No increase in mortality for most overweight people, study finds

BMI’s link with mortality may also vary by age, per two decades of data on more than half a million US adults

Peer-Reviewed Publication

PLOS

 

IMAGE: THE STUDY HIGHLIGHTS THE INCREASING RESERVATIONS OF USING BMI ALONE TO DRIVE CLINICAL DECISIONS. view more 

CREDIT: MOE MAGNERS, PEXELS, CC0 (HTTPS://CREATIVECOMMONS.ORG/PUBLICDOMAIN/ZERO/1.0/)

Body mass index (BMI) may not increase mortality independently of other risk factors in adults, according to a new study published this week in the open-access journal PLOS ONE by Aayush Visaria and Soko Setoguchi of Rutgers University, US.

The prevalence of overweight and obesity has risen dramatically over the last 25 years, and it is well-established that elevated BMI can contribute to several cardio-metabolic conditions. However, studies that have analyzed the association between BMI and all-cause mortality have been inconsistent. Most US studies have used data from the 1960s through 1990s and have included predominantly non-Hispanic White adults. 

In the new work, the researchers retrospectively studied data on 554,332 US adults from the 1999-2018 National Health Interview Survey and the 2019 US National Death Index. BMI was calculated using self-reported height and weight and participants were divided into 9 BMI categories for the analysis. Information on demographics, socio-behavioral factors, comorbidities and healthcare access was also available. On average, participants were 46 years old, 50% female and 69% non-Hispanic White. 35% of those included in the study had a BMI between 25 and 30, which is typically defined as overweight, and 27.2% had a BMI above or equal to 30, typically defined as obese.

Over a median follow-up of 9 years and a maximum follow-up of 20 years, the researchers observed 75,807 deaths. The risk of all-cause mortality was similar across a wide range of BMI categories. For older adults, there was no significant increase in mortality for any BMI between 22.5 and 34.9, which extends into the BMI categories typically considered obese. For younger adults, there was no significant increase in mortality for any BMI between 22.5 and 27.4. Overall, for adults with a BMI of 30 or over, there was a 21% to 108% increased mortality risk attributed to their weight. The patterns observed in the overall population remained largely the same in men and women and across races and ethnicities.

The authors conclude that further studies incorporating weight history, body composition and morbidity outcomes are needed to fully characterize BMI-mortality associations, but say that BMI in the overweight range is generally not associated with increased risk of all-cause mortality.

The authors add: “Our study highlights the increasing reservations of using BMI alone to drive clinical decisions. There is no clear increase in all-cause mortality across a range of traditionally normal and overweight BMI ranges; however, that is not to say that morbidity is similar across these BMI ranges. Future studies will need to assess incidence of cardio-metabolic morbidities.”

#####

In your coverage please use this URL to provide access to the freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0287218

Citation: Visaria A, Setoguchi S (2023) Body mass index and all-cause mortality in a 21st century U.S. population: A National Health Interview Survey analysis. PLoS ONE 18(7): e0287218. https://doi.org/10.1371/journal.pone.0287218

Author Countries: USA

Funding: The authors received no specific funding for this work.

---

JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0287218 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Body mass index and all-cause mortality in a 21st century U.S. population: A National Health Interview Survey analysis

ARTICLE PUBLICATION DATE

5-Jul-2023

Sunscreen leaching poses minimal threat to aquatic wildlife

Reports and Proceedings

SOCIETY FOR EXPERIMENTAL BIOLOGY

 

IMAGE: THIS IS A MATURE DAPHNIA MAGNA IMAGED UNDER A MICROSCOPE AT 20X MAGNIFICATION. THE PHOTO WAS TAKEN AT THE END OF THE 21 DAY EXPOSURE TO SUNSCREEN SO THAT WE COULD MEASURE ITS BODY LENGTH. THE BLACK SPHERES ON THE BOTTOM LEFT ARE DEVELOPING EGGS. view more 

CREDIT: AARON BOYD

New research reveals that sunscreen contamination may be less harmful to wildlife than previously thought. This study by Aaron Boyd, a PhD candidate at the University of Alberta in Edmonton, Canada, demonstrates how exposure to sunscreen is actually a low risk for small aquatic animals compared to some of the suncream’s individual chemicals.

Sunscreens contain ultraviolet filters (UVFs) which have been found to be toxic to marine life such as corals, leading to the ban of some UVFs in Hawaii and Palau. If sunscreen is applied to the skin before swimming in lakes and rivers, these UVFs and other chemicals will leach into surrounding waters.

Mr Boyd’s research investigates how the chemical cocktail in sunscreen interacts to affect marine life, instead of just focusing on the UVFs and other chemicals on their own. “Researchers overwhelmingly perform studies testing the toxicity of UVFs in isolation by exposing test organisms to one chemical at a time,” says Mr Boyd. “In fact, less than 3% of aquatic toxicology studies published to date have investigated whole sunscreen mixtures, leaving a massive knowledge gap to be addressed.”

This research compared the long-term toxicity of five different sunscreen mixtures, as well as their individual UVFs, on Daphnia water fleas. Daphnia are invertebrates that are commonly found in freshwater lakes throughout the world and are a good indicator of how pollution affects aquatic life.

“We were very surprised to find that sunscreen mixtures are much less toxic to Daphnia than what would be expected based on the quantity of each UV filter present within the mixtures,” says Mr Boyd. “In fact, we found that Daphnia could survive long-term exposure to sunscreens containing octocrylene at concentrations >50x higher than what would be completely lethal to all Daphnia had they been exposed to the UVF alone.”

The rate at which new chemicals are developed and released into the environment is much faster than the rate at which scientists can proper study the consequences of contamination. “As a result,” says Mr Boyd, “it's important that we utilize our limited research resources effectively by identifying which contaminants are likely to cause harm to the environment, and which contaminants are lower risk.”

“We found that the other components of the sunscreen mixtures reduced the toxicity to such a large extent that perhaps these chemicals are not a contamination concern in most environments, allowing for us to reallocate our limited research resources towards identifying other contaminants that could be much more concerning,” says Mr Boyd. “This potentially indicates that the vast majority of studies investigating the toxicity of individual UV filters could be overestimating the toxicity of these chemicals in aquatic environments.”

Mr Boyd still strongly recommends the use of sunscreen when spending time outdoors. “Regardless of any potential environmental toxicity of sunscreens, always wear sunscreen when going outside for an extended period of time. The threat of cancer is much more severe than the potential effects that sunscreen contamination may cause!”

Artificial cells demonstrate that "life finds a way"

Peer-Reviewed Publication

INDIANA UNIVERSITY

 

IMAGE: ELECTRON MICROGRAPH OF A CLUSTER OF MINIMAL CELLS MAGNIFIED 15,000 TIMES. THE SYNTHETICALLY STREAMLINED BACTERIUM, MYCOPLASMA MYCOIDES, CONTAINS LESS THAN 500 GENES. view more 

CREDIT: THE IMAGES BY TOM DEERINCK AND MARK ELLISMAN OF THE NATIONAL CENTER FOR IMAGING AND MICROSCOPY RESEARCH AT THE UNIVERSITY OF CALIFORNIA AT SAN DIEGO.

“Listen, if there's one thing the history of evolution has taught us is that life will not be contained. Life breaks free. It expands to new territories, and it crashes through barriers painfully, maybe even dangerously, but . . . life finds a way,” said Ian Malcolm, Jeff Goldblum's character in Jurassic Park, the 1993 science fiction film about a park with living dinosaurs.

You won't find any Velociraptors lurking around evolutionary biologist Jay T. Lennon's lab; however, Lennon, a professor in the College of Arts and Sciences Department of Biology at Indiana University Bloomington, and his colleagues have found that life does indeed find a way. Lennon's research team has been studying a synthetically constructed minimal cell that has been stripped of all but its essential genes. The team found that the streamlined cell can evolve just as fast as a normal cell—demonstrating the capacity for organisms to adapt, even with an unnatural genome that would seemingly provide little flexibility.

“It appears there’s something about life that’s really robust,” says Lennon. “We can simplify it down to just the bare essentials, but that doesn’t stop evolution from going to work.”

For their study, Lennon's team used the synthetic organism, Mycoplasma mycoides JCVI-syn3B—a minimized version of the bacterium M. mycoides commonly found in the guts of goats and similar animals. Over millennia, the parasitic bacterium has naturally lost many of its genes as it evolved to depend on its host for nutrition. Researchers at the J. Craig Venter Institute in California took this one step further. In 2016, they eliminated 45 percent of the 901 genes from the natural M. mycoides genome—reducing it to the smallest set of genes required for autonomous cellular life. At 493 genes, the minimal genome of M. mycoides JCVI-syn3B is the smallest of any known free-living organism. In comparison, many animal and plant genomes contain more than 20,000 genes.

In principle, the simplest organism would have no functional redundancies and possess only the minimum number of genes essential for life. Any mutation in such an organism could lethally disrupt one or more cellular functions, placing constraints on evolution. Organisms with streamlined genomes have fewer targets upon which positive selection can act, thus limiting opportunities for adaptation.

Although M. mycoides JCVI-syn3B could grow and divide in laboratory conditions, Lennon and colleagues wanted to know how a minimal cell would respond to the forces of evolution over time, particularly given the limited raw materials upon which natural selection could operate as well as the uncharacterized input of new mutations.

“Every single gene in its genome is essential,” says Lennon in reference to M. mycoides JCVI-syn3B. “One could hypothesize that there is no wiggle room for mutations, which could constrain its potential to evolve.”

The researchers established that M. mycoides JCVI-syn3B, in fact, has an exceptionally high mutation rate. They then grew it in the lab where it was allowed to evolve freely for 300 days, equivalent to 2000 bacterial generations or about 40,000 years of human evolution.

The next step was to set up experiments to determine how the minimal cells that had evolved for 300 days performed in comparison to the original, non-minimal M. mycoides as well as to a strain of minimal cells that hadn't evolved for 300 days. In the comparison tests, the researchers put equal amounts of the strains being assessed together in a test tube. The strain better suited to its environment became the more common strain.

They found that the non-minimal version of the bacterium easily outcompeted the unevolved minimal version. The minimal bacterium that had evolved for 300 days, however, did much better, effectively recovering all of the fitness that it had lost due to genome streamlining. The researchers identified the genes that changed the most during evolution. Some of these genes were involved in constructing the surface of the cell, while the functions of several others remain unknown.

Details about the study can be found in a paper recently featured in Nature. Roy Z. Moger-Reischer, a Ph.D. student in the Lennon lab at the time of the study, is first author on the paper.

Understanding how organisms with simplified genomes overcome evolutionary challenges has important implications for long-standing problems in biology—including the treatment of clinical pathogens, the persistence of host-associated endosymbionts, the refinement of engineered microorganisms, and the origin of life itself. The research done by Lennon and his team demonstrates the power of natural selection to rapidly optimize fitness in the simplest autonomous organism, with implications for the evolution of cellular complexity. In other words, it shows that life finds a way.

Electron micrograph of a cluster of minimal cells magnified 15,000 times. The synthetically streamlined bacterium, Mycoplasma mycoides, contains less than 500 genes.

CREDIT

Image by Tom Deerinck and Mark Ellisman of the National Center for Imaging and Microscopy Research at the University of California at San Diego.

JOURNAL

Nature

DOI

10.1038/s41586-023-06288-x 

ARTICLE TITLE

Evolution of a minimal cell

ARTICLE PUBLICATION DATE

5-Jul-2023

Researchers peer into Earth's inner core: Data show solid metal sphere is 'textured'

by University of Utah

Credit: Pixabay/CC0 Public Domain

At the center the Earth is a solid metal ball, a kind of "planet within a planet," whose existence makes life on the surface possible, at least as we know it.

How Earth's inner core formed, grew and evolved over time remains a mystery, one that a team of University of Utah-led researchers is seeking to plumb with the help of seismic waves from naturally occurring earthquakes. While this 2,442-kilometer-diameter sphere comprises less than 1% of the Earth's total volume, its existence is responsible for the planet's magnetic field, without which Earth would be a much different place.

But the inner core is not the homogenous mass that was once assumed by scientists, but rather it's more like a tapestry of different "fabric," according to Guanning Pang, a former Ph.D. student in the university's Department of Geology and Geophysics.

"For the first time we confirmed that this kind of inhomogeneity is everywhere inside the inner core," Pang said. Now a post-doctoral researcher at Cornell University, Pang is the lead author of a new study, published in Nature that opens a window into the deepest reaches of Earth. He conducted the study as part of his Ph.D. dissertation at Utah.

The other final frontier

"What our study was about was trying to look inside the inner core," said university seismologist Keith Koper, who oversaw the study. "It's like a frontier area. Anytime you want to image the interior of something, you have to strip away the shallow effects. So this is the hardest place to make images, the deepest part, and there's still things that are unknown about it."

This research harnessed a special dataset generated by a global network of seismic arrays set up to detect nuclear blasts. In 1996, the United Nations established the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, CTBTO, to ensure compliance with the international treaty that bans such explosions.

Its centerpiece is the International Monitoring System (IMS), featuring four systems for detecting explosions using advanced sensing instruments sited all over the world. While their purpose is to enforce an international ban on nuclear detonations, they have yielded troves of data scientists can use to shed new light on what's going on in Earth's interior, oceans and atmosphere.

This data have facilitated research that illuminated meteor blasts, identified a colony of pygmy blue whales, advanced weather prediction, and provided insights into how icebergs form.

While Earth's surface has been thoroughly mapped and characterized, its interior is much harder to study since it cannot be directly accessed. The best tools for sensing this hidden realm are earthquakes' seismic waves propagating from the planet's thin crust and vibrating through its rocky mantle and metallic core.

"The planet formed from asteroids that were sort of accreting [in space]. They're running into each other and you generate a lot of energy. So the whole planet, when it's forming up, is melting," Koper said. "It's simply that the iron is heavier and you get what we call core formation. The metals sink to the middle, and the liquid rock is outside, and then it essentially freezes over time. The reason all the metals are down there is because they're heavier than the rocks."

Planet within a planet

For the past few years, Koper's lab has been analyzing seismic data sensitive to the inner core. A previous study, led by Pang identified variations between the rotations of Earth and its inner core that may have triggered a shift in the length of the day in 2001 to 2003.

Earth's core, which measures about 4,300 miles across, is comprised mostly of iron and some nickel, along with a few other elements. The outer core remains liquid, enveloping the solid inner core.

"It's like a planet within a planet that has its own rotation and it's decoupled by this big ocean of molten iron," said Koper, a geology professor who directs the U of U Seismograph Stations, or UUSS.

The protective field of magnetic energy surrounding Earth is created by convection occurring within the liquid outer core, which extends 2,260 kilometers (1,795 miles) above the solid core, he said. The molten metal rises above the solid inner core, cools as it approaches Earth's rocky mantle and sinks. This circulation generates the bands of electrons enveloping the planet. Without Earth's solid inner core, this field would be much weaker and the planetary surface would be bombarded with radiation and solar winds that would strip away the atmosphere and render the surface uninhabitable.

For the new study, the team looked at seismic data recorded by 20 arrays of seismometers placed around the world including two in Antarctica. The closest to Utah is outside Pinedale, Wyo. These instruments are inserted in boreholes drilled up to 10 meters into granite formations and arranged in patterns to concentrate the signals they receive, similar to the way parabolic antennae work.

Pang analyzed seismic waves from 2,455 earthquakes, all exceeding magnitude 5.7, or about the strength of the 2020 quake that rocked Salt Lake City. The way these waves bounced off the inner core help map its internal structure.

Smaller quakes do not generate waves strong enough to be useful for the study.

"This signal that comes back from the inner core is really tiny. The size is about on the order of a nanometer," Koper said. "What we're doing is looking for a needle in a haystack. So these baby echoes and reflections are very hard to see."

The core is changing

Scientists first used seismic waves to determine that the inner core was solid in 1936. Before the discovery by Danish seismologist Inge Lehmann, it was assumed the entire core was liquid since it is exceedingly hot, approaching 10,000 degrees Fahrenheit, about the temperature on the sun's surface.

At some point in Earth's history, the inner core started "nucleating," or solidifying, under the intense pressures existing at the center of the planet. It remains unknown when that process began, but the U team gleaned important clues from the seismic data, which revealed a scattering effect associated with waves that penetrated to the core's interior.

"Our biggest discovery is the inhomogeneity tends to be stronger when you get deeper. Toward the center of the Earth it tends to be stronger," Pang said.

"We think that this fabric is related to how fast the inner core was growing. A long time ago the inner core grew really fast. It reached an equilibrium, and then it started to grow much more slowly," Koper said. "Not all of the iron became solid, so some liquid iron could be trapped inside."

Participating in the study were researchers from University of Southern California, the Université de Nantes in France, and the Los Alamos National Laboratory.

More information: Guanning Pang, Enhanced inner core fine-scale heterogeneity towards Earth's centre, Nature (2023). DOI: 10.1038/s41586-023-06213-2. www.nature.com/articles/s41586-023-06213-2

Journal information: Nature 

Provided by University of Utah 

Bouncing seismic waves reveal distinct layer in Earth's inner core

Utah seismologists peer into Earth's inner core

Tapping seismic data, new research shows solid metal sphere is 'textured'

Peer-Reviewed Publication

UNIVERSITY OF UTAH

 

At the center the Earth is a solid metal ball, a kind of “planet within a planet,” whose existence makes life on the surface possible, at least as we know it.

How Earth’s inner core formed, grew and evolved over time remains a mystery, one that a team of University of Utah-led researchers is seeking to plumb with the help of seismic waves from naturally occurring earthquakes. While this 2,442-kilometer-diameter sphere comprises less than 1% of the Earth’s total volume, its existence is responsible for the planet’s magnetic field, without which Earth would be a much different place.

But the inner core is not the homogenous mass that was once assumed by scientists, but rather it’s more like a tapestry of different “fabric,” according to Guanning Pang, a former PhD student in the U.’s Department of Geology and Geophysics.

“For the first time we confirmed that this kind of inhomogeneity is everywhere inside the inner core,” Pang said. Now a post-doctoral researcher at Cornell University, Pang is the lead author of a new study, published July 5 in Nature that opens a window into the deepest reaches of Earth. He conducted the study as part of his PhD dissertation at Utah.

The other final frontier

“What our study was about was trying to look inside the inner core,” said U seismologist Keith Koper, who oversaw the study. “It’s like a frontier area. Anytime you want to image the interior of something, you have to strip away the shallow effects. So this is the hardest place to make images, the deepest part, and there’s still things that are unknown about it.”

This research harnessed a special dataset generated by a global network of seismic arrays set up to detect nuclear blasts. In 1996, the United Nations established the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, CTBTO, to ensure compliance with the international treaty that bans such explosions.

Its centerpiece is the International Monitoring System (IMS), featuring four systems for detecting explosions using advanced sensing instruments sited all over the world. While their purpose is to enforce an international ban on nuclear detonations, they have yielded troves of data scientists can use to shed new light on what’s going on in Earth’s interior, oceans and atmosphere.

This data has facilitated research that illuminated meteor blasts, identified a colony of pygmy blue whales, advanced weather prediction, and provided insights into how icebergs form.

While Earth’s surface has been thoroughly mapped and characterized, its interior is much harder to study since it cannot be directly accessed. The best tools for sensing this hidden realm are earthquakes’ seismic waves propagating from the planet’s thin crust and vibrating through its rocky mantle and metallic core.

“The planet formed from asteroids that were sort of accreting [in space]. They’re running into each other and you generate a lot of energy. So the whole planet, when it’s forming up, is melting,” Koper said. “It’s simply that the iron is heavier and you get what we call core formation. The metals sink to the middle, and the liquid rock is outside, and then it essentially freezes over time. The reason all the metals are down there is because they’re heavier than the rocks.”

Planet within a planet

For the past few years, Koper’s lab has been analyzing seismic data senstivite to the inner core. A previous study, led by Pang identified variations between the rotations of Earth and its inner core that may have triggered a shift in the length of the day in 2001 to 2003. 

Earth’s core, which measures about 4,300 miles across, is comprised mostly of iron and some nickel, along with a few other elements. The outer core remains liquid, enveloping the solid inner core.

“It’s like a planet within a planet that has its own rotation and it’s decoupled by this big ocean of molten iron,” said Koper, a geology professor who directs the U of U Seismograph Stations, or UUSS.

The protective field of magnetic energy surrounding Earth is created by convection occurring within the liquid outer core, which extends 2,260 kilometers (1,795 miles) above the solid core, he said. The molten metal rises above the solid inner core, cools as it approaches Earth’s rocky mantle and sinks. This circulation generates the bands of electrons enveloping the planet. Without Earth’s solid inner core, this field would be much weaker and the planetary surface would be bombarded with radiation and solar winds that would strip away the atmosphere and render the surface uninhabitable.

For the new study, the U team looked at seismic data recorded by 20 arrays of seismometers placed around the world including two in Antarctica. The closest to Utah is outside Pinedale, Wyo. These instruments are inserted in boreholes drilled up to 10 meters into granite formations and arranged in patterns to concentrate the signals they receive, similar to the way parabolic antennae work.

Pang analyzed seismic waves from 2,455 earthquakes, all exceeding magnitude 5.7, or about the strength of the 2020 quake that rocked Salt Lake City. The way these waves bounced off the inner core help map its internal structure.

Smaller quakes do not generate waves strong enough to be useful for the study. 

“This signal that comes back from the inner core is really tiny. The size is about on the order of a nanometer,” Koper said.  “What we’re doing is looking for a needle in a haystack. So these baby echoes and reflections are very hard to see.”

The core is changing

Scientists first used seismic waves to determine that the inner core was solid in 1936. Before the discovery by Danish seismologist Inge Lehmann, it was assumed the entire core was liquid since it is exceedingly hot, approaching 10,000 degrees Fahrenheit, about the temperature on the sun’s surface.

At some point in Earth’s history, the inner core started “nucleating,” or solidifying, under the intense pressures existing at the center of the planet. It remains unknown when that process began, but the U team gleaned important clues from the seismic data, which revealed a scattering effect associated with waves that penetrated to the core’s interior.

“Our biggest discovery is the inhomogeneity tends to be stronger when you get deeper. Toward the center of the Earth it tends to be stronger,” Pang said.

“We think that this fabric is related to how fast the inner core was growing. A long time ago the inner core grew really fast. It reached an equilibrium, and then it started to grow much more slowly,” Koper said. “Not all of the iron became solid, so some liquid iron could be trapped inside.”

Participating in the study, which was funded by the National Science Foundation, were researchers from University of Southern California, the Université de Nantes in France, and the Los Alamos National Laboratory.

---

JOURNAL

Nature

DOI

10.1038/s41586-023-06213-2 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Enhanced inner core fine-scale heterogeneity towards Earth’s centre

ARTICLE PUBLICATION DATE

5-Jul-2023

Martian dunes eroded by a shift in prevailing winds after the planet's last ice age

Peer-Reviewed Publication

CHINESE ACADEMY OF SCIENCES HEADQUARTERS

 

IMAGE: THE MARTIAN DUNE FORMATION AND MARTIAN CLIMATE IN THE ZHURONG ROVER EXPLORATION ZONE view more 

CREDIT: NAOC

Detailed analysis of data obtained by the Zhurong rover of dunes located on the southern Utopian Plain of Mars suggests the planet underwent a major shift in climate that accompanied changes in prevailing winds. This shift likely occurred about 400,000 years ago, which coincides with the end of the last glacial period on Mars.

Researchers from the National Astronomical Observatories, Institute of Geology and Geophysics and Institute of Tibetan Plateau Research of the Chinese Academy of Sciences, in collaboration with colleagues from Brown University, assessed the surface structure and chemical composition of Martian dunes to determine the age of sand structures and prevailing wind directions at different locations near the Zhurong rover landing site.

The team found that the prevailing wind direction on the southern Utopian Plain shifted nearly 70° from northeast to northwest, eroding crescent-shaped dunes formed during the last glacial period into dark, longitudinal ridges after the last Martian ice age.

The study was published in Nature on July 5, 2023.

"The exploration and research on the climate evolution of Mars has been of great concern for a long time. Mars is the most similar planet to Earth in the Solar System. Understanding Martian climate processes promises to uncover details of the evolution and history of Earth and other planets in our Solar System," said Prof. LI Chunlai from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC), principal investigator of the study.

Prior research suggested that the Martian climate has changed over time, but the inability to directly measure and sample geological formations on Mars limited scientists' ability to validate and better characterize the planet's climate processes. LI's team used high-resolution orbital cameras and the Zhurong rover's terrain and multispectral cameras, surface composition analyzers and meteorological measuring instruments to finally obtain in situ data directly from the Martian surface.

The research team estimated that a change in the angle of the rotational axis of Mars caused the planet to exit its most recent ice age. The effects of this change were subsequently captured by the morphology, orientation, physical properties and stratigraphy, or layering, of dunes on the southern Utopian Plain of Mars, where the Zhurong rover landed.

The study was designed to integrate rover-scale data of dune formations and weather conditions to not only confirm a change in prevailing wind direction with the close of the last ice age, but also improve general circulation models used to predict finer-scale changes in seasonal wind direction. Importantly, prevailing wind data and dune stratigraphy at the rover landing area were consistent with the presence of ice and dust layers found at middle and higher latitudes of the planet.

A great deal of effort is being invested in characterizing the ancient climate of Mars over the course of the Amazonian epoch, which began between 3.55 and 1.8 billion years ago and continues to this day.

"Understanding the Amazonian climate is essential to explain the current Martian landscape, volatile matter reservoirs and atmospheric state, and to relate these current observations and active processes to models of the ancient climate of Mars. Observations of the current climate of Mars can help refine physical models of Martian climate and landscape evolution, and even form new paradigms," said LI.

In situ studies on the Martian surface have enormous scientific value, and the Zhurong rover will be busy collecting data for some time. "We will continue to study both Amazonian and present-day climate to promote the knowledge regarding the last two billion years of Martian climate history, including its environment and processes," said LI.

---

JOURNAL

Nature

DOI

10.1038/s41586-023-06206-1 

ARTICLE TITLE

Martian dunes indicative of wind regime shift in line with end of ice age

ARTICLE PUBLICATION DATE

5-Jul-2023

Similar to humans, elephants also vary what they eat for dinner every night

Peer-Reviewed Publication

BROWN UNIVERSITY

PROVIDENCE, R.I. [Brown University] — Elephants eat plants. That’s common knowledge to biologists and animal-loving schoolchildren alike. Yet figuring out exactly what kind of plants the iconic herbivores eat is more complicated.

A new study from a global team that included Brown conservation biologists used innovative methods to efficiently and precisely analyze the dietary habits of two groups of elephants in Kenya, down to the specific types of plants eaten by which animals in the group. Their findings on the habits of individual elephants help answer important questions about the foraging behaviors of groups, and aid biologists in understanding the conservation approaches that best keep elephants not only sated but satisfied.

The study was published in the journal Royal Society Open Science.

“It’s really important for conservationists to keep in mind that when animals don’t get enough of the foods that they need, they may survive — but they may not prosper,” said study author Tyler Kartzinel, an assistant professor of environmental studies and of ecology, evolution and organismal biology at Brown. “By better understanding what each individual eats, we can better manage iconic species like elephants, rhinos and bison to ensure their populations can grow in sustainable ways.”

One of the main tools that the scientists used to conduct their study is called DNA metabarcoding, a cutting-edge genetic technique that allows researchers to identify the composition of biological samples by matching the extracted DNA fragments representing an elephant’s food to a library of plant DNA barcodes.

Brown has been developing applications for this technology, said Kartzinel, and bringing together researchers from molecular biology and the computational side to solve problems faced by conservationists in the field.

This is the first use of DNA metabarcoding to answer a long-term question about social foraging ecology, which is how members of a social group — such as a family — decide what foods to eat, Kartzinel said.

“When I talk to non-ecologists, they are stunned to learn that we have never really had a clear picture of what all of these charismatic large mammals actually eat in nature,” Kartzinel said. “The reason is that these animals are difficult and dangerous to observe from up-close, they move long distances, they feed at night and in thick bush and a lot of the plants they feed on are quite small.”

Not only are the elephants hard to monitor, but their food can be nearly impossible to identify by eye, even for an expert botanist, according to Kartzinel, who has conducted field research in Kenya.

Understanding an elephant’s favorite foods

The research group compared the new genetic technique to a method called stable isotope analysis, which involves a chemical analysis of animal hair. Two of the study authors, George Wittemyer at Colorado State University and Thure Cerling at the University of Utah, had previously shown that elephants switch from eating fresh grasses when it rains to eating trees during the long dry season. While this advanced study by allowing researchers to identify broad-scale dietary patterns, they still couldn’t discern the different types of plants in the elephant’s diet.

The scientists had saved fecal samples that had been collected in partnership with the non-profit organization Save the Elephants when Wittemyer and Cerling were conducting the stable isotopes analyses almost 20 years ago. Study author Brian Gill, then a Brown post-doctoral associate, determined that the samples were still usable even after many years in storage.

The team coupled combined analyses of carbon stable isotopes from the feces and hair of elephants with dietary DNA metabarcoding, GPS-tracking and remote-sensing data to evaluate the dietary variation of individual elephants in two groups. They matched each unique DNA sequence in the sample to a collection of reference plants — developed with the botanical expertise of Paul Musili, director of the East Africa Herbarium at the National Museums of Kenya — and compared the diets of individual elephants through time.

In their analysis, they showed that dietary differences among individuals were often far greater than had been previously assumed, even among family members that foraged together on a given day.

This study helps address a classic paradox in wildlife ecology, Kartzinel said: “How do social bonds hold family groups together in a world of limited resources?”In other words, given that elephants all seemingly eat the same plants, it’s not obvious why competition for food doesn’t push them apart and force them to forage independently.

The simple answer is that elephants vary their diets based not only on what’s available but also their preferences and physiological needs, said Kartzinel. A pregnant elephant, for example, may have different cravings and requirements at various times in her pregnancy.

While the study wasn’t designed to explain social behavior, these findings help inform theories of why a group of elephants may forage together: The individual elephants don’t always eat exactly the same plants at the same time, so there will usually be enough plants to go around.

These findings may offer valuable insights for conservation biologists. To protect elephants and other major species and create environments in which they can successfully reproduce and grow their populations, they need a variety of plants to eat. This may also decrease the chances of inter-species competition and prevent the animals from poaching human food sources, such as crops.

“Wildlife populations need access to diverse dietary resources to prosper,” Kartzinel said. “Each elephant needs variety, a little bit of spice — not literally in their food, but in their dietary habits.”

This work was supported by the National Science Foundation (DEB-1930820, DEB-2026294, DEB-2046797, and OIA-2033823).

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JOURNAL

Royal Society Open Science

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Foraging history of individual elephants using DNA metabarcoding

ARTICLE PUBLICATION DATE

5-Jul-2023

COI STATEMENT

We thank the Kenyan Office of the President, Kenya Wildlife Service, the 507 National Commission for Science, Technology and Innovation (NACOSTI) of Kenya, and the 508 county governments of Samburu and Buffalo Springs National Reserves for permission to conduct this research. Elephant movement data were collected and procured by the Save the 510 Elephants Tracking Animals for Conservation Program supported by I. Douglas-Hamilton and 511 individual elephant monitoring was conducted with the Save the Elephants field team, notably David Daballen, Chris Leadismo, and Daniel Lentipo.

France's Supreme Court rejects groups' request for slavery reparations in case from Martinique



PARIS (AP) — France’s highest court has rejected a request by three groups seeking reparations for slavery in a case that originated on the French Caribbean island of Martinique.

The court’s decision on Wednesday said that no one produced evidence showing they had “suffered individually” any damage from the crimes that their ancestors had been subjected to.

One of the lawyers pursuing the case, Alain Manville, called it a “political decision” and said he believed the large amount of money that France would have to pay in reparations was a major consideration for the court. He expressed hope for making the case more global, bringing in “all Afro-descendants” in a move that he believes would lead French judges to see the case differently.

“We will succeed in this process,” Manville said. “I don't know when.”

Slavery was abolished in France in 1848, but before that had a significant slave trade, shipping more than 1 million Africans to colonies in the Americas. The International Movement for Reparations and two other groups launched efforts in pursuit of reparations in 2005. French courts have repeatedly rejected their request, but the European Court of Human Rights kept their efforts alive by making their claims admissible.

Another lawyer pursuing the case for reparations, Patrice Spinosi, in an emailed statement said the groups would approach the European Court of Human Rights for a new appeal.

The issue of reparations is widely debated across the Caribbean, where an estimated 5 million slaves were brought over by colonial powers, including Britain and France, and forced to toil on sugar plantations and other fields under brutal conditions.

In 2022, an appeals court in Martinique, which is an overseas department of France, rejected the groups’ request, noting that there’s a statute of limitations for those crimes and that a French law already allows the implementation of certain measures meant to “bring a memorial contribution to the recognition of slavery and the slave trade” and that it is not for the judiciary to decide if those measures are sufficient.

Another lawyer pursuing the case, Georges Emmanuel Germany, said France's highest court was “outside the post-colonial reality” and asserted that it doesn't recognize slavery as a crime against humanity.

Cara Anna, The Associated Press