Stripes may be cool -- but they don't cool zebras down

Barrels used in the experiment.

Susanne Åkesson, a biologist at Lund University in Sweden, refutes the theory that zebras have striped fur to stay cool in the hot sun. That hypothesis is wrong, she and her colleagues show in a study recently published in Scientific Reports.

There has been an ongoing discussion among researchers, dating back to Darwin, on why zebras have their signature black and white stripes.

One of several theories is that it keeps them cool in the sunshine. The black stripes get warmer than the white areas, and the theory states that this creates small vortexes when the hotter air above the dark fur meets the cooler air above the white fur. According to the theory these vortexes works as a fan to cool the body.

To test this theory, the researchers filled big metal barrels with water and covered them with skin imitations in different colours: black and white stripes, black, white, brown and grey. They then placed the barrels in the sun and later measured the temperature in each barrel. Not surprisingly, the black one was the hottest and the white one the coolest. The striped and grey barrels were similar, and in these the temperature did not go down.

"The stripes didn't lower the temperature. It turns out stripes don't actually cool zebras," says Susanne Åkesson.

Eight years ago she and her colleagues from Hungary and Spain presented another theory, where they claim that bright fur works as an optical protection against blood-sucking horseflies and other insects that bite. Horseflies are attracted by polarised light, the sort of light that appears when sunbeams are reflected on a dark surface. If the sunbeams are reflected on a white surface there will be no polarised light -- hence the protection.

Two years ago Susanne Åkesson, the Hungarian physicist Gábor Horváth and their colleauges were awarded with the Ig Nobel Prize for their research on polarised light, horseflies and why these blood-sucking insects bother dark horses a lot more than they bother white horses.

From Science Daily

Novel HIV vaccine candidate is safe and induces immune response in healthy adults and monkeys

Scientists are working to develop a preventative vaccine that could finally put an end to the epidemic for which there are 1.8 million new infections each year.

New research published in The Lancet shows that an experimental HIV-1 vaccine regimen is well-tolerated and generated comparable and robust immune responses against HIV in healthy adults and rhesus monkeys. Moreover, the vaccine candidate protected against infection with an HIV-like virus in monkeys.

Based on the results from this phase 1/2a clinical trial that involved nearly 400 healthy adults, a phase 2b trial has been initiated in southern Africa to determine the safety and efficacy of the HIV-1 vaccine candidate in 2,600 women at risk for acquiring HIV. This is one of only five experimental HIV-1 vaccine concepts that have progressed to efficacy trials in humans in the 35 years of the global HIV/AIDS epidemic.

Previous HIV-1 vaccine candidates have typically been limited to specific regions of the world. The experimental regimens tested in this study are based on 'mosaic' vaccines that take pieces of different HIV viruses and combine them to elicit immune responses against a wide variety of HIV strains.

"These results represent an important milestone. This study demonstrates that the mosaic Ad26 prime, Ad26 plus gp140 boost HIV vaccine candidate induced robust immune responses in humans and monkeys with comparable magnitude, kinetics, phenotype, and durability and also provided 67% protection against viral challenge in monkeys," says Professor Dan Barouch, Director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center and Professor of Medicine at Harvard Medical School, Boston, USA who led the study.

He adds: "These results should be interpreted cautiously. The challenges in the development of an HIV vaccine are unprecedented, and the ability to induce HIV-specific immune responses does not necessarily indicate that a vaccine will protect humans from HIV infection. We eagerly await the results of the phase 2b efficacy trial called HVTN705, or 'Imbokodo', which will determine whether or not this vaccine will protect humans against acquiring HIV."

Almost 37 million people worldwide are living with HIV/AIDS, with an estimated 1.8 million new cases every year. A safe and effective preventative vaccine is urgently needed to curb the HIV pandemic.

In the 35 years of the HIV epidemic, only four HIV vaccine concepts have been tested in humans, and only one has provided evidence of protection in an efficacy trial -- a canarypox vector prime, gp120 boost vaccine regimen tested in the RV144 trial in Thailand lowered the rate of human infection by 31% but the effect was considered too low to advance the vaccine to common use.

A key hurdle to HIV vaccine development has been the lack of direct comparability between clinical trials and preclinical studies. To address these methodological issues, Barouch and colleagues evaluated the leading mosaic adenovirus serotype 26 (Ad26)-based HIV-1 vaccine candidates in parallel clinical and pre-clinical studies to identify the optimal HIV vaccine regimen to advance into clinical efficacy trials.

The APPROACH trial recruited 393 healthy, HIV-uninfected adults (aged 18-50 years) from 12 clinics in east Africa, South Africa, Thailand, and the USA between February 2015 and October 2015. Volunteers were randomly assigned to receive either one of seven vaccine combinations or a placebo, and were given four vaccinations over the course of 48 weeks.

To stimulate, or 'prime', an initial immune response, each volunteer received an intramuscular injection of Ad26.Mos.HIV at the start of the study and again 12 weeks later. The vaccine containing 'mosaic' HIV Env/Gag/Pol antigens was created from many HIV strains, delivered using a nonreplicating common-cold virus (Ad26).

To 'boost' the level of the body's immune response, volunteers were given two additional vaccinations at week 24 and 48 using various combinations of Ad26.Mos.HIV or a different vaccine component called Modified Vaccinia Ankara (MVA) with or without two different doses of clade C HIV gp140 envelope protein containing an aluminium adjuvant.

Results showed that all vaccine regimens tested were capable of generating anti-HIV immune responses in healthy individuals and were well tolerated, with similar numbers of local and systemic reactions reported in all groups, most of which were mild-to-moderate in severity. Five participants reported at least one vaccine-related grade 3 adverse event such as abdominal pain and diarrhea, postural dizziness, and back pain. No grade 4 adverse events or deaths were reported.

In a parallel study, the researchers assessed the immunogenicity and protective efficacy of the same Ad26-based mosaic vaccine regimens in 72 rhesus monkeys using a series repeated challenges with simian-human immunodeficiency virus (SHIV) -- a virus similar to HIV that infects monkeys.

The Ad26/Ad26 plus gp140 vaccine candidate induced the greatest immune responses in humans and also provided the best protection in monkeys -- resulting in complete protection against SHIV infection in two-thirds of the vaccinated animals after six challenges.

The authors note several limitations, including the fact that that the relevance of vaccine protection in rhesus monkeys to clinical efficacy in humans remains unclear. They also note that there is no definitive immunological measurement that is known to predict protection against HIV-1 in humans.

Writing in a linked Comment, Dr George Pavlakis and Dr Barbara Felber from the National Cancer Institute at Frederik, Maryland, USA say: "Efficacy studies are necessary to determine protective ability in humans and also for the discovery of correlates of protection and for determining whether the same or different immune correlates apply for different vaccine regimens. It remains to be determined whether improved efficacy over RV144 will be achieved by either of the present efficacy trials (NCT02968849; NCT03060629). New vaccine concepts and vectors are in development and can progress to efficacy trials, which is an important process since development of an AIDS vaccine remains urgent. Despite unprecedented advances in HIV treatment and prophylaxis, the number of people living with HIV infection continues to increase worldwide. Implementation of even a moderately effective HIV vaccine together with the existing HIV prevention and treatment strategies is expected to contribute greatly to the evolving HIV/AIDS response. It is therefore essential that a commitment to pursue multiple vaccine development strategies continues at all stages."

Read more at Science Daily

Global warming may be twice what climate models predict

What will the future hold?

Future global warming may eventually be twice as warm as projected by climate models under business-as-usual scenarios and even if the world meets the 2°C target sea levels may rise six metres or more, according to an international team of researchers from 17 countries.

The findings published last week in Nature Geoscience are based on observational evidence from three warm periods over the past 3.5 million years when the world was 0.5°C-2°C warmer than the pre-industrial temperatures of the 19th Century.

The research also revealed how large areas of the polar ice caps could collapse and significant changes to ecosystems could see the Sahara Desert become green and the edges of tropical forests turn into fire dominated savanna. "Observations of past warming periods suggest that a number of amplifying mechanisms, which are poorly represented in climate models, increase long-term warming beyond climate model projections," said lead author, Prof Hubertus Fischer of the University of Bern.

"This suggests the carbon budget to avoid 2°C of global warming may be far smaller than estimated, leaving very little margin for error to meet the Paris targets."

To get their results, the researchers looked at three of the best-documented warm periods, the Holocene thermal maximum (5000-9000 years ago), the last interglacial (129,000-116,000 years ago) and the mid-Pliocene warm period (3.3-3 million years ago).

The warming of the first two periods was caused by predictable changes in the Earth's orbit, while the mid-Pliocene event was the result of atmospheric carbon dioxide concentrations that were 350-450ppm -- much the same as today.

Combining a wide range of measurements from ice cores, sediment layers, fossil records, dating using atomic isotopes and a host of other established paleoclimate methods, the researchers pieced together the impact of these climatic changes.

In combination, these periods give strong evidence of how a warmer Earth would appear once the climate had stabilized. By contrast, today our planet is warming much faster than any of these periods as human caused carbon dioxide emissions continue to grow. Even if our emissions stopped today, it would take centuries to millennia to reach equilibrium.

The changes to the Earth under these past conditions were profound -- there were substantial retreats of the Antarctic and Greenland ice sheets and as a consequence sea-levels rose by at least six metres; marine plankton ranges shifted reorganising entire marine ecosystems; the Sahara became greener and forest species shifted 200 km towards the poles, as did tundra; high altitude species declined, temperate tropical forests were reduced and in Mediterranean areas fire-maintained vegetation dominated.

"Even with just 2°C of warming -- and potentially just 1.5°C -- significant impacts on the Earth system are profound," said co-author Prof Alan Mix of Oregon State University.

"We can expect that sea-level rise could become unstoppable for millennia, impacting much of the world's population, infrastructure and economic activity."

Yet these significant observed changes are generally underestimated in climate model projections that focus on the near term. Compared to these past observations, climate models appear to underestimate long term warming and the amplification of warmth in Polar Regions.

"Climate models appear to be trustworthy for small changes, such as for low emission scenarios over short periods, say over the next few decades out to 2100. But as the change gets larger or more persistent, either because of higher emissions, for example a business-as-usual-scenario, or because we are interested in the long term response of a low emission scenario, it appears they underestimate climate change.," said co-author Prof Katrin Meissner, Director of the University of New South Wales Climate Change Research Centre.

Read more at Science Daily

Fragment of impacting asteroid recovered in Botswana

Botswana meteorite.

On Saturday, June 23, 2018, a team of experts from Botswana, South Africa, Finland and the United States of America recovered a fresh meteorite in Botswana´s Central Kalahari Game Reserve (CKGR).

The meteorite is one of the fragments of asteroid 2018 LA which collided with Earth on June 2, 2018 and turned into a meteor fireball that detonated over Botswana a few seconds after entering the atmosphere. The incident was witnessed by a number of spectators in Botswana and neighbouring countries and was captured on numerous security cameras.

Asteroid 2018 LA was detected in space eight hours before hitting Earth. It was detected by the Catalina Sky Survey, operated by the University of Arizona and sponsored by NASA as part of its Planetary Defence mission. This is the third time in history that an asteroid inbound to hit Earth was detected early and only the second time that fragments were recovered. After disruption, the asteroid fragments were blown by the wind while falling down, scattering over a wide area. Calculations of the landing area were done independently by a US-based group headed by Peter Jenniskens, a subject expert of the NASA-sponsored SETI Institute in California, as well as Esko Lyytinen and Jarmo Moilanen of the Finnish Fireball Network (FFN).

The first meteorite was found after five days of walking and scouring around by a team of geoscientists from Botswana International University of Science and Technology (BUIST), Botswana Geoscience Institute (BGI) and University of Botswana´s Okavango Research Institute (ORI). The Department of Wildlife and National Parks granted access and deployed park rangers for protection and participation in the search. The importance of the find is two-fold: It has enormous scientific value and it allows to better calibrate the so-called "Earth Defense" against impacting asteroids.

Jenniskens, who traveled to Botswana to assist in the search, teamed up with Oliver Moses (from ORI), to gather security surveillance videos in Rakops and Maun, to get better constraints on the position and altitude of the fireball´s explosion. Professor Alexander Proyer, from BIUST, led the joint expedition while Mohutsiwa Gabadirwe, BGI senior curator, coordinated access to the protected fall area in the game reserve. Professor Roger Gibson, Head of School at the School of Geosciences at the University of the Witwatersrand in Johannesburg, South Africa, also assisted in locating the fall area. The meteorite was eventually spotted by BIUST geologist Lesedi Seitshiro. The search for more fragments of the meteorite continues. Dr Fulvio Franchi of BIUST, is leading the follow-up search team joined by Tomas Kohout of the FFN and the University of Helsinki.

Read more at Science Daily

Ancient DNA testing solves 100-year-old controversy in Southeast Asian prehistory

Skull from a Hòabìnhian person from Gua Cha archaeological site, Malaysian Peninsula.

Two competing theories about the human occupation of Southeast Asia have been debunked by ground-breaking analysis of ancient DNA extracted from 8,000 year-old skeletons.

Southeast Asia is one of the most genetically diverse regions in the world, but for more than 100 years scientists have disagreed about which theory of the origins of the population of the area was correct.

One theory believed the indigenous Hòabìnhian hunter-gatherers who populated Southeast Asia from 44,000 years ago adopted agricultural practices independently, without the input from early farmers from East Asia. Another theory, referred to as the 'two-layer model' favours the view that migrating rice farmers from what is now China replaced the indigenous Hòabìnhian hunter-gatherers.

Academics from around the world collaborated on new research just published in Science which found that neither theory is completely accurate. Their study discovered that present-day Southeast Asian populations derive ancestry from at least four ancient populations.

DNA from human skeletal remains from Malaysia, Thailand, the Philippines, Vietnam, Indonesia, Laos and Japan dating back as far as 8,000 years ago was extracted for the study - scientists had previously only been successful in sequencing 4,000-year-old samples from the region. The samples also included DNA from Hòabìnhian hunter-gatherers and a Jomon from Japan - a scientific first, revealing a long suspected genetic link between the two populations.

In total, 26 ancient human genome sequences were studied by the group and they were compared with modern DNA samples from people living in Southeast Asia today.

The pioneering research is particularly impressive because the heat and humidity of Southeast Asia means it is one of the most difficult environments for DNA preservation, posing huge challenges for scientists.

Professor Eske Willerslev, who holds positions both at St John's College, University of Cambridge, and the University of Copenhagen, led the international study.

He explained: "We put a huge amount of effort into retrieving ancient DNA from tropical Southeast Asia that could shed new light on this area of rich human genetics. The fact that we were able to obtain 26 human genomes and shed light on the incredible genetic richness of the groups in the region today is astonishing."

Hugh McColl, PhD student at the Centre for GeoGenetics in the Natural History Museum of Denmark of the University of Copenhagen, and one of the lead authors on the paper, said: "By sequencing 26 ancient human genomes - 25 from South East Asia, one Japanese Jōmon - we have shown that neither interpretation fits the complexity of Southeast Asian history. Both Hòabìnhian hunter-gatherers and East Asian farmers contributed to current Southeast Asian diversity, with further migrations affecting islands in South East Asia and Vietnam. Our results help resolve one of the long-standing controversies in Southeast Asian prehistory."

Dr Fernando Racimo, Assistant Professor at the Centre for GeoGenetics in the Natural History Museum of the University of Copenhagen, the other lead author, said: "The human occupation history of Southeast Asia remains heavily debated. Our research spanned from the Hòabìnhian to the Iron Age and found that present-day Southeast Asian populations derive ancestry from at least four ancient populations. This is a far more complex model than previously thought."

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First dogs in the Americas arrived from Siberia, disappeared after European contact

A ritual burial of two dogs at a site in Illinois near St. Louis suggests a special relationship between humans and dogs at this location and time (660 to 1350 years ago).

A study reported in the journal Science offers an enhanced view of the origins and ultimate fate of the first dogs in the Americas. The dogs were not domesticated North American wolves, as some have speculated, but likely followed their human counterparts over a land bridge that once connected North Asia and the Americas, the study found.

This is the first comprehensive genomic study of ancient dogs in the Americas to analyze nuclear DNA, which is inherited from both parents, along with mitochondrial DNA, which is passed down only from mothers to their offspring. By comparing genomic signatures from 71 mitochondrial and seven nuclear genomes of ancient North American and Siberian dogs spanning a period of 9,000 years, the research team was able to gain a clearer picture of the history of the first canine inhabitants of the Americas.

The oldest dog remains in the Americas date to about 9,000 years ago, many thousands of years after people began migrating over a land bridge connecting present-day Siberia and Alaska. The ancient dogs analyzed in the new study likely originated in Siberia, the researchers found. The dogs dispersed to every part of the Americas, migrating with their human counterparts.

These dogs persisted for thousands of years in the Americas, but almost completely vanished after European contact, the researchers found.

"This suggests something catastrophic must have happened, and it's likely associated with European colonization," said senior lead author Laurent Frantz, a lecturer at Queen Mary University and co-investigator at the University of Oxford. "But we just do not have the evidence to explain this sudden disappearance yet."

"By looking at genomic data along with mitochondrial data, we were able to confirm that dogs came to the Americas with humans, and that nearly all of that diversity was lost -- most likely as a result of European colonization," said Kelsey Witt, who led the mitochondrial DNA genome work as a graduate student in the laboratory of University of Illinois anthropology professor Ripan Malhi, who also is an author of the study.

"Few modern dogs have any trace of these ancient lineages," said Witt, now a postdoctoral researcher at the University of California, Merced.

The team also discovered that the genomic signature of a transmissible cancer that afflicts dogs appears to be one of the last "living" remnants of the genetic heritage of dogs that populated the Americas prior to European contact.

"This suggests that this tumor originated in or near the Americas," Witt said.

The new findings reinforce the idea that early human and dog inhabitants of the Americas faced many of the same challenges after European contact, Malhi said.

Read more at Science Daily

Frigid polar oceans, not balmy coral reefs, are species-formation hot spots

Greenland icebergs

Tropical oceans teem with the dazzle and flash of colorful reef fishes and contain far more species than the cold ocean waters found at high latitudes. This well-known "latitudinal diversity gradient" is one of the most famous patterns in biology, and scientists have puzzled over its causes for more than 200 years.

One frequently advanced explanation is that warm reef environments serve as evolutionary hot spots for species formation. But a new study that analyzed the evolutionary relationships between more than 30,000 fish species concludes that the fastest rates of species formation have occurred at the highest latitudes and in the coldest ocean waters.

Over the past several million years, cool-water and polar ocean fishes formed new species twice as fast as the average species of tropical fish, according to the new study, which is scheduled for publication July 4 in the journal Nature.

"These findings are both surprising and paradoxical," said University of Michigan evolutionary biologist Daniel Rabosky, lead author of the study. "A number of hypotheses explain extreme tropical diversity as the result of faster rates of species formation, but it's never been tested in fishes.

"Our results are counterintuitive and unexpected, because we find that speciation is actually fastest in the geographic regions with the lowest species richness."

The authors admit they cannot fully explain their results, which are incompatible with the idea that the tropics serve as an evolutionary cradle for marine fish diversity. The findings also raise questions about whether the rapid cold-ocean speciation the team documented reflects a recent and ongoing expansion of marine diversity there.

Common sense suggests that a high rate of new species formation will eventually lead to impressive levels of biodiversity. But that depends on how many of the newly formed species survive and how many go extinct. And extinction rates could not be addressed through the methods used in the current study.

"The number of species you find in a region is largely a balance between the rate at which new species form and the rate at which extinction eliminates them," Rabosky said. "The rapid speciation of fishes in cold, high-latitude oceans that we documented will only cause diversity to increase if it is generally higher than extinction.

"Extinction is the missing piece of this puzzle, but it's the most difficult thing to understand. We're now using both fossils and new statistical tools to try to get a handle on what extinction might have been doing in both the polar regions and the tropics."

In the study, Rabosky and colleagues from eight institutions tested the widely held assumption that species-formation rates are fastest in the tropics by examining the relationship between latitude, species richness and the rate of new species formation among marine fishes. They assembled a time-calibrated evolutionary tree of all 31,526 ray-finned fish species, then focused their analysis on marine species worldwide.

Genetic data were available for more than one-third of the fish species analyzed in the study, and the evolutionary tree was time-calibrated using a database of 139 fossil taxa.

An evolutionary tree, also known as a phylogenetic tree, is a branching diagram showing the inferred evolutionary relationships among various species. The tree assembled for this project is one of the largest time-calibrated phylogenetic trees ever created for any group of animals, according to Rabosky.

The researchers estimated geographic ranges for most of the marine fish species, including all species with genetic data. Then they used complex mathematical and statistical models to estimate the rates at which different groups of fishes split into new species.

"The computational challenges for analyzing these types of data are pretty extreme," said study co-author Michael Alfaro, an evolutionary biologist at the University of California, Los Angeles. The analyses in the study required the equivalent of thousands of desktop computers running continuously for many months, he said.

Some of the fastest rates of new species formation occurred in Antarctic icefish and their relatives. Other temperate and polar groups with exceptionally high speciation rates include snailfish, eelpouts and rockfish.

Three of the largest coral reef-associated fish groups -- wrasses, damselfish and gobies -- showed low to moderate rates of species formation.

"The fact that coral reefs support many more fish species than polar regions despite these lower rates may have a lot to do with their long history of connectivity and ability to act as a refugia," said co-author Peter Cowman of the Australia Research Council Centre of Excellence for Coral Reef Studies, and previously of Yale University. "Our research certainly paints coral reef diversity in a new light."

"Who would have thought that you'd have these really explosive rates of species formation happening in the coldest Antarctic waters, where water is literally at the freezing point and fish like the icefish have to have all kinds of really crazy adaptations to live there, like special antifreeze proteins in their blood to keep it from freezing," Rabosky said.

Rabosky is an associate professor in the U-M Department of Ecology and Evolutionary Biology and an associate curator at the U-M Museum of Zoology.

The authors of the Nature paper, in addition to Rabosky, Alfaro and Cowman, are U-M's Jonathan Chang, Pascal Title and Matt Friedman; Lauren Sallan of the University of Pennsylvania; Kristin Kaschner of the University of Freiburg; Cristina Garilao of GEOMAR Helmholtz Centre for Ocean Research; Thomas Near of Yale University; and Marta Coll of the Institute of Marine Science in Barcelona, Spain.

Read more at Science Daily

Bacteria-powered solar cell converts light to energy, even under overcast skies

Using bacteria that convert light to energy could be a step toward wider adoption of solar power in places where overcast skies are common.

University of British Columbia researchers have found a cheap, sustainable way to build a solar cell using bacteria that convert light to energy.

Their cell generated a current stronger than any previously recorded from such a device, and worked as efficiently in dim light as in bright light.

This innovation could be a step toward wider adoption of solar power in places like British Columbia and parts of northern Europe where overcast skies are common. With further development, these solar cells -- called "biogenic" because they are made of living organisms -- could become as efficient as the synthetic cells used in conventional solar panels.

"Our solution to a uniquely B.C. problem is a significant step toward making solar energy more economical," said Vikramaditya Yadav, a professor in UBC's department of chemical and biological engineering who led the project.

Solar cells are the building blocks of solar panels. They do the work of converting light into electrical current. Previous efforts to build biogenic solar cells have focused on extracting the natural dye that bacteria use for photosynthesis. It's a costly and complex process that involves toxic solvents and can cause the dye to degrade.

The UBC researchers' solution was to leave the dye in the bacteria. They genetically engineered E. coli to produce large amounts of lycopene -- a dye that gives tomatoes their red-orange colour and is particularly effective at harvesting light for conversion to energy. The researchers coated the bacteria with a mineral that could act as a semiconductor, and applied the mixture to a glass surface.

With the coated glass acting as an anode at one end of their cell, they generated a current density of 0.686 milliamps per square centimetre -- an improvement on the 0.362 achieved by others in the field.

"We recorded the highest current density for a biogenic solar cell," said Yadav. "These hybrid materials that we are developing can be manufactured economically and sustainably, and, with sufficient optimization, could perform at comparable efficiencies as conventional solar cells."

The cost savings are difficult to estimate, but Yadav believes the process reduces the cost of dye production to about one-tenth of what it would be otherwise. The holy grail, Yadav said, would be finding a process that doesn't kill the bacteria, so they can produce dye indefinitely.

Read more at Science Daily

Our human ancestors walked on two feet but their children still had a backup plan

This is the 3.32 million-year-old Australopithecus afarensis foot from Dikika, Ethiopia, superimposed over a footprint from a human toddler.

More than 3 million years ago, our ancient human ancestors, including their toddler-aged children, were standing on two feet and walking upright, according to a new study published in Science Advances.

"For the first time, we have an amazing window into what walking was like for a 2½-year-old, more than 3 million years ago," says lead author, Jeremy DeSilva, an associate professor of anthropology at Dartmouth College, who is one of the world's foremost authorities on the feet of our earliest ancestors. "This is the most complete foot of an ancient juvenile ever discovered."

The tiny foot, about the size of a human thumb, is part of a nearly complete 3.32-million-year-old skeleton of a young female Australopithecus afarensis discovered in 2002 in the Dikika region of Ethiopia by Zeresenay (Zeray) Alemseged, a professor of organismal biology and anatomy at the University of Chicago and senior author of the study. Alemseged is internationally known as a leading paleontologist on the study of human origins and human evolution.

"Placed at a critical time and the cusp of being human, Australopithecus afarensis was more derived than Ardipithecus (a facultative biped) but not yet an obligate strider like Homo erectus. The Dikika foot adds to the wealth of knowledge on the mosaic nature of hominin skeletal evolution" explained Alemseged.

Given that the fossil of the tiny foot is the same species as the famous Lucy fossil and was found in the same vicinity, it is not surprising that the Dikika child was erroneously labeled "Lucy's baby" by the popular press, though this youngster lived more than 200,000 years before Lucy.

In studying the fossil foot's remarkably preserved anatomy, the research team strived to reconstruct what life would have been like years ago for this toddler and how our ancestors survived. They examined what the foot would have been used for, how it developed and what it tells us about human evolution. The fossil record indicates that these ancient ancestors were quite good at walking on two legs. "Walking on two legs is a hallmark of being human. But, walking poorly in a landscape full of predators is a recipe for extinction," explained DeSilva.

Read more at Science Daily

New world record for direct solar water-splitting efficiency

Teams from the California Institute of Technology, the University of Cambridge, Technische Universitaet Ilmenau, and the Fraunhofer Institute for Solar Energy Systems ISE participated in the development work. One part of the experiments took place at the Institute for Solar Fuels in the Helmholtz-Zentrum Berlin.

Photovoltaics are a mainstay of renewable-energy supply systems, and sunlight is abundantly available worldwide but not around the clock. One solution for dealing with this fluctuating power generation is to store sunlight in the form of chemical energy, specifically by using sunlight to produce hydrogen. This is because hydrogen can be stored easily and safely, and used in many ways whether in a fuel cell to directly generate electricity and heat, or as feedstock for manufacturing combustible fuels. If you combine solar cells with catalysts and additional functional layers to form a monolithic photoelectrode as a single block, then splitting water becomes especially simple: the photocathode is immersed in an aqueous medium and when light falls on it, hydrogen is formed on the front side and oxygen on the back.

For the monolithic photocathode investigated here, the research teams combined additional functional layers with a highly efficient tandem cell made of III-V semiconductors developed at Fraunhofer ISE. This enabled them to reduce the surface reflectivity of the cell, thereby avoiding considerable losses caused by parasitic light absorption and reflection. "This is also where the innovation lies," explains Prof. Hans-Joachim Lewerenz, Caltech, USA: "Because we had already achieved an efficiency of over 14 per cent for an earlier cell in 2015, which was a world record at the time. Here we have replaced the anti-corrosion top layer with a crystalline titanium dioxide layer that not only has excellent anti-reflection properties, but to which the catalyst particles also adhere." And Prof. Harry Atwater, Caltech, adds: "In addition, we have also used a new electrochemical process to produce the rhodium nanoparticles that serve to catalyse the water-splitting reaction. These particles are only ten nanometres in diameter and are therefore optically nearly transparent, making them ideally suited for the job."

Under simulated solar radiation, the scientists achieved an efficiency of 19.3 per cent in dilute aqueous perchloric acid, while still reaching 18.5 per cent in an electrolyte with neutral pH. These figures approach the 23 per cent theoretical maximum efficiency that can be achieved with the inherent electronic properties for this combination of layers.

"The crystalline titanium-dioxide layer not only protects the actual solar cell from corrosion, but also improves charge transport thanks to its advantageous electronic properties," says Dr. Matthias May, who carried out part of the efficiency determination experiments at the HZB Institute for Solar Fuels in the forerunner laboratory to the Solar-Fuel Testing Facility of the Helmholtz Energy Materials Foundry (HEMF). The record figure now published is based on work that May had already begun as a doctoral student at the HZB and for which he was awarded the Helmholtz Association Doctoral Prize for the field of energy research in 2016. "We were able to increase the operating life to almost 100 hours. This is a major advance compared to previous systems that had already corroded after 40 hours. Nevertheless, there is still a lot to be done," May explains.

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Neuroscientists uncover secret to intelligence in parrots

Not-so-bird brain: Neuroscientists discover the mechanism responsible for cognition in intelligent birds, like this parrot.

University of Alberta neuroscientists have identified the neural circuit that may underlay intelligence in birds, according to a new study. The discovery is an example of convergent evolution between the brains of birds and primates, with the potential to provide insight into the neural basis of human intelligence.

"An area of the brain that plays a major role in primate intelligence is called the pontine nuclei," explained Cristian Gutierrez-Ibanez, postdoctoral fellow in the Department of Psychology. "This structure transfers information between the two largest areas of the brain, the cortex and cerebellum, which allows for higher-order processing and more sophisticated behaviour. In humans and primates, the pontine nuclei are large compared to other mammals. This makes sense given our cognitive abilities."

Birds have very small pontine nuclei. Instead, they have a similar structure called the medial spiriform nucleus (SpM) that has similar connectivity. Located in a different part of the brain, the SpM does the same thing as the pontine nuclei, circulating information between the cortex and the cerebellum. "This loop between the cortex and the cerebellum is important for the planning and execution of sophisticated behaviours," said Doug Wylie, professor of psychology and co-author on the new study.

Not-so-bird brain

Using samples from 98 birds from the largest collection of bird brains in the world, including everything from chickens and waterfowl to parrots and owls, the scientists studied the brains of birds, comparing the relative size of the SpM to the rest of the brain. They determined that parrots have a SpM that is much larger than that of other birds.

"The SpM is very large in parrots. It's actually two to five times larger in parrots than in other birds, like chickens," said Gutierrez. "Independently, parrots have evolved an enlarged area that connects the cortex and the cerebellum, similar to primates. This is another fascinating example of convergence between parrots and primates. It starts with sophisticated behaviours, like tool use and self-awareness, and can also be seen in the brain. The more we look at the brains, the more similarities we see."

Next, the research team hopes to study the SpM in parrots more closely, to understand what types of information go there and why.

Read more at Science Daily

Combining antibiotics changes their effectiveness

Combining antibiotics changes their effectiveness.

The effectiveness of antibiotics can be altered by combining them with each other, non-antibiotic drugs or even with food additives. Depending on the bacterial species, some combinations stop antibiotics from working to their full potential whilst others begin to defeat antibiotic resistance, report EMBL researchers and collaborators in Nature on July 4.

In the first large-scale screening of its kind, scientists profiled almost 3000 drug combinations on three different disease-causing bacteria. The research was led by EMBL group leader Nassos Typas.

Overcoming antibiotic resistance

Overuse and misuse of antibiotics has led to widespread antibiotic resistance. Specific combinations of drugs can help in fighting multi-drug resistant bacterial infections, but they are largely unexplored and rarely used in clinics. That is why in the current paper, the team systematically studied the effect of antibiotics paired with each other, as well as with other drugs and food additives in different species.

Whilst many of the investigated drug combinations lessened the antibiotics' effect, there were over 500 drug combinations which improved antibiotic outcome. A selection of these positive pairings was also tested in multi-drug resistant bacteria, isolated from infected hospital patients, and were found to improve antibiotic effects.

Clinical vanillin?

When vanillin -- the compound that gives vanilla its distinctive taste -- was paired with one particular antibiotic known as spectinomycin, it helped the antibiotic to enter bacterial cells and inhibit their growth. Spectinomycin was originally developed in the early-1960s for treating gonorrhoea but is rarely used nowadays due to the bacterial resistance that was developed against it. However, in combination with vanillin it could become clinically relevant once again and used for other disease-causing microbes. "Of the combinations tested, this was one of the most effective and promising synergies we identified," says Ana Rita Brochado, first author on the paper and research scientist at EMBL. Pairings such as this could extend the arsenal of weapons in the war against antibiotic resistance.

Curiously, however, vanillin lessened the effect of many other types of antibiotics. The paper showed that vanillin works in a similar way to aspirin to decrease the activity of many antibiotics -- although its effects in human cells have not been tested, they are most likely different.

According to Nassos Typas, combinations of drugs that decrease the effect of antibiotics could also be beneficial to human health. "Antibiotics can lead to collateral damage and side effects because they target healthy bacteria as well. But the effects of these drug combinations are highly selective, and often only affect a few bacterial species. In the future, we could use drug combinations to selectively prevent the harmful effects of antibiotics on healthy bacteria. This would also decrease antibiotic resistance development, as healthy bacteria would not be put under pressure to evolve antibiotic resistance, which can later be transferred to dangerous bacteria."

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Even phenomenally dense neutron stars fall like a feather

This is an artist impression of the triple star system PSR J0337+1715, which is located about 4,200 light-years from Earth. This system provides a natural laboratory to test fundamental theories of gravity.

Einstein's understanding of gravity, as outlined in his general theory of relativity, predicts that all objects fall at the same rate, regardless of their mass or composition. This theory has passed test after test here on Earth, but does it still hold true for some of the most massive and dense objects in the known universe, an aspect of nature known as the Strong Equivalence Principle? An international team of astronomers has given this lingering question its most stringent test ever. Their findings, published in the journal Nature, show that Einstein's insights into gravity still hold sway, even in one of the most extreme scenarios the Universe can offer.

Take away all air, and a hammer and a feather will fall at the same rate -- a concept explored by Galileo in the late 1500s and famously illustrated on the Moon by Apollo 15 astronaut David Scott.

Though a bedrock of Newtonian physics, it took Einstein's theory of gravity to express how and why this is so. To date, Einstein's equations have passed all tests, from careful laboratory studies to observations of planets in our solar system. But alternatives to Einstein's general theory of relativity predict that compact objects with extremely strong gravity, like neutron stars, fall a little differently than objects of lesser mass. That difference, these alternate theories predict, would be due to a compact object's so-called gravitational binding energy -- the gravitational energy that holds it together.

In 2011, the National Science Foundation's (NSF) Green Bank Telescope (GBT) discovered a natural laboratory to test this theory in extreme conditions: a triple star system called PSR J0337+1715, located about 4,200 light-years from Earth. This system contains a neutron star in a 1.6-day orbit with a white dwarf star, and the pair in a 327-day orbit with another white dwarf further away.

"This is a unique star system," said Ryan Lynch of the Green Bank Observatory in West Virginia, and coauthor on the paper. "We don't know of any others quite like it. That makes it a one-of-a-kind laboratory for putting Einstein's theories to the test."

Since its discovery, the triple system has been observed regularly by the GBT, the Westerbork Synthesis Radio Telescope in the Netherlands, and the NSF's Arecibo Observatory in Puerto Rico. The GBT has spent more than 400 hours observing this system, taking data and calculating how each object moves in relation to the other.

How were these telescopes able to study this system? This particular neutron star is actually a pulsar. Many pulsars rotate with a consistency that rivals some of the most precise atomic clocks on Earth. "As one of the most sensitive radio telescopes in the world, the GBT is primed to pick up these faint pulses of radio waves to study extreme physics," Lynch said. The neutron star in this system pulses (rotates) 366 times per second.

"We can account for every single pulse of the neutron star since we began our observations," said Anne Archibald of the University of Amsterdam and the Netherlands Institute for Radio Astronomy and principal author on the paper. "We can tell its location to within a few hundred meters. That is a really precise track of where the neutron star has been and where it is going."

If alternatives to Einstein's picture of gravity were correct, then the neutron star and the inner white dwarf would each fall differently toward the outer white dwarf. "The inner white dwarf is not as massive or compact as the neutron star, and thus has less gravitational binding energy," said Scott Ransom, an astronomer with the National Radio Astronomy Observatory in Charlottesville, Virginia, and co-author on the paper.

Through meticulous observations and careful calculations, the team was able to test the system's gravity using the pulses of the neutron star alone. They found that any acceleration difference between the neutron star and inner white dwarf is too small to detect.

"If there is a difference, it is no more than three parts in a million," said coauthor Nina Gusinskaia of the University of Amsterdam. This places severe constraints on any alternative theories to general relativity.

This result is ten times more precise that the previous best test of gravity, making the evidence for Einstein's Strong Equivalence Principle that much stronger. "We're always looking for better measurements in new places, so our quest to learn about new frontiers in our Universe is going to continue," concluded Ransom.

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The Gaia Sausage: The major collision that changed the Milky Way galaxy

An impression of the encounter between the Milky Way galaxy and the smaller Sausage galaxy about 8 billion to 10 billion years ago. The record of this ancient encounter is still preserved in the velocities and chemistry of the stars.

An international team of astronomers has discovered an ancient and dramatic head-on collision between the Milky Way and a smaller object, dubbed the "Sausage" galaxy. The cosmic crash was a defining event in the early history of the Milky Way and reshaped the structure of our galaxy, fashioning both its inner bulge and its outer halo, the astronomers report in a series of new papers.

The astronomers propose that around 8 billion to 10 billion years ago, an unknown dwarf galaxy smashed into our own Milky Way. The dwarf did not survive the impact: It quickly fell apart, and the wreckage is now all around us.

"The collision ripped the dwarf to shreds, leaving its stars moving in very radial orbits" that are long and narrow like needles, said Vasily Belokurov of the University of Cambridge and the Center for Computational Astrophysics at the Flatiron Institute in New York City. The stars' paths take them "very close to the centre of our galaxy. This is a telltale sign that the dwarf galaxy came in on a really eccentric orbit and its fate was sealed."

The new papers in the Monthly Notices of the Royal Astronomical Society, The Astrophysical Journal Letters and arXiv.org outline the salient features of this extraordinary event. Several of the papers were led by Cambridge graduate student GyuChul Myeong. He and colleagues used data from the European Space Agency's Gaia satellite. This spacecraft has been mapping the stellar content of our galaxy, recording the journeys of stars as they travel through the Milky Way. Thanks to Gaia, astronomers now know the positions and trajectories of our celestial neighbours with unprecedented accuracy.

The paths of the stars from the galactic merger earned them the moniker "the Gaia Sausage," explained Wyn Evans of Cambridge. "We plotted the velocities of the stars, and the sausage shape just jumped out at us. As the smaller galaxy broke up, its stars were thrown onto very radial orbits. These Sausage stars are what's left of the last major merger of the Milky Way."

The Milky Way continues to collide with other galaxies, such as the puny Sagittarius dwarf galaxy. However, the Sausage galaxy was much more massive. Its total mass in gas, stars and dark matter was more than 10 billion times the mass of our sun. When the Sausage crashed into the young Milky Way, its piercing trajectory caused a lot of mayhem. The Milky Way's disk was probably puffed up or even fractured following the impact and would have needed to regrow. And Sausage debris was scattered all around the inner parts of the Milky Way, creating the 'bulge' at the galaxy's centre and the surrounding 'stellar halo.'

Numerical simulations of the galactic mashup can reproduce these features, said Denis Erkal of the University of Surrey. In simulations run by Erkal and colleagues, stars from the Sausage galaxy enter stretched-out orbits. The orbits are further elongated by the growing Milky Way disk, which swells and becomes thicker following the collision.

Evidence of this galactic remodelling is seen in the paths of stars inherited from the dwarf galaxy, said Alis Deason of Durham University. "The Sausage stars are all turning around at about the same distance from the centre of the galaxy." These U-turns cause the density in the Milky Way's stellar halo to decrease dramatically where the stars flip directions. This discovery was especially pleasing for Deason, who predicted this orbital pileup almost five years ago. The new work explains how the stars fell into such narrow orbits in the first place.

The new research also identified at least eight large, spherical clumps of stars called globular clusters that were brought into the Milky Way by the Sausage galaxy. Small galaxies generally do not have globular clusters of their own, so the Sausage galaxy must have been big enough to host a collection of clusters.

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Biological switch reliably turns protein expression on at will

The left-hand group has no gene editing RNA or BOC. The next group has BOC but no RNA, and the third has RNA, but no BOC. The right-hand group has both gene editing machinery and BOC. BOC activates the switch and non-fluorescent pups result.

A biological switch that reliably turns protein expression on at will has been invented by University of Bath and Cardiff University scientists. The switch enables control of genome editing tools that might one day regulate cascades of desired genetic changes through entire populations.

This new switching method should work for any protein in any species and uses a cheap, non-toxic amino acid as the control switch -- the 'on' mode requires the presence of an amino acid called BOC.

In contrast to other reported switches, this method does not use antibiotics, removing risks of selecting for bacterial antibiotic resistance, and neither is it 'leaky' -- a situation in which proteins are expressed even when in 'off' mode, a problem faced by current methods that depend on temperature or light. The switch, an amino acid similar to lysine, is cheap, plentiful, non-toxic and should be environmentally-friendly.

The research teams in Bath and Cardiff successfully demonstrated the switch in both cultured cells and in early-stage mouse embryos without any detectable target protein expression activity in the absence of BOC.

The method extends a principle called genetic code expansion. To demonstrate the principle the team used transgenic mice carrying a gene that makes their skin glow green under UV light. When the genetic code expansion toolkit adapted for genome editing was present in embryos from the mice, their genomic DNA was efficiently edited to remove the fluorescence gene, but only when BOC was present. In the absence of BOC, no editing occurred. Embryos edited in this way could develop into mice that did not fluoresce, but without BOC no editing had occurred, so these mice remained green.

The study is published in the journal Scientific Reports.

The switch offers the potential to control a host of biological processes with the addition of BOC. These may include research and practical applications, in the laboratory test-tube, whole animals or both. For example, it might be used to address how certain proteins effect aging of cells in culture or animals. Clinically, it may provide a means to switch on proteins to enhance regenerative processes and could offer a new tier of control in gene therapy.

One exciting potential application would be in using the switch in gene drive technology. Gene drives can use the CRISPR-Cas9 system in a way that ensures all offspring in sexually reproducing species inherit a particular genetic segment, overcoming the 50% chance of inheritance that sexual reproduction might otherwise confer upon it.

Characteristics endowed by a gene drive can spread rapidly through a population regardless of whether or not they are advantageous -- for instance trials have been done using gene drives to spread genes in mosquitoes that make females infertile, intending to crash the population of the malaria-spreading insect.

However, multiple challenges must be met before gene drive usage is likely to be authorised. Once initiated, they are difficult or impossible to control and may work over wider areas than desired, for example straying across international borders. They may have unintended environmental consequences or give rise to resistance. Regulating gene drives by making Cas9 BOC-switchable promises to ameliorate these problems.

Professor Tony Perry, who led the Bath team from the Department of Biology & Biochemistry, said: "Our switch is a way of controlling the expression of any protein via genetic code expansion.

"What sets our work apart is the potential for this as an environmentally friendly switch across large distances, which no previous method really enables. For example you can imagine controlling gene drive activity in livestock herds by adding or removing BOC from feedstuffs as required.

"Gene editing has enormous potential across biological science, from biomedicine to food security, in insects, plants and animals."

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Marine mammals most at risk from increased Arctic ship traffic

Beluga whales in the pack ice in West Greenland. Ships using the Northwest Passage would travel through Baffin Bay off Greenland’s west coast.

In August 2016, the first large cruise ship traveled through the Northwest Passage, the northern waterway linking the Atlantic and Pacific oceans. The following year, the first ship without an icebreaker plied the Northern Sea Route, a path along Russia's Arctic coast that was, until recently, impassable by unescorted commercial vessels.

In recent decades parts of the Arctic seas have become increasingly ice-free in late summer and early fall. As sea ice is expected to continue to recede due to climate change, seasonal ship traffic from tourism and freight is projected to rise. A study from the University of Washington and the University of Alaska Fairbanks is the first to consider potential impacts on the marine mammals that use this region during fall and identify which will be most vulnerable.

The study is published the week of July 2 in the Proceedings of the National Academy of Sciences. "We know from more temperate regions that vessels and whales don't always mix well, and yet vessels are poised to expand into this sensitive region," said lead author Donna Hauser, who did the research as a postdoctoral researcher at the UW and is now a research assistant professor at the University of Alaska Fairbanks. "Even going right over the North Pole may be passable within a matter of decades. It raises questions of how to allow economic development while also protecting Arctic marine species."

The study looked at 80 subpopulations of the seven marine mammals that live in the Arctic and identified their risks on or near major shipping routes in September, a month when the Arctic Ocean has the most open water.

Forty-two of these subpopulations would be exposed to vessel traffic, and the degree of exposure plus the particular characteristics of each species determine which are most sensitive.

The most vulnerable marine mammals were found to be narwhals, or tusked whales. These animals migrate through parts of the Northwest Passage to and from their summertime habitats.

"Narwhals have all the traits that make them vulnerable to vessel disturbances -- they stick to really specific areas, they're pretty inflexible in where they spend the summer, they live in only about a quarter of the Arctic, and they're smack dab in the middle of shipping routes," said co-author Kristin Laidre, a polar scientist at UW Applied Physics Laboratory's Polar Science Center. "They also rely on sound, and are notoriously skittish and sensitive to any kind of disturbance."

Other mammals found to be vulnerable were beluga and bowhead whales. Walruses also were vulnerable because some populations are relatively small and known to live along shipping routes, compared to generally large and widely distributed populations of ringed and bearded seals, which were shown to be less vulnerable.

The study found the least vulnerable animals were polar bears, which are largely on land during September, and don't rely on underwater sound for communication or navigation. Shipping in other seasons may have a greater impact.

The paper also identified two "pinch points," narrow passageways where ships and animals are most likely to intersect. These are the Bering Strait that separates the U.S. and Russia, and Lancaster Sound in the northern Canadian territory of Nunavut. These regions had a risk of conflicts two to three times higher than on other parts of the shipping route.

"These obligatory pinch points are used by migratory species to get in and out of the Arctic, but they are also necessary passageways for vessels using these sea routes," Hauser said. "Identifying the relative risks in Arctic regions and among marine mammals can be helpful when establishing strategies to deal with potential effects."

Travel through the Arctic Ocean is already beginning, with the Russian route having the most potential for commercial ships. The Northern Sea Route had more than 200 ships from 2011 to 2016, all of which were large vessels. More than 100 vessels passed through the Northwest Passage during that time, with more than half being small, private vessels like personal yachts.

The International Maritime Organization in May established the first international guidelines for vessel traffic in the Arctic Ocean. The voluntary code was proposed by the U.S. and Russia to identify safe routes through the Bering Strait.

The new study could help to create future guidelines, prioritize different measures to protect marine mammals and identify areas needing further study, the authors said.

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Oldest evidence of horse veterinary care discovered in Mongolia

Horses congregate near a deer stone site in Bayankhongor, in central Mongolia's Khangai mountains.

A team of scholars, led by William Taylor of the Max Planck Institute for the Science of Human History, analyzed horse remains from an ancient Mongolian pastoral culture known as the Deer Stone-Khirigsuur Culture (ca. 1300-700 BC). Deer stones, with their beautiful deer carvings, and their accompanying stone mounds (khirigsuurs) are famous for the impressive horse burials that are found alongside them in the dozens, hundreds, or even thousands. Through careful study of skeletal remains from these burials, published in Proceedings of the National Academy of Sciences and funded in part by a grant from the National Geographic Society, Taylor and colleagues found that Deer Stone-Khirigsuur people began using veterinary dental procedures to remove baby teeth that would have caused young horses pain or difficulty with feeding -- the world's oldest known evidence for veterinary dental care.

Previous research has shown that these early herders were the first in eastern Eurasia to rely heavily on horses as livestock for food products, and may have been among the first to use horses for mounted riding. Drawing on insights from his Mongolian colleagues, Jamsranjav Bayarsaikhan and Tumurbaatar Tuvshinjargal of the National Museum of Mongolia, Taylor argues that the development of horseback riding and a horse-based pastoral economy was a key driver for the invention of equine veterinary care. "We may think of veterinary care as kind of a Western science," he says, "but herders in Mongolia today practice relatively sophisticated procedures using very simple equipment. This results of our study show that a careful understanding of horse anatomy and a tradition of care was first developed, not in the sedentary civilizations of China or the Mediterranean, but centuries earlier, among the nomadic people whose livelihood depended on the well-being of their horses."

Additionally, Taylor and his team discovered that changes in horse dentistry accompanied major developments in horse control technology, including the incorporation of bronze and metal mouthpieces into bridles used for riding. This equipment, which spread into eastern Eurasia during the early first millennium BC, gave riders more nuanced control over horses, and allowed them to be used for new purposes -- especially warfare. However, using metal to control horses also introduced new oral problems, including painful interactions with a vestigial tooth that develops in some animals, known as a "wolf tooth." Taylor and his team discovered that, as herders began to use metal bits, they also developed a method for extracting this problematic tooth -- similar to the way most veterinary dentists would remove it today.

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'Cataclysmic' collision shaped Uranus' evolution

The collision with Uranus of a massive object twice the size of Earth that caused the planet's unusual spin, from a high-resolution simulation using over ten million particles, coloured by their internal energy.

Uranus was hit by a massive object roughly twice the size of Earth that caused the planet to tilt and could explain its freezing temperatures, according to new research.

Astronomers at Durham University, UK, led an international team of experts to investigate how Uranus came to be tilted on its side and what consequences a giant impact would have had on the planet's evolution.

The team ran the first high-resolution computer simulations of different massive collisions with the ice giant to try to work out how the planet evolved.

The research confirms a previous study which said that Uranus' tilted position was caused by a collision with a massive object -- most likely a young proto-planet made of rock and ice -- during the formation of the solar system about 4 billion years ago.

The simulations also suggested that debris from the impactor could form a thin shell near the edge of the planet's ice layer and trap the heat emanating from Uranus' core. The trapping of this internal heat could in part help explain Uranus' extremely cold temperature of the planet's outer atmosphere (-216 degrees Celsius, -357 degrees Fahrenheit), the researchers said.

The findings are published in The Astrophysical Journal.

Lead author Jacob Kegerreis, PhD researcher in Durham University's Institute for Computational Cosmology, said: "Uranus spins on its side, with its axis pointing almost at right angles to those of all the other planets in the solar system. This was almost certainly caused by a giant impact, but we know very little about how this actually happened and how else such a violent event affected the planet.

"We ran more than 50 different impact scenarios using a high-powered super computer to see if we could recreate the conditions that shaped the planet's evolution.

"Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today."

There has been a question mark over how Uranus managed to retain its atmosphere when a violent collision might have been expected to send it hurtling into space.

According to the simulations, this can most likely be explained by the impact object striking a grazing blow on the planet. The collision was strong enough to affect Uranus' tilt, but the planet was able to retain the majority of its atmosphere.

The research could also help explain the formation of Uranus' rings and moons, with the simulations suggesting the impact could jettison rock and ice into orbit around the planet. This rock and ice could have then clumped together to form the planet's inner satellites and perhaps altered the rotation of any pre-existing moons already orbiting Uranus.

The simulations show that the impact could have created molten ice and lopsided lumps of rock inside the planet. This could help explain Uranus' tilted and off-centre magnetic field.

Uranus is similar to the most common type of exoplanets -- planets found outside of our solar system -- and the researchers hope their findings will help explain how these planets evolved and understand more about their chemical composition.

Co-author Dr Luis Teodoro, of the BAER/NASA Ames Research Center, said: "All the evidence points to giant impacts being frequent during planet formation, and with this kind of research we are now gaining more insight into their effect on potentially habitable exoplanets."

Read more at Science Daily

Cracking the genetic code of koalas

Mother koala with baby on her back.

A team of Australian and international scientists, led by Professor Rebecca Johnson, Director of the Australian Museum Research Institute and Professor Katherine Belov, University of Sydney, have made a significant break-through successfully sequencing the full koala genome, with the findings published today in Nature Genetics.

Considered to be the most complete marsupial genome sequenced to date, it is in terms of quality, on par with the human genome. The highly accurate genomic data will provide scientists with new information that will inform conservation efforts, aid in the treatment of diseases, and help to ensure the koala's long-term survival.

"The Koala Genome Consortium has been an ambitious journey affording us great insights into the genetic building blocks that make up a koala -- one of Australia's, as well as the world's, most charismatic and iconic mammals," Professor Johnson said.

"This milestone has come from our vision to use genomics to conserve this species. The genetic blueprint has not only unearthed a wealth of data regarding the koalas unusual and highly specialised diet of eucalyptus leaves, but also provides important insights into their immune system, population diversity and the evolution of koalas," she said.

Co-lead author at the University of Sydney, Professor of Comparative Genomics, Katherine Belov said:

"The genome provides a springboard for the conservation of this biologically unique species."

The Australian led consortium of scientists comprised 54 scientists from 29 different institutions across seven countries. They have sequenced over 3.4 billion base pairs and more than 26,000 genes in the Koala genome -- which makes it slightly larger than the human genome. Unlocking the genomic sequence gives scientists unprecedented insights into the unique biology of the koala.

Professor Johnson said the uneven response of koala populations throughout their range was one of the major challenges facing broad scale management of the species.

"The genome enables a holistic and scientifically grounded approach to koala conservation," she said. "Australia has the highest mammal extinction record of any country during the Anthropocene.

"Koala numbers have plummeted in northern parts of its range since European settlement, but have increased in some southern parts, notably in Victoria and South Australia."

Director and CEO, Australian Museum, Kim McKay, AO congratulated Professor Johnson and the team on this achievement.

"Today we celebrate the completion of the highest quality, marsupial genome sequencing undertaken to date. This work was brought about through the meticulous efforts not only of Professor Johnson and Professor Belov, but also the contributions from many other Australian Museum scientists, as well as scientists from around the nation and the world. It will usher in a new era in our understanding and conservation of the iconic koala," she said.

Professor Jennifer Graves, AO, Distinguished Professor of Genetics, La Trobe University and winner of the 2017 PM's Prize for Science, said: "We could never have imagined, when we were pioneering koala genetics in the 1980s, that one day we'd have the entire koala genome sequence. This opens up all sorts of ways we can monitor the genetic health of koala populations."

The Koala Genome Consortium announced the establishment of the project in 2013 with its first unassembled draft genome. The collective aim was to steer their research towards ensuring the long-term survival of this important marsupial while simultaneously increasing Australia's genomics capability.

Since then, researchers have worked tirelessly to assemble this genome into the most complete and accurate marsupial genome to date and annotate its 26,000 genes for analysis. The koala genome has been sequenced to an accuracy of 95.1%, which is comparable to that of the human genome.

The 3.4 billion base pairs of the published Koala genome were sequenced at the Ramaciotti Centre for Genomics, at the University of New South Wales, using new sequencing technology.

"We then assembled the genome with supercomputers, allowing the Consortium to then study the >20,000 genes of this unique species," said Professor Marc Wilkins, Director, Ramaciotti Centre for Genomics, UNSW.

Consortium members from the Earlham Institute (EI), (Norwich, UK) identified that koalas have two large expansions in a gene family known to be integral to detoxification, the Cytochrome P450 gene family of metabolic enzymes. They found these genes to be expressed in many koala tissues, particularly in the liver; indicating they have a very important function in detoxification and likely allowed koalas to become dietary specialists.

As Professor Johnson explains, "this probably helped them to find their niche to survive, as they could rely on a food source that would have less competition from other species who were not able to detoxify as effectively."

Dr Will Nash in the Haerty Group at Earlham Institute, said: "Gene duplication can lead to copies of genes associated with specific functions being retained in the genome. In the Koala, the largest group of retained copies make an enzyme that breaks down toxins. This means the Koala has evolved an excellent toolkit to deal with eating highly toxic eucalypts, one made up of lots of copies of the same (or very similar) tools."

According to Professor Belov, another important discovery was the characterisation of the composition of koala milk. Like all marsupials, koalas do the majority of their development in the pouch. They are born without an immune system after 34-36 days gestation and spend ~6 months developing in the pouch.

"We characterised the main components of the mothers' milk -- which is crucial for koala joeys -- born the size of a kidney bean and weighing half of one gram," Professor Belov said.

"We identified genes that allow the koala to finetune milk protein composition across the stages of lactation, to meet the changing needs of their young."

"Thanks to the high-quality genome, the team was able to analyse and discover koala-specific milk proteins that are critical for various stages of development. It also appears these proteins may have an antimicrobial role, showing activity against a range of bacterial and fungal species, including Chlamydia pecorum, the strain known to cause ocular and reproductive disease in koalas," she said.

Chlamydia causes infertility and blindness and has severely impacted koala populations in New South Wales and Queensland. Using information gained from the koala genome, scientists hope to develop a vaccine to fight diseases like Chlamydia.

Professor Peter Timms, University of the Sunshine Coast said: "In addition to Chlamydia, the other major infection that is threatening the species is koala retrovirus (KoRV), however very little is presently known about it. The complete koala genome has been instrumental in showing that an individual koala can have many (more than a hundred) insertions of KoRV into its genome, including many versions of KoRV.

"This information will enable to determine which strains of KoRV are more dangerous and to assist with our development of a KoRV vaccine," he said.

One of the most threatening processes to koala survival is loss of habitat through land clearing and urbanisation which results in a reduction of habitat connectivity, reduced genetic diversity and puts koalas at high risk of inbreeding. The results of inbreeding can be highly detrimental to survival of those koala populations as it leads to reduced genetic diversity.

Professor Johnson added: "For the first time, using over 1000 genome linked markers, we are able to show that NSW and QLD populations show significant levels of genetic diversity and long-term connectivity across regions.

"Ensuring this genetic diversity is conserved in concert with other conservation measures to protect habitat, reduce vehicle strikes, dog attacks and disease, are the keys to the long-term survival of the koala."

Dr Graham Etherington in the Di Palma Group at the Earlham Institute, said: "With its puppy-dog looks, the Koala is an internationally recognised species. But this iconic Australian marsupial is not just a pretty face.

"The Koala genome assembly is by far the most comprehensive marsupial genomic resource to date, which allows us an insight into how this unique animal came to be and provides us with information about potential threats to its survival. It also provides us with an excellent platform to launch further marsupial genome projects that could look into potential genetic reservoirs of previously unknown anti-microbial genes that could be leveraged for human health.

"Additionally, it provides us with an incredible amount of information about genetic diversity across different populations of koalas that can be used as a benchmark for further studies on other endangered marsupial species."

This genomic sequencing represents the new generation of science-based conservation policy as it has already been integrated as an important pillar into the NSW Koala Strategy 2018.

All of the sequence data generated by The Koala Genome Consortium has been deposited into public databases and made freely available to scientists around the world.

"Not only does open data promote the best interests of science, it also maximises the benefits that the koala populations, and the public, receive from such research," Professor Johnson said.

The koala (Phascolarctos cinereus) is a native tree-dwelling Australian marsupial that is one of the world's most fascinating and iconic mammals. Not only is the koala synonymous with Australia it is also a powerful international symbol for the preservation and conservation of our natural world.

Wild koalas are currently found in eucalypt forest and woodlands across Eastern Australia (Victoria, New South Wales and Queensland) and have been translocated to other sites, such as south eastern South Australia and onto some islands such as Kangaroo Island, South Australia and French Island,Victoria.

Their unique and highly specific diet of eucalyptus (gum) tree leaves, has resulted in koalas being especially vulnerable to habitat loss due to the clearing of native vegetation for agriculture and urban development. The Australian Federal government lists koala populations in Queensland, New South Wales and Australian Capital Territory as 'Vulnerable' under national environment law.

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Stability of Earth: Scientists propose solution to 'Gaia puzzle'

Earth.

Scientists may have solved a long-standing puzzle over why conditions on Earth have remained stable enough for life to evolve over billions of years. The 'Gaia' hypothesis proposed that living things interacting with inorganic processes somehow keep the planet in a state where life can persist -- despite threats such as a brightening sun, volcanoes and meteorite strikes.

The puzzle of how this might work has divided experts for decades, but a team led by scientists from the University of Exeter have proposed a solution. They say stability could come from "sequential selection" in which situations where life destabilises the environment tend to be short-lived and result in further change until a stable situation emerges, which then tends to persist.

Once this happens, the system has more time to acquire further traits that help to stabilise and maintain it -- a process known as "selection by survival alone."

"We can now explain how the Earth has accumulated stabilising mechanisms over the past 3.5 billion years of life on the planet," said Professor Tim Lenton, of the University of Exeter.

"The central problem with the original Gaia hypothesis was that evolution via natural selection cannot explain how the whole planet came to have stabilising properties over geologic timescales."

"Instead, we show that at least two simpler mechanisms work together to give our planet with life self-stabilising properties."

He added: "Our findings can help explain how we came to be here to wonder about this question in the first place."

Professor Dave Wilkinson, of the University of Lincoln, who was also involved in the research, added: "I have been involved in trying to figure out how

Gaia might work for over 20 years -- finally it looks like a series of promising ideas are all coming together to provide the understanding I have been searching for."

Dr James Dyke, of the University of Southampton, also an author on the paper, said: "As well as being important for helping to estimate the probability of complex life elsewhere in the universe, the mechanisms we identify may prove crucial in understanding how our home planet may respond to drivers such as human-produced climate change and extinction events."

Creating transformative solutions to the global changes that humans are now causing is a key focus of the University of Exeter's new Global Systems Institute, directed by Professor Lenton, who said: "We can learn some lessons from Gaia on how to create a flourishing, sustainable, stable future for 9-11 billion people this century."

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Loss of lemurs might endanger many of Madagascar's largest tree species

This is a Black-and-white ruffed lemur.

Widespread logging and hunting have endangered virtually all of Madagascar's 100-plus species of iconic lemurs, and a new study by Rice University ecologists illustrates how saving the animals may also be key to saving the island's largest trees.

"Forest loss is a huge problem in Madagascar right now, but our study suggests that just saving the trees is not enough," said Amy Dunham, associate professor of biosciences at Rice and co-author of a paper appearing online today in a special issue of the International Journal of Primatology. "Not only are we facing the loss of these unique, charismatic animals, we're also losing their role in the ecosystem. Without lemurs, the rainforests themselves will change because the lemurs alone disperse the seeds of many of the forests' largest hardwoods."

The study builds upon nearly a decade of collaborative work by Dunham and lead author Onja Razafindratsima at the island nation's Ranomafana National Park.

Lemurs mostly eat fruit, and for many of the largest trees in Madagascar, lemurs are the only animals large enough to ingest the seeds of their fruit. By dispersing seeds throughout the forest in their scat, lemurs serve as the unwitting gardeners of these large canopy trees.

In earlier work, Razafindratsima meticulously tracked 24 groups of lemurs for three years and showed that the seeds of one species of canopy tree had a 300 percent greater chance of sprouting and becoming a sapling when they were dispersed by lemurs as opposed to simply falling to the ground.

"That work and other studies have suggested that lemur loss is likely to reduce regeneration of trees that rely on lemurs for seed dispersal," Dunham said. "In the latest study, we wanted to take a broader approach to understanding how the forest might change with lemur loss."

In 2016, Rice undergraduate Anecia Gentles joined Dunham's research group and spent a year examining characteristics of rainforest trees and programming computational models to estimate how the forest would change if lemurs disappeared. Rice graduate student Andrea Drager also joined the effort, and the team showed that lemurs are not only important as gardeners of the forest but also likely play an important role in forest carbon sequestration.

"We found that lemurs are the primary seed dispersers of the largest canopy trees," said Gentles, who graduated from Rice in May. "The models suggested that the loss of lemurs and the trees they disperse could lead to increasing abundances of smaller, fast-growing tree species with lighter wood."

Dunham said, "The biggest trees in Madagascar are dense hardwoods that grow more slowly but also store more carbon. They also tend to have the biggest seeds."

The team used trait measurements from more than 7,000 trees of nearly 300 species. The data were collected as part of the Tropical Ecology Assessment and Monitoring (TEAM) Network, a yearslong effort led by study co-authors Jean-Claude Razafimahaimodison and Claude Ralazampirenena, Malagasy scientists from the Centre ValBio, a research station at Ranomafana National Park.

"We used TEAM Network data, new data and previously published data on animal seed dispersal in the park to make models that show what would happen if lemur-dispersed trees started disappearing and were replaced by trees whose seeds are dispersed by birds, the wind or other methods less affected by human activities," Dunham said.

The models explored how the makeup of the forests might change in different scenarios ranging from one in which lemur-dispersed trees declined by 25 percent to an extreme case where all lemur-dispersed trees were wiped out.

"There still would be a forest, but the makeup of trees would be quite different, and the forest's ability to sequester carbon would be greatly diminished," Dunham said. "For example, in the case where all lemur-dispersed trees disappear from just one hectare of forest, a patch of 2 1/2 acres, the average loss of above-ground biomass is 24 metric tons -- or almost 53,000 pounds."

She said the findings have implications for initiatives like the United Nations' REDD program, which incentivizes carbon sequestration through forest conservation.

"The goal of such programs is to preserve forests, because there's a lot of carbon in the biomass of trees," Dunham said. "At the same time, tropical forest ecosystems globally are threatened by the loss of large fruit-eating animals, and there's growing evidence that we need to think more holistically about conserving functioning ecosystems in order to save forests.

"For Malagasy forests, our study connects the dots and shows that integrated forest protection and lemur conservation are required in order to maximize carbon-storage potential," she said.

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