Rise of oxygen on Earth: Initial estimates off by 100 million years

Permanent oxygenation occurred much later than previously thought

UNIVERSITY OF CALIFORNIA - RIVERSIDE

Research News

 

IMAGE: RESEARCH TEAM LEADER SPRAYS WATER ON DRILL CORES TO SEE SEDIMENTARY ROCKS AND SELECT SAMPLES FOR THIS STUDY. view more 

CREDIT: ANDREY BEKKER/UCR

New research shows the permanent rise of oxygen in our atmosphere, which set the stage for life as we know it, happened 100 million years later than previously thought.

A significant rise in oxygen occurred about 2.43 billion years ago, marking the start of the Great Oxidation Episode -- a pivotal moment in Earth's history. 

An international research team including a UC Riverside scientist analyzed rocks from South Africa formed during this event. Findings, published this week in the journal Nature, include the discovery that oxygen fluctuated dramatically after its early appearance until it became a permanent constituent of the atmosphere much later.

These fluctuations reinforce a direct link between atmospheric oxygen and concentrations of greenhouse gases such as methane, helping to explain some of the most extreme climate changes in the planet's past.

During the same period, ancient Earth experienced four glaciations -- periods when the whole planet was covered with ice and snow for millions of years. According to UC Riverside geologist Andrey Bekker, changes in atmospheric oxygen levels began and ended these events. 

Scientists have often wondered how the planet could have emerged from the periods in which ice and snow covered everything, including the oceans. According to Bekker, increases in atmospheric oxygen levels resulted in low concentrations of greenhouse gases, such as methane and carbon dioxide. This ushered in global glaciations by maintaining surface conditions below the water-freezing temperature. 

Volcanoes also continued to erupt on the frozen planet, building required high levels of carbon dioxide in the atmosphere to exit from climatic catastrophe by warming the planet and melting the snow and ice.

"Before this work, we all wondered why the fourth glacial event happened if oxygen was already a steady component in the atmosphere," Becker said. "We found it was not steady. The permanent rise of oxygen actually occurred after the fourth, final glaciation in the Paleoproterozoc Era, and not before it, and this solves what had previously been a major puzzle in our understanding." 

The Great Oxidation Episode ushered in a 1.5 billion-year period of subsequent environmental stability, which lasted until a second major transitional period, marked by rising atmospheric oxygen and similar climatic changes at the end of the Precambrian time. 

"We thought once oxygen increased it wouldn't ever return back to lower levels," Bekker said. "Now we have learned it fluctuated to very low levels and this could have dramatic implications in terms of understanding extinction events and the evolution of life."

Open questions include the reasons for these multiple fluctuations, and whether complex life could have evolved and then died out again in response to them, said Simon Poulton, a biogeochemist at Leeds University who led the research. 

"We cannot begin to understand the causes and consequences of atmospheric oxygenation, the most significant control on Earth's habitability, if we do not know when permanent atmospheric oxygenation actually occurred," he said. "Now at last we have that piece of the puzzle."

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CAPTION

Changes in atmospheric oxygen levels began and ended four glaciations -- periods when the whole planet was covered with ice and snow for millions of years.

CREDIT

Wikimedia

THE ANWSER IS INTERNATIONALISM

'Vaccine Nationalism' is a threat to equitable access and herd immunity

BRIGHAM AND WOMEN'S HOSPITAL

Research News

WHO Ingrid Katz, MD, MHS, Associate Physician, Department of Medicine, Brigham and Women's Hospital; lead author of a new Perspective piece published in the New England Journal of Medicine.

WHAT While the U.S. has begun to vaccinate millions of Americans each day, COVID-19 vaccine supplies around the world remain scarce. Experts estimate that 80 percent of people in low-resource countries will not receive a vaccine in 2021. At the time of the paper's writing, the global vaccination rate was 6.7 million doses per day -- a rate at which it would take 4.6 years to achieve global herd immunity. In a new Perspective piece in the New England Journal of Medicine, Katz and colleagues highlight the need to treat essential medical services as public goods, rather than market commodities. To truly protect U.S. residents and their neighbors, they urge the federal government to reinforce global vaccine distribution efforts.

"The early competitive procurement of vaccines by the United States and purchases by other high-resource countries have fed a widespread assumption that each country will be solely responsible for its own population," the authors write. "Such vaccine nationalism perpetuates the long history of powerful countries securing vaccines and therapeutics at the expense of less-wealthy countries; it is short-sighted, ineffective, and deadly."

Through the COVID-19 Vaccines Global Access (COVAX) program, the U.S. and the G7 nations have committed to vaccinating at least 20 percent of the populations of participating low- and middle-income countries by the end of 2021. But this falls far below the broader goal of achieving herd immunity by vaccinating at least 70 to 85 percent of the population and substantially increases the likelihood that new viral variants will emerge.

Drawing upon lessons learned from the HIV pandemic, when most low-resource countries could not access lifesaving therapies, the authors argue that the government should invest in what some experts are calling the President's Emergency Plan for Vaccine Access and Relief (PEPVAR), a spin-off of the 2003 President's Emergency Plan for AIDS Relief (PEPFAR). This latter plan was founded to deliver antiretroviral therapies globally, and a program like PEPVAR could draw upon pre-existing strategies to scale up the delivery of vaccines beyond COVAX's commitments. Like the plan for AIDS relief, it could leverage partnerships with governmental and multilateral organizations to improve vaccine access. Equally important is ensuring vaccine supply, and the authors posit that the World Trade Organization may be justified in temporarily waiving pharmaceutical patent protections to substantially reduce the costs of manufacturing vaccines.

"The United States has an unusual and urgent opportunity to ensure that COVID-19 vaccines are available to all," the authors write. "By investing in multilateral partnerships with a sense of shared commitment and employing a global allocation strategy that increases supply and manufacturing, we can meet the urgent challenge of COVID-19, while creating sustainable infrastructures and health systems for the future."

Marxist Summer School - The Internationale : Free Download, Borrow, and Streaming : Internet Archive

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Making cleaner, greener plastics from waste fish parts

AMERICAN CHEMICAL SOCIETY

Research News

 

IMAGE: USING FISH OIL, RESEARCHERS HAVE MADE A POLYURETHANE-LIKE MATERIAL. view more 

CREDIT: MIKHAILEY WHEELER

WASHINGTON, April 5, 2021 -- Polyurethanes, a type of plastic, are nearly everywhere -- in shoes, clothes, refrigerators and construction materials. But these highly versatile materials can have a major downside. Derived from crude oil, toxic to synthesize, and slow to break down, conventional polyurethanes are not environmentally friendly. Today, researchers discuss devising what they say should be a safer, biodegradable alternative derived from fish waste -- heads, bones, skin and guts -- that would otherwise likely be discarded.

The researchers will present their results today at the spring meeting of the American Chemical Society (ACS). ACS Spring 2021 is being held online April 5-30. Live sessions will be hosted April 5-16, and on-demand and networking content will continue through April 30. The meeting features nearly 9,000 presentations on a wide range of science topics.

If developed successfully, a fish-oil based polyurethane could help meet the immense need for more sustainable plastics, says Francesca Kerton, Ph.D., the project's principal investigator. "It is important that we start designing plastics with an end-of-life plan, whether it's chemical degradation that turns the material into carbon dioxide and water, or recycling and repurposing."

To make the new material, Kerton's team started out with oil extracted from the remains of Atlantic salmon, after the fish were prepared for sale to consumers. "I find it interesting how we can make something useful, something that could even change the way plastics are made, from the garbage that people just throw out," says Mikhailey Wheeler, a graduate student who is presenting the work at the meeting. Both Kerton and Wheeler are at Memorial University of Newfoundland (Canada).

The conventional method for producing polyurethanes presents a number of environmental and safety problems. It requires crude oil, a non-renewable resource, and phosgene, a colorless and highly toxic gas. The synthesis generates isocyanates, potent respiratory irritants, and the final product does not readily break down in the environment. The limited biodegradation that does occur can release carcinogenic compounds. Meanwhile, demand for greener alternatives is growing. Previously, others have developed new polyurethanes using plant-derived oils to replace petroleum. However, these too come with a drawback: The crops, often soybeans, that produce the oil require land that could otherwise be used to grow food.

Leftover fish struck Kerton as a promising alternative. Salmon farming is a major industry for coastal Newfoundland, where her university is located. After the fish are processed, leftover parts are often discarded, but sometimes oil is extracted from them. Kerton and her colleagues developed a process for converting this fish oil into a polyurethane-like polymer. First, they add oxygen to the unsaturated oil in a controlled way to form epoxides, molecules similar to those in epoxy resin. After reacting these epoxides with carbon dioxide, they link the resulting molecules together with nitrogen-containing amines to form the new material.

But does the plastic smell fishy? "When we start the process with the fish oil, there is a faint kind of fish smell, but as we go through the steps, that smell disappears," Kerton says.

Kerton and her team described this method in a paper last August, and since then, Wheeler has been tweaking it. She has recently had some success swapping out the amine for amino acids, which simplifies the chemistry involved. And while the amine they used previously had to be derived from cashew nut shells, the amino acids already exist in nature. Wheeler's preliminary results suggest that histidine and asparagine could fill in for the amine by linking together the polymer's components.

In other experiments, they have begun examining how readily the new material would likely break down once its useful life is over. Wheeler soaked pieces of it in water, and to speed up the degradation for some pieces, she added lipase, an enzyme capable of breaking down fats like those in the fish oil. Under a microscope, she later saw microbial growth on all of the samples, even those that had been in plain water, an encouraging sign that the new material might biodegrade readily, Wheeler says.

Kerton and Wheeler plan to continue testing the effects of using an amino acid in the synthesis and studying how amenable the material is to the microbial growth that could hasten its breakdown. They also intend to study its physical properties to see how it might potentially be used in real world applications, such as in packaging or fibers for clothing.

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A press conference on this topic will be held Thursday, April 8, at 11 a.m. Eastern time online at http://www.acs.org/acsspring2021conferences.

The researchers acknowledge support and funding from the Natural Sciences and Engineering Research Council of Canada and Memorial University of Newfoundland.

 

Paleopharmaceuticals from Baltic amber might fight drug-resistant infections

AMERICAN CHEMICAL SOCIETY

Research News

 

IMAGE: BALTIC AMBER IS NOT ONLY BEAUTIFUL, BUT ALSO A POTENTIAL SOURCE OF NEW ANTIBIOTICS. view more 

CREDIT: CONNOR MCDERMOTT

WASHINGTON, April 5, 2021 -- For centuries, people in Baltic nations have used ancient amber for medicinal purposes. Even today, infants are given amber necklaces that they chew to relieve teething pain, and people put pulverized amber in elixirs and ointments for its purported anti-inflammatory and anti-infective properties. Now, scientists have pinpointed compounds that help explain Baltic amber's therapeutic effects and that could lead to new medicines to combat antibiotic-resistant infections.

The researchers will present their results today at the spring meeting of the American Chemical Society (ACS). ACS Spring 2021 is being held online April 5-30. Live sessions will be hosted April 5-16, and on-demand and networking content will continue through April 30. The meeting features nearly 9,000 presentations on a wide range of science topics.

Each year in the U.S., at least 2.8 million people get antibiotic-resistant infections, leading to 35,000 deaths, according to the U.S. Centers for Disease Control and Prevention. "We knew from previous research that there were substances in Baltic amber that might lead to new antibiotics, but they had not been systematically explored," says Elizabeth Ambrose, Ph.D., who is the principal investigator of the project. "We have now extracted and identified several compounds in Baltic amber that show activity against gram-positive, antibiotic-resistant bacteria."

Ambrose's interest originally stemmed from her Baltic heritage. While visiting family in Lithuania, she collected amber samples and heard stories about their medicinal uses. The Baltic Sea region contains the world's largest deposit of the material, which is fossilized resin formed about 44 million years ago. The resin oozed from now-extinct pines in the Sciadopityaceae family and acted as a defense against microorganisms such as bacteria and fungi, as well as herbivorous insects that would become trapped in the resin.

Ambrose and graduate student Connor McDermott, who are at the University of Minnesota, analyzed commercially available Baltic amber samples, in addition to some that Ambrose had collected. "One major challenge was preparing a homogeneous fine powder from the amber pebbles that could be extracted with solvents," McDermott explains. He used a tabletop jar rolling mill, in which the jar is filled with ceramic beads and amber pebbles and rotated on its side. Through trial and error, he determined the correct ratio of beads to pebbles to yield a semi-fine powder. Then, using various combinations of solvents and techniques, he filtered, concentrated and analyzed the amber powder extracts by gas chromatography-mass spectrometry (GC-MS).

Dozens of compounds were identified from the GC-MS spectra. The most interesting were abietic acid, dehydroabietic acid and palustric acid -- 20-carbon, three-ringed organic compounds with known biological activity. Because these compounds are difficult to purify, the researchers bought pure samples and sent them to a company that tested their activity against nine bacterial species, some of which are known to be antibiotic resistant.

"The most important finding is that these compounds are active against gram-positive bacteria, such as certain Staphylococcus aureus strains, but not gram-negative bacteria," McDermott says. Gram-positive bacteria have a less complex cell wall than gram-negative bacteria. "This implies that the composition of the bacterial membrane is important for the activity of the compounds," he says. McDermott also obtained a Japanese umbrella pine, the closest living species to the trees that produced the resin that became Baltic amber. He extracted resin from the needles and stem and identified sclarene, a molecule present in the extracts that could theoretically undergo chemical transformations to produce the bioactive compounds the researchers found in Baltic amber samples.

"We are excited to move forward with these results," Ambrose says. "Abietic acids and their derivatives are potentially an untapped source of new medicines, especially for treating infections caused by gram-positive bacteria, which are increasingly becoming resistant to known antibiotics."

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A press conference on this topic will be held Monday, April 5, at 11 a.m. Eastern time online at http://www.acs.org/acsspring2021conferences.

The researchers acknowledge support and funding from the University of Minnesota Engebretson Drug Design and Development Grant and the Office of the Vice President for Research Grant-in-Aid of Research, Artistry, and Scholarship Program.

 

New paper shows benefits of Louisiana coastal restoration to soil carbon sequestration

THE WATER INSTITUTE OF THE GULF

Research News 

BATON ROUGE, La. (March 2021) - Without restoration efforts in coastal Louisiana, marshes in the state could lose half of their current ability to store carbon in the soil over a period of 50 years, according to a new paper published in American Geophysical Union Journal of Geophysical Research Biogeosciences.

"This reduction in capacity could significantly alter the global carbon budget, given that Louisiana's marsh soils account for between 5 and 21 percent of the global soil carbon storage in tidally influenced wetlands," said Melissa Baustian, lead author and coastal ecologist at The Water Institute of the Gulf.

The article, "Long-term carbon sinks in marsh soils of coastal Louisiana are at risk to wetland loss" examined 24 south Louisiana sites located within four marsh habitats defined by the amount of saltwater influence - fresh, intermediate, brackish, and saline. Carbon sink is a reservoir that stores more carbon than it releases.

By working with colleagues from U.S. Geological Survey, Vernadero Group, Abt Associates, and Tulane University the team used marsh habitat maps from 1949 to 2013, deep soil cores, soil carbon accumulation rates, and maps of future marsh area, to confirm the importance of considering historical habitats when evaluating a coastal areas' long-term ability to store carbon in the soil. Due to the evolving nature of coastal wetland habitats, simply looking at current conditions might not reflect how much carbon was buried historically or how much carbon can be buried in the future, especially in Louisiana where land loss is a continuing concern.

"Protection and restoration of these marshes is vital to help protect the pool of buried carbon in the soils, and to prevent release of carbon to the atmosphere from soil oxidation," Baustian said.

As Louisiana continues to build projects contained with its 50-year Coastal Master Plan, Gov. John Bel Edwards announced in August that the Institute, led by Baustian, will be working with the state to quantify the carbon sink potential of coastal Louisiana with and without restoration projects in the state's 2017 Coastal Master Plan to examine how these potential coastal carbon sinks could help reach the Governor's greenhouse gas emissions goals of 2025, 2030, and 2050.

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Lightning strikes will more than double in Arctic as climate warms

UCI-led team reports that an increase in lightning will drive both wildfires and warming above Arctic Circle

UNIVERSITY OF CALIFORNIA - IRVINE

Research News

 

Irvine, Calif. -- In 2019, the National Weather Service in Alaska reported spotting the first-known lightning strikes within 300 miles of the North Pole. Lightning strikes are almost unheard of above the Arctic Circle, but scientists led by researchers at the University of California, Irvine have published new research in the journal Nature Climate Change detailing how Arctic lightning strikes stand to increase by about 100 percent over northern lands by the end of the century as the climate continues warming.

"We projected how lightning in high-latitude boreal forests and Arctic tundra regions will change across North America and Eurasia," said Yang Chen, a research scientist in the UCI Department of Earth System Science who led the new work. "The size of the lightning response surprised us because expected changes at mid-latitudes are much smaller."

The finding offers a glimpse into the changes that're in store for the Arctic as the planet continues warming; it suggests Arctic weather reports during summertime will be closer to those seen today far to the south, where lightning storms are more common.

James Randerson, a professor in UCI's Department of Earth System Science who co-authored the study, was part of a NASA-led field campaign that studied wildfire occurrence in Alaska during 2015, which was a extreme year for wildfires in the state. "2015 was an exceptional fire year because of a record number of fire starts," Randerson said. "One thing that got us thinking was that lightning was responsible for the record-breaking number of fires."

This led Chen to look at over-twenty-year-old NASA satellite data on lighting strikes in northern regions, and construct a relationship between the flash rate and climatic factors. By using future climate projections from multiple models used by the United Nations, the team estimated a significant increase in lightning strikes as a result of increases in atmospheric convection and more intense thunderstorms.

A lightning strike bump could open a Pandora's box of related troubles. Fires, Randerson explained, burn away short grasses, mosses, and shrubs that are important components of Arctic tundra ecosystems. Such plants cover much of the landscape, and one thing they do is keep the seeds of trees from taking root in the soil. After a fire burns away low-lying plants, however, seeds from trees can more easily grow on bare soil, allowing forests stands to expand north. Evergreen forests will replace what's typically a snow-covered landscape; snow's white hue reflects sunlight back out into space, but darker forests absorb solar energy, helping warm the region even further.

And there's more trouble: more fires mean more permafrost -- perennially frozen soil that defines much of the Arctic landscape -- will melt as the fires strip away protective insulative layers of moss and dead organic matter that keep soils cool. Permafrost stores a lot of organic carbon that, if melted out of the ice, will convert to greenhouse gases carbon dioxide and methane, which, when released, will drive even more warming.

The lighting finding comes of the heels of another study that, led by Randerson, published in the Journal of Geophysical Research on Monday, April 5 describes how amplified Arctic warming and the melting of the Greenland ice sheet will scramble food webs in the surrounding oceans.

Now, Chen and Randerson say, scientists need to start paying more attention to the frequency of Arctic lightning strikes so they can gauge how the story unfolds in the coming decades.

"This phenomenon is very sporadic, and it's very difficult to measure accurately over long time periods," said Randerson. "It's so rare to have lightning above the Arctic Circle." Their results, he hopes, will galvanize calls for new satellite missions that can monitor Arctic and boreal latitudes for lightning strikes and the fires they might ignite.

Back in 2019, the National Weather Service in Alaska released a special announcement about the North Pole lightning strikes. Such announcements, however, may struggle to make headlines by the end of the century.

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This work, funded by the U.S. Department of Energy Office of Science, NASA's Interdisciplinary Science and Carbon Monitoring System programs, and DOE's Next Generation Ecosystem Experiment Arctic project, includes researchers from the University of California, Berkeley; Lawrence Berkeley National Laboratory; Harvard University and Vrije Universiteit Amsterdam.

Increased winter snowmelt threatens western water resources

UNIVERSITY OF COLORADO AT BOULDER

Research News

 

IMAGE: COMBINED PHOTOS OF THE SENATOR BECK BASIN IN THE COLORADO SAN JUAN MOUNTAINS DURING INCREASINGLY WARMER MONTHS. view more 

CREDIT: JEFFREY DEEMS/CIRES AND MATTHEW KENNEDY/CU BOULDER EXTREME ICE SURVEY

More snow is melting during winter across the West, a concerning trend that could impact everything from ski conditions to fire danger and agriculture, according to a new University of Colorado Boulder analysis of 40 years of data.

Researchers found that since the late 1970s, winter's boundary with spring has been slowly disappearing, with one-third of 1,065 snow measurement stations from the Mexican border to the Alaskan Arctic recording increasing winter snowmelt. While stations with significant melt increases have recorded them mostly in November and March, the researchers found that melt is increasing in all cold season months--from October to March.

Their new findings, published today in Nature Climate Change, have important implications for water resource planning and may indicate fewer pristine powder days and crustier snow for skiers.

"Particularly in cold mountain environments, snow accumulates over the winter--it grows and grows--and gets to a point where it reaches a maximum depth, before melt starts in the spring," said Keith Musselman, lead author on the study and research associate ,at the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado Boulder.

But the new research found that melt before April 1 has increased at almost half of more than 600 stations in western North America, by an average of 3.5% per decade.

"Historically, water managers use the date of April 1 to distinguish winter and spring, but this distinction is becoming increasingly blurred as melt increases during the winter," said Noah Molotch, co-author on the study, associate professor of geography and fellow at INSTAAR.

Snow is the primary source of water and streamflow in western North America and provides water to 1 billion people globally. In the West, snowy mountains act like water towers, reserving water up high until it melts, making it available to lower elevations that need it during the summer, like a natural drip irrigation system.

"That slow trickle of meltwater that reliably occurs over the dry season is something that we have built our entire water infrastructure on in the West," said Musselman. "We rely very heavily on that water that comes down our rivers and streams in the warm season of July and August."

More winter snowmelt is effectively shifting the timing of water entering the system, turning that natural drip irrigation system on more frequently in the winter, shifting it away from the summer, he said.

This is a big concern for water resource management and drought prediction in the West, which depends heavily on late winter snowpack levels in March and April. This shift in water delivery timing could also affect wildfire seasons and agricultural irrigation needs.

Wetter soils in the winter also have ecological implications. One, the wet soils have no more capacity to soak up additional water during spring melt or rainstorms, which can increase flash flooding. Wetter winter soils also keep microbes awake and unfrozen during a time they might otherwise lay dormant. This affects the timing of nutrient availability, water quality and can increase carbon dioxide emissions.

An underutilized data source

Across the western U.S., hundreds of thin, fluid-filled metal pillows are carefully tucked away on the ground and out of sight from outdoor enthusiasts. These sensors are part of an extensive network of long-running manual and automated snow observation stations, which you may have even used data from when looking up how much snow is on your favorite snowshoeing or Nordic skiing trail.

This new study is the first to compile data from all 1,065 automated stations in western North America, providing valuable statistical insight into how mountain snow is changing.

And by using automated, continuously recording snowpack stations instead of manual, monthly observations, the new research shows that winter melt trends are very widespread--at three-times the number of stations with snowpack declines, according to Musselman.

Snowpack is typically measured by calculating how much water will be produced when it melts, known as snow-water equivalent (SWE), which is affected by how much snow falls from the sky in a given season. But because winter snowpack melt is influenced more by temperature than by precipitation, it is a better indicator of climate warming over time.

"These automated stations can be really helpful to understand potential climate change impacts on our resources," said Musselman. "Their observations are consistent with what our climate models are suggesting will continue to happen."

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Other authors on this publication include Nans Addor at the University of Exeter and Julie Vano at the Aspen Global Change Institute.

 SURPRIZE, WE WERE NOT VEGAN

Humans were apex predators for two million years

What did our ancestors eat during the stone age? Mostly meat

TEL-AVIV UNIVERSITY

VEGETARIANISM AND VEGANISM ARE THE PRODUCT 

OF INDUSTRIALIZED URABANISM

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IMAGE: HUMAN BRAIN view more 

CREDIT: DR. MIKI BEN DOR

Researchers at Tel Aviv University were able to reconstruct the nutrition of stone age humans. In a paper published in the Yearbook of the American Physical Anthropology Association, Dr. Miki Ben-Dor and Prof. Ran Barkai of the Jacob M. Alkov Department of Archaeology at Tel Aviv University, together with Raphael Sirtoli of Portugal, show that humans were an apex predator for about two million years. Only the extinction of larger animals (megafauna) in various parts of the world, and the decline of animal food sources toward the end of the stone age, led humans to gradually increase the vegetable element in their nutrition, until finally they had no choice but to domesticate both plants and animals - and became farmers.

"So far, attempts to reconstruct the diet of stone-age humans were mostly based on comparisons to 20th century hunter-gatherer societies," explains Dr. Ben-Dor. "This comparison is futile, however, because two million years ago hunter-gatherer societies could hunt and consume elephants and other large animals - while today's hunter gatherers do not have access to such bounty. The entire ecosystem has changed, and conditions cannot be compared. We decided to use other methods to reconstruct the diet of stone-age humans: to examine the memory preserved in our own bodies, our metabolism, genetics and physical build. Human behavior changes rapidly, but evolution is slow. The body remembers."

In a process unprecedented in its extent, Dr. Ben-Dor and his colleagues collected about 25 lines of evidence from about 400 scientific papers from different scientific disciplines, dealing with the focal question: Were stone-age humans specialized carnivores or were they generalist omnivores? Most evidence was found in research on current biology, namely genetics, metabolism, physiology and morphology.

"One prominent example is the acidity of the human stomach," says Dr. Ben-Dor. "The acidity in our stomach is high when compared to omnivores and even to other predators. Producing and maintaining strong acidity require large amounts of energy, and its existence is evidence for consuming animal products. Strong acidity provides protection from harmful bacteria found in meat, and prehistoric humans, hunting large animals whose meat sufficed for days or even weeks, often consumed old meat containing large quantities of bacteria, and thus needed to maintain a high level of acidity. Another indication of being predators is the structure of the fat cells in our bodies. In the bodies of omnivores, fat is stored in a relatively small number of large fat cells, while in predators, including humans, it's the other way around: we have a much larger number of smaller fat cells. Significant evidence for the evolution of humans as predators has also been found in our genome. For example, geneticists have concluded that "areas of the human genome were closed off to enable a fat-rich diet, while in chimpanzees, areas of the genome were opened to enable a sugar-rich diet."

Evidence from human biology was supplemented by archaeological evidence. For instance, research on stable isotopes in the bones of prehistoric humans, as well as hunting practices unique to humans, show that humans specialized in hunting large and medium-sized animals with high fat content. Comparing humans to large social predators of today, all of whom hunt large animals and obtain more than 70% of their energy from animal sources, reinforced the conclusion that humans specialized in hunting large animals and were in fact hypercarnivores.

"Hunting large animals is not an afternoon hobby," says Dr. Ben-Dor. "It requires a great deal of knowledge, and lions and hyenas attain these abilities after long years of learning. Clearly, the remains of large animals found in countless archaeological sites are the result of humans' high expertise as hunters of large animals. Many researchers who study the extinction of the large animals agree that hunting by humans played a major role in this extinction - and there is no better proof of humans' specialization in hunting large animals. Most probably, like in current-day predators, hunting itself was a focal human activity throughout most of human evolution. Other archaeological evidence - like the fact that specialized tools for obtaining and processing vegetable foods only appeared in the later stages of human evolution - also supports the centrality of large animals in the human diet, throughout most of human history."

The multidisciplinary reconstruction conducted by TAU researchers for almost a decade proposes a complete change of paradigm in the understanding of human evolution. Contrary to the widespread hypothesis that humans owe their evolution and survival to their dietary flexibility, which allowed them to combine the hunting of animals with vegetable foods, the picture emerging here is of humans evolving mostly as predators of large animals.

"Archaeological evidence does not overlook the fact that stone-age humans also consumed plants," adds Dr. Ben-Dor. "But according to the findings of this study plants only became a major component of the human diet toward the end of the era."

Evidence of genetic changes and the appearance of unique stone tools for processing plants led the researchers to conclude that, starting about 85,000 years ago in Africa, and about 40,000 years ago in Europe and Asia, a gradual rise occurred in the consumption of plant foods as well as dietary diversity - in accordance with varying ecological conditions. This rise was accompanied by an increase in the local uniqueness of the stone tool culture, which is similar to the diversity of material cultures in 20th-century hunter-predators, long periods of similarity and continuity were observed in stone tools, regardless of local ecological conditions.

In contrast, during the two million years when, according to the researchers, humans were apex "Our study addresses a very great current controversy - both scientific and non-scientific," says Prof. Barkai. "For many people today, the Paleolithic diet is a critical issue, not only with regard to the past, but also concerning the present and future. It is hard to convince a devout vegetarian that his/her ancestors were not vegetarians, and people tend to confuse personal beliefs with scientific reality. Our study is both multidisciplinary and interdisciplinary. We propose a picture that is unprecedented in its inclusiveness and breadth, which clearly shows that humans were initially apex predators, who specialized in hunting large animals. As Darwin discovered, the adaptation of species to obtaining and digesting their food is the main source of evolutionary changes, and thus the claim that humans were apex predators throughout most of their development may provide a broad basis for fundamental insights on the biological and cultural evolution of humans."

CAPTION

the evolution of the HTL during the Pleistocene as we interpret it, based on the totality of the evidence.

CREDIT

Dr. Miki Ben Dor

 

What are forever chemicals, and do they last forever? (video)

AMERICAN CHEMICAL SOCIETY

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IMAGE: FOREVER CHEMICALS ARE KNOWN FOR BEING WATER-, HEAT- AND OIL-RESISTANT, WHICH MAKES THEM USEFUL IN EVERYTHING FROM RAIN JACKETS TO FIREFIGHTING FOAMS. BUT THE CHEMISTRY THAT MAKES THEM SO USEFUL... view more 

CREDIT: THE AMERICAN CHEMICAL SOCIETY

WASHINGTON, April 5, 2021 -- Forever chemicals are known for being water-, heat- and oil-resistant, which makes them useful in everything from rain jackets to firefighting foams. But the chemistry that makes them so useful also makes them stick around in the environment and in us -- and that could be a bad thing: https://youtu.be/tqKEG5LxPiY.

Ozone pollution harms maize crops, study finds

CARL R. WOESE INSTITUTE FOR GENOMIC BIOLOGY, UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN

Research News

 

IMAGE: MAIZE EXPERIMENTAL FIELD PLOT FUMIGATED WITH ELEVATED OZONE (GREEN PIPES). MAIZE LEAF SAMPLES WERE COLLECTED FROM SIMILAR RINGS THROUGHOUT THE GROWING SEASON, TO UNDERSTAND THE RESPONSE IN DIVERSE MAIZE LINES. view more 

CREDIT: AINSWORTH LAB

Although stratospheric ozone protects us by filtering out the sun's ultraviolet radiation, tropospheric ozone is a harmful pollutant. A new study has shown that ozone in the lower layers of the atmosphere decreases crop yields in maize and changes the types of chemicals that are found inside the leaves.

Ozone is formed when nitrous oxide, released from industries and tail pipes of cars, is broken down by sunlight and chemically reacts to form ozone. Researchers at the University of Illinois Urbana-Champaign have been studying the effects of ozone pollution on crops for over 20 years at a unique facility where crops can be grown under real-world farm field conditions but with increased concentrations of ozone pollution.

"Ozone pollution is higher in the northern hemisphere, and peaks in the warmer, summer months. High concentrations of ozone pollution overlap temporally and spatially with crop growth, so it is important to study how the high ozone concentrations affect crop yields," said Jessica Wedow, a former PhD student in the Ainsworth lab.

The researchers looked at three types of maize: two inbred lines B73 and Mo17, and the hybrid cross B73 × Mo17. Surprisingly, they found that chronic ozone stress caused a 25% decrease in yield in the hybrid crops while the inbred plants remained unaffected. The hybrid plants also aged faster than the inbred crops.

To understand why B73 × Mo17 was affected, the researchers measured the chemical composition of the leaves. "The inbred plants did not respond to ozone. On the other hand, the hybrid plants produced more α?tocopherol and phytosterols, which help quench reactive oxygen molecules and stabilize the chloroplast membranes," Wedow said. These results suggest that the since the hybrid maize is more sensitive to ozone exposure, they may be producing more chemicals that deal with the consequences of chronic ozone stress.

"This study provides clues to improve maize tolerance to ozone pollution," said Lisa Ainsworth (GEGC), the Research Leader of the USDA ARS Global Change and Photosynthesis Research Unit. The group is currently studying whether these responses are consistent across other important grasses, including those used for bioenergy.

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The paper "Age-dependent increase in a-tocopherol and phytosterols in maize leaves exposed to elevated ozone pollution" was published in Plant Direct and can be found at https://doi.org/10.1002/pld3.307. The study was funded by the NSF Plant Genome Research Program.