel is subjected to sand and dust storms from several directions: northeast from the Sahara, northwest from Saudi Arabia and southwest from the desert regions of Syria. The airborne dust carried in these storms affects the health of people and ecosystems alike. New research at the Weizmann Institute of Science suggests that part of the effect might not be in the particles of dust but rather in bacteria that cling to them, traveling many kilometers in the air with the storms.

Some of these bacteria might be pathogenic -- harmful to us or the environment -- and a few of them also carry genes for antibiotic resistance. Others may induce ecosystem functions such as nitrogen fixation. Prof. Yinon Rudich and his research group, including postdoctoral fellow Dr. Daniela Gat and former research student Yinon Mazar, in Weizmann's Earth and Planetary Sciences Department investigated the genetics of the windborne bacteria arriving along with the dust.

"In essence, we investigated the microbiome of windborne dust," says Rudich. "The microbiome of a dust storm originating in the Sahara is different from one blowing in from the Saudi or Syrian deserts, and we can see the fit between the bacterial population and the environmental conditions existing in each area."

The researchers found that during a dust storm the concentration of bacteria and the number of bacterial species present in the atmosphere rise sharply, so people walking outdoors in these storms are exposed to many more bacteria than usual.

Rudich and his team then explored the genes in these bacteria, checking for antibiotic resistance -- a trait that can arise owing to elevated use of antibiotics but also naturally, especially in soil bacteria. Antibiotic resistance has been defined by the World Health Organization as one of the primary global health challenges of the twenty-first century, and its main driver is the overuse of antibiotics. But bacteria can pass on the genes for antibiotic resistance, so any source of resistance is concerning. How many different genes for antibiotic resistance come to Israel from the various dust storms, and how prevalent are these genes?

Rudich says that the study enabled the researchers to identify a "signature" for each source of bacteria based on the prevalence of antibiotic resistant genes, which revealed whether the genes were local or imported from distant deserts. "We found that as more 'mixing' occurs between local dust and that which comes from far off, the lower the contribution of the imported antibiotic resistance genes." In other words, antibiotic resistance coming from Africa or Saudi Arabia is still a very minor threat compared to that caused and spread by human activity, especially animal husbandry. Also participating in this research were Dr. Eddie Cytryn of the Volcani Center and Prof. Yigal Erel of the Hebrew University of Jerusalem.

Read more at Science Daily

Chimpanzee 'super strength' and what it might mean in human muscle evolution

Since at least the 1920s, anecdotes and some studies have suggested that chimpanzees are "super strong" compared to humans, implying that their muscle fibers, the cells that make up muscles, are superior to humans.

But now a research team reports that contrary to this belief, chimp muscles' maximum dynamic force and power output is just about 1.35 times higher than human muscle of similar size, a difference they call "modest" compared with historical, popular accounts of chimp "super strength," being many times stronger than humans.

Further, says biomechanist Brian Umberger, an expert in musculoskeletal biomechanics in kinesiology at the University of Massachusetts Amherst, the researchers found that this modest performance advantage for chimps was not due to stronger muscle fibers, but rather the different mix of muscle fibers found in chimpanzees compared to humans.

As the authors explain, the long-standing but untested assumption of chimpanzees' exceptional strength, if true, "would indicate a significant and previously unappreciated evolutionary shift in the force and/or power-producing capabilities of skeletal muscle" in either chimps or humans, whose lines diverged some 7 or 8 million years ago.

Umberger was part of the team led by Matthew O'Neill at the University of Arizona College of Medicine, Phoenix, and others at Stony Brook University, Harvard and Ohio State University. Details of this work, supported in part by a National Science Foundation grant to Umberger, appear in the current early online edition of Proceedings of the National Academy of Sciences.

The researchers began by critically examining the scientific literature, where studies reported a wide range of estimates for how chimpanzees outstrip humans in strength and power, averaged about 1.5 times over all. But Umberger says reaching this value from such disparate reports "required a lot of analysis on our part, accounting for differences between subjects, procedures and so on." He and colleagues say 1.5 times is considerably less than anecdotal reports of chimps being several-fold stronger, but it is still a meaningful difference and explaining it could advance understanding of early human musculoskeletal evolution.

Umberger adds, "There are nearly 100 years of accounts suggesting that chimpanzees must have intrinsically superior muscle fiber properties compared with humans, yet there had been no direct tests of that idea. Such a difference would be surprising, given what we know about how similar muscle fiber properties are across species of similar body size, such as humans and chimps."

He explains that muscle fiber comes in two general types, fast-twitch, fast and powerful but fatigue quickly, and slow-twitch, which are slower and less powerful but with good endurance. "We found that within fiber types, chimp and human muscle fibers were actually very similar. However, we also found that chimps have about twice as many fast-twitch fibers as humans," he notes.

For this work, the team used an approach combining isolated muscle fiber preparations, experiments and computer simulations. They directly measured the maximum isometric force and maximum shortening velocity of skeletal muscle fibers of the common chimpanzee. In general, they found that chimp limb and trunk skeletal muscle fibers are similar to humans and other mammals and "generally consistent with expectations based on body size and scaling."

Umberger, whose primary scientific contribution was in interpreting how muscle properties will affect whole-animal performance, developed computer simulation models that allowed the researchers to integrate the various data on individual muscle properties and assess their combined effects on performance.

O'Neill, Umberger and colleagues also measured the distribution of muscle fiber types and found it to be quite different in humans and chimps, who also have longer muscle fibers than humans. They combined individual measurements in the computer simulation model of muscle function to better understand what the combined effects of the experimental observations were on whole-muscle performance. When all factors were integrated, chimp muscle produces about 1.35 times more dynamics force and power than human muscle.

Umberger says the advantage for chimps in dynamic strength and power comes from the global characteristics of whole muscles, rather than the intrinsic properties of the cells those muscles are made of. "The flip side is that humans, with a high percentage of slow-twitch fibers, are adapted for endurance, such as long-distance travel, at the expense of dynamic strength and power. When we compared chimps and humans to muscle fiber type data for other species we found that humans are the outlier, suggesting that selection for long distance, over-ground travel may have been important early in the evolution of our musculoskeletal system."

Read more at Science Daily

Jun 26, 2017

Bird's eye perspective

Susana da Silva made a quilt inspired by the patterning of cells in the chick retina. The gray circle represents the high-acuity area, or rod-free zone.
Humans belong to a select club of species that enjoy crisp color vision in daylight, thanks to a small spot in the center of the retina at the back of the eye. Other club members include monkeys and apes, various fish and reptiles, and many birds, which must home in on their scurrying dinners from afar or peck at tiny seeds.

Less clear is what controls the formation of the high-acuity spot, known as the fovea in humans.

Harvard Medical School researchers have now provided the first insight into this perplexing question by studying an unusual model: chickens.

Connie Cepko, Bullard Professor of Genetics and Neuroscience at HMS, and Susana da Silva, a postdoctoral fellow in the Cepko lab, found that formation of the high-acuity area in chicks requires suppression of retinoic acid, a derivative of vitamin A known to play many important roles in embryonic development.

In addition to deepening our understanding of how humans acquired sensitive daytime vision, the findings, reported June 22 in Developmental Cell, could help regenerative medicine researchers model healthy human eyes.

If the discoveries hold true in humans, the work might also one day provide clues about how to combat macular degeneration, the leading cause of vision loss among people age 50 and older. The macula is the part of the retina where the fovea is found.

"I think it's important to understand how you build this specialized area in the retina that's responsible for any major activity you do during the day, such as reading, driving, recognizing faces and using the phone," said da Silva. "It would also be exciting if people can use what we learn from this basic developmental question to treat diseases affecting the retina."

Most of the human retina -- the photosensitive part of the eye that translates light into nerve signals and relays them to the brain -- is lined with rod cells, which allow us to see well in dim light. The fovea, however, consists almost entirely of cone cells, which respond to color and bright light.

Twenty years ago, a researcher in Cepko's lab discovered that chickens also have a rod-free zone.

Although it's not yet clear how closely the chickens' high-acuity areas match ours, Cepko believes it's a good place to start asking questions -- especially since scientists' usual collection of mammalian model organisms, including mice, rats, rabbits and guinea pigs, don't have anything like a fovea.

In the new studies of chick embryos, Cepko and da Silva found that the complex patterning of cells in the rod-free zone formed because of a drop in retinoic acid that occurred only in that area of the retina and only for a brief time during development.

What spurred the drop? Probing further, the researchers found that the answer lay in a shifting balance between enzymes that create and those that destroy retinoic acid.

Enzymes known as retinaldehyde dehydrogenases, or Raldhs, ordinarily make retinoic acid in the retina. But Cepko and da Silva discovered that as cones and ganglion cells formed, levels of the enzymes Cyp26a1 and Cyp26c1 surged, breaking down retinoic acid faster than Raldhs could produce it.

When retinoic acid levels fell, a protein called fibroblast growth factor 8, or Fgf8, flourished, the investigators found. Fgf8 is another well-known molecule in embryonic development that often works with retinoic acid to stimulate and pattern cell growth.

Once their work was done, the Cyp26a1 and Cyp26c1 enzymes ebbed away, allowing Raldhs to replenish retinoic acid in the rod-free zone.

Cepko and da Silva saw similar expression patterns for Raldhs and Cyp26a1 in human retinal tissue, suggesting that something similar happens in people.

"This is the first mechanism we've uncovered for how this area forms," said Cepko. "We don't know where it will lead, but it's pretty exciting."

Stem cell researchers have made remarkable progress in building so-called organoids that mimic human eyes so they can study human health and disease. But they have run into a problem that the new study may help them solve.

"People can grow these incredible little eyes from stem cells, but so far no one's been able to form a fovea," said Cepko, who is also an HMS professor of ophthalmology at Massachusetts Eye and Ear.

She believes the trouble may arise because the researchers add retinoic acid to their cell cultures.

"We're suggesting that removing retinoic acid at the right time, adding Fgf8 or otherwise manipulating these two molecules may allow them to generate a fovea," she said.

It's also possible that the research will provide a foundation for investigating why the macula is so prone to disease, which could in turn lead to new treatments.

"Macular degeneration is a major problem for the aging population, and we don't understand why that area is vulnerable," said Cepko.

But Cepko and da Silva are driven mainly by the excitement of answering questions about the retina, learning about human development and probing evolutionary relationships between species.

Read more at Science Daily

Here's Why Finding ‘Missing Link’ Black Holes Is So Hard

For decades, while astronomers have detected black holes equal in mass either to a few suns or millions of suns, the missing-link black holes in between have eluded discovery. Now, a new study suggests such intermediate-mass black holes may not exist in the modern-day universe because of the rate at which black holes grow.

Scientists think stellar-mass black holes — up to a few times the sun's mass — form when giant stars die and collapse in on themselves. Over the years, astronomers have detected a number of stellar-mass black holes in the nearby universe, and in 2010, researchers detected the first such black hole outside the local cluster of nearby galaxies known as the Local Group.

As big as stellar-mass black holes might seem, they are tiny in comparison to the so-called supermassive black holes that are millions to billions of times the sun's mass, which form the hearts of most, if not all, large galaxies. The oldest supermassive black holes found to date include one found in 2015 — with a mass of about 12 billion solar masses — that existed when the universe was only about 875 million years old. This finding and others suggest that many black holes were born in the dawn of time, back when the universe was smaller and matter was more concentrated, making it easier for them to form and grow.

Much remains uncertain about how black holes reach supermassive girth and influence the universe around them. As such, astronomers want to analyze intermediate-mass black holes of about 100 to 10,000 solar masses that they expect would serve as the middle stages between stellar-mass and supermassive black holes.

However, while astronomers have discovered a number of potential intermediate-mass black holes, the evidence remains inconclusive, said astrophysicists Tal Alexander at the Weizmann Institute of Science in Rehovot, Israel, and Ben Bar-Or at the Institute for Advanced Study in Princeton, New Jersey.

Now these researchers suggest the dearth of these missing links may be due to the rate at which black holes may grow. They detailed their findings online June 19 in the journal Nature Astronomy.

In recent years, scientists have discovered a dozen or so instances of black holes devouring stars. If black holes grew solely by consuming stars and dense, compact objects such as white dwarfs and neutrons stars instead of, say, giant clouds of gas or dark matter, the researchers estimated that black holes would still grow at the relatively constant rate of one solar mass per 10,000 years. (If they could eat gas or dark matter, they could grow even faster, but the data regarding such materials in the early universe is more open to question.)

Although one solar mass per 10,000 years may not seem especially quick, it means that even a stellar-mass black hole could grow completely past the intermediate-mass stage after 10 billion years. In comparison, the universe is about 13.8 billion years old.

These findings suggest that the seeds for supermassive black holes "were created quite early on in galaxies, when things were more dense," Bar-Or told Space.com. These seeds already exceeded intermediate-mass stage by about 1.6 billion to 2.2 billion years after the Big Bang — "some or even most of the black holes may have passed the supermassive-black-hole mass threshold even earlier," Alexander told Space.com.

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A Massive Marine Extinction in Earth's History Was Just Discovered

Illustration of the giant shark Carcharocles megalodon, which died along with other large marine species during a newly identified extinction event.
The largest known shark that ever lived, Carcharocles megalodon, ruled the seas for over 20 million years. The enormous toothy predator, which could grow to about 60 feet long, seemed indestructible. Even now, the shark’s status is so legendary that — like a powerful celebrity — only one word is sufficient to name it: megalodon.

“Megalodon lived all around the world, during a time in which the oceans were warmer than today,” biologist and marine species specialist Catalina Pimiento said. “Our research suggests it was a cosmopolitan giant shark that was able to live in different latitudes, as ocean temperature didn’t determine its distribution. We also know it used shallow water productive areas as nurseries.”

Life appeared to be pretty good for this dominant apex predator, until disaster struck. Pimiento and an international team of researchers determined that megalodon did not die out alone. When the gigantic shark went extinct around 2.6 million years ago, so too did a third of all other large marine species. The previously unknown “Pliocene marine megafauna extinction” is described in the journal Nature Ecology & Evolution.

Pimiento conducted the research at the Paleontological Institute and Museum of the University of Zurich with her colleagues John Griffin, Christopher Clements, Daniele Silvestro, Sara Varela, Mark Uhen, and Carlos Jaramillo. The team made their determinations after a meta-analysis that looked at numerous prior studies concerning the fossil record of sharks, marine mammals, sea birds, and sea turtles.

“The work of hundreds of paleontologists over many years allowed us to characterize this extinction,” said Pimiento. “Most of these works have been catalogued in a public database: The Paleobiology Database.”

The scientists found that, in addition to megalodon, species of big sea cows and baleen whales also went extinct 2-3 million years ago. As many as 43 percent of sea turtle species, 35 percent of seabirds and 9 percent of sharks also died out at this time.

The drivers of the die-out are not precisely known, but the researchers note that violent sea level fluctuations coincided with the extinction event. Coastal habitats were significantly reduced as a result. Marine mammals that megalodon feasted on started to decline, while new competitors evolved.

The researchers analyzed a phenomenon called functional diversity, which generally concerns the range of characteristics and behaviors that organisms exhibit in communities and ecosystems. During the newly identified extinction event, 17 percent of the total diversity of ecological functions in the marine ecosystem disappeared, and 21 percent changed.

Particularly impacted were warm-blooded animals, suggesting that large, homeothermic species could be more vulnerable to extinction when major changes occur in their environments.

“Today, larger marine animals are more susceptible because they are targeted by humans,” Pimiento said.

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Laser That’s a Billion Times Brighter Than the Sun Reveals New Behavior in Light

A scientist at work in the Extreme Light Laboratory at the University of Nebraska-Lincoln, where physicists using the brightest light ever produced were able to change the way photons scatter from electrons.
Researchers at the University of Nebraska-Lincoln have generated the brightest light ever produced on Earth, and it may change the way we look at the universe – quite literally.

Donald Umstadter, head of the university's Extreme Light Laboratory, worked with colleagues in physics and astronomy to design an experiment in which pulses of light one billion times brighter than the surface of the sun were shot into an extremely tiny space. To facilitate the experiment, the research team fired up the lab's Diocles Laser, a room-sized assembly of optical equipment that can reach a peak power output greater than all the world's power plants combined.

The trick is that the laser produces bursts of light that only last a tiny fraction of a second.

“That makes high power, equivalent to a trillion light bulbs, but only for a very short amount of time — less than a trillionth of a second,” Umstadter said. “We then concentrate that power into a tiny spot, a millionth of a meter in size. That makes high intensity or brightness.”

By aiming the laser bursts at an intersecting stream of electrons, with precision down to a millionth of a meter, the researchers were able to observe how photons behave when striking a single electron.

It turns out that, at this level of brightness, the photons misbehave rather spectacularly. The high-energy illumination essentially knocks the electrons out of their usual alignment, scattering light in a fundamentally different way. The impact rattles the electrons into a figure-eight “quiver” pattern, shooting off additional photons at different angles, shapes, and wavelengths. The phenomenon, mathematically predicted in various theories, had never before been confirmed in the laboratory.

The team's research was funded by the US Air Force, US Department of Energy, the Department of Homeland Security's Domestic Nuclear Detection Office, and US and Chinese national science foundations. Thee findings are published in the journal Nature Photonics.

The really interesting part, Umstadter said, is that the scattering of photons can actually change the way we perceive illuminated objects. Under normal conditions, when light is increased, the perceived object looks brighter, but otherwise appears the same as in lower-light conditions.

Under the ultra-bright light of the Diocles laser, however, scientists can actually see things that are otherwise invisible to the human eye.

“It is amazing,” Umstadter said. “The light's coming off at different angles, with different colors, depending on how bright it is. What it reveals for the first time is the motion of electrons oscillating in the light fields at nearly the speed of light. They oscillate in a different pattern than they do in normal light.”

As a practical matter, the new technique can generate three-dimensional images with unprecedented resolution and accuracy. The additional photons ejected from the illuminated electrons act like super-powered X-rays. Doctors could use this kind of imaging to spot tumors or microfractures that would otherwise be missed by standard X-ray machines.

The technology can also be used to map circuitry on the molecular level, which will be useful for manufacturers who are increasingly building semiconductors on the nanoscopic scale. The super x-ray properties could also be used at airport security checkpoints, to make sure that that laptop computer is really a laptop computer.

“The higher X-ray energies we produce can be used to see through thickly shielded materials, nearly a meter thickness of steel, for cargo inspection, or non-destructive testing and evaluation of critical components,” Umstadter said.

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