Quiet viruses alter body's response to vaccines, pathogens

UC Davis researchers have shown that low levels of cytomegalovirus (CMV) have a significant impact on microbe and immune cell populations and how the immune system responds to the influenza vaccine. The study was published in the Journal of Virology.

"Subclinical CMV infection alters the immune system and the gut microbiota in the host and that impacts how we respond to vaccines, environmental stimuli and pathogens," said Satya Dandekar, who chairs the Department of Medical Microbiology and Immunology at UC Davis and was senior author on the paper. She is also a core scientist in the infectious diseases unit at the California National Primate Research Center at UC Davis.

"This study highlights the role of these silent, latent viral infections that are totally asymptomatic," she said.

A member of the herpes family, CMV is a common virus that infects as many as 90 percent of adults in Africa and 70 percent in the U.S. and Europe. However, though CMV is ubiquitous, it is generally not dangerous. The exception is people whose immune systems are compromised, for example by HIV.

While the vast majority of CMV infections are subclinical, that does not mean the virus is inert. Researchers in the Dandekar lab, including first authors Clarissa Santos Rocha and Lauren Hirao, wanted to understand how CMV might be affecting its hosts.

In the study, animals infected with CMV had higher levels of Firmicutes and other butyrate-producing bacteria. Butyrates are short-chain fatty acids that reduce inflammation but may also boost genes that help CMV persist in the body.

Infected animals also showed increased lymphocytes and cytokine-producing (inflammatory) T cells. These differences leveled off when the animals were moved indoors. CMV infection generally increased immune activity but also diminished antibodies responding to influenza vaccination.

"There's a high degree of variation at the population level of how people respond to vaccines," said Dandekar, "and all the factors that contribute to these variations are not fully understood. Our paper shows the subclinical CMV infections may be one of the issues that contributes to that immune variation. This opens a new opportunity to come up with novel approaches to optimize and position the immune system to have higher quality responses to vaccines."

More work needs to be done to understand how CMV impacts vaccine responses. However, the immune system's constant efforts to control the virus may divert resources it might otherwise devote to other threats. From here, the Dandekar lab will be testing other vaccines in CMV-infected animals and generally working to better understand how subclinical viruses affect the immune system.

Read more at Science Daily

The rules of attraction: Scientists find elusive molecule that helps sperm find egg

Scientists affiliated with the Marine Biological Laboratory (MBL) have identified a key molecule driving chemoattraction between sperm and egg cells in marine invertebrates. The study was recently published in Nature Communications.

More than 100 years ago, MBL Director F.R. Lillie of the University of Chicago discovered that eggs from marine invertebrates release a chemical factor that attracts sperm, a process called chemotaxis. Sperm, for their part, swim up a chemical gradient to reach the egg, assisted by a pulsatile rise in calcium ion (Ca2+) concentration in the sperm tail that controls its beating.

In past years, many of the cellular components that translate chemoattractant stimulation into a Ca2+ response have been revealed, but a crucial ingredient has been missing. A prerequisite for Ca2+ ions from the sperm's environment being able to enter the tail is that the sperm cell's pH becomes more alkaline. The molecule that brings about this change in pH has been elusive.

In this new report, U. Benjamin Kaupp, a MBL Whitman Center Scientist from the Center of Advanced European Studies (Caesar) in Bonn, Germany, identifies this molecule. Kaupp spent 18 summers at the MBL conducting research in the footsteps of F.R. Lillie's original quest.

The molecule that Kaupp and colleagues identified allows sodium ions to flow into the sperm cell and, in exchange, transports protons out of the cell. Such so-called sodium/proton exchangers have been known for a long time, but this one is special. It is a chimaera that shares structural features with ion channels, called pacemaker channels, which control our heartbeat and electrical activity in the brain.

This sodium/proton exchange in the sperm cell, like in the pacemaker channels, is activated by a stretch of positively charged amino acids called the voltage sensor. When sperm capture chemoattractant molecules, the voltage becomes more negative, because potassium channels open and potassium ions leave the cell. The voltage-sensor registers this voltage change and the exchanger begins exporting protons from the cell; the cell's interior becomes more alkaline. When this mechanism is disabled, the Ca2+ pulses in the sperm tail are suppressed, and sperm are lost on their voyage to the egg.

From Science Daily

The end-Cretaceous extinction unleashed modern shark diversity

This is PhD student Mohamad Bazzi with a fossil lamniform shark tooth.

A study that examined the shape of hundreds of fossilized shark teeth suggests that modern shark biodiversity was triggered by the end-Cretaceous mass extinction event, about 66 million years ago.

This finding is reported this week in Current Biology.

As part of a larger scientific endeavour aiming to understand the diversity of fossil sharks, a group of researchers from Uppsala University, Sweden, and the University of New England, Australia, have explored how certain groups of sharks responded to the mass extinction that killed-off non-bird dinosaurs and marked the end of the Cretaceous period and the Mesozoic era.

Much like several other vertebrate groups during the Cretaceous (142-66 million years ago), shark diversity looked very different from today. Ground sharks (Carcharhiniformes) are the most diverse shark group living today, with over 200 different species. However, while dinosaurs dominated terrestrial environments during the Cretaceous, Mackerel sharks (Lamniformes) were the dominant shark forms of the sea.

"Our study found that the shift from lamniform- to carcharhiniform-dominated assemblages may well have been the result of the end-Cretaceous mass extinction," said project leader and Uppsala doctoral student Mohamad Bazzi.

Sharks are one of the major groups that survived the Cretaceous-Palaeogene mass extinction and, today, carcharhiniforms are typified by forms such as the Tiger, Hammerhead, and Blacktip Reef sharks and lamniforms by the Great White and Mako sharks.

"Unlike other vertebrates, the cartilaginous skeletons of sharks do not easily fossilize and so our knowledge of these fishes is largely limited to the thousands of isolated teeth they shed throughout their lives," says Mr. Bazzi. "Fortunately, shark teeth can tell us a lot about their biology, including information about diet, which can shed light on the mechanisms behind their extinction and survival."

The team used "cutting-edge" analytical techniques to explore the variation of tooth shape in carcharhiniforms and lamniforms and measured diversity by calculating the range of morphological variation, also called disparity.

"Going into this study, we knew that sharks underwent important losses in species richness across the extinction." said Dr. Nicolás Campione at the University of New England, who co-devised the project. "But to our surprise, we found virtually no change in disparity across this major transition. This suggests to us that species richness and disparity may have been decoupled across this interval."

Despite this seemingly stable pattern, the study found that extinction and survival patterns were substantially more complex. Morphologically, there were differential responses to extinction between lamniform and carcharhiniform sharks, with evidence for a selective extinction of lamniforms and a subsequent proliferation of carcharhiniforms (the largest order of living sharks today) in the immediate aftermath of the extinction.

"Carcharhiniforms are the most common shark group today and it would seem that the initial steps towards this dominance started approximately 66 million years ago," said Mr. Bazzi, who remarks that further research is still needed to understand the diversity patterns of other shark groups, along with the relationship between diet and tooth morphology.

Although the mechanisms that triggered such a shift in sharks can be difficult to interpret. The team hypothesises that changes in food availability may have played an important role. The end-Cretaceous extinction saw to major losses in marine reptiles and cephalopods (e.g. squids) and the post-extinction world saw the rise of bony fishes. In addition, it is likely that the loss of apex predators (such as lamniforms and marine reptiles) benefited mid-trophic sharks, a role fulfilled by many carcharhiniforms.

"By studying their teeth, we are able to get a glimpse at the lives of extinct sharks," said Dr. Campione, "and by understanding the mechanisms that have shaped their evolution in the past, perhaps we can provide some insights into how to mitigate further losses in current ecosystems."

Read more at Science Daily

Locusts help uncover the mysteries of smell

A palate-clearing sniff of coffee inspired Barani's smell research.

Understanding how a sensory input becomes an experience -- how molecules released by a blooming flower, for instance, become the internal experience of smelling a rose -- has for millennia been a central question of philosophy.

In more recent times, it has also been a question for scientists. One way to approach it is to understand the physical brain processes behind sensory experiences. Historically, scientists have proposed different ways to describe what is happening by positing that a certain set of neurons must fire; a certain sequence of firing that must occur; or a combination of the two.

But according to a research team from the School of Engineering & Applied Science at Washington University in St. Louis, these descriptions do not account for the variability of the real world. Smells do not occur in a vacuum. The team wanted to find out what happened when sensory input was presented in sequences, more akin to what happens in the real world.

They turned to locusts.

In a paper slated for publication in Nature Communications, researchers found that in locusts, only a subset of neurons associated with a particular scent would fire when that scent was presented in a dynamic environment that included other scents. Although there was not a one-to-one relationship between a pattern of neurons activated and a specific smell, the researchers were able to determine how the locusts could still recognize a scent; it comes down to the locust being flexible in its interpretation.

"There is variability because of stimulus history," said Barani Raman, associate professor of biomedical engineering, "so flexibility is necessary to compensate."

For the experiments, the team of Washington University engineers, which included Raman, graduate research assistants Srinath Nizampatnam and Rishabh Chandak, and Debajit Saha, a postdoctoral research fellow, first had to train the locusts in the same way one might train a dog, namely, Pavlov's dog. A machine administered a puff of the target scent, hexanol, to hungry locusts, then rewarded the locusts with a treat: grass. After enough rounds (usually six), the locusts would open up palps -- small organs outside of their mouths that function in a similar way to lips or tongues in humans -- after they smelled hexanol, in anticipation of the grass.

Once the locusts were trained, the testing began. The locusts were exposed to the "target" odor, hexanol either on its own, or after the introduction of a different scent, called a "distractor."

Each time the target odor was introduced on its own, a locust's neural activity was the same. But when the locusts were exposed to a distractor smell first, different combinations of neurons fired when the locusts were subsequently exposed to the target.

This is the variability based on context. What has been previously smelled (and even unrelated brain states, such as hunger) can affect how a brain reacts to the same input. If that were the end of it, though, smells would rarely, if ever, be recognizable.

Imagine entering a coffee shop and buying a freshly baked chocolate chip cookie. As you bring it to your mouth, you inhale and smell that comforting, chocolate chip cookie smell. The next day, you head to a tea shop. Another batch of freshly baked cookies calls your name. If variability (induced by prior exposure to tea or coffee) alone determined how smells are processed, the scent of tea shop cookie, wafting into your nose after a strong Earl Grey, couldn't possibly smell the same as it did after you caught a whiff of Sumatra at the coffee shop.

But just as humans recognize the smell of a chocolate chip cookie in either setting, the locusts recognized the target -- even though their neurons were firing in a variety of different ways -- as evidenced by their palps, which opened as per their conditioning.

So there had to be more to the story than variability when it came to recognizing smells. The team wanted to know if there was a pattern, or a way to discern, via brain activity, how the locusts were smelling the target odorant despite the variability in brain activity.

As it turned out, there is a way. "The rules are very simple," Raman said. "An OR-of-ANDs logical operation was sufficient to compensate for variability and allow flexible decoding."

Think of an "ideal" chair: it has four legs, a seat, two armrests, and back support. If you only recognized a chair with all of these, and only these, attributes, you would miss out on a lot of good chairs -- those on a pedestal, those without armrests, etc. To be able to generalize, there needs to be some flexibility in what's recognized as a chair. One simple way is to allow any object that has any two or three out of the four features usually associated with chair, if present, to be recognized as a chair.

The OR-of-ANDs logical operation for recognizing chair might be [four legs AND seat] OR [seat AND back support]. In the same way, locusts show a fixed pattern of brain activity when smelling the target odorant alone, but only some flexible combination involving just some of those same neurons will fire when smelling the target after smelling, say, an apple.

What subset of neurons that fire depends, in large part, on what the distractor smell is; the neurons that are activated by the target alone will continue to fire, but those that are in common to both the distractor and the target will either not be activated or their activity will be reduced.

In this way, the uniqueness of neural response to the target odorant is enhanced. Like perfume after a whiff of coffee, if the target odorant shared few neurons with the distractor, the cross-talk between the smells was less and the history/context is reset.

Going forward, the team plans to see if its results hold in another organism: the fruit fly. The researchers also will investigate how other sources of variability such as short-term memory might affect how smells are perceived. There is, of course, another organism of interest: humans.

The main inspiration for this research was the use of coffee beans to clear the olfactory pallet, so to speak, in perfume shops.

Read more at Science Daily

Plants can tell the time using sugars

The plant as a clock

A new study by an international team of scientists, including the University of Bristol, has discovered that plants adjust their daily circadian rhythm to the cycle of day and night by measuring the amount of sugars in their cells.

Plants, animals, fungi and some bacteria can estimate the time of day through their circadian rhythms.

These rhythms are regulated by an internal 'circadian clock', and how these clocks operate is a topic of importance for both agriculture and medicine. For example, changes in circadian rhythms have contributed to domestication of crops.

In the study published today, in the journal Current Biology, the research team involving the Universities of Bristol, Cambridge, Campinas, Sao Paulo and Melbourne has discovered a process that adjusts the timing of the plant body clock so that it stays in tune with the environment.

They found that sugars made from photosynthesis are sensed, and this leads to the plant falling into rhythm with changes in energy provision throughout the day.

Dr Antony Dodd of the University of Bristol's School of Biological Sciences, said: "Our findings show the first mechanism in plants that shifts the circadian rhythm backwards or forwards to synchronise it with the environment.

"The plant continuously measures the amount of sugar in the cells and uses this information to make the required adjustments."

Plants need circadian their rhythms to be correctly synchronised with the timing of day and night, so their activities are matched to the time of day.

For example, circadian rhythms control the time when plants grow, when their flowers open and release scent, and allow plants to carefully use energy reserves so they do not starve in the night.

Circadian rhythms also help plants to detect changes in the seasons, which is crucial to ensure our crops mature in the correct season.

Dr Dodd added: "This means that the discovery of a mechanism that synchronizes the plant body clock with the time in the environment has identified a new process that could be exploited in future to improve crop performance."

From Science Daily

Heatwave and climate change having negative impact on our soil say experts

Drought alters soil at microbial level.

The recent heatwave and drought could be having a deeper, more negative effect on soil than we first realised say scientists.

This could have widespread implications for plants and other vegetation which, in turn, may impact on the entire ecosystem.

That's because the organisms in soil are highly diverse and responsible not only for producing the soil we need to grow crops, but also other benefits such as cleaning water and regulating greenhouse gas emissions.

The new study, led by researchers at The University of Manchester and published today (02/08/2018) in Nature Communications, provides new insight into how a drought alters soil at microbial level. It shows that expected changes in climate will affect UK soil and that soil is not as tough as previously thought.

Due to climate change, disturbances such as drought are increasing in intensity and frequency. These extreme weather conditions change vegetation composition and soil moisture, which in turn impacts the soil's underlying organisms and microbial networks.

By studying how microbes react to severe drought, the study provides a better understanding of how underground soil networks respond to such environmental disturbances.

Lead author, Dr Franciska de Vries, from Manchester's School of Earth and Environmental Sciences, explains: "Soils harbour highly diverse microbial communities that are crucial for soil to function as it should.

"A major challenge is to understand how these complex microbial communities respond to and recover from disturbances, such as climate extremes, which are predicted to increase in frequency and intensity with climate change.

"These microbial communities within the soil play a crucial role in any ecosystem. But it wasn't known how soil networks respond to such disturbances until now."

Sequencing of soil DNA for the study was conducted at the Centre for Ecology & Hydrology (CEH). Dr Robert Griffiths, a molecular microbial ecologist at CEH, said: "This study further identifies those key organisms affected by drought, which will guide future research to predict how future soil microbial functions are affected by climate change."

The research team tested the effects of summer drought on plant communities consisting of four common grassland species. They found that drought increased the abundance of a certain fast-growing, drought-tolerant grass. With greater aboveground vegetation comes an increased rate of evapotranspiration, or cycling of water from plants to the atmosphere, lowering the overall soil moisture.

Science conducted as part of Lancaster University's Hazelrigg grassland experiment was key to the findings.

Professor Nick Ostle, from the Lancaster Environment Centre, said: "Our hot and dry summer this year is a 'wake up' to prepare for future weather stresses. We have just had the hottest ten years in UK history. This work shows that continued summer droughts will change soil biology. This matters as we plan for ensuring food security that depends on healthy soil."

Unlike past research, this study considered the multitude of direct and indirect interactions occurring between different microbial organisms in soil. Rather than focusing on select attributes of bacteria and fungi, this research takes a comprehensive approach to studying soil ecosystems.

Read more at Science Daily

Study challenges evolution of FOXP2 as human-specific language gene

First author Elizabeth Atkinson extracts DNA as part of her research on human gene FOXP2.

FOXP2, a gene implicated in affecting speech and language, is held up as a textbook example of positive selection on a human-specific trait. But in a paper published August 2 in the journal Cell, researchers challenge this finding. Their analysis of genetic data from a diverse sample of modern people and Neanderthals saw no evidence for recent, human-specific selection of FOXP2 and revises the history of how we think humans acquired language.

"A paper published in 2002 (Enard et al., Nature 418, 869-872) claimed there was a selective sweep relatively recently in human evolutionary history that could largely account for our linguistic abilities and even help explain how modern humans were able to flourish so rapidly in Africa within the last 50-100,000 years," says senior author Brenna Henn, a population geneticist at Stony Brook University and UC Davis. "I was immediately interested in dating the selective sweep and re-analyzing FOXP2 with larger and more diverse datasets, especially in more African populations."

Henn says that when the original 2002 work was done, the researchers did not have access to the modern sequencing technology that now provides data on whole genomes, so they only analyzed a small fraction of the FOXP2 gene in about 20 individuals, most of whom were of Eurasian descent. "We wanted to test whether their hypothesis stood up against a larger, more diverse dataset that more explicitly controlled for human demography," she says.

FOXP2 is highly expressed during brain development and regulates some muscle movements, aiding in language production. When the gene isn't expressed, it causes a condition called specific language impairment in which people may perform normally on cognitive tests but cannot produce spoken language. FOXP2 has also been shown to regulate language-like behaviors in mice and songbirds.

"In the past five years, several archaic hominin genomes have been sequenced, and FOXP2 was among the first genes examined because it was so important and supposedly human specific," says first author Elizabeth Atkinson of Stony Brook University and the Broad Institute of Harvard and MIT. "But this new data threw a wrench in the 2002 paper's timeline, and it turns out that the FOXP2 mutations we thought to be human specific, aren't."

Atkinson and her colleagues assembled mostly publicly available data from diverse human genomes -- both modern and archaic -- and analyzed the entire FOXP2 gene while comparing it to the surrounding genetic information to better understand the context for its evolution. Despite attempting a series of different statistical tests, they were unable to replicate this idea that there was any positive selection occurring for FOXP2.

"FOXP2 is still a textbook example taught in every evolutionary biology class despite the recent data from archaic DNA," says co-author Sohini Ramachandran, an evolutionary and computational biologist at Brown University. "So while we're not questioning the functional work of FOXP2 or its role in language production, we're finding that the story of FOXP2 is really more complex than we'd ever imagined."

The researchers hope that this paper will serve as a template for other population geneticists to conduct similar projects on human evolutionary history in the future.

Read more at Science Daily

VLA detects possible extrasolar planetary-mass magnetic powerhouse

Artist's conception of SIMP J01365663+0933473, an object with 12.7 times the mass of Jupiter, but a magnetic field 200 times more powerful than Jupiter's. This object is 20 light-years from Earth.

Astronomers using the National Science Foundation's Karl G. Jansky Very Large Array (VLA) have made the first radio-telescope detection of a planetary-mass object beyond our Solar System. The object, about a dozen times more massive than Jupiter, is a surprisingly strong magnetic powerhouse and a "rogue," traveling through space unaccompanied by any parent star.

"This object is right at the boundary between a planet and a brown dwarf, or 'failed star,' and is giving us some surprises that can potentially help us understand magnetic processes on both stars and planets," said Melodie Kao, who led this study while a graduate student at Caltech, and is now a Hubble Postdoctoral Fellow at Arizona State University.

Brown dwarfs are objects too massive to be considered planets, yet not massive enough to sustain nuclear fusion of hydrogen in their cores -- the process that powers stars. Theorists suggested in the 1960s that such objects would exist, but the first one was not discovered until 1995. They originally were thought to not emit radio waves, but in 2001 a VLA discovery of radio flaring in one revealed strong magnetic activity.

Subsequent observations showed that some brown dwarfs have strong auroras, similar to those seen in our own Solar System's giant planets. The auroras seen on Earth are caused by our planet's magnetic field interacting with the solar wind. However, solitary brown dwarfs do not have a solar wind from a nearby star to interact with. How the auroras are caused in brown dwarfs is unclear, but the scientists think one possibility is an orbiting planet or moon interacting with the brown dwarf's magnetic field, such as what happens between Jupiter and its moon Io.

The strange object in the latest study, called SIMP J01365663+0933473, has a magnetic field more than 200 times stronger than Jupiter's. The object was originally detected in 2016 as one of five brown dwarfs the scientists studied with the VLA to gain new knowledge about magnetic fields and the mechanisms by which some of the coolest such objects can produce strong radio emission. Brown dwarf masses are notoriously difficult to measure, and at the time, the object was thought to be an old and much more massive brown dwarf.

Last year, an independent team of scientists discovered that SIMP J01365663+0933473 was part of a very young group of stars. Its young age meant that it was in fact so much less massive that it could be a free-floating planet -- only 12.7 times more massive than Jupiter, with a radius 1.22 times that of Jupiter. At 200 million years old and 20 light-years from Earth, the object has a surface temperature of about 825 degrees Celsius, or more than 1500 degrees Farenheit. By comparison, the Sun's surface temperature is about 5,500 degrees Celsius.

The difference between a gas giant planet and a brown dwarf remains hotly debated among astronomers, but one rule of thumb that astronomers use is the mass below which deuterium fusion ceases, known as the "deuterium-burning limit," around 13 Jupiter masses.

Simultaneously, the Caltech team that originally detected its radio emission in 2016 had observed it again in a new study at even higher radio frequencies and confirmed that its magnetic field was even stronger than first measured.

"When it was announced that SIMP J01365663+0933473 had a mass near the deuterium-burning limit, I had just finished analyzing its newest VLA data," said Kao.

The VLA observations provided both the first radio detection and the first measurement of the magnetic field of a possible planetary mass object beyond our Solar System.

Such a strong magnetic field "presents huge challenges to our understanding of the dynamo mechanism that produces the magnetic fields in brown dwarfs and exoplanets and helps drive the auroras we see," said Gregg Hallinan, of Caltech.

"This particular object is exciting because studying its magnetic dynamo mechanisms can give us new insights on how the same type of mechanisms can operate in extrasolar planets -- planets beyond our Solar System. We think these mechanisms can work not only in brown dwarfs, but also in both gas giant and terrestrial planets," Kao said.

"Detecting SIMP J01365663+0933473 with the VLA through its auroral radio emission also means that we may have a new way of detecting exoplanets, including the elusive rogue ones not orbiting a parent star," Hallinan said.

Kao and Hallinan worked with J. Sebastian Pineda who also was a graduate student at Caltech and is now at the University of Colorado Boulder, David Stevenson of Caltech, and Adam Burgasser of the University of California San Diego. They are reporting their findings in the Astrophysical Journal.

Read more at Science Daily

Modern Flores Island pygmies show no genetic link to extinct 'hobbits'

A modern pygmy population evolved short stature independently of the extinct 'hobbit' pygmy species that lived on the same island -- Indonesia's Flores Island -- tens of thousands of years earlier, report Princeton's Serena Tucci, Joshua Akey and an international team of researchers. In this illustration, the modern pygmy village, Rampasasa, is shown at left; in the center, a modern Rampasasa pygmy wearing the traditional head covering and clothing is juxtaposed against the face of a Homo floresiensis reconstruction; at right, pygmy elephants play in the Liang Bua cave where theH. floresiensis fossils were discovered in 2004.

Two pygmy populations on the same tropical island. One went extinct tens of thousands of years ago; the other still lives there. Are they related?

It's a simple question that took years to answer.

As no one has been able to recover DNA from the fossils of Homo floresiensis (nicknamed the "hobbit"), researchers had to create a tool for finding archaic genetic sequences in modern DNA.

The technique was developed by scientists in the lab of Joshua Akey, a professor of ecology and evolutionary biology and the Lewis-Sigler Institute for Integrative Genomics at Princeton University.

"In your genome -- and in mine -- there are genes that we inherited from Neanderthals," said Serena Tucci, a postdoctoral research associate in Akey's lab. "Some modern humans inherited genes from Denisovans [another extinct species of humans], which we can check for because we have genetic information from Denisovans.

"But if you want to look for another species, like Floresiensis, we have nothing to compare, so we had to develop another method: We 'paint' chunks of the genome based on the source. We scan the genome and look for chunks that come from different species -- Neanderthal, Denisovans, or something unknown."

She used this technique with the genomes of 32 modern pygmies living in a village near the Liang Bua cave on Flores Island in Indonesia, where H. floresiensis fossils were discovered in 2004.

"They definitely have a lot of Neanderthal," said Tucci, who was the first author on a paper published Aug. 3 in the journal Science that detailed their findings. "They have a little bit of Denisovan. We expected that, because we knew there was some migration that went from Oceania to Flores, so there was some shared ancestry of these populations."

But there were no chromosomal "chunks" of unknown origins.

"If there was any chance to know the hobbit genetically from the genomes of extant humans, this would have been it," said Richard "Ed" Green, an associate professor of biomolecular engineering at the University of California-Santa Cruz (UCSC) and a corresponding author on the paper. "But we don't see it. There is no indication of gene flow from the hobbit into people living today."

The researchers did find evolutionary changes associated with diet and short stature. Height is very heritable, and geneticists have identified many genes with variants linked to taller or shorter stature. Tucci and her colleagues analyzed the Flores pygmy genomes with respect to height-associated genes identified in Europeans, and they found a high frequency of genetic variants associated with short stature.

"It sounds like a boring result, but it's actually quite meaningful," Green said. "It means that these gene variants were present in a common ancestor of Europeans and the Flores pygmies. They became short by selection acting on this standing variation already present in the population, so there's little need for genes from an archaic hominin to explain their small stature."

The Flores pygmy genome also showed evidence of selection in genes for enzymes involved in fatty acid metabolism, called FADS enzymes (fatty acid desaturase). These genes have been associated with dietary adaptations in other fish-eating populations, including the Inuit in Greenland.

Fossil evidence indicates H. floresiensis was significantly smaller than the modern Flores pygmies, standing about 3.5 feet tall (106 centimeters, shorter than the average American kindergartener), while modern pygmies average about 15 inches taller (145 centimeters). Floresiensis also differed from H. sapiens and H. erectus in their wrists and feet, probably due to the need to climb trees to evade Komodo dragons, said Tucci.

Dramatic size changes in animals isolated on islands is a common phenomenon, often attributed to limited food resources and freedom from predators. In general, large species tend to get smaller and small species tend to get larger on islands. At the time of H. floresiensis, Flores was home to dwarf elephants, giant Komodo dragons, giant birds and giant rats, all of which left bones in the Liang Bua cave.

"Islands are very special places for evolution," Tucci said. "This process, insular dwarfism, resulted in smaller mammals, like hippopotamus and elephants, and smaller humans."

Their results show that insular dwarfism arose independently at least twice on Flores Island, she said, first in H. floresiensis and again in the modern pygmies.

Read more at Science Daily

Astronomers blown away by historic stellar blast

Color image taken with the Hubble Space Telecope’s WFPC2 camera, showing the dumbbell-shaped cloud of gas and dust around the star. This nebula contains more than 10 times the mass of our Sun, which was ejected by Eta Carinae in the 19th century Great Eruption.

Imagine traveling to the Moon in just 20 seconds! That's how fast material from a 170 year old stellar eruption sped away from the unstable, eruptive, and extremely massive star Eta Carinae.

Astronomers conclude that this is the fastest jettisoned gas ever measured from a stellar outburst that didn't result in the complete annihilation of the star.

The blast, from the most luminous star known in our galaxy, released almost as much energy as a typical supernova explosion that would have left behind a stellar corpse. However, in this case a double-star system remained and played a critical role in the circumstances that led to the colossal blast.

Over the past seven years a team of astronomers led by Nathan Smith, of the University of Arizona, and Armin Rest, of the Space Telescope Science Institute, determined the extent of this extreme stellar blast by observing light echoes from Eta Carinae and its surroundings.

Light echos occur when the light from bright, short-lived events are reflected off of clouds of dust, which act like distant mirrors redirecting light in our direction. Like an audio echo, the arriving signal of the reflected light has a time delay after the original event due to the finite speed of light. In the case of Eta Carinae, the bright event was a major eruption of the star that expelled a huge amount of mass back in the mid-1800s during what is known as the "Great Eruption." The delayed signal of these light echoes allowed astronomers to decode the light from the eruption with modern astronomical telescopes and instruments, even though the original eruption was seen from Earth back in the mid-19th century. That was a time before modern tools like the astronomical spectrograph were invented.

"A light echo is the next best thing to time travel," Smith said. "That's why light echoes are so beautiful. They give us a chance to unravel the mysteries of a rare stellar eruption that was witnessed 170 years ago, but using our modern telescopes and cameras. We can also compare that information about the event itself with the 170-year old remnant nebula that was ejected. This was a behemoth stellar explosion from a very rare monster star, the likes of which has not happened since in our Milky Way Galaxy."

The Great Eruption temporarily promoted Eta Carinae to the second brightest star visible in our nighttime sky, vasty outshining the energy output every other star in the Milky Way, after which the star faded from naked eye visibility. The outburst expelled material (about 10 times more than the mass of our Sun) that also formed the bright glowing gas cloud known as the Homunculus. This dumbbell-shaped remnant is visible surrounding the star from within a vast star-forming region. The eruptive remnant can even be seen in small amateur telescopes from the Earth's Southern Hemisphere and equatorial regions, but is best seen in images obtained with the Hubble Space Telescope.

The team used instruments on the 8-meter Gemini South telescope, Cerro Tololo Inter-American Observatory 4-meter Blanco telescope, and the Magellan Telescope at Las Campanas Observatory to decode the light from these light echoes and to understand the expansion speeds in the historical explosion. "Gemini spectroscopy helped pin down the unprecedented velocities we observed in this gas, which clocked in at between about 10,000 to 20,000 kilometers per second," according to Rest. The research team, Gemini Observatory, and Blanco telescope are all supported by the U.S. National Science Foundation (NSF).

"We see these really high velocities all the time in supernova explosions where the star is obliterated." Smith notes. However, in this case the star survived, and explaining that led the researchers into new territory. "Something must have dumped a lot of energy into the star in a short amount of time," said Smith. The material expelled by Eta Carinae is travelling up to 20 times faster than expected for typical winds from a massive star so, according to Smith and his collaborators, enlisting the help of two partner stars might explain the extreme outflow.

The researchers suggest that the most straightforward way to simultaneously explain a wide range of observed facts surrounding the eruption and the remnant star system seen today is with an interaction of three stars, including a dramatic event where two of the three stars merged into one monster star. If that's the case, then the present-day binary system must have started out as triple system, with one of those two stars being the one that swallowed its sibling.

"Understanding the dynamics and environment around the largest stars in our galaxy is one of the most difficult areas of astronomy," said Richard Green, Director of the Division of Astronomical Sciences at NSF, the major funding agency for Gemini. "Very massive stars live short lives compared to stars like our Sun, but nevertheless catching one in the act of a major evolutionary step is statistically unlikely. That's why a case like Eta Carinae is so critical, and why NSF supports this kind of research."

Chris Smith, Head of Mission at the AURA Observatory in Chile and also part of the research team adds a historical perspective. "I'm thrilled that we can see light echoes coming from an event that John Herschel observed in the middle of the 19th century from South Africa," he said. "Now, over 150 years later we can look back in time, thanks to these light echoes, and unveil the secrets of this supernova wannabe using the modern instrumentation on Gemini to analyze the light in ways Hershel couldn't have even imagined!"

Eta Carinae is an unstable type of star known as a Luminous Blue Variable (LBV), located about 7,500 light years from Earth in a young star forming nebula found in the southern constellation of Carinae. The star is one of the intrinsically brightest in our galaxy and shines some five million times brighter than our Sun with a mass about one hundred times greater. Stars like Eta Carinae have the greatest mass-loss rates prior to undergoing supernova explosions, but the amount of mass expelled in Eta Carinae's 19th century Great Eruption exceeds any others known.

Eta Carinae will probably undergo a true supernova explosion sometime within the next half-million years at most, but possibly much sooner. Some types of supernovae have been seen to experience eruptive blasts like that of Eta Carinae in only the few years or decades before their final explosion, so some astronomers speculate that Eta Carinae might blow sooner rather than later.

Read more at Science Daily