Clays In Antarctica From Millions Of Years Ago Reveal Past Climate Changes

Members of the TASMANDRAKE research group of the Andalusian Earth Sciences Institute (IACT), which pertains to the University of Granada and CSIC, have published a research paper in the prestigious international journal Scientific Reports describing their analysis of clays from Antarctica dating back 35.5 million years, to reconstruct past climate changes.

Glaucony grains observed under an electron microscope
[Credit: University of Granada]

Their study was conducted in the area known as Drake Passage—the body of water that separates South America from Antarctica, between Cape Horn (Chile) and the South Shetland Islands (Antarctica). The results help to better understand the climatic conditions prior to the formation of the Antarctic Circumpolar Current, thus evaluating possible links between the development of the ice sheet in Antarctica and the changes in the tectonic and paleoceanographic configuration. Such questions constitute key facets of past climate functioning that provide boundary conditions for today's climate models, which predict a general rise in sea levels over the coming centuries.

The article analyses the relevance as a climatic indicator of the mineral commonly known as 'glauconite', which is more properly termed 'the glauconia facies' or 'glauconia'. This is a type of green clay, formed mainly in shallow marine environments (<500 15="" below="" br="" c="" conditions.="" m="" oxygenation="" specific="" temperatures="" under="" very="" with="">
The existence of this clay formation in the Antarctic region has received little scholarly attention to date compared to other geological records on the planet. The characteristic green-coloured mineral has been observed around Antarctica and the Antarctic Ocean in sedimentary sequences of the Terminal Eocene Event—that is, before one of the main climatic transitions in Earth's history. The Eocene–Oligocene climate transition took place approximately 34–33.6 million years ago.

Northwest region of the Antarctic Peninsula (South Shetland Islands)
[Credit: University of Granada]

This scientific contribution describes, for the first time in the Antarctic Ocean, a glauconitisation event (in which glauconia was formed) approximately 35.5 million years ago in the Weddell Sea, northeast of the Antarctic Peninsula between South America and Antarctica.

The formation of glauconia 35.5 million years ago marks the onset of progressive sea level rise in the north Weddell Sea during the Terminal Eocene. The results of this scientific study thus provide new insights regarding changes in paleoceanographic conditions just prior to the Eocene–Oligocene climate transition and the controversial opening and deepening of Drake Passage.

Studying the weather of the past to predict the future

The separation of the Antarctic continent from South America and Oceania allowed bodies of water to transfer freely between the Pacific and Atlantic Oceans. This new circulation of bodies of water resulted in the Circumpolar Current and, with it, the thermal insulation of the Antarctic and the formation of the ice cap on a continental scale.



Map of Antarctica showing the location of the Antarctic Circumpolar Current (ACC), which flows from west to east.

The ACC is a fundamental element in the deep global circulation connecting the Pacific, Atlantic, and Indian

Oceans. It is therefore an important part of the global ocean circulation network that distributes

heat around the Earth [Credit: University of Granada]

The opening of Drake Passage between South America and the Antarctic Peninsula is therefore considered one of the most important events in the history of the Earth's oceanic and atmospheric circulation. However, in the absence of dating for the formation of the sedimentary basins of Drake Passage, it is difficult to specify the precise age when the Passage began to open up and the Circumpolar Current started to form. The glauconia analysis conducted by the TASMANDRAKE research group contributes to progress in this area of study.

To put these changes into perspective, Adrian Lopez Quiros, the principal author of the research, notes that "it is necessary to study the past to understand the present and help predict the future," by better understanding the tectonic, climatic, and paleoceanographic conditions that led to the onset and subsequent evolution of this important ocean current.

The United Nations' Intergovernmental Panel on Climate Change (IPCC), a major reference source for climate forecasts, established several possible future climate scenarios in 2014. However, the new data, when comparing simulations with real-world data, predict even greater impacts than those previously foreseen in the IPCC climate scenarios. Therefore, climate change is developing faster than previously thought. With its research, the TASMANDRAKE group aims to provide new variables for these models—focusing on sediments and geophysics—to ensure that its results reflect real-life events even more accurately, especially in terms of the transoceanic currents, global warming, and rising sea levels.

Source: University of Granada [January 23, 2020]

'Doomsday Clock' Closer To Midnight Than Ever

"We are now expressing how close the world is to catastrophe in seconds – not hours, or even minutes,"

The Doomsday Clock on Thursday ticked down to 100 seconds to midnight, symbolizing the greatest level of peril to humanity since its creation in 1947 as the threat posed by climate change and a growing nuclear race loomed large.
1/23/2020

"We are now expressing how close the world is to catastrophe in seconds – not hours, or even minutes," said Rachel Bronson, president of the Bulletin of the Atomic Scientists in announcing the change
[Credit: Carolyn Kaster/Associated Press]

The danger level was compounded by information warfare and disruptive technologies ranging from deepfake video and audio to the militarization of space and the development of hypersonic weapons.

"We are now expressing how close the world is to catastrophe in seconds—not hours, or even minutes," said Rachel Bronson, president of the Bulletin of the Atomic Scientists, in announcing the change.

The decision on the clock is taken by panels of experts, including 13 Nobel laureates. It was originally set at seven minutes to midnight, and the previous worst—two minutes to midnight—held from 2018 to 2019 as well as 1953. The furthest it has ever been is 17 minutes, following the end of the Cold War in 1991.

On the nuclear front, the arms control boundaries that helped prevent catastrophe over the last half century are being dismantled and may be gone by next year, said subject expert Sharon Squassoni.

This includes the demise in 2019 of the Intermediate-Range Nuclear Forces (INF) Treaty, with the US and Russia entering a new competition to deploy once banned weapons. The US has suggested it won't extend New START, an arms reduction treaty signed in 2010.

"This year could see not just the complete collapse of the Iran nuclear deal," added Squassoni, with Tehran boosting its enrichment efforts.

And despite initial hopes US President Donald Trump's unorthodox approach to North Korea may produce results, no real progress ensued, said Squassoni, with Pyongyang instead vowing to press ahead with a new strategic weapon.



The Doomsday Clock on Thursday ticked down to 100 seconds to midnight
[Credit: Iris Royer De Vericourt/AFP]

On climate, two major UN summits fell dismally short of the action required to limit long-term warming to the goals laid out by the Paris Agreement that scientists say is necessary to prevent catastrophe.

The effects were already apparent in the record-breaking heat waves and floods India faced in 2019, and the wildfires that raged from the Arctic to Australia.

"If humankind pushes the climate into the opposite of an ice age," said Sivan Kartha, a scientist at the Stockholm Environmental Institute, "we have no reason to be confident that such a world will remain hospitable to human civilization."

Yet the experts took heart in mounting climate activism spearheaded by a youth movement that is spurring some governments to action.

Misinformation campaigns and fake news catalyzed by deepfake videos are potent threats to social cohesion, while the rise of AI weapons like drones that attack targets without human supervision create new uncertainty.

Russia meanwhile has announced a new hypersonic glide missile and the US is testing its own weapons that severely limit response times of targeted nations.

Space, long an arena for international cooperation, is also becoming increasingly militarized with multiple countries testing projectile and laser anti-satellite weapons and the US creating a new military branch, the Space Force.

"We ask world leaders to join us in 2020 as we work to pull humanity back from the brink," said Mary Robinson, chair of The Elders leadership group and former president of Ireland.

"Now is the time to come together—to unite and to act."

Source: AFP [January 23, 2020]
Scientists move 'Doomsday Clock' to latest time in history

By Don Jacobson

Bulletin of Atomic Scientists Executive Chair Jerry Brown 

announces Thursday the "Doomsday Clock" was moved

 forward 20 seconds to its latest time in history.

 Photo by Ken Cedeno/UPI | License Photo

Jan. 23 (UPI) -- The Bulletin of Atomic Scientists on Thursday moved up its "Doomsday Clock" to 100 seconds before midnight -- the closest it's ever come to symbolic world destruction in the gauge's 73-year history.

The group set the clock -- which symbolically reflects how close the world is to "midnight," or its destruction -- ahead by 20 seconds during the event Thursday, to 11:58 p.m., and 20 seconds. It had been at two minutes to midnight since 2018.


The group's moving the clock reflects all relative events that occurred in 2019.

Before Thursday, two minutes to midnight had been the closest the clock has been to midnight -- having reached that point just twice since the clock was established. The first was 1953 during the Cold War and followed the first U.S. test of a thermonuclear weapon.

Former California Gov. Jerry Brown, the group's executive chairman, former Irish President Mary Robinson and former U.N. Secretary-General Ban Ki-moon unveiled the new position at Thursday's event.

Bulletin of Atomic Scientists President and CEO Rachel Bronson said the move reflected the opinion of the scientists that the world had entered "a two-minute warning" for its survival.

"When the board kept the clock at two minutes to midnight in 2019, we argued then that the global situation was abnormal, and that this 'new abnormal' was simply too volatile and too dangerous to accept as a continuing state of world affairs," she said. "Today we feel no more optimistic."

The decision was made by the group's science and security board following a year in which man-made threats to humanity, such as nuclear proliferation and climate change, were hastened by moves away from international cooperation, she said. The science board found that both nuclear and climate change situations worsened last year.

The Bulletin of Atomic Scientists first began the tradition in 1947 as a way to gauge the world's proximity to nuclear holocaust. In 2007 the group added climate change as a factor in the clock's setting.

"We have seen influential leaders denigrate and discard the most effective methods for addressing complex threats -- international agreements with strong verification regimes -- in favor of their own narrow interests and domestic political gain," Bronson said.

The furthest the clock has ever been from midnight was set in 1991, at 11:43, or 17 minutes from "doomsday," after the United States signed the first Strategic Arms Reduction Treaty and the Soviet Union dissolved.

Ancient Statue Found In Cambodia's Siem Reap

Siem Reap Provincial Environment Department officials and archaeologists are conducting research on a large Makara animal statue carved on a rock at the Phnom Kulen National Park in Siem Reap province’s Svay Loeu district.1/23/2020

Credit: Khmer Times

Provincial Department of Environment director Sun Kong said yesterday the head portion of the broken statue was found by a resident on Saturday and the officials went to inspect the site on Sunday.

He added that the statue was made of sandstone during the sixth century and the body was broken into pieces, noting that officials found 13 pieces of the body nearby the site

Credit: Khmer Times

Mr Kong said: “According to the experts, this Makara animal statue is one that we have never seen before. It is approximately 2.14 metres in length and about 0.97 metres high. We have not yet moved the body parts or excavated the head from the site and have told park rangers in the area to guard it in order for officials from relevant ministries and institutions to come and study in detail about the site’s history and reconstruct the pieces.”

He noted that experts have not found a foundation of any temple at the site and believe it was just carved out on the rock.

Credit: Khmer Times

Chhim Samrithy, 38, a craftsman from the province who discovered the statue, said yesterday he spotted it on Saturday while searching for bamboo. “I usually walk in the forest to look for some unique and sacred objects and suddenly spotted this rare statue,” he said. “After seeing it, I took environmental officials and archaeologists to the site and also helped to find some of the missing pieces of the statue.”

Long Kosal, Apsara Authority spokesman, said that the authorities’ archaeologists visited the site yesterday and will conduct additional studies to add it to the records.

Credit: Khmer Times

He said: “The Kulen National Park area is rich in ancient artefects, both above and below the ground. Therefore, I urge people, especially those living in the area, to avoid excavating or clearing archaeological sites. If they find ancient objects, please report to the authorities for research to be done to preserve them for future generations.”

Author: Pech Sotheary | Source: Khmer Times [January 23, 2020]

The Salt Of The Comet

More than 30 years ago, the European comet mission Giotto flew past Halley's comet. The Bernese ion mass spectrometer IMS, led by Prof. em. Hans Balsiger, was on board. A key finding from the measurements taken by this instrument was that there appeared to be a lack of nitrogen in Halley's coma - the nebulous covering of comets which forms when a comet passes close to the sun.

1/20/2020 

Gas and dust rise from "Chury's" surface as the comet approaches the
point of its orbit closest to the sun  [Credit: ESA/Rosetta/NAVCAM]

Although nitrogen (N) was discovered in the form of ammonia (NH3) and hydrocyanic acid (HCN), the incidence was far removed from the expected cosmic incidence. More than 30 years later, researchers have solved this mystery thanks to a happy accident.

This is a result of the analysis of data from the Bernese mass spectrometer ROSINA, which collected data on the comet 67P/Churyumov-Gerasimenko, called Chury for short, on board the ESA space probe Rosetta (see info box below).

Risky flight through the comet Chury's dust cloud

Less than a month before the end of the Rosetta mission, the space probe was just 1.9 km above the surface of Chury as it flew through a dust cloud from the comet. This resulted in a direct impact of dust in the ion source of the mass spectrometer ROSINA-DFMS (Rosetta Orbiter Sensor for Ion and Neutral Analysis-Double Focusing Mass Spectrometer), led by the University of Bern. Kathrin Altwegg, lead researcher on ROSINA and co-author of the new study published in the prestigious journal Nature Astronomy, says: "This dust almost destroyed our instrument and confused Rosetta's position control."

A plume of dust from Comet 67P/Churyumov–Gerasimenko, seen by
 the OSIRIS Wide Angle Camera on ESA's Rosetta spacecraft on 
3 July 2016. The shadow of the plume is cast across the basin, which
 is in the Imhotep region

[Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA]

Thanks to the flight through the dust cloud, it was possible to detect substances which normally remain in the cold environment of the comet on the dust particles and therefore cannot be measured. The amount of particles, some of which had never before been measured on a comet, was astonishing. In particular, the incidence of ammonia, the chemical compound of nitrogen and hydrogen with the formula NH3, was suddenly many times greater.

"We came up with the idea that the incidence of ammonia in the ROSINA data could potentially be traced back to the occurrence of ammonium salts," explains Altwegg. "As a salt, ammonia has a much higher evaporation temperature than ice and is therefore mostly present in the form of a solid in the cold environment of a comet. It has not been possible to measure these solids either through remote sensing with telescopes or on the spot until now."

Ammonium salt and its role in the emergence of life

Extensive laboratory work was needed in order to prove the presence of these salts in cometary ice. "The ROSINA team has found traces of five different ammonium salts: ammonium chloride, ammonium cyanide, ammonium cyanate, ammonium formate and ammonium acetate," says the chemist on the ROSINA team and co-author of the current study, Dr. Nora Hanni.

Ammonium chloride is one of five different ammonium salts the ROSINA team has found traces of [Credit: University of Bern]

"Until now, the apparent absence of nitrogen on comets was a mystery. Our study now shows that it is very probable that nitrogen is present on comets, namely in the form of ammonium salts," Hanni continues.

The ammonium salts discovered include several astrobiologically relevant molecules which may result in the development of urea, amino acids, adenine and nucleotides. Kathrin Altwegg says: "This is definitely a further indication that comet impacts may be linked with the emergence of life on Earth."

Source: University of Bern [January 20, 2020]

Remains Of Pre-Hispanic Sweat Lodge Found Near La Merced, Mexico City

Archaeologists have discovered the remains of a pre-Hispanic sweat lodge near La Merced, a market area in the historic center of Mexico City.

1/23/2020 

Credit: Edith Camacho, INAH

The National Institute of Anthropology and History (INAH) said in a statement Tuesday that the temazcal, as a domed, pre-Hispanic sweat lodge made out of mud or stone is known, was found during an excavation at a property on Talavera street, which is now known for the sale of baby Jesus statues.

Temazcales were used by indigenous people in Mesoamerica for medicinal purposes, spiritual rituals and childbirth.

Credit: Edith Camacho, INAH

Archaeologists found blocks made out of adobe and tezontle –a volcanic rock – that were used to build the sweat lodge as well as a bathtub used to heat the structure with steam. Based on the remains they found, the INAH team concluded that the temazcal was five meters long and about three meters wide.

INAH said the discovery has allowed archaeologists to pinpoint the location of Temazcaltitlan, one of the oldest neighborhoods of Tenochtitlan, the Mexica capital that would become Mexico City.

Credit: Edith Camacho, INAH

According to a chronicle of pre-Hispanic times in Tenochtitlan, a temazcal was built in Temazcaltitlan to bathe and purify Quetzalmoyahuatzin, a noble Mexica girl.

Hernando Alvarado Tezozomoc, a noble indigenous man who lived in colonial times, wrote in his Cronica Mexicayotl that ordinary residents of Tenochtitlan also bathed there.

Credit: Edith Camacho, INAH

The head of the INAH team that found the temazcal said the discovery is the first concrete evidence of Temazcaltitlan’s vocation as a center of bathing and purification.

Victor Esperon Calleja said the neighborhood belonged to the district of Teopan (also known as Zoquipan), which was the first territory built on Lake Texcoco and occupied by the Mexicas. It is believed that the female deities of earth, fertility, water and the pre-Hispanic beverage pulque were also worshipped in Temazcaltitlan.

Credit: Edith Camacho, INAH

In addition to the temazcal remains, on the same Talavera street property archaeologists found the remnants of a home that was possibly inhabited by a noble indigenous family shortly after the Spanish conquest and structures of a tannery, which operated during the last century of colonial rule before Mexico gained its independence in the early 19th century.

“The findings suggest that in the 16th century this area was more populated than we initially thought,” Esperon said.

Credit: Edith Camacho, INAH

“Given that it was an area of chinampas [floating agricultural gardens], it was thought that there were few houses but at this property we have evidence of the wooden pilings and stones that were used for the wall foundations [of a home],” he added.

Esperon said that the methods used to build the house allowed archaeologists to date it to the first century of colonial rule between 1521 and 1620.

The walls of the four-room home were decorated with red motifs and its floor was made of adobe blocks, features that the archaeologist said indicated that it was “inhabited by an indigenous family, possibly of noble origin.”

The tannery, Esperon said, likely made leather from cattle slaughtered at the San Lucas abattoir, which was located close to where the Pino Suarez Metro station now stands.

Source: Mexico News Daily [January 23, 2020]

EVEN BEFORE AUSTRALIA'S WILDFIRES

Platypus On Brink Of Extinction

Australia's devastating drought is having a critical impact on the iconic platypus, a globally unique mammal, with increasing reports of rivers drying up and platypuses becoming stranded.1/21/2020 

The platypus is one of the world's strangest animals
[Credit: Torsten Blackwood/AFP]

Platypuses were once considered widespread across the eastern Australian mainland and Tasmania, although not a lot is known about their distribution or abundance because of the species' secretive and nocturnal nature.

A new study led by UNSW Sydney's Centre for Ecosystem Science, funded through a UNSW-led Australian Research Council project and supported by the Taronga Conservation Society, has for the first time examined the risks of extinction for this intriguing animal.

Published in the international scientific journal Biological Conservation this month, the study examined the potentially devastating combination of threats to platypus populations, including water resource development, land clearing, climate change and increasingly severe periods of drought.

Lead author Dr Gilad Bino, a researcher at the UNSW Centre for Ecosystem Science, said action must be taken now to prevent the platypus from disappearing from our waterways.

"There is an urgent need for a national risk assessment for the platypus to assess its conservation status, evaluate risks and impacts, and prioritise management in order to minimise any risk of extinction," Dr Bino said.

Alarmingly, the study estimated that under current climate conditions and due to land clearing and fragmentation by dams, platypus numbers almost halved, leading to the extinction of local populations across about 40 per cent of the species' range, reflecting ongoing declines since European colonisation.

UNSW Sydney's Centre for Ecosystem Science leads new research into
the extinction risk of the platypus [Credit: Tahnael Hawke]

Under predicted climate change, the losses forecast were far greater because of increases in extreme drought frequencies and duration, such as the current dry spell.

Dr Bino added: "These dangers further expose the platypus to even worse local extinctions with no capacity to repopulate areas."

Documented declines and local extinctions of the platypus show a species facing considerable risks, while the International Union for Conservation of Nature (IUCN) recently downgraded the platypus' conservation status to "Near Threatened".

But the platypus remains unlisted in most jurisdictions in Australia - except South Australia, where it is endangered.

Director of the UNSW Centre for Ecosystem Science and study co-author Professor Richard Kingsford said it was unfortunate that platypuses lived in areas undergoing extensive human development that threatened their lives and long-term viability.

"These include dams that stop their movements, agriculture which can destroy their burrows, fishing gear and yabby traps which can drown them and invasive foxes which can kill them," Prof Kingsford said.

The UNSW-led project raises concerns about the decline
of platypus populations [Credit: UNSW Science]

Study co-author Professor Brendan Wintle at The University of Melbourne said it was important that preventative measures were taken now.

"Even for a presumed 'safe' species such as the platypus, mitigating or even stopping threats, such as new dams, is likely to be more effective than waiting for the risk of extinction to increase and possible failure," Prof Wintle said.

"We should learn from the peril facing the koala to understand what happens when we ignore the warning signs."

Dr Bino said the researchers' paper added to the increasing body of evidence which showed that the platypus, like many other native Australian species, was on the path to extinction.

"There is an urgent need to implement national conservation efforts for this unique mammal and other species by increasing monitoring, tracking trends, mitigating threats, and protecting and improving management of freshwater habitats," Dr Bino said.

The platypus research team is continuing to research the ecology and conservation of this enigmatic animal, collaborating with the Taronga Conservation Society, to ensure its future by providing information for effective policy and management.

Source: University of New South Wales [January 21, 2020]

Domesticated Wheat Has Complex Parentage

Certain types of domesticated wheat have complicated origins, with genetic contributions from wild and cultivated wheat populations on opposite sides of the Fertile Crescent. Terence Brown and colleagues at the University of Manchester report these findings in a new paper published in the open-access journal PLOS ONE.
1/22/2020 

Credit: WikiCommons

A wild form of wheat called emmer wheat was one of the first plant species that humans domesticated. Emmer is not grown widely today, but gave rise to the durum wheat used for pasta and hybridized with another grass to make bread wheat, so its domestication was an important step in the transition from hunting and gathering to agriculture.

While the archaeological record suggests that cultivation began in the southern Levant region bordering the eastern edge of the Mediterranean Sea around 9,500 years ago, genetic studies point to an origin in the northern region of the Fertile Crescent, in what is now Turkey. To clarify emmer's origins, researchers screened 189 types of wild and domesticated wheats and used the more that 1 million genetic variations that they identified to piece together the genetic relationships between different kinds of wheat.

Based on the analysis, the researchers propose that an emmer crop, which humans cultivated but had not yet domesticated, spread from the southern Levant to southeast Turkey, where it mixed with a wild emmer population and ultimately yielded the first domesticated variety. The results of this hybridization can be detected in wild emmer plants in Turkey today.

The complex evolutionary relationships between wild emmer and cultivated wheat varieties uncovered by the analysis are similar to the interbreeding that occurred between wild and cultivated populations of other grain crops, such as barley and rice.

The authors add: "We used next-generation DNA sequencing technologies to detect hundreds of thousands of variants in the genomes of wild and cultivated emmer wheat, giving us an unprecedented insight into the complexity of its domestication process. The patterns we observed do not fit well with a simplistic model of fast and localized domestication event but suggest instead a long process of cultivation of wild wheat by hunter-gatherer communities connected throughout the Fertile Crescent, prior to the emergence of a fully domesticated wheat form."

Source: Public Library of Science [January 22, 2020]

Life's Frankenstein Beginnings

When the Earth was born, it was a mess. Meteors and lightning storms likely bombarded the planet's surface where nothing except lifeless chemicals could survive. How life formed in this chemical mayhem is a mystery billions of years old. Now, a new study offers evidence that the first building blocks may have matched their environment, starting out messier than previously thought.

1/22/2020 

Szostak believes the earliest cells developed on land in ponds or pools, 

potentially in volcanically active regions. Ultraviolet light, lightning strikes,

 and volcanic eruptions all could have helped spark the chemical reactions

necessary for life formation [Credit: Don Kawahigashi/Unsplash]

Life is built with three major components: RNA and DNA--the genetic code that, like construction managers, program how to run and reproduce cells--and proteins, the workers that carry out their instructions. Most likely, the first cells had all three pieces. Over time, they grew and replicated, competing in Darwin's game to create the diversity of life today: bacteria, fungi, wolves, whales and humans.

But first, RNA, DNA or proteins had to form without their partners. One common theory, known as the "RNA World" hypothesis, proposes that because RNA, unlike DNA, can self-replicate, that molecule may have come first. While recent studies discovered how the molecule's nucleotides--the A, C, G and U that form its backbone--could have formed from chemicals available on early Earth, some scientists believe the process may not have been such a straightforward path.

"Years ago, the naive idea that pools of pure concentrated ribonucleotides might be present on the primitive Earth was mocked by Leslie Orgel as 'the Molecular Biologist's Dream,'" said Jack Szostak, a Nobel Prize Laureate, professor of chemistry and chemical biology and genetics at Harvard University, and an investigator at the Howard Hughes Medical Institute. "But how relatively modern homogeneous RNA could emerge from a heterogeneous mixture of different starting materials was unknown."

In a paper published in the Journal of the American Chemical Society, Szostak and colleagues present a new model for how RNA could have emerged. Instead of a clean path, he and his team propose a Frankenstein-like beginning, with RNA growing out of a mixture of nucleotides with similar chemical structures: arabino- deoxy- and ribonucleotides (ANA, DNA, and RNA).

In the Earth's chemical melting pot, it's unlikely that a perfect version of RNA formed automatically. It's far more likely that many versions of nucleotides merged to form patchwork molecules with bits of both modern RNA and DNA, as well as largely defunct genetic molecules, such as ANA. These chimeras, like the monstrous hybrid lion, eagle and serpent creatures of Greek mythology, may have been the first steps toward today's RNA and DNA.

"Modern biology relies on relatively homogeneous building blocks to encode genetic information," said Seohyun Kim, a postdoctoral researcher in chemistry and first author on the paper. So, if Szostak and Kim are right and Frankenstein molecules came first, why did they evolve to homogeneous RNA?

Kim put them to the test: He pitted potential primordial hybrids against modern RNA, manually copying the chimeras to imitate the process of RNA replication. Pure RNA, he found, is just better--more efficient, more precise, and faster--than its heterogeneous counterparts. In another surprising discovery, Kim found that the chimeric oligonucleotides--like ANA and DNA--could have helped RNA evolve the ability to copy itself. "Intriguingly," he said, "some of these variant ribonucleotides have been shown to be compatible with or even beneficial for the copying of RNA templates."

If the more efficient early version of RNA reproduced faster than its hybrid counterparts then, over time, it would out-populate its competitors. That's what the Szostak team theorizes happened in the primordial soup: Hybrids grew into modern RNA and DNA, which then outpaced their ancestors and, eventually, took over.

"No primordial pool of pure building blocks was needed," Szostak said. "The intrinsic chemistry of RNA copying chemistry would result, over time, in the synthesis of increasingly homogeneous bits of RNA. The reason for this, as Seohyun has so clearly shown, is that when different kinds of nucleotides compete for the copying of a template strand, it is the RNA nucleotides that always win, and it is RNA that gets synthesized, not any of the related kinds of nucleic acids."

So far, the team has tested only a fraction of the possible variant nucleotides available on early Earth. So, like those first bits of messy RNA, their work has only just begun.

Source: Harvard University [January 22, 2020]

Driven By Earth's Orbit, Climate Changes In Africa May Have Aided Human Migration

1/27/2020 


In 1961, John Kutzbach, then a recent college graduate, was stationed in France as an aviation weather forecaster for the U.S. Air Force. There, he found himself exploring the storied caves of Dordogne, including the prehistoric painted caves at Lascoux.

An aerial view of northern Africa, the Arabian Peninsula and the Mediterranean Basin.

 A new study led by University of Wisconsin–Madison’s John Kutzbach shows that

 changes in Earth’s orbit, greenhouse gases, and ice sheets influenced the planet’s

 climate over the last 140,000 years and may have provided wetter, greener corridors 

at times that permitted human migration out of Africa and into the Middle East 

[Credit: Google Earth]

Thinking about the ancient people and animals who would have gathered in these caves for warmth and shelter, he took up an interest in glaciology. "It was interesting to me, as a weather person, that people would live so close to an ice sheet," says Kutzbach, emeritus University of Wisconsin-Madison professor of atmospheric and oceanic sciences and the Nelson Institute for Environmental Studies.

Kutzbach went on to a career studying how changes in Earth's movements through space - the shape of its orbit, its tilt on its axis, its wobble - and other factors, including ice cover and greenhouse gases, affect its climate. Many years after reveling at Ice Age cave art, today he's trying to better understand how changes in Earth's climate may have influenced human migration out of Africa.

In a recent study published in the Proceedings of the National Academy of Sciences, Kutzbach and a team of researchers trace changes in climate and vegetation in Africa, Arabia and the Mediterranean going back 140,000 years to aid others studying the influences underlying human dispersal.

The study describes a dynamic climate and vegetation model that explains when regions across Africa, areas of the Middle East, and the Mediterranean were wetter and drier and how the plant composition changed in tandem, possibly providing migration corridors throughout time.

"We don't really know why people move, but if the presence of more vegetation is helpful, these are the times that would have been advantageous to them," Kutzbach says.

The model also illuminates relationships between Earth's climate and its orbit, greenhouse gas concentrations, and its ice sheets.

For instance, the model shows that around 125,000 years ago, northern Africa and the Arabian Peninsula experienced increased and more northerly-reaching summer monsoon rainfall that led to narrowing of the Saharan and Arabian deserts due to increased grassland. At the same time, in the Mediterranean and the Levant (an area that includes Syria, Lebanon, Jordan, Israel and Palestine), winter storm track rainfall also increased.

These changes were driven by Earth's position relative to the sun. The Northern Hemisphere at the time was as close as possible to the sun during the summer, and as far away as possible during the winter. This resulted in warm, wet summers and cold winters.

"It's like two hands meeting," says Kutzbach. "There were stronger summer rains in the Sahara and stronger winter rains in the Mediterranean."

Given the nature of Earth's orbital movements, collectively called Milankovitch cycles, the region should be positioned this way roughly every 21,000 years. Every 10,000 years or so, the Northern Hemisphere would then be at its furthest point from the sun during the summer, and closest during winter.

Indeed, the model showed large increases in rainfall and vegetation at 125,000, at 105,000, and at 83,000 years ago, with corresponding decreases at 115,000, at 95,000 and at 73,000 years ago, when summer monsoons decreased in magnitude and stayed further south.

Between roughly 70,000 and 15,000 years ago, Earth was in a glacial period and the model showed that the presence of ice sheets and reduced greenhouse gases increased winter Mediterranean storms but limited the southern retreat of the summer monsoon. The reduced greenhouse gases also caused cooling near the equator, leading to a drier climate there and reduced forest cover.

These changing regional patterns of climate and vegetation could have created resource gradients for humans living in Africa, driving migration outward to areas with more water and plant life.

For the study, the researchers, including Kutzbach's UW-Madison colleagues Ian Orland and Feng He, along with researchers at Peking University and the University of Arizona, used the Community Climate System Model version 3 from the National Center for Atmospheric Research. They ran simulations that accounted for orbital changes alone, combined orbital and greenhouse gas changes, and a third that combined those influences plus the influence of ice sheets.

It was Kutzbach who, in the 1970s and 1980s, confirmed that changes in Earth's orbit can drive the strength of summer monsoons around the globe by influencing how much sunlight, and therefore, how much warming reaches a given part of the planet.

Forty years ago, there was evidence for periodic strong monsoons in Africa, but no one knew why, Kutzbach says. He showed that orbital changes on Earth could lead to warmer summers and thus, stronger monsoons. He also read about periods of "greening" in the Sahara, often used to explain early human migration into the typically-arid Middle East.

"My early work prepared me to think about this," he says.

His current modeling work mostly agrees with collected data from each region, including observed evidence from old lake beds, pollen records, cave features, and marine sediments. A recent study led by Orland used cave records in the Levant to show that summer monsoons reached into the region around 125,000 years ago.

"We get some things wrong (in the model)," says Kutzbach, so the team continues to refine it. For instance, the model doesn't get cold enough in southern Europe during the glacial period and not all vegetation changes match observed data. Computing power has also improved since they ran the model.

"This is by no means the last word," Kutzbach says. "The results should be looked at again with an even higher-resolution model."

Author: Kelly April Tyrrell | Source: University of Wisconsin-Madison [January 27, 2020]

New Predatory Dinosaur Added To Australia's Prehistory

1/29/2020 


Evidence of agile, carnivorous two-legged dinosaurs known as noasaurids have been found across the now dispersed land masses that once formed the ancient southern supercontinent of Gondwana, but never in Australia—until now.



The Lightning Ridge noasaurid bone in approximate life position,
with a human for scale [Credit: Tom Brougham]
Researchers identified a single neck bone found in an opal mine near the outback town of Lightning Ridge, New South Wales, as belonging to a noasaurid, and then realised that another fossil discovered in 2012 along the south coast of Victoria was from the same group.

Noasaurid are a rare group of theropod dinosaurs—two legged carnivores—that lived in the middle to late Cretaceous Period, between about 120 and 66 million years ago. Noasaurids were small-bodied dinosaurs, many with peculiar facial features, typically less than two metres long and weighing about 20 kilograms.

The recognition of this new group of dinosaurs in Australia by palaeontologists from the Palaeoscience Research Centre at the University of New England and the Australian Opal Centre in Lightning Ridge adds a missing piece to a puzzle.

"It was assumed that noasaurids must have lived in Australia because their fossils have been found on other southern continents that, like Australia, were once part of the Gondwanan supercontinent," said lead scientist, Dr. Tom Brougham of the Palaeoscience Research Centre. "These recent fossil finds demonstrate for the first time that noasaurids once roamed across Australia. Discoveries of theropods are rare in Australia, so every little find we make reveals important details about our unique dinosaur fauna."

The researchers compared the 100 million-year-old Lightning Ridge neck bone with those from other carnivorous dinosaurs and quickly realised it was different from anything that had been found in Australia to date. "When we looked at what features this bone has compared to those of other theropods, we found that it matched closely with this strange group of dinosaurs called noasaurids," Dr. Brougham said.

This prompted us to re-examine an ankle bone of a dinosaur that was discovered in Victoria in 2012, about 20 million years older than the Lightning Ridge bone, and using the same methods we concluded that this also belonged to a noasaurid. In addition, this ankle bone is approximately the same age, or perhaps even older, than the oldest known noasaurids, which come from South America."

Noasaurids were similar in size to, and lived at the same time as, a more well-known group of carnivorous dinosaurs called dromaeosaurids or 'raptors'—infamously represented by Velociraptor in Jurassic Park—and were probably also active predators. However, while Velociraptor and kin have representatives from all over the world, noasaurids were known only from several of the southern continents (South America, Africa, Madagascar and India), which formed the supercontinent of Gondwana before it started breaking apart in the Cretaceous.

The study was published today in the journal Scientific Reports.

Source: University of New England [January 29, 2020]