Site of asteroid impact changed the history of life

Mass extinction only occurred when the asteroid having 9-km diameter hit the orange areas.

An asteroid, also known as the Chicxulub Impactor, hit Earth some 66 million years ago, causing a crater 180 km wide. The impact of the asteroid heated organic matter in rocks and ejected it into the atmosphere, forming soot in the stratosphere.

Soot is a strong, light-absorbing aerosol that caused global climate changes that triggered the mass extinction of dinosaurs, ammonites, and other animals, and led to the macroevolution of mammals and the appearance of humans.

Based on results of a new study, the researchers say that the probability of the mass-extinction occurring was only 13 percent. This is because the catastrophic chain of events could only have occurred if the asteroid had hit the hydrocarbon-rich areas occupying approximately 13 percent of Earth's surface.

Led by Tohoku University Professor Kunio Kaiho, the researchers came by their hypothesis by calculating the amount of soot in the stratosphere and estimating climate changes caused by soot using a global climate model developed at the Meteorological Research Institute. The results are significant because they explain the pattern of extinction and survival.

During the study, Kaiho thought that the amount of soot and temperature anomaly might have been affected by the amount of sedimentary organic-matter. So, he analyzed the amount of sedimentary organic-matter in Earth to obtain readings of temperature anomaly caused by soot in the stratosphere.

Naga Oshima of the Meteorological Research Institute conducted the global climate model calculations to obtain temperature anomalies caused by various amounts of soot injected into the stratosphere.

Kaiho clarified the relationship between the findings and concluded that the significant cooling and mass-extinction event could have only have occurred if the asteroid had hit hydrocarbon-rich areas occupying approximately 13 percent of Earth's surface.

If the asteroid had hit a low-medium hydrocarbon area on Earth (occupying approximately 87 percent of Earth's surface), mass extinction could not have occurred and the Mesozoic biota could have persisted beyond the Cretaceous/Paleogene boundary.

The site of the asteroid impact, therefore, changed the history of life on Earth.

According to the study, soot from hydrocarbon-rich areas caused global cooling of 8-11°C and cooling on land of 13-17°C. It also caused a decrease in precipitation by approximately 70-85 percent on land and a decrease of approximately 5-7°C in seawater temperature at a 50-m water depth, leading to mass extinction of life forms including dinosaurs and ammonites.

At the time, these hydrocarbon-rich areas were marine coastal margins, where the productivity of marine algae was generally high and sedimentary rocks were thickly deposited. Therefore, these areas contained a high amount of organic matter, part of which became soot from the heat of the asteroid's impact.

Thus, the researchers concluded that the Chicxulub impact occurred in a hydrocarbon-rich area and is a rare case of mass extinction being caused at such an impact site.

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How a 'shadow zone' traps the world's oldest ocean water

This is a schematic illustration of water currents.

New research from an international team has revealed why the oldest water in the ocean in the North Pacific has remained trapped in a shadow zone around 2km below the sea surface for over 1000 years.

To put it in context, the last time this water encountered the atmosphere the Goths had just invaded the Western Roman Empire.

The research suggests the time the ancient water spent below the surface is a consequence of the shape of the ocean floor and its impact on vertical circulation.

"Carbon-14 dating had already told us the most ancient water lied in the deep North Pacific. But until now we had struggled to understand why the very oldest waters huddle around the depth of 2km," said lead author from the University of New South Wales, Dr Casimir de Lavergne. "What we have found is that at around 2km below the surface of the Indian and Pacific Oceans there is a 'shadow zone' with barely any vertical movement that suspends ocean water in an area for centuries.

The shadow zone is an area of almost stagnant water sitting between the rising currents caused by the rough topography and geothermal heat sources below 2.5km and the shallower wind driven currents closer to the surface.

Before this research, models of deep ocean circulation did not accurately account for the constraint of the ocean floor on bottom waters. Once the researchers precisely factored it in they found the bottom water can not rise above 2.5km below the surface, leaving the region directly above isolated.

While the researchers have unlocked one part of the puzzle their results also have the potential to tell us much more.

"When this isolated shadow zone traps millennia old ocean water it also traps nutrients and carbon which have a direct impact on the capacity of the ocean to modify climate over centennial time scales," said fellow author from Stockholm University, Dr Fabien Roquet.

From Science Daily

Understanding the Berlin patient's unexpected cure of HIV

Research associate Jason Reed performs cell culture maintenance in the Sacha lab.

A decade ago, the medical world was shocked when a patient in Berlin, Germany, had been declared free of HIV after receiving a stem cell transplant to treat cancer. Doctors have repeatedly tried to replicate the result, but this HIV cure has evaded other patients so far.

Dr. Jonah Sacha and colleagues at OHSU's Vaccine & Gene Therapy Institute are among the many scientists who are seeking to understand why the much-studied "Berlin patient" was so fortunate. Now, they've developed a new way to understand his cure. Sacha's team has shown a species of monkey called Mauritian cynomolgus macaques can successfully receive stem cell transplants.

Researchers have long used a different monkey species to research stem cell transplants, but that species' biological characteristics means it can't be reliably used to find good donor matches to mimic human stem transplants.

In a paper published Nov. 10 in the journal Nature Communications, Sacha and colleagues report they successfully performed stem transplants on two monkeys more than a year ago that continue to lead healthy lives today. The recipients did not suffer from the many common adverse effects of stem transplants, including the grueling graft-versus-host disease, which can cause severe liver damage, rashes, diarrhea and even death.

The finding provides Sacha a critical tool needed to explore how the Berlin patient was cured. As a result of the finding, researchers can also use Mauritian cynomolgus macaques to improve stem cell transplant outcomes for human patients with other blood-related conditions such as leukemia and sickle-cell disease.

From Science Daily

Finger and toe fossils belonged to tiny primates 45 million years ago

The fossils provide further evidence that early anthropoids were minuscule creatures.

At Northern Illinois University, Dan Gebo opens a cabinet and pulls out a drawer full of thin plastic cases filled with clear gelatin capsules. Inside each numbered capsule is a tiny fossil -- some are so small they rival the diminutive size of a mustard seed.

It's hard to imagine that anyone would be able to recognize these flecks as fossils, much less link them to an ancient world that was very different from our own, yet has quite a bit to do with us -- or the evolution of us.

The nearly 500 finger and toe bones belonged to tiny early primates -- some half the size of a mouse. During the mid-Eocene period, about 45 million years ago, they lived in tree canopies and fed on fruit and insects in a tropical rainforest in what is now China.

The fossilized phalanges are described in detail in a new study by Gebo and colleagues, published online this fall ahead of print in the Journal of Human Evolution.

Representing nine different taxonomic families of primates and as many as 25 species, the specimens include numerous fossils attributed to Eosimias, the very first anthropoid known to date, and three fossils attributed to a new and much more advanced anthropoid. The anthropoid lineage would later include monkeys, apes and humans.

"The fossils are extraordinarily small, but in terms of quantity this is the largest single assemblage of fossil primate finger and toe specimens ever recorded," said Gebo, an NIU professor of anthropology and biology who specializes in the study of primate anatomy.

All of the finger and toe fossils imply tree-dwelling primates with grasping digits in both hands and feet. Many of the smaller fossils are between 1 and 2 millimeters in length, and the animals would have ranged in full body size from 10 to 1,000 grams (0.35 to 35.3 ounces).

"The new study provides further evidence that early anthropoids were minuscule creatures, the size of a mouse or smaller," Gebo said. "It also adds to the evidence pointing toward Asia as the initial continent for primate evolution. While apes and fossil humans do come from Africa, their ancestors came from Asia."

The newly described fossils were originally recovered from a commercial quarry near the village of Shanghuang in the southern Jiangsu Province of China, about 100 miles west of Shanghai. In recent decades, Shanghuang has become well-known among paleontologists.

"Shanghuang is truly an amazingly diverse fossil primate locality, unequaled across the Eocene," Gebo said. "Because no existing primate communities show this type of body-size distribution, the Shanghuang primate fauna emphasizes that past ecosystems were often radically different from those we are familiar with today."

Co-author Christopher Beard, a paleontologist at the University of Kansas in Lawrence who has been working on Shanghuang fossils for 25 years, said the limestone in the quarry is of Triassic age -- from the very beginning of the Age of Dinosaurs some 220 million years ago. Owing to a subsequent phase of erosion, the limestone developed large fissures containing fossil-rich sediments dating to the middle Eocene, after dinosaurs went extinct.

In the early 1990s, more than 10 tons of fossil-bearing matrix were collected from the fissures and shipped to the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and the Carnegie Museum of Natural History in Pittsburgh. There, the matrix was washed and screened, yielding fossil bones and teeth from ancient mammals, many of which remain to be identified.

"Because of commercial exploitation of the quarry site, the fossil-bearing fissure-fillings at Shanghuang are now exhausted," Beard said. "So, the fossils that we currently have are all that will ever be found from this site."

Gebo was initially recruited during the late 1990s to spearhead research on primate limb and ankle bones from Shanghuang. That led to two publications in 2000, when he and colleagues first announced the discovery of 45 million-year-old, thumb-length primates, the smallest ever recovered, from this same site. The work identifying body parts also helped cement the status of Eosimias, first identified by Beard on the basis of jaw fragments discovered at the site, as an extremely primitive anthropoid lying at the very beginning of our lineage's evolutionary past.

In more recent years, Gebo found additional specimens, sifting through miscellaneous elements from Shanghuang both at the Carnegie Museum and the University of Kansas. He brought the delicate and minuscule finger and toe fossils to NIU for study using traditional and electron-scanning microscopes.

The fossils that endured the millennia may be small but still have a story to tell. "We can actually identify different types of primates from the shapes of their fingers and toes," Gebo said.

Primates are mammals, characterized by having bigger brains, grasping hands and feet, nails instead of claws and eyes located in the front of the skull. Living prosimians, or living lower primates, include lemurs and tarsiers, and have broader fingertips. In contrast, most living anthropoids, also known as higher primates, have narrow fingertips.

Fossils from the unnamed advanced anthropoid are narrow, Gebo said.

"These are the earliest known examples of those narrow fingers and toes that are key to anthropoid evolution," he added. "We can see evolution occurring at this site, from the broader finger or toe tips to more narrow."

Unlike other prehistoric forests across the globe that have a mixture of large and small primates, Shanghuang's fossil record is unique in being nearly absent of larger creatures.

The unusual size distribution is likely the result of a sampling bias, Gebo said. Researchers might be missing the larger primate fauna because of processes affecting fossil preservation, and for similar reasons scientists at other Eocene localities could be missing the small-sized fauna.

"Many of the fossil specimens from Shanghuang show evidence of partial digestion by predatory birds, which may have specialized on preying upon the small primates and other mammals that are so common at Shanghuang, thus explaining the apparent bias toward small fossil species there," Beard added.

Read more at Science Daily

Fruit fly brains inform search engines of the future

This illustration represents a fruit fly executing a similarity search algorithm based on odor.

Every day, websites you visit and smartphone apps that you use are crunching huge sets of data to find things that resemble each other: products that are similar to your past purchases; songs that are similar to tunes you've liked; faces that are similar to people you've identified in photos. All these tasks are known as similarity searches, and the ability to perform these massive matching games well -- and fast -- has been an ongoing challenge for computer scientists.

Now, Salk and University of California San Diego scientists have discovered that the fruit fly brain has an elegant and efficient method of performing similarity searches. For flies, it helps them identify odors that are most similar to those they've encountered before, so they know how to behave in response to the odor, such as to approach or avoid it. New details on the fly's computational approach to smelly similarity searches, described in the journal Science on November 9, 2017, could inform computer algorithms of the future.

"This is a problem that pretty much every technology company with any kind of information retrieval system has to solve, so it's been something that computer scientists have studied for years," says Saket Navlakha, assistant professor in Salk's Integrative Biology Laboratory and lead author of the new paper. "Now, we have this new approach to similarity searches thanks to the fly."

The way most computerized data systems categorize items -- from songs to images -- to optimize similarity searches is by reducing the amount of information associated with each item. These systems assign short "hashes" to each item so that similar items are more likely to be assigned the same or a similar hash compared to two very different items. (Hashes are a kind of digital shorthand, the way a bitly is a shorter version of a URL.) Assigning hashes in this way is called "locality-sensitive hashing" to computer scientists. When searching for similar items, a program looks through the hashes, rather than the original items, to find similarities quickly.

Navlakha was chatting with colleague Charles Stevens, a professor in Salk's Molecular Neurobiology Laboratory and a coauthor of the new work, who had studied fly olfaction, when the former realized that flies -- and all animals -- are constantly faced with similarity searches as well. So he started combing the literature on the brain circuitry behind fly olfaction to work out just how flies identify similar smells.

"In the natural world, you're not going to encounter exactly the same odor every time; there's going to be some noise and fluctuation," Navlakha explains. "But if you smell something that you've previously associated with a behavior, you need to be able to identify that similarity and recall that behavior." So if a fruit fly knows that the smell of a rotting banana means mealtime, it needs to respond the same way when it encounters a very similar smell, even if it never experienced that exact smell before.

Navlakha and his collaborators' review of the literature revealed that when fruit flies first sense an odor, 50 neurons fire in a combination that's unique to that smell. But rather than hashing that information by reducing the number of hashes associated with the odor, as computer programs would, flies do the opposite -- they expand the dimension. The 50 initial neurons lead to 2,000 neurons, spreading out the input so that each smell has an even more distinct fingerprint among those 2,000 neurons. The brain then stores only the 5 percent of those 2,000 neurons with the top activity as the "hash" for that odor. The whole paradigm helps the brain notice similarities better than it would compared to reducing the dimension, Navlakha says.

"Say you have a bunch of people clustered by their relationships, and they're bunched into a crowded room," he explains. "Then take the same people and relationships, but have them spread out on a football field. It will be much easier to see the structure of relationships and draw boundaries between groups in the expanded space relative to the crowded space."

While Navlakha and his collaborators did not reveal the actual mechanism by which flies are storing odor information -- that was already available in the literature -- they are the first to analyze how this process maximizes speed and efficiency for similarity searches. When they applied the process to three standard datasets computer scientists use to test search algorithms, they found that the fly approach improved performance. This approach, they think, may inform computer programs someday.

"Pieces of this approach had been used in the past by computer scientists, but evolution put it together in a very unique way," says Navlakha.

Navlakha's collaborators say that the study is among the first to make such concrete parallels between neural circuits in the brain and information processing algorithms used in computer science.

"For the past 20 years I've been interested in random projections [a core component of locality-sensitive hashing for similarity search] as they apply to algorithms running on computers," says Sanjoy Dasgupta, a professor of computer science and engineering at the UCSD Jacobs School of Engineering and first author of the new paper. "It never occurred to me that similar operations may be at work in nature."

Read more at Science Daily

Crested pigeons use feathers to sound the alarm

Australian Crested pigeon (Ochyphaps lophotes).

Many animals will sound an alarm to alert other members of their group of impending danger. Now, researchers reporting in Current Biology on November 9 have shown that crested pigeons do this in a surprisingly non-vocal way. One of their main flight feathers produces a critical high-pitched sound as the birds fly away. As they flap faster to escape a predator, that alarm signal automatically increases in tempo.

Importantly, the researchers also show that other crested pigeons flee when they hear that sound. The findings confirm that the sound is a bona fide signal, not just a side effect of flight.

"Crested pigeons signal danger with noisy wings, not voices," says Trevor Murray of The Australian National University. "It shows that birds really can use their feathers as 'musical instruments' to communicate with others."

Charles Darwin proposed the idea of non-vocal "instruments" in birds about 150 years ago, but it has been a difficult idea to test. Scientists had long known that crested pigeons make loud sounds when they fly. For that reason, they are sometimes called "whistle-winged pigeons." The Australian National University lab led by Robert Magrath earlier found that other pigeons pay attention to those sounds.

To confirm that the whistling feathers were indeed an alarm signal, in this new study, the researchers shot high-speed video and conducted feather-removal experiments. These studies show that the birds' unusually narrow eighth primary wing feather produces a distinct note with each downstroke. The sound also changes as birds flap faster, such that those fleeing danger produce wing sounds with a higher tempo.

In fact, the birds' wings produce alternating high and low notes in flight. The researchers' experiments showed that the eighth primary wing feather is responsible for the high notes. The low notes come from the ninth primary feather. But, playback experiments showed, only the high notes are critical for sounding an alarm.

When the researchers played flight sounds to other pigeons, individuals were much more likely to flee upon hearing the flight of a bird with an intact eighth primary feather. When they played the sound of a pigeon with that eighth feather removed, they often just looked around instead of taking off.

"We show that the crested pigeon produces an acoustic alarm signal with its wings and that it is an intrinsically reliable signal of danger," Murray says. "The alarm signal is intrinsically reliable because pigeons flap faster to escape predators, and this fast flapping automatically produces the high-tempo alarm signal."

Crested pigeons are not the only birds known to produce unusually loud sounds with their wings, the researchers note. Pigeons in general fly noisily. Hummingbirds and manikins are also well known for their wing sounds. They hope that future studies will explore the evolution of wing sounds in other bird species.

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Deep-sea fish reveals twilight trick

The two pearlside species studied, Maurolicus muelleri (top) and Maurolicus mucronatus (bottom).

A new type of cell has been found in the eye of a deep-sea fish, and scientists say the discovery opens a new world of understanding about vision in a variety of light conditions.

University of Queensland scientists found the new cell type in the deep-sea pearlside fish (Maurolicus spp.), which have an unusual visual system adapted for twilight conditions.

Dr Fanny de Busserolles at UQ's Queensland Brain Institute said the retina of most vertebrate animals -- including humans -- contained two photoreceptor types: rods for vision in dim light, and cones for daytime vision. Each had different light-sensitive proteins.

"Deep-sea fish, which live at ocean depths below 200m, are generally only active in the dark, so most species have lost all their cones in favour of light-sensitive rods," Dr de Busserolles said.

Pearlsides differed in that they were mostly active at dusk and dawn, close to the water's surface where light levels are intermediate.

"Previously it was thought that pearlsides had retinas composed entirely of rods, but our new study has found this isn't the case," Dr de Busserolles said.

"Humans use their cones during the day our rods at night, but during twilight, although not ideal, we use a combination of both.

"Pearlsides, being active mainly during twilight, have developed a completely different solution.

"Instead of using a combination of rods and cones, they combine aspects of both cells into a single and more efficient photoreceptor type."

The researchers found that the cells -- which they have termed "rod-like cones" for their shapes under the microscope -- were tuned perfectly to the pearlsides' specific light conditions.

Research leader Professor Justin Marshall said the study was significant.

"It improves understanding of how different animals see the world and how vision might have helped them to conquer even the most extreme environments, including the deep sea," Professor Marshall said.

"Humans love to classify everything into being either black or white.

"However our study shows the truth might be very different from previous theories.

Read more at Science Daily

Astronomers discover a star that would not die

This is an artist's impression of a Supernova.

An international team of astronomers led by Las Cumbres Observatory (LCO) has made a bizarre discovery; a star that refuses to stop shining.

Supernovae, the explosions of stars, have been observed in the thousands and in all cases they marked the death of a star.

But in a study published today in the journal Nature, the team discovered a remarkable exception; a star that exploded multiple times over a period of more than fifty years. Their observations, which include data from Keck Observatory on Maunakea, Hawaii, are challenging existing theories on these cosmic catastrophes.

"The spectra we obtained at Keck Observatory showed that this supernova looked like nothing we had ever seen before. This, after discovering nearly 5,000 supernovae in the last two decades," said Peter Nugent, Senior Scientist and Division Deputy for Science Engagement in the Computational Research Division at Lawrence Berkeley National Laboratory who co-authored the study. "While the spectra bear a resemblance to normal hydrogen-rich core-collapse supernova explosions, they grew brighter and dimmer at least five times more slowly, stretching an event which normally lasts 100 days to over two years."

Researchers used the Low Resolution Imaging Spectrometer (LRIS) on the Keck I telescope to obtain spectrum of the star's host galaxy, and the Deep Imaging and Multi-Object Spectrograph (DEIMOS) on Keck II to obtain high-resolution spectra of the unusual star itself.

The supernova, named iPTF14hls, was discovered in September of 2014 by the Palomar Transient Factory. At the time, it looked like an ordinary supernova. Several months later, LCO astronomers noticed the supernova was growing brighter again after it had faded.

When astronomers went back and looked at archival data, they were astonished to find evidence of an explosion in 1954 at the same location. This star somehow survived that explosion and exploded again in 2014.

"This supernova breaks everything we thought we knew about how they work. It's the biggest puzzle I've encountered in almost a decade of studying stellar explosions," said lead author Iair Arcavi, a NASA Einstein postdoctoral fellow at LCO and the University of California Santa Barbara.

The study calculated that the star that exploded was at least 50 times more massive than the sun and probably much larger. Supernova iPTF14hls may have been the most massive stellar explosion ever seen. The size of this explosion could be the reason that our conventional understanding of the death of stars failed to explain this event.

Supernova iPTF14hls may be the first example of a "Pulsational Pair Instability Supernova."

"According to this theory, it is possible that this was the result of star so massive and hot that it generated antimatter in its core," said co-author Daniel Kasen, an associate professor in the Physics and Astronomy Departments at UC Berkeley and a scientist at Lawrence Berkeley Lab. "That would cause the star to go violently unstable, and undergo repeated bright eruptions over periods of years."

That process may even repeat over decades before the star's large final explosion and collapse to a black hole.

"These explosions were only expected to be seen in the early universe and should be extinct today. This is like finding a dinosaur still alive today. If you found one, you would question whether it truly was a dinosaur," said Andy Howell, leader of the LCO supernova group and co-author of the study.

Indeed, the "Pulsational Pair Instability" theory may not fully explain all the data obtained for this event. For example, the energy released by the supernova is more than the theory predicts. This supernova may be something completely new.

Astronomers continue to monitor iPTF14hls, which remains bright three years after it was discovered.

Read more at Science Daily

A giant, prehistoric otter's surprisingly powerful bite

Digital, 3-D reconstructions show the skulls -- including the jaws -- of the roughly 15-pound common otter Lutra lutra (left), and the roughly 110-pound Siamogale melilutra, a giant prehistoric otter with a surprisingly powerful bite (right).

A massive, wolf-sized otter that lived about 6 million years ago may have been a dominant predator in its time, according to a new study analyzing the animal's jaws.

The research provides insight into the ecological niche that the oversized creature may have filled in the wetlands of southwest China, where it lived. The otter, Siamogale melilutra, weighed about 110 pounds -- bigger than any living otter.

"We started our study with the idea that this otter was just a larger version of a sea otter or an African clawless otter in terms of chewing ability, that it would just be able to eat much larger things. That's not what we found," says Z. Jack Tseng, PhD, who led the project. Tseng is an assistant professor of pathology and anatomical sciences in the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo, and a research associate with the American Museum of Natural History and the Natural History Museum of Los Angeles County.

When scientists used computers to simulate how biting would strain S. melilutra's jaws, they concluded that the animal had much firmer jaw bones than expected. This stiffness would have given the otter a surprisingly strong bite -- even for its size.

"We don't know for sure, but we think that this otter was more of a top predator than living species of otters are," Tseng says. "Our findings imply that Siamogale could crush much harder and larger prey than any living otter can."

Modern otters have a varied diet, with different species dining on foods that range from plants and rodents to fish, crabs and clams. Based on the new study's findings, S. melilutra's jaws would have been strong enough to crush the shells of big mollusks or the bones of birds and small mammals like rodents, though what exactly it ate is unknown.

The study will be published on Nov. 9 in Scientific Reports. The research team included Denise F. Su of the Cleveland Museum of Natural History; Xiaoming Wang of the Natural History Museum of Los Angeles County, American Museum of Natural History, and Chinese Academy of Sciences; Stuart C. White of UCLA; and Xueping Ji of the Yunnan Institute of Cultural Relics and Archaeology in China.

An otter like no other

To better understand S. melilutra, Tseng and colleagues compared the prehistoric critter to its living counterparts.

The team used computed tomography (CT) scans of skulls to create 3-D, computerized models showing how the jaw bones of 10 of the 13 known living otter species bend under biting forces. (One rare otter was left out because researchers could not find bones to scan, and two others were excluded due to their similarity to other species).

The team also made a model for S. melilutra, using CT scans of fossils as a guide. The work included a painstaking, digital reconstruction of the cranium based on a crushed fossil.

A comparison of all the otter jaw simulations revealed a linear relationship between jaw stiffness and animal size: Smaller otters had sturdier jaws. But S. melilutra was an outlier: The massive mammal's modeled jaws were six times sturdier than expected. This strength, paired with the creature's size, would have made it a formidable hunter.

"At the time that the otter lived, the area where its remains were found included a swamp or a shallow lake surrounded by evergreen forest or dense woodland," said Su, a paleoecologist at the Cleveland Museum of Natural History and one of the leaders of the Shuitangba Project that discovered the fossil otter. "There was a diverse aquatic fauna at Shuitangba, including fish, crab, mollusks, turtles and frogs, as well as many different species of water birds, all of which could have been potential prey for S. melilutra."

In this wet and forested environment, the otter's jaw power could have given it an edge over predators that could not hunt in water or smash the shells of aquatic prey.

"Carnivores are known to evolve powerful jaws, often for the purpose of cracking the bones of their prey," said Wang, a curator in the Vertebrate Paleontology Department of the Natural History Museum of Los Angeles County. "In the shallow swamp of South China, it's possible that an abundance of big clams drove these giant otters to acquire their rare traits, including their crushing teeth and robust jaws." Wang, along with Su, White and Ji, was a member of the research team that first reported the discovery of the giant otter's fossils in January.

Jaw strength and diet

Besides providing insight into S. melilutra, the new study raises general questions about the relationship between jaw power and diet in animals.

Typically, scientists expect to find more powerful jaws in creatures that eat harder foods. But according to the new study, these two traits don't match up in living otters: Jaw strength correlated with size, regardless of meal choice.

Tool use may help explain this discrepancy, allowing some otters with a relatively weak bite to tackle tough foods: "Sea otters, for example, swim on their backs and use their chests as a platform for crushing their food with stones," Tseng says.

But tool use can't completely account for the pattern that the scientists saw, and more research needs to be done to understand the unexpected trend.

For now, Tseng believes it's still possible to draw some conclusions about S. melilutra based on its unusual mandibular strength. "We think the anatomy means something because it doesn't fall within the usual pattern that we see in other otters," he says. "The strong jaws suggest that the primitive otter probably did not have the tool-using capability, and combined with the giant size, it was likely a top predator."

Read more at Science Daily

Height and weight evolved at different speeds in the bodies of our ancestors

Femoral head bones of different species illustrating the size range in the hominin lineage. From top to bottom: Australopithecus afarensis (4-3 million years; ~40 kg, 130 cm); Homo ergaster (1.9-1.4 million years; 55-60 kg; ~165 cm); Neanderthal (200.000-30.000 years; ~70 kg; ~163 cm).

A wide-ranging new study of fossils spanning over four million years suggests that stature and body mass advanced at different speeds during the evolution of hominins -- the ancestral lineage of which Homo sapiens alone still exist.

Published today in the journal Royal Society Open Science, the research also shows that, rather than steadily increasing in size, hominin bodies evolved in "pulse and stasis" fluctuations, with some lineages even shrinking.

The findings are from the largest study of hominin body sizes, involving 311 specimens dating from earliest upright species of 4.4m years ago right through to the modern humans that followed the last ice age.

While researchers describe the physical evolution of assorted hominin species as a "long and winding road with many branches and dead ends," they say that broad patterns in the data suggest bursts of growth at key stages, followed by plateaus where little changed for many millennia.

The scientists were surprised to find a "decoupling" of bulk and stature around one and a half million years ago, when hominins grew roughly 10cm taller but would not consistently gain any heft for a further million years, with an average increase of 10-15kgs occurring around 500,000 years ago.

Before this event, height and weight in hominin species appeared to evolve roughly "in concert," say the authors of this first study to jointly analyse both aspects of body size over millions of years.

"An increase solely in stature would have created a leaner physique, with long legs and narrow hips and shoulders. This may have been an adaptation to new environments and endurance hunting, as early Homo species left the forests and moved on to more arid African savannahs," says lead author Dr Manuel Will from Cambridge's Department of Archaeology, and a Research Fellow at Gonville and Caius College.

"The higher surface-to-volume ratio of a tall, slender body would be an advantage when stalking animals for hours in the dry heat, as a larger skin area increases the capacity for the evaporation of sweat."

"The later addition of body mass coincides with ever-increasing migrations into higher latitudes, where a bulkier body would be better suited for thermoregulation in colder Eurasian climates," he says.

However, Dr Will points out that, while these are valid theories, vast gaps in the fossil record continue to mask absolute truths. In fact, Will and colleagues often had to estimate body sizes from highly fragmented remains -- in some cases from just a single toe bone.

The study found body size to be highly variable during earlier hominin history, with a range of differently shaped species: from broad, gorilla-like Paranthropus to the more wiry or 'gracile' Australopithecus afarensis. Hominins from four million years ago weighed a rough average of 25kg and stood at 125-130cm.

As physicality morphs over deep time, increasingly converging on larger body sizes, the scientists observe three key "pulses" of significant change.

The first occurs with the dawn of our own defined species bracket, Homo, around 2.2-1.9m years ago. This period sees a joint surge in both height (around 20 cm) and weight (between 15-20kg).

Stature then separated from heft with a height increase alone of 10cm between 1.4-1.6m years ago, shortly after the emergence of Homo erectus. "From a modern perspective this is where we see a familiar stature reached and maintained. Body mass, however, is still some way off," explains Will.

It's not until a million years later (0.5-0.4m years ago) that consistently heavier hominins appear in the fossil record, with an estimated 10-15kg greater body mass signalling adaptation to environments north of the Mediterranean.

"From then onwards, average body height and weight stays more or less the same in the hominin lineage, leading ultimately to ourselves," says Will.

There are, however, a couple of exceptions to this grand narrative: Homo naledi and Homo floresiensis*. Recently discovered remains suggest these species swam against the tide of increasing body size through time.

"They may have derived from much older small-bodied ancestors, or adapted to evolutionary pressures occurring in small and isolated populations," says Will. Floresiensis was discovered on an Indonesian island.

"Our study shows that, other than these two species, hominins that appear after 1.4m years ago are all larger than 140cm and 40kg. This doesn't change until human bodies diversify again in just the last few thousand years."

"These findings suggest extremely strong selective pressures against small body sizes which shifted the evolutionary spectrum towards the larger bodies we have today."

Will and colleagues say evolutionary pressures that may have contributed include 'cladogenesis': the splitting of a lineage, with one line -- the smaller-bodied one, in this case -- becoming extinct, perhaps as a result of inter-species competition.

They also suggest that sexual dimorphism -- the physical distinction between genders, with females typically smaller in mammals -- was more prevalent in early hominin species but then steadily ironed out by evolution.

Study co-author Dr Jay Stock, also from Cambridge's Department of Archaeology, suggests this growth trajectory may continue.

"Many human groups have continued to get taller over just the past century. With improved nutrition and healthcare, average statures will likely continue to rise in the near future. However, there is certainly a ceiling set by our genes, which define our maximum potential for growth," Stock says.

Read more at Science Daily

Boy Who Lost 80 Percent of His Epidermis Healed with Genetically Altered Skin

Gene therapy to treat a skin disease

When the 7-year-old boy arrived at the burn center in Germany, he had already lost 60 percent of his epidermis and was being treated around the clock with morphine. The child wasn’t the victim of a terrible fire, but was the carrier of a rare genetic disease called junctional epidermolysis bullosa (JEB) that had produced blisters and open wounds all over his body since birth. A staph infection had driven him to the verge of death.

The surgical team in Germany quickly exhausted conventional skin graft techniques — skin from the boy’s father was rejected — and were ready to give up when they came upon an experimental gene therapy in Italy. The method, which had only been used twice on much smaller grafts, used genetic editing to correct a mutation that prevented the epidermis from properly binding to the underlying dermis.

As the surgeons and researchers reported in an article published in the journal Nature, the boy underwent three skin graft surgeries in late 2015 and early 2016 using sheets of his own genetically corrected skin grown in the Italian lab. At the time of the first surgery, he had lost 80 percent of his total epidermal skin layer and the prognosis was dire. Just eight months later, he walked out of the intensive care unit with a completely healthy, self-renewing, and stretchable epidermis.

“To make it clear, we didn’t have any options to treat this child,” Tobias Hirsch, a surgeon with the burn center at the Ruhr University Hospital in Bochum, Germany, told journalists during a press briefing. “We initially decided to do palliative care, because there was no chance to save his life. And now the kid is back to school, he’s playing soccer, and spending holidays with his siblings. There’s a tremendous increase in quality of life.”

The experimental gene therapy treatment was developed by Michele De Luca at the Center for Regenerative Medicine at the University of Modena and Reggio Emilia in Modena, Italy. Patients suffering from JEB have a mutation in one or more of three genes (LAMA3, LAMB3, or LAMC2) that disrupts the production of laminin 5, a protein that’s critical to forming the bottom-most layer of the epidermis.

An estimated 500,000 people worldwide suffer from various forms of epidermolysis bullosa. Without a cure, 40 percent of individuals with JEB don’t survive past early childhood, primarily due to skin cancers that are also strongly associated with the disease.

Even though the 7-year-old boy was stricken with a particularly severe form of JEB, surgeons were able to salvage a small biopsy of healthy skin tissue and send it to De Luca’s lab in Italy, where he used a retroviral vector to replace the boy’s faulty LAMB3 gene with a fully expressed version.

The new skin cells were then grown out on fibrin protein scaffolds that were shipped in sheets to the hospital in Germany. In total, the new epidermal sheets needed to cover more than nine square feet (0.85 square meters) of the boy’s body, far more than had ever been attempted with a JEB patient.

Just a few weeks after the first operation, in which all four of the boys limbs were grafted with the genetically altered skin, the new epidermis had stabilized and stratified, said De Luca in the press briefing. The second operation, which grafted the remaining skin on the back and torso, was equally successful. However, the boy needed to immobilized and fed through a tube throughout the months-long ordeal.

Nearly two years later, the boy’s new skin has gone through 20 monthly renewal cycles, and heals and stretches just like a healthy epidermis. While doctors want to avoid excessive biopsies, genetic testing shows that the regenerating skin cells all carry the fixed gene. What’s amazing, said the boy’s surgeons, is that his skin doesn’t even need to be treated with any special creams or ointments, which are a daily requirement for most burn grafts. The boy, who had once been on a constant morphine drip, doesn’t even take any medications.

Read more at Seeker

European Hunter-Gatherers Interbred With Farmers From the Near East

Sampling of petrous bone from a human skull

The Neolithic Period, which lasted from about 9,000 to 3,000 BC, often seems as mysterious as the famous megaliths associated with it, such as Stonehenge in England and Ggantija in Malta. It included, however, one of the most important shifts in human history: the gradual transition from hunter-gatherer groups to farming communities.

Early populations from Europe and the Near East were not just farming, though. Extensive new DNA evidence reveals that they were making love, with hunter-gatherers frequently interbreeding with farmers.

The findings, published in the journal Nature, confirm earlier speculation about what happened when the two groups met and help to explain the ancestry of European people today. As it turns out, people of European heritage all have a little hunter-gatherer in their genetic makeup.

“It’s likely that most Europeans today retain a small proportion of ancestry from pre-farming groups who lived in the same region of the continent,” lead author Mark Lipson of Harvard Medical School’s department of genetics told Seeker.

For the new study, Lipson, senior author David Reich, and their colleagues analyzed the genomes of 180 ancient individuals who lived between 6,000 and 2,200 BC and were from what are now Hungary, Germany, and Spain.

An Early Neolithic grave from Bátaszék (Hungary), which was part of the DNA analyses.

The authors next built mathematical models that describe how ancient populations might have interacted as they moved from place to place.

The models show that for each of the three regions included in the study, the arrival of farmers prompted interbreeding with local hunter-gatherers. This trend was seen repeatedly over time, with the liaisons leaving distinct genetic signatures in each geographical region.

“I think, by nature, groups of people are more likely to mix and interact than not, regardless of cultural differences,” Lipson said. “We do find, though, that the admixture continued over an extended period, so it wasn’t all immediate.”

The liaisons appear to have been particularly consistent, however, in Hungary, the region in which the researchers had the most number of ancient DNA samples.

The data also suggest that farmers tended to travel a lot, while hunter-gatherers were more apt to stay fairly close to home.

“High population densities among farmers led them to expand to additional arable land,” Lipson said. “During this period, it seems likely that hunter-gatherers were not migrating such long distances, but our knowledge is not complete.”

It would appear to be equally challenging to distinguish hunter-gatherers from farmers in the archaeological record and from DNA. Lipson indicated that the differences between the two are surprisingly not too difficult to tease apart.

He explained that artifacts and remains left behind by farmers and hunter-gatherers are distinctive to each group.

“On an individual level, differences in diet can also be detected by isotope ratios in bones and teeth,” he said. “And in places where farmers and hunter-gatherers are genetically differentiated, we can measure that by comparing their relationships to other populations.”

The DNA evidence further sheds light on the origins of the Neolithic farmers. Most appear to have been migrants from Anatolia, an area that today falls within Turkey. In geographic terms, this is the area bounded to the north by the Black Sea, to the east and south by the Southeastern Taurus Mountains and the Mediterranean Sea, and to the west by the Aegean Sea and the Sea of Marmara.

Middle Neolithic collective grave of La Mina, Spain during excavation

Anatolia was within the Fertile Crescent, also known as the cradle of civilization. This crescent-shaped region contains comparatively moist and fertile areas in what is otherwise an arid and semi-arid part of the present Middle East.

Going back even further in time than the Neolithic, prior research shows European hunter-gatherers had about the same amount of Neanderthal-derived ancestry as present-day East Asians, “which is slightly more than Neolithic Anatolians,” Lipson said.

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Bonobos help strangers without being asked

Close primate cousins with whom we share 99 percent of our DNA, bonobos will help strangers even when there is no immediate payback, and without having to be asked first.

A passer-by drops something and you spring to pick it up. Or maybe you hold the door for someone behind you. Such acts of kindness to strangers were long thought to be unique to humans, but recent research on bonobos suggests our species is not as exceptional in this regard as we like to think.

Famously friendly apes from Africa's Congo Basin, bonobos will go out of their way to help strangers too, said Jingzhi Tan, a postdoctoral associate in evolutionary anthropology at Duke University.

A previous study by Tan and associate professor of evolutionary anthropology Brian Hare found that bonobos share food with strangers. Now, in a new series of experiments, the team is trying to find out just how far this kindness goes.

The researchers studied wild-born bonobos at the Lola ya Bonobo sanctuary in the Democratic Republic of Congo.

In one experiment, they found that bonobos will help a stranger get food even when there is no immediate payback.

Sixteen bonobos were led one at a time into one of two adjacent rooms separated by a fence. The researchers hung a piece of apple from a rope just above the empty room, visible but out of reach.

The apes couldn't access the fruit or the rope. But if they climbed the fence they could reach a wooden pin holding the rope to the ceiling and release the dangling fruit, causing it to drop within reach of any bonobo that entered the next room.

The bonobos released the fruit roughly four times more often when an unfamiliar bonobo was in the adjacent room than when the room was empty.

What's more, the bonobos didn't wait to be asked for help, they just offered it. The researchers changed the size of the mesh surrounding the stranger's room so that in some trials they were able to stick their arms through the openings in the screen to beg for the treat, and in other trials they were not. The bonobos helped just as often whether the stranger gestured for help or not.

Bonobos' impulse to feel for strangers isn't entirely under conscious control, the researchers also found. In another experiment, they had 21 bonobos watch a series of short videos. In some videos, the apes saw a familiar group member either yawning or making a neutral expression. In other videos they watched complete strangers from the Columbus Zoo in the U.S. behaving the same way.

Just as watching another person yawn can make you yawn, yawning is contagious in bonobos too. Previous studies suggest the phenomenon is linked to a basic form of empathy called "emotional contagion," when one person's mood triggers similar emotions in others around them.

The researchers found that stranger yawns were just as contagious as those of groupmates.

The impulse to be nice to strangers is likely to evolve in species where the benefits of bonding with outsiders outweigh the costs, said Tan, now a postdoctoral scholar at the University California, San Diego.

Female bonobos leave the group where they were born to join a new group when they reach adulthood, where they form bonds with other unrelated adults they've never met. Bonobos, like humans, may simply be eager to make a good first impression.

Read more at Science Daily

Humankind's earliest ancestors discovered in southern England

These are fossil teeth under electron microscope.

Fossils of the oldest mammals related to humankind have been discovered on the Jurassic Coast of Dorset.

The two teeth are from small, rat-like creatures that lived 145 million years ago in the shadow of the dinosaurs. They are the earliest undisputed fossils of mammals belonging to the line that led to human beings.

They are also the ancestors to most mammals alive today, including creatures as diverse as the Blue Whale and the Pigmy Shrew. The findings are published in the Journal, Acta Palaeontologica Polonica, in a paper by Dr Steve Sweetman, Research Fellow at the University of Portsmouth, and co-authors from the same university. Dr Sweetman, whose primary research interest concerns all the small vertebrates that lived with the dinosaurs, identified the teeth but it was University of Portsmouth undergraduate student, Grant Smith who made the discovery.

Dr Sweetman said: "Grant was sifting through small samples of earliest Cretaceous rocks collected on the coast of Dorset as part of his undergraduate dissertation project in the hope of finding some interesting remains. Quite unexpectedly he found not one but two quite remarkable teeth of a type never before seen from rocks of this age. I was asked to look at them and give an opinion and even at first glance my jaw dropped!"

"The teeth are of a type so highly evolved that I realised straight away I was looking at remains of Early Cretaceous mammals that more closely resembled those that lived during the latest Cretaceous -- some 60 million years later in geological history. In the world of palaeontology there has been a lot of debate around a specimen found in China, which is approximately 160 million years old. This was originally said to be of the same type as ours but recent studies have ruled this out. That being the case, our 145 million year old teeth are undoubtedly the earliest yet known from the line of mammals that lead to our own species."

Dr Sweetman believes the mammals were small, furry creatures and most likely nocturnal. One, a possible burrower, probably ate insects and the larger may have eaten plants as well.

He said: "The teeth are of a highly advanced type that can pierce, cut and crush food. They are also very worn which suggests the animals to which they belonged lived to a good age for their species. No mean feat when you're sharing your habitat with predatory dinosaurs!"

The teeth were recovered from rocks exposed in cliffs near Swanage which has given up thousands of iconic fossils. Grant, now reading for his Master's degree at The University of Portsmouth, said that he knew he was looking at something mammalian but didn't realise he had discovered something quite so special. His supervisor, Dave Martill, Professor of Palaeobiology, confirmed that they were mammalian, but suggested Dr Sweetman, a mammal expert should see them.

Professor Martill said: "We looked at them with a microscope but despite over 30 years' experience these teeth looked very different and we decided we needed to bring in a third pair of eyes and more expertise in the field in the form of our colleague, Dr Sweetman.

"Steve made the connection immediately, but what I'm most pleased about is that a student who is a complete beginner was able to make a remarkable scientific discovery in palaeontology and see his discovery and his name published in a scientific paper. The Jurassic Coast is always unveiling fresh secrets and I'd like to think that similar discoveries will continue to be made right on our doorstep."

Read more at Science Daily

The Closest Exoplanet to Earth May Have Neighbors

An artist's impression of the newly detected dusty belts around the sun's nearest neighbor, the red dwarf Proxima Centauri, and its potentially rocky world.

The nearest alien planet to Earth may not be an only child.

Astronomers have spotted a dusty ring around the nearby star Proxima Centauri, hinting at the existence of other planets in addition to the famous Proxima b, a new study reports.

"This result suggests that Proxima Centauri may have a multiple-planet system with a rich history of interactions that resulted in the formation of a dust belt," study lead author Guillem Anglada, an astronomer at the Instituto de Astrofisica de Andalucia in Spain, said in a statement. "Further study may also provide information that might point to the locations of as-yet unidentified additional planets."

Proxima Centauri is a red dwarf that lies about 4.2 light-years from Earth, in the southern constellation of Centaurus (The Centaur). In 2016, researchers spotted Proxima b, an apparently Earth-size world orbiting the star in what seems to be the habitable zone, the region where liquid water could exist on the surface. The star itself is about the same age as the sun. (Coincidentally, the team that discovered Proxima b was led by Guillem Anglada-Escudé of Queen Mary University of London, a part of Anglada's team but no relation to the author of the new research.)

Anglada and his colleagues studied Proxima Centauri using the Atacama Large millimeter/submillimeter Array (ALMA), a network of telescopes in Chile. The researchers discovered a belt of dusty material containing about 1 percent the mass of Earth. The belt — which lies a few hundred million kilometers from the star, far beyond Proxima b's orbit — has a temperature of about minus 328 degrees Fahrenheit (minus 230 degrees Celsius), roughly the same temperature of the solar system's Kuiper Belt, researchers said.

This image of the sky around the bright binary star Alpha Centauri AB also shows the much fainter red dwarf star, Proxima Centauri, the closest star to our own solar system. The photo was created from pictures forming part of the Digitized Sky Survey 2. The blue halo around Alpha Centauri AB is an artifact of the photographic process; the binary is really pale yellow in color, like the sun.

The dusty material might range in size from grains of only a few millimeters to asteroid-like bodies several kilometers across, study team members said. Dust belts like this are thought to be the remains of material that didn’t manage to clump together to form planets, they added.

ALMA also spotted signs of a possible second dust ring, about 10 times farther from the star than the other one, though this feature awaits confirmation. If the outer ring does indeed exist, its material would be very cold, lying so far from a star that is much smaller and dimmer than the sun.

The faint outer belt could prove useful to astronomers: Studying its shape could yield a better understanding of Proxima b's mass, which is not known very well at the moment, the researchers said.

Read more at Seeker

One of the Oldest and Most Distant Objects in the Universe Has Been Discovered

Distant galaxies are visible in the Hubble Space Telescope's eXtreme Deep Field, which was released in 2012 and based on 22 days of exposure time. The search for extremely distant galaxies continues today.

Astronomers have confirmed the discovery of one the oldest and most distant objects ever known in the universe — a star-forming galaxy 12.8 billion light-years away that started forming within a billion years of the Big Bang that kickstarted everything.

The galaxy, known as G09 83808, was first spotted by the Herschel space telescope, but it only showed up as a blur. The astronomers who made the find wanted more information, so they relayed the data to a team that used the Large Millimeter Telescope, which hosts the largest steerable dish in the world atop the summit of Volcán Sierra Negra, in the Galapagos.

With the 50-meter-diameter LMT dish, astronomers confirmed that G09 83808 is the oldest object ever found by that telescope. Only one other object — a similar galaxy that’s slightly older and more distant — has ever been found by other telescopes.

The research was led by Jorge Zavala, then a graduate student working under LMT director David Hughes. (Hughes is now a postdoctoral research fellow at the University of Texas.) The results were published in the journal Nature Astronomy.

G09 83808 provides almost unique insights into the early days of our universe after the cosmos was formed 13.7 billion years ago.

"Seeing an object within the first billion years is remarkable because the universe was fully ionized, that is, it was too hot and too uniform to form anything for the first 400 million years," said Min Yun, an astrophysicist at the University of Massachusetts Amherst who participated in the research, in a statement. "So our best guess is that the first stars and galaxies and black holes all formed within the first half a billion to one billion years. This new object is very close to being one of the first galaxies ever to form."

Objects such as G09 83808 are difficult to see because they are surrounded by gigantic dust clouds, keeping them out of view from observatories such as the Hubble Space Telescope, which best observes in visible and infrared wavelengths. The LMT is better positioned to look at objects of this kind because it uses millimeter-length wavelengths that can peer through obscuring dust.

Gravitational lensing also helped the astronomers with observations. This phenomenon magnifies light as it passes by a large object, making more distant objects look larger. G09 83808 appeared 10 times brighter and closer than it actually is because there is a large galaxy in between the object and Earth, which helped magnify G09 83808 through gravitational lensing.

LMT will be fully operational this winter and able to peer at more objects that are very old and have a high redshift. Redshift refers to the speed at which the universe expands. More distant objects have a larger redshift.

Read more at Seeker

Some Butterflies Have Been Fooling Others for 2 Million Years

Several different swallowtail butterfly variations showing mimicry and polymorphism, or different forms of the same species. In the center, a female Papilio polytes that mimics another species, which is toxic to predators.

Red-bodied swallowtail butterflies look so delicate and beautiful that their discoverers named them after flower colors, such as crimson rose. But these eye-catching insects are more sinister than one might imagine.

If an unfortunate predator — even a human — decides to eat one, gagging and severe vomiting may follow. The aftermath is so miserable that victims rarely prey on the butterflies again.

The common Mormon swallowtail butterfly (Papilio polytes), conversely, tastes delicious to birds and other predators. That poses survival challenges for the insects, so females of the species have evolved the ability to look just like toxic red-bodied swallowtails.

Female common Mormons sport different colors, patches, and patterns, though, and only some mimic red-bodied swallowtails. This multi-form phenomenon reminded early entomologists of Mormons who historically practiced polygamy, whereby men may have several wives.

New research on common Mormons and other butterflies published in the journal Nature Communications finds that some populations of these insects have maintained multiple female forms — including mimics — for millions of years.

Understanding the genetic processes that led to these imposters could facilitate research on what are known as “sex-limited” traits and diseases in humans. This means that the conditions tend to affect one sex more than the other.

Lead author Wei Zhang of the University of Chicago’s department of ecology and evolution said the research helps to address classic evolutionary questions and better understand sex-limited traits and diseases in other organisms.

“As far as we know, sex-limited traits and diseases widely exist in many sexually reproducing species as well as in humans, such as baldness and red-green color blindness,” she said.

Common rose swallowtail butterfly

In a prior study, Zhang, senior author Marcus Kronforst, and their team determined that the entire sex-limited mimicry phenomenon in common Mormons and other butterflies is controlled by a single gene named doublesex.

“The doublesex gene is involved in the sex determination of many insects and it gains additional duty in controlling mimicry in some Papilio butterflies,” Zhang said.

The gene actually inverted, or flipped, about 2 million years ago, with this topsy-turvy version dictating wing patterns in females. Doublesex is classified as being a supergene, which usually refers to groups of several tightly linked genes that are inherited together. In this case, however, the supergene is a single multi-tasking gene and not a group.

For the new study, the researchers reconstructed the evolutionary history of the doublesex gene by analyzing whole-genome sequence data from common Mormon butterflies and several similar species to see how they are related to each other and how their copies of the gene compare.

The scientists shared that the most closely related species to the common Mormon butterfly, spangle, is spread across mainland Asia from India to Japan and did not develop mimicry. In this species, both males and females look alike.

Other swallowtail species that spread from the mainland to islands in the Philippines and Indonesia developed three or four distinct forms, a feature known as polymorphism. Other swallowtails spread further into Papua New Guinea and the northeast coast of Australia. But females within those species display only one disguised wing pattern.

Several different swallowtail butterfly variations showing mimicry and polymorphism, or different forms of the same species. Row 1: A female and male Papilio protenor, the species that is closely related to Papilo polytes, the focal of the new study. In P. protenor, males and female look the same and they do not mimic. Row 2: Papilio ambrax, a species where males and females look different and the female is a mimic. In this species, there is no female polymorphism. The new study shows that its evolutionary ancestor was polymorphic, but females lost that trait and only display the mimetic form. Row 3: Polymorphic Papilio polytes, (L-R) A mimetic female form (one of 3 mimetic forms in this species), a non-mimetic female, and the male. Row 4: A distantly related swallowtail, Pachliopta aristolochiae. This is the toxic species that the species in the new study mimic.

The researchers attempted to match the patterns they saw in the genome sequence data to possible explanations for how mimicry developed over time and place in the various butterflies. The evidence supports that once the doublesex gene flipped, a process called balancing selection occurred.

Kronforst said if one mimetic color pattern becomes too common in a population, predators learn that it is palatable because they frequently encounter the mimic and not the toxic model.

“The process can cause the mimetic species to evolve to match multiple models, leading to polymorphism,” he said.

Models, in this case, refer to species that the imposter is mimicking.

Zhang added that various wing forms can also result from members of the same species being geographically widespread, leading insects to mimic different local toxic butterflies.

The researchers observed some butterfly populations maintaining multiple female forms for millions of years, while others lost their original, undisguised form. Historically, the smallest butterfly groups, such as the ones that spread to Australia, lost the polymorphism, allowing genetic drift — essentially genetic variation due to chance — and natural selection to weed out the original form.

Common Mormon female butterfly

The findings reveal the surprising role of chance in both the spread and loss of a beneficial trait, which for certain swallowtails is the mimicry of poisonous butterflies. They also show how powerful a single gene can be.

While humans do not have a doublesex gene, we have numerous other supergenes.

“The supergenes exist in many animals and plants,” Zhang explained. “For example, the human major histocompatibility complex (MHC) contains a group of tightly-linked genes that are functionally related and play roles in the human immune system.”

The basic laws of genetics underlying the evolution of doublesex and MHC supergenes are the same. Understanding these processes can shed light on the evolution of not just beneficial traits, but also deleterious ones.

Read more at Seeker

Fish provide insight into the evolution of the immune system

New findings help to explain why we humans have some immune genes that are almost identical to those of chimpanzees.

New research from the University of East Anglia (UEA), UK, and Dalhousie University, Canada, reveals how immune systems can evolve resistance to parasites.

A study, published in Nature Communications, solves the enigma of how species can adapt and change their immune system to cope with new parasitic threats -- whilst at the same time showing little or no evolutionary change in critical immune function over millions of years.

The findings help to explain why we humans have some immune genes that are almost identical to those of chimpanzees.

Scientists from UEA and Dalhousie University studied how Guppy fish (Poecilia reticulata) adapt to survive by studying their immune genes, known as the Major Histocompatibility Complex or MHC genes.

They found that guppies fine-tune these genes in each location, enabling them to adapt and survive in many different and extreme environments. Despite this adaptation, genes maintained critical function of tens of millions of years.

The discovery could improve scientists' understanding of how related species can adapt and change their immune system to cope with new threats from parasites while simultaneously sharing similar function.

Dr Jackie Lighten from UEA led the study. He said: "Guppies are a small, colourful fish native to South America, Trinidad and Tobago. They are a fantastic model for researching the ecology and evolution of vertebrates.

"MHC genes are an important line of defence in the immune system in vertebrates, including humans. Because parasites evolve quicker than their vertebrate hosts, immune genes need to be highly diverse to keep up with parasites and prevent infections.

"MHC genes produce protein structures that are on the external surface of cells. These genes are diverse and so produce an array of proteins, each of which presents a specific part of a parasite or pathogen that has attempted to infect the body. The specific shape of the protein dictates which parasites it can recognize, and signals to the immune system to prevent infection."

The study looked at MHC genetic variation in 59 guppy populations across Trinidad, Tobago, Barbados, and Hawaii. The authors found hundreds of different immune variants, but these so called 'alleles' appear to be clustered in a smaller number of functional groups or 'supertypes'.

Prof van Oosterhout, also from UEA's School of Environmental Sciences, said: "Each supertype protects the host against a specific group of parasites, and these supertypes were common across populations, and species, irrespective of the location.

"However, the alleles that make up a supertype track the rapid evolution of the parasites, and they too are evolving rapidly. These alleles are largely specific to each population, and they help in the 'fine-tuning' of the immune response to the specific (local) parasites that attack the host in that population."

Before this study, scientists debated how these immune genes can evolve rapidly (which is necessary to keep up with the fast-evolving parasites), whilst also showing little or no evolutionary change in their function over millions of years, as observed between humans and chimpanzees. This study resolves that debate.

Prof Bentzen from Dalhousie University said: "Although this study focused on MHC genes in vertebrates, the evolutionary dynamics described in it likely apply to other gene families, for example resistance genes and those which prevent self-fertilization in plants (self-incompatibility loci) that are caught up in their own evolutionary races."

Read more at Science Daily

Potential 'missing link' in chemistry that led to life on Earth discovered

This study is part of an ongoing effort by scientists around the world to find plausible routes for the epic journey from pre-biological chemistry to cell-based biochemistry.

Chemists at The Scripps Research Institute (TSRI) have found a compound that may have been a crucial factor in the origins of life on Earth.

Origins-of-life researchers have hypothesized that a chemical reaction called phosphorylation may have been crucial for the assembly of three key ingredients in early life forms: short strands of nucleotides to store genetic information, short chains of amino acids (peptides) to do the main work of cells, and lipids to form encapsulating structures such as cell walls. Yet, no one has ever found a phosphorylating agent that was plausibly present on early Earth and could have produced these three classes of molecules side-by-side under the same realistic conditions.

TSRI chemists have now identified just such a compound: diamidophosphate (DAP).

"We suggest a phosphorylation chemistry that could have given rise, all in the same place, to oligonucleotides, oligopeptides, and the cell-like structures to enclose them," said study senior author Ramanarayanan Krishnamurthy, associate professor of chemistry at TSRI. "That in turn would have allowed other chemistries that were not possible before, potentially leading to the first simple, cell-based living entities."

The study, reported in Nature Chemistry, is part of an ongoing effort by scientists around the world to find plausible routes for the epic journey from pre-biological chemistry to cell-based biochemistry.

Other researchers have described chemical reactions that might have enabled the phosphorylation of pre-biological molecules on the early Earth. But these scenarios have involved different phosphorylating agents for different types of molecule, as well as different and often uncommon reaction environments.

"It has been hard to imagine how these very different processes could have combined in the same place to yield the first primitive life forms," said Krishnamurthy.

He and his team, including co-first authors Clémentine Gibard, Subhendu Bhowmik, and Megha Karki, all postdoctoral research associates at TSRI, showed first that DAP could phosphorylate each of the four nucleoside building blocks of RNA in water or a paste-like state under a wide range of temperatures and other conditions.

With the addition of the catalyst imidazole, a simple organic compound that was itself plausibly present on the early Earth, DAP's activity also led to the appearance of short, RNA-like chains of these phosphorylated building blocks.

Moreover, DAP with water and imidazole efficiently phosphorylated the lipid building blocks glycerol and fatty acids, leading to the self-assembly of small phospho-lipid capsules called vesicles -- primitive versions of cells.

DAP in water at room temperature also phosphorylated the amino acids glycine, aspartic acid and glutamic acid, and then helped link these molecules into short peptide chains (peptides are smaller versions of proteins).

"With DAP and water and these mild conditions, you can get these three important classes of pre-biological molecules to come together and be transformed, creating the opportunity for them to interact together," Krishnamurthy said.

Krishnamurthy and his colleagues have shown previously that DAP can efficiently phosphorylate a variety of simple sugars and thus help construct phosphorus-containing carbohydrates that would have been involved in early life forms. Their new work suggests that DAP could have had a much more central role in the origins of life.

"It reminds me of the Fairy Godmother in Cinderella, who waves a wand and 'poof,' 'poof,' 'poof,' everything simple is transformed into something more complex and interesting," Krishnamurthy said.

DAP's importance in kick-starting life on Earth could be hard to prove several billion years after the fact. Krishnamurthy noted, though, that key aspects of the molecule's chemistry are still found in modern biology.

"DAP phosphorylates via the same phosphorus-nitrogen bond breakage and under the same conditions as protein kinases, which are ubiquitous in present-day life forms," he said. "DAP's phosphorylation chemistry also closely resembles what is seen in the reactions at the heart of every cell's metabolic cycle."

Krishnamurthy now plans to follow these leads, and he has also teamed with early-Earth geochemists to try to identify potential sources of DAP, or similarly acting phosphorus-nitrogen compounds, that were on the planet before life arose.

Read more at Science Daily

Mammals Remained in the Shadows Until Dinosaurs Went Extinct

An artist's impression of Mesozoic animals found fossilized in the Kayenta rock formation. It depicts Dilophosaurus (dinosaur) at the back, Kayentatherium (Mesozoic mammal) in the center, and Kayentachelys (Mesozoic turtle) at the front.

Not all was doom and gloom after dinosaurs went extinct around 65 million years ago. Before that time, when Tyrannosaurus rex and other large predators lurked, mammals were mostly small and scrappy creatures of the night.

After non-avian dinosaurs died out, mammals began to come out of the shadows. New research published in the journal Nature Ecology & Evolution reports that mammals only started to become diurnal — active during the day — when dinosaurs were gone for good.

“The first mammals who became active in the daytime may have done so for a variety of reasons, such as reduced predation risk in the daytime or increased ecological opportunity in the absence of dinosaurs,” lead author Roi Maor of Tel Aviv University told Seeker.

Maor and his colleagues Tamar Dayan, Henry Ferguson-Gow, and Kate Jones had a daunting task: The fossil record reveals little about the activity patterns of animals. Dayan said researchers observe a living mammal to see if it is active at night or in the day. But, he added fossil evidence from mammals often suggests that they were nocturnal even if they were not.

“Many subsequent adaptations that allow us to live in daylight are in our soft tissues,” Dayan said.

Recreation of dinosaur extinction at the Deccan Traps in Western Ghats, India

To get around that problem, the researchers analyzed data from 2,415 species of mammals alive today, their relatedness to other existent mammal species, and their connections to known ancestors. They then used computer algorithms to reconstruct the likely activity patterns of the mammals that lived in the past.

Several theories exist that seek to explain the origins of mammals and their family trees. The researchers, therefore, constructed two different mammalian family trees portraying alternative timelines for the evolution of mammals.

The results show the same phenomenon: Mammals switched to daytime activity shortly after the dinosaurs disappeared.

The scientists found that the ancestors of simian or higher primates, such as monkeys, gorillas and humans, were among the first to give up nocturnal activity.

The discovery helps to explain why these primates are the only mammals that evolved adaptations to seeing well in daylight. This is largely because all other mammals lack a fovea, which is a small depression in the retina of the eye where visual acuity is highest.

“No mammals, except monkeys and apes, have more than two types of cones — sensitive to short and long light wavelengths — in their retinae, and their vision has been compared to a red-green colorblind human,” Maor said.

According to the “nocturnal bottleneck hypothesis,” Maor said mammals co-existed alongside dinosaurs thanks to the segregation of the two groups’ ecological niches along a temporal day–night axis.

In short, the first mammals essentially evolved to avoid diurnal dinosaurs.

“It follows that when dinosaurs went extinct, they freed niche space to be taken by other species, including mammals, for which the daytime would have been a novel niche,” Maor said. “According to ecological theory, entering a novel niche may allow a species to evade predators and-or competitors present in its original niche, giving it an advantage that may lead to evolutionary success.”

Recreation of Tyrannosaurus rex

Maor stopped short at saying that this advantage might have given the ancestors of humans an evolutionary edge, such as setting the stage for the later emergence of our relatively big brains and sharp eyesight during daylight hours. The visual acuity and color perception of healthy humans and other simians is comparable to those of diurnal reptiles and birds — animal groups that never left the daytime niche.

It is important to note that not all living primates are diurnal. Slow lorises, many lemurs, and other primates are strictly nocturnal. In fact, diurnal species are still a minority within all mammals.

“In our data set, there are about 26 percent diurnal species and 60 percent nocturnal ones, and the proportions among all mammals would be very similar,” Maor explained.

Read more at Seeker