Antarctic Circumpolar Current flows more rapidly in warm phases

In future the intensity of the Antarctic Circumpolar Current could increase, accelerating climate change

ALFRED WEGENER INSTITUTE, HELMHOLTZ CENTRE FOR POLAR AND MARINE RESEARCH

Research News

 

Our planet's strongest ocean current, which circulates around Antarctica, plays a major role in determining the transport of heat, salt and nutrients in the ocean. An international research team led by the Alfred Wegener Institute has now evaluated sediment samples from the Drake Passage. Their findings: during the last interglacial period, the water flowed more rapidly than it does today. This could be a blueprint for the future and have global consequences. For example, the Southern Ocean's capacity to absorb CO2 could decrease, which would in turn intensify climate change. The study has now been published in the journal Nature Communications.

The Antarctic Circumpolar Current (ACC) is the world's strongest ocean current. Since there are no landmasses blocking its way, the West Wind Drift drives the water unhindered eastwards around the Antarctic in a clockwise direction. As a result, a gigantic ring-shaped current forms, linking together the Pacific, Atlantic and Indian Oceans in the south. The ACC is the central distribution point in global ocean circulation - also known as the 'global conveyor belt' - and as such influences oceanic heat transport and marine material cycles around the planet. Major changes in the ACC therefore have global consequences.

"Although the ACC plays an important role in tomorrow's climate, our understanding of its behaviour is still extremely limited," says Dr Shuzhuang Wu, a researcher at the Marine Geosciences Section of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and first author of the study released in Nature Communications. "In order to remove the related uncertainties in the climate models and to improve future forecasts, we urgently need paleo-data, which we can use to reconstruct the conditions and behaviour of the ACC in the past."

The only constriction on the ACC's circular route is the Drake Passage between the southern tip of South America and the Northern tip of the Antarctic Peninsula. Here, no less than 150 million cubic metres of ocean water per second force their way through the Passage - more than 150 times the amount of water flowing in all of Earth's rivers. This bottleneck is an ideal place to observe changes in the overall current. Accordingly, in 2016, AWI researchers travelled to the Drake Passage on board the research icebreaker Polarstern to investigate the sediment deposits from past millennia. "The bottom current here is so strong that in many places the sediment is simply washed away," explains the leader of the expedition and co-author of the study, Dr Frank Lamy. "Nevertheless, using the Polarstern's sediment echo sounder, we were able to detect the pockets of sediment and collect samples, including a core from a depth of 3,100 meters, measuring more than 14 metres in length. This was a significant achievement, since the last comparable cores from the Drake Passage dated back to the 1960s."

The sediments from the new core accumulated over the last 140,000 years. As such, they cover an entire glacial-interglacial cycle, and contain information from the last glacial period, which began 115,000 years ago and ended 11,700 years ago, as well as from the preceding Eemian interglacial period, which began 126,000 years ago.

By analysing the particle size in the deposited sediments, the research team was able to reconstruct the flow speed and the volume of water transported by the ACC in the Drake Passage. Based on the high percentage of small particles at the height of the last glacial period, the researchers calculated that the speed was slower compared to today, and there was a significantly smaller volume of water. This was due to the weaker westerlies and the more extensive sea ice in the Passage. This means that during the glacial period, the ACC's main driver blew more weakly, and the area of exposed water was smaller. In contrast, the extremely large particles at the height of the interglacial period indicated a high flow speed and a flow rate 10-15 percent higher than today.

"At the height of the last interglacial period from 115,000 to 130,000 years before today, the global temperature was on average 1.5° to 2° C warmer than it is today. Accordingly, the Circumpolar Current could accelerate as global warming progresses," says Lamy. "That would have far-reaching effects on the climate. On the one hand, the ACC shapes other ocean currents like the Gulf Stream, which in turn plays a role in determining the weather in Northwest Europe. On the other, the oceans absorb roughly a third of the surplus CO2 from the atmosphere. However, a more rapid ACC would promote the transport of CO2-rich deep water to the surface. Accordingly, the ocean's capacity to absorb atmospheric CO2 could decline significantly, and the concentration in the air could rise more quickly. In the long term, large parts of the Southern Ocean could even become sources of CO2."

###

Original publication:

Shuzhuang Wu, Lester Lembke-Jene, Frank Lamy, Helge W. Arz, Norbert Nowaczyk, Wenshen Xiao, Xu Zhang, H. Christian Hass, Ju?rgen Titschack, Xufeng Zheng, Jiabo Liu, Levin Dumm, Bernhard Diekmann, Dirk Nu?rnberg, Ralf Tiedemann, Gerhard Kuhn: Orbital- and millennial-scale Antarctic Circumpolar Current variability in Drake Passage over the past 140,000 years. Nature Communications (2021), DOI: 10.1038/s41467-021-24264-9

New knowledge of Earth's mantle helps to explain Indonesia's explosive volcanoes

UPPSALA UNIVERSITY

Research News

 

IMAGE: AGUNG, A VOLCANO IN BALI, HAD AN EXPLOSIVE ERUPTION IN 2018. view more 

CREDIT: O.L. ANDERSEN

Indonesia's volcanoes are among the world's most dangerous. Why? Through chemical analyses of tiny minerals in lava from Bali and Java, researchers from Uppsala University and elsewhere have found new clues. They now understand better how the Earth's mantle is composed in that particular region and how the magma changes before an eruption. The study is published in Nature Communications.

Frances Deegan, the study's first author and a researcher at Uppsala University's Department of Earth Sciences, summarises the findings.

"Magma is formed in the mantle, and the composition of the mantle under Indonesia used to be only partly known. Having better knowledge of Earth's mantle in this region enables us to make more reliable models for the chemical changes in magma when it breaks through the crust there, which is 20 to 30 kilometres thick, before an eruption."

The composition of magma varies greatly from one geological environment to another, and has a bearing on the kind of volcanic eruption that occurs. The Indonesian archipelago was created by volcanism, caused by two of Earth's continental tectonic plates colliding there. In this collision, Indo-Australian plate slides beneath the Eurasian plate at a speed of some 7 cm annually. This process, known as subduction, can cause powerful earthquakes. The tsunami disaster of 2004, for example, was caused by movements along this particular plate boundary.

Volcanism, too, arises in subduction zones. When the sinking tectonic plate descends into the mantle, it heats up and the water it contains is released, causing the surrounding rock to start melting. The result is volcanoes that are often explosive and, over time, build up arc-shaped groups of islands. Along the Sunda Arc, comprising Indonesia's southern archipelago, several cataclysmic volcanic eruptions have taken place. Examples are Krakatoa in 1883, Mount Tambora in 1815 and Toba, which had a massive super-eruption some 72,000 years ago.

Magma reacts chemically with surrounding rock when it penetrates Earth's crust before breaking out on the surface. It can therefore vary widely among volcanoes. To get a better grasp of the origin of volcanism in Indonesia, the researchers wanted to find out the composition of the "primary" magma, that is derived from the mantle itself. Since samples cannot be taken directly from the mantle, geologists studied minerals in lava recently ejected from four volcanoes: Merapi and Kelut in Java, and Agung and Batur in Bali.

Using the powerful ion beams from a secondary ion mass spectrometry (SIMS) instrument, an ultramodern form of mass spectrometer, the researchers examined crystals of pyroxene. This mineral is one of the first to crystallise from a magma. What they wanted to determine was the ratio of the oxygen isotopes 16O and 18O, which reveals a great deal about the source and evolution of magma.

"Lava consists of roughly 50 per cent oxygen, and Earth's crust and mantle differ hugely in their oxygen isotope composition. So, to trace how much material the magma has assimilated from the crust after leaving the mantle, oxygen isotopes are very useful," Frances Deegan says.

The researchers found that the oxygen composition of pyroxene minerals from Bali had hardly been affected at all during their journey through Earth's crust. Their composition was fairly close to their original state, indicating that a minimum of sediment had been drawn down into the mantle during subduction. An entirely different pattern was found in the minerals from Java.

"We were able to see that Merapi in Java exhibited an isotope signature very different from those of the volcanoes in Bali. It's partly because Merapi's magma interacts intensively with Earth's crust before erupting. That's highly important because when magma reacts with, for instance, the limestone that's found in central Java right under the volcano, the magma becomes full to bursting point with carbon dioxide and water, and the eruptions get more explosive. That may be why Merapi's so dangerous. It's actually one of the deadliest volcanoes in Indonesia: it's killed nearly 2,000 people in the past 100 years, and the most recent eruption claimed 400 lives," says Professor Valentin Troll of Uppsala University's Department of Earth Sciences.

The study is a collaboration among researchers at Uppsala University, the Swedish Museum of Natural History in Stockholm, the University of Cape Town in South Africa, the University of Freiburg in Germany and Vrije Universiteit (VU) Amsterdam in the Netherlands. The results of the study enhance our understanding of how volcanism in the Indonesian archipelago works.

"Indonesia is densely populated, and everything that gives us a better grasp of how these volcanoes work is valuable, and helps us to be better prepared for when the volcanoes erupt," says Frances Deegan.

###

Deegan, F.M., et al. (2021), Sunda arc mantle source δ18O value revealed by intracrystal isotope analysis. Nature Communications. DOI: 10.1038/s41467-021-24143-3

CAPTION

The SIMS instrument at the Swedish Museum of Natural History in Stockholm, which the researchers used to investigate the oxygen isotope composition of minerals in various lavas from Indonesia.

CREDIT

Frances Deegan

Tiny ancient bird from China shares skull features with Tyrannosaurus rex

CHINESE ACADEMY OF SCIENCES HEADQUARTERS

Research News

 

IMAGE: DIGITAL RECONSTRUCTION OF THE NEW MESOZOIC BIRD FOSSIL SKELETON (SCALE BAR: 10 MM). view more 

CREDIT: WANG MIN

Researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences have discovered a 120-million-year-old partial fossil skeleton of a tiny extinct bird that fits in the palm of the hand and preserves a unique skull with a mix of dinosaurian and bird features.

The two-centimeter-long (0.75 inch) skull of the fossil shares many structural and functional features with the gigantic Tyrannosaurus rex, indicating that early birds kept many features of their dinosaurian ancestors and their skulls functioned much like those of dinosaurs rather than living birds.

Their findings were published in Nature Communications on June 23.

The bird was deposited 120 million years ago in a shallow lake in what is today Liaoning Province in northeastern China.

Through detailed reconstruction of the bird family tree, the researchers demonstrated that the new fossil bird species belongs to an extinct group of birds called enantiornithines, or "opposite birds." They are the most diverse group of birds from the time of the dinosaurs in the Cretaceous and have been found all over the world.

In living birds, the quadrate is one of the most movable bones in the skull and allows for the unique feature of living birds known as "kinetic skull," which allows the upper jaw to move independently of the brain and the lower jaw.

In contrast with living birds, however, the skull of this new "opposite bird", as well as those of dinosaurs like Tyrannosaurus rex and the close dinosaurian relatives of birds (e.g., troodontids and dromaeosaurs), is not kinetic. Instead, its bones are "locked up" and unable to move.

The temporal regions (sides) of the skull of this bird fossil are very different from living birds. This new species has two bony arches for jaw muscle attachment like those found in reptiles such as lizards, alligators, and dinosaurs, making the rear of the skull rigid and resistant to movement among the bones.

"When reconstructing all parts of the skull three-dimensionally from the high resolution CT scans of the fossil, I had a problem figuring out one bone in particular," said Dr. WANG Min, the lead and corresponding author of the study. He said his colleague Dr. Thomas Stidham proposed that the bone was the pterygoid and looked "exactly like that of the dromaeosaur Linheraptor." The fossil has the first well-preserved pterygoid bone found in an early bird.

The researchers compared CT scans of the bird skull to scans of the skull of the well-known dromaeosaur Linheraptor from Inner Mongolia, China. The results showed that many other features of the rear portion of the skull, including the shape of the basisphenoid bone and its connections with other skull bones, also resemble dromaeosaurs rather than living birds.

"The fossil bird and dinosaurs also lack the discrete contact between the pterygoid and quadrate near the palate that is used in skull kinesis in living birds. In combination with the 'locked up' temporal bones, the difference in the palate structure also points to the absence of kinesis among early birds," said Dr. Stidham, co-author of the study.

Furthermore, the team's discovery and meticulous anatomical research help to reinforce the already well-supported contention, based on many different lines of evidence, that birds are not only living dinosaurs, but evolved from the branch of dinosaurs that includes troodontids and dromaeosaurs like the "four-winged" Microraptor and swift Velociraptor.

"Having a 'dinosaur' skull on a bird body certainly did not stop the enantiornithines, or other early birds, from being highly successful in places all around the world for tens of millions of years during the Cretaceous," said Dr. WANG.

CAPTION

Digital reconstruction of the new Mesozoic bird skull with expanded detail of the dinosaur-like palatal bones, i.e., the basisphenoid (red), pterygoid (pink), and quadrate (purple). The stars indicate the two parts of the pterygoid prong that extend behind the eye.

CREDIT

WANG Min

Research team discovers Arctic dinosaur nursery

UNIVERSITY OF ALASKA FAIRBANKS

Research News

 

IMAGE: GREG ERICKSON AND PAT DRUCKENMILLER PLACE A PLASTER JACKET ON A BONE FOUND ALONG THE COLVILLE RIVER ON ALASKA'S NORTH SLOPE. view more 

CREDIT: PHOTO BY KEVIN MAY

Images of dinosaurs as cold-blooded creatures needing tropical temperatures could be a relic of the past.

University of Alaska Fairbanks and Florida State University scientists have found that nearly all types of Arctic dinosaurs, from small bird-like animals to giant tyrannosaurs, reproduced in the region and likely remained there year-round.

Their findings are detailed in a new paper published in the journal Current Biology.

"It wasn't long ago that people were pretty shocked to find out that dinosaurs lived up in the Arctic 70 million years ago," said Pat Druckenmiller, the paper's lead author and director of the University of Alaska Museum of the North. "We now have unequivocal evidence they were nesting up there as well. This is the first time that anyone has ever demonstrated that dinosaurs could reproduce at these high latitudes."

The findings counter previous hypotheses that the animals migrated to lower latitudes for the winter and laid their eggs in those warmer regions. It's also compelling evidence that they were warm-blooded.

For more than a decade, Druckenmiller and Gregory Erickson, a Florida State University professor of biological science, have conducted fieldwork in the Prince Creek Formation in northern Alaska. They have unearthed many dinosaur species, most of them new to science, from the bluffs above the Colville River.

Their latest discoveries are tiny teeth and bones from seven species of perinatal dinosaurs, a term that describes baby dinosaurs that are either just about to hatch or have just hatched.

"One of the biggest mysteries about Arctic dinosaurs was whether they seasonally migrated up to the North or were year-round denizens," said Erickson, a co-author of the paper. "We unexpectedly found remains of perinates representing almost every kind of dinosaur in the formation. It was like a prehistoric maternity ward."

Recovering the bones and teeth, some no larger than the head of a pin, requires perseverance and a sharp eye. In the field, the scientists hauled buckets of sediment from the face of the bluffs down to the river's edge, where they washed the material through smaller and smaller screens to remove large rocks and soil.

Once back at their labs, Druckenmiller, Erickson and co-author Jaelyn Eberle from the University of Colorado, Boulder, screened the material further. Then, teaspoon by teaspoon, the team, which included graduate and undergraduate students, examined the remaining sandy particles under microscopes to find the bones and teeth.

"Recovering these tiny fossils is like panning for gold," Druckenmiller said. "It requires a great amount of time and effort to sort through tons of sediment grain-by-grain under a microscope. The fossils we found are rare but are scientifically rich in information."

Next, the scientists worked with Caleb Brown and Don Brinkman from the Royal Tyrrell Museum of Palaeontology in Alberta, Canada, to compare the fossils to those from other sites at lower latitudes. Those comparisons helped them conclude that the bones and teeth were from perinatal dinosaurs.

Once they knew the dinosaurs were nesting in the Arctic, they realized the animals lived their entire lives in the region.

Erickson's previous research revealed that the incubation period for these types of dinosaurs ranges from three to six months. Because Arctic summers are short, even if the dinosaurs laid their eggs in the spring, their offspring would be too young to migrate in the fall.

Global temperatures were much warmer during the Cretaceous, but the Arctic winters still would have included four months of darkness, freezing temperatures, snow and little fresh vegetation for food.

"As dark and bleak as the winters would have been, the summers would have had 24-hour sunlight, great conditions for a growing dinosaur if it could grow quickly enough before winter set in," said Brown, a paleontologist at the Royal Tyrrell Museum.

Year-round Arctic residency provides a natural test of the animals' physiology, Erickson added.

"We solved several long-standing mysteries about the dinosaur reign, but opened up a new can of worms," he said. "How did they survive Arctic winters?"

"Perhaps the smaller ones hibernated through the winter," Druckenmiller said. "Perhaps others lived off poor-quality forage, much like today's moose, until the spring."

Scientists have found warm-blooded animal fossils in the region, but no snakes, frogs or turtles, which were common at lower latitudes. That suggests the cold-blooded animals were poorly suited for survival in the cold temperatures of the region.

"This study goes to the heart of one of the longest-standing questions among paleontologists: Were dinosaurs warm-blooded?" Druckenmiller said. "We think that endothermy was probably an important part of their survival."

###

 

CAPTION

The research team's camp sits on the banks of the Colville River on Alaska's North Slope, with the bluffs rising in the background.

CREDIT

Photo by Patrick Druckenmiller

CAPTION

Illustration showing a pair of adult tyrannosaurs and their young living in the Arctic during the Cretaceous Period.

CREDIT

Art by James Havens

Multiple dinosaur species not only lived in the Arctic, they also nested there

CELL PRESS

Research News

 

IMAGE: THIS PHOTOGRAPH SHOWS PERINATAL (BABY) DINOSAUR BONES AND TEETH FROM THE PRINCE CREEK FORMATION, NORTHERN ALASKA (PENNY IS 19 MM IN DIAMETER). view more 

CREDIT: PATRICK DRUCKENMILLER

In the 1950s, researchers made the first unexpected discoveries of dinosaur remains at frigid polar latitudes. Now, researchers reporting in the journal Current Biology on June 24 have uncovered the first convincing evidence that several species of dinosaur not only lived in what's now Northern Alaska, but they also nested there.

"These represent the northernmost dinosaurs known to have existed," says Patrick Druckenmiller of the University of Alaska Museum of the North. "We didn't just demonstrate the presence of perinatal remains--in the egg or just hatched--of one or two species, rather we documented at least seven species of dinosaurs reproducing in the Arctic."

Previous studies at a handful of other sites provided tantalizing bits of evidence that one or two species of indeterminate dinosaurs were capable of nesting near or just above the Arctic or Antarctic circles, he says, but this study is the first to show unequivocal evidence of nesting at extremely high latitudes. Environmental conditions at this time and place indicate challenging seasonal extremes, with an average annual temperature of about 6 degrees Celsius (about 40 degrees Fahrenheit). There also would have been about four months of full winter darkness with freezing conditions.

Druckenmiller and co-author Gregory Erickson from Florida State University have a longstanding project to document the ancient Arctic ecosystem of the Prince Creek Formation in Northern Alaska, including its dinosaurs, mammals, and other vertebrates. They also want to know how they lived there, given the challenging environment. The environment is also a difficult place to work.

"The field season is short in the Arctic and access is very difficult--aircraft and small boats are required," Druckenmiller says. "To make matters more challenging, the only way to see the rocks is in river-cut steep bluffs along the largest river in Northern Alaska, the Colville. These bluffs are dangerous, prone to catastrophic collapses, making it hard to safely find and extract fossils. As such, we have focused on finding discrete bonebed horizons where we can more efficiently excavate many bones. In the process, we've also discovered numerous new microfossil deposits that have provided for a wealth of new knowledge about the whole ecosystem that lived in the Arctic over 70 million years ago."

Over the course of about a decade of painstaking work, the researchers, aided by many students they've enlisted over the years, have now found hundreds of small baby dinosaur bones, including tiny teeth from individuals that were either still in the egg or had just hatched out. The Arctic dinosaurs they've uncovered include small- and large-bodied herbivorous species including hadrosaurids (duck-billed dinosaurs), ceratopsians (horned dinosaurs and leptoceratopsians), thescelosaurs and carnivores (tyrannosaurs, troodontids, and dromaeosaurs).

"It wasn't that long ago that the idea of finding any dinosaurs in such extreme latitudes and environments was a surprise," Druckenmiller says. "To then find out that most if not all of those species also reproduced in the Arctic is really remarkable. We have long been asked, 'Have you found any eggs?' To that we have, and still answer 'no.' But, we have something much better: the actual baby dinosaurs themselves."

The findings add to evidence that the dinosaurs didn't just spend time at these extreme latitudes, but they most likely lived there as year-round residents. Their evidence suggests both smaller dinosaurs and larger species, such as duck-billed dinosaurs, horned dinosaurs, and a tyrannosaur that more likely could have migrated to warmer climes, resided in the Arctic.

"Year-round residency in the Arctic provides a natural test of dinosaurian physiology," Erickson says. "Cold-blooded terrestrial vertebrates like amphibians, lizards, and crocodilians have yet to be found, only warm-blooded birds and mammals--and dinosaurs. I think that this is some of the most compelling evidence that dinosaurs were in fact warm-blooded."

Erickson says they now have new questions about how dinosaurs survived Arctic winters. It's likely they had unique strategies to cope with darkness, cold temperatures, and food limitation, the researchers say.

###

Current Biology, Druckenmiller et al.: "Nesting at Extreme Polar Latitudes by Non-Avian Dinosaurs" https://www.cell.com/current-biology/fulltext/S0960-9822(21)00739-9

Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit http://www.cell.com/current-biology. To receive Cell Press media alerts, contact press@cell.com.

CAPTION

This photograph shows researcher Greg Erickson excavating along the Colville River, northern Alaska.

CREDIT

Patrick Druckenmiller

Newly sequenced genome of extinct giant lemur sheds light on animal's biology

PENN STATE

Research News

 

IMAGE: PART OF THE COLLECTION OF THE LABORATORY OF PRIMATOLOGY AND PALEONTOLOGY AT THE UNIVERSITY OF ANTANANARIVO, THE JAWBONE THAT THE TEAM USED IN ITS STUDY HAD ORIGINALLY BEEN DISCOVERED AT... view more 

CREDIT: GEORGE PERRY, PENN STATE

UNIVERSITY PARK, Pa. -- Using an unusually well-preserved subfossil jawbone, a team of researchers -- led by Penn State and with a multi-national team of collaborators including scientists from the Université d'Antananarivo in Madagascar -- has sequenced for the first time the nuclear genome of the koala lemur (Megaladapis edwardsi), one of the largest of the 17 or so giant lemur species that went extinct on the island of Madagascar between about 500 and 2,000 years ago. The findings reveal new information about this animal's position on the primate family tree and how it interacted with its environment, which could help in understanding the impacts of past lemur extinctions on Madagascar's ecosystems.

"More than 100 species of lemurs live on Madagascar today, but in recent history, the diversity of these animals was even greater," said George Perry, associate professor of anthropology and biology, Penn State. "From skeletal remains and radiocarbon dating, we know that at least 17 species of lemurs have gone extinct, and that these extinctions happened relatively recently. What's fascinating is that all the extinct lemurs were bigger than the ones that survived, and some substantially so; for example, the one we studied weighed about 180 pounds."

Perry explained that much is unknown about the biology of these extinct lemurs and what their ecosystems were like. There is even uncertainty about how they were related to each other and to the extant lemurs that are alive today. This is due, in part, he said, to the difficulty inherent in working with ancient DNA, especially from animals that lived in tropical and sub-tropical locations.

"While many nuclear genomes of extinct animals have now been sequenced since the first extinct animal -- the woolly mammoth -- had its nuclear genome sequenced at Penn State in 2008, relatively few of these species have been from warmer climates due to faster DNA degradation in these conditions," said Perry. "For example, to date, Penn State's Ancient DNA Laboratory has screened hundreds of extinct lemur subfossils [or ancient bones that have not yet gone through the process of turning into rock]. Yet only two of our samples had sufficient DNA preservation for us to attempt to sequence the nuclear genome. The M. edwardsi jawbone was the best preserved."

Part of the collection of the Laboratory of Primatology and Paleontology at the University of Antananarivo, the jawbone that the team used in its study -- which was published today (June 22) in the journal Proceedings of the National Academy of Sciences -- had originally been discovered at Beloha Anavoha in southern Madagascar. Carbon-14 dating, a commonly used method for determining the age of archeological artifacts of a biological origin, revealed that the M. edwardsi jawbone was about 1,475 years old.

The team used a fragment of the jawbone to sequence the nuclear genome of M. edwardsi. Nuclear DNA contains information about both parents, whereas mitochondrial DNA, which is also used to study extinct species, only contains information about the mother.

In addition to M. edwardsi, the team newly sequenced the genomes of two extant -- or currently living -- lemur species: the weasel sportive lemur (Lepilemur mustelinus) and the red-fronted lemur (Eulemur rufifrons). The DNA from these species came from ear punches that members of the team, led by Edward E. Louis Jr., director of conservation genetics at Omaha's Henry Doorly Zoo and Aquarium and general director of the Madagascar Biodiversity Partnership, obtained from wild-caught individuals.

"Previous studies based on skull and teeth comparisons suggested that M. edwardsi was closely related to L. mustelinus," said Stephanie Marciniak, postdoctoral scholar in anthropology, Penn State. "However, our genetic analyses revealed that M. edwardsi is more closely related to E. rufifrons."

According to Perry, the first genetic study of M. edwardsi -- conducted in 2005 by Anne Yoder, Braxton Craven Professor of Evolutionary Biology at Duke University and her team, and now a co-author of the current paper -- was an analysis of a small fragment of the species' mitochondrial DNA.

"When Anne and her team observed the phylogenetic placement of Megaladapis to be more closely related to Eulemur than to Lepilemur, it was somewhat of a shock, in a cool way," he said. "But uncertainty about the relationship between Megaladapis and other lemurs has continued to linger among scientists. That 2005 study was a really important one, and now with the more sophisticated technology available to us today, we robustly confirmed that major finding."

In addition to extant lemur species, the team also compared M. edwardsi's genome to the genomes of dozens of more distantly related species, including golden snub-nosed colobine monkeys, which are folivores, and horses, which are herbivores.

"We found similarities between M. edwardsi and these two species in some of the genes that encode protein products that function in the biodegradation of plant toxins and in nutrient absorption, consistent with dental evidence suggesting that M. edwardsi was folivorous," said Marciniak.

Specifically, the researchers identified similarities between M. edwardsi and the golden snub-nosed monkey across genes with hydrolase activity functions, and between M. edwardsi and horse across genes with brush border functions.

"Hydrolases help to break down plant secondary compounds, while brush border microvilli play crucial roles in nutrient absorption and chemical breakdown in the gut," said Marciniak.

In the future, the team plans to analyze DNA from additional extinct lemurs and non-lemur primates with the goal of continuing to fill in the gaps in the primate family tree.

"For now," said Perry, "we are excited to have been able to analyze M. edwardsi's nuclear genome sequence for insights into the evolutionary biology and behavioral ecology of this extinct animal and to have resolved its phylogenetic relationship with some other extant lemurs."

CAPTION

More than 100 species of lemurs live on Madagascar today, but in recent history, the diversity of these animals was even greater. This illustration shows a Madagascar forest scene with several extant, or living, lemurs along with subfossil skulls of extinct lemurs.

CREDIT

MARIJA STOJKOVIC

Other Penn State authors include Mehreen Mughal, graduate student in bioinformatics and genomics, and Richard Bankoff, graduate student in anthropology. Authors from Université d'Antananarivo include Heritiana Randrianatoandro, graduate student; Jeannot Randrianasy, head of the Laboratoire de Primatologie et Paléontologie des Vertébrés; and Brigitte Raharivololona, head of the Anthropobiologie et Développement Durable Mention. Other authors include Laurie Godfrey, professor emerita, University of Massachusetts, Amherst; Christina Bergey, assistant professor of molecular biosciences, Rutgers University; Brooke Crowley, associate professor of geology; Kathleen Muldoon, associate professor of anatomy, Midwestern University; Stephan Schuster, professor of biological sciences, Nanyang Technological University; Ripan Malhi, professor of anthropology, University of Illinois Urbana-Champaign; Edward Louis Jr., director of the Department of Conservation Genetics, Omaha Henry Doorly Zoo; and Logan Kistler, curator of archaeobotany and archaeogenetics, Smithsonian Institution.

The College of Liberal Arts and Huck Institutes of the Life Sciences at Penn State, the National Science Foundation and the Ahmanson Foundation supported this research.

Comet strike may have sparked key shift in human civilization

UNIVERSITY OF EDINBURGH

Research News

    SHARE

 PRINT  E-MAIL

IMAGE: ARCHAEOLOGICAL SITE IN ARIZONA, U.S., WITH A DISTINCTIVE BLACK LAYER, INDICATING SUBSTANTIAL ENVIRONMENTAL CHANGES BEGINNING ABOUT 10,800 BC, WITH IMPACT DEBRIS AT ITS BASE. view more 

CREDIT: COMET RESEARCH GROUP

A cluster of comet fragments believed to have hit Earth nearly 13,000 years ago may have shaped the origins of human civilisation, research suggests.

Possibly the most devastating cosmic impact since the extinction of the dinosaurs, it appears to coincide with major shifts in how human societies organised themselves, researchers say.

Their analysis backs up claims that an impact occurred prior to start of the Neolithic period in the so-called Fertile Crescent of southwest Asia.

During that time, humans in the region - which spans parts of modern-day countries such as Egypt, Iraq and Lebanon - switched from hunter-gatherer lifestyles to ones centred on agriculture and the creation of permanent settlements.

It is thought that the comet strike - known as the Younger Dryas impact - also wiped out many large animal species and ushered in a mini ice age that lasted more than 1,000 years.

Since it was proposed in 2007, the theory about the catastrophic comet strike has been the subject of heated debate and much academic research. Now, researchers from the University of Edinburgh have reviewed evidence assessing the likelihood that an impact took place, and how the event may have unfolded.

The team says a large body of evidence supports the theory that a comet struck around 13,000 years ago. Researchers analysed geological data from four continents, particularly North America and Greenland, where the largest fragments are thought to have struck.

Their analysis highlights excess levels of platinum, signs of materials melted at extremely high temperatures and the detection of nanodiamonds known to exist inside comets and form during high-energy explosions. All of this evidence strongly supports the impact theory, researchers say.

The team says further research is needed to shed more light on how it may have affected global climate and associated changes in human populations or animal extinctions.

The research is published in the journal Earth-Science Reviews. An Open Access version of the paper is available here: https://www.research.ed.ac.uk/en/publications/the-younger-dryas-impact-hypothesis-review-of-the-impact-evidence

Dr Martin Sweatman, of the University of Edinburgh's School of Engineering, who led the study, said: "This major cosmic catastrophe seems to have been memorialised on the giant stone pillars of Göbekli Tepe, possibly the 'World's first temple', which is linked with the origin of civilisation in the Fertile Crescent of southwest Asia. Did civilisation, therefore, begin with a bang?"

###