Thursday, June 27, 2024

PALEONTOLOGY

Ammonites went out with a diverse bang—and not a long, slow fizzle—in the Late Cretaceous

A new study used museum collections to map ammonite diversity around the globe before their total extinction and found they were not in decline prior to their extinction alongside non-avian dinosaurs 66 million years ago

NATURAL HISTORY MUSEUM OF LOS ANGELES COUNTY

Ammonites basking under the Late Cretaceous sun. Artwork by Callum Pursall — IMAGE:
AMMONITES BASKING UNDER THE LATE CRETACEOUS SUN. ARTWORK BY CALLUM PURSALL (@CPURSALL ON X)
view more
CREDIT: ARTWORK BY CALLUM PURSALL

Los Angeles, CA (June 27, 2024) —A new study published in the journal Nature Communications led by paleontologists at the University of Bristol along with a team of international researchers, including Dr. Austin Hendy, Curator of Invertebrate Paleontology at the Natural History Museum of Los Angeles County, finds that instead of fizzling out ahead of their extinction, ammonoids were still going strong across the globe in the Late Cretaceous. Made possible by museum collections, the new study compared their diversity across the globe just prior to extinction, unearthing the complex evolutionary history of their final chapter for the first time.

Ammonoids, marine mollusks often distinguished by their coiled shells, are one of paleontology’s great icons. They flourished in Earth’s oceans for more than 350 million years until their extinction during the same chance event that wiped out the dinosaurs 66 million years ago. Some paleontologists, however, have argued the diversity of ammonites (the last major lineage of ammonoids) was declining well before their extinction at the end of the Cretaceous Period and that their demise was inevitable.

“Ammonites had an amazing evolutionary history. With their formidable shells and powerful tentacles they innovated the act of swimming. They could grow to as big as a car or to just a few millimeters in diameter. They played equally disparate roles in their ecosystems, from predators near the top of the food web to filter feeding off plankton,” said Hendy.

“Understanding how and why biodiversity has changed through time is very challenging,” said lead author Dr. Joseph Flannery-Sutherland. “The fossil record tells us some of the story, but it is often an unreliable narrator. Patterns of diversity can just reflect patterns of sampling, essentially where and when we have found new fossil species, rather than actual biological history. Analyzing the existing Late Cretaceous ammonite fossil record as though it were the complete, global story is probably why previous researchers have thought they were in long-term ecological decline.”

To overcome this issue, the team assembled a new database of Late Cretaceous ammonite fossils to help fill in the sampling gaps in their record. “We drew on museum collections to provide new sources of specimens rather than just relying on what had already been published,” said co-author Cameron Crossan, a 2023 graduate of the University of Bristol’s Palaeobiology MSc program. “This way, we could be sure that we were getting a more accurate picture of their biodiversity prior to their total extinction.”

Using their database, the team then analyzed how ammonite speciation—forming distinct new species—and extinction rates varied in different parts of the globe. If ammonites were in decline through the Late Cretaceous, then their extinction rates would have been generally higher than their speciation rates wherever the team looked. Instead, the team found that the balance of speciation and extinction changed both through geological time and between different geographic regions.

“These differences in ammonoid diversification around the world is a crucial part of why their Late Cretaceous story has been misunderstood,” said senior author Dr. James Witts of the Natural History Museum, London. “Their fossil record in parts of North America is very well sampled, but if you looked at this alone, then you might think that they were struggling while they were actually flourishing in other regions. Their extinction really was a chance event and not an inevitable outcome.”

Environmental Factors vs Competition
So, what was responsible for the continued success of ammonites through the Late Cretaceous? To answer this question, the team looked at potential factors that might have caused their diversity to change over time. They were particularly interested in whether their speciation and extinction rates were driven mainly by environmental conditions like ocean temperature and sea level or by biological processes like pressure from predators and competition between ammonites.

“What we found was that the causes of ammonite speciation and extinction were as geographically varied as the rates themselves,” said co-author Dr. Corinne Myers of the University of New Mexico. “You couldn’t just look at their total fossil record and say that it was driven entirely by changing temperature, for example. It was more complex than that and depended on where in the world they were living.”

JOURNAL

Nature Communications

DOI

10.1038/s41467-024-49462-z

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Late Cretaceous ammonoids show that drivers of diversification are regionally heterogeneous

ARTICLE PUBLICATION DATE

27-Jun-2024

Ammonites’ fate sealed by meteor strike that wiped out dinosaurs

UNIVERSITY OF BRISTOL

Fig 1 — IMAGE:
AMMONITES BASKING UNDER THE LATE CRETACEOUS SUN.
view more
CREDIT: CALLUM PURSALL (@CPURSALL ON X)

Ammonites were not in decline before their extinction, scientists have found.

The marine molluscs with coiled shells and one of palaeontology’s great icons flourished in Earth’s oceans for more than 350 million years until they died out during the same chance event that wiped out the dinosaurs 66 million years ago.

Some palaeontologists have argued that their demise was inevitable and that ammonite diversity was decreasing long before they went extinct at the end of the Cretaceous.

However new research, published today in Nature Communications and led by palaeontologists at the University of Bristol, shows that their fate was not set in stone. Instead, the final chapter in ammonite evolutionary history is more complex.

“Understanding how and why biodiversity has changed through time is very challenging,” said lead author Dr Joseph Flannery-Sutherland. “The fossil record tells us some of the story, but it is often an unreliable narrator. Patterns of diversity can just reflect patterns of sampling, essentially where and when we have found new fossil species, rather than actual biological history.

“Analysing the existing Late Cretaceous ammonite fossil record as though it were the complete, global story is probably why previous researchers have thought they were in long-term ecological decline.”

To overcome this issue, the team assembled a new database of Late Cretaceous ammonite fossils to help fill in the sampling gaps in their record. “We drew on museum collections to provide new sources of specimens rather than just relying on what had already been published,” said co-author Cameron Crossan, a 2023 graduate of the University of Bristol’s Palaeobiology MSc programme. “This way we could be sure that we were getting a more accurate picture of their biodiversity prior to their total extinction.”

Using their database, the team then analysed how ammonite speciation and extinction rates varied in different parts of the globe. If ammonites were in decline through the Late Cretaceous, then their extinction rates would have been generally higher than their speciation rates wherever the team looked. What the team instead found was that the balance of speciation and extinction changed both through geological time and between different geographic regions.

“These differences in ammonoid diversification around the world is a crucial part of why their Late Cretaceous story has been misunderstood,” said senior author Dr James Witts of the Natural History Museum, London. “Their fossil record in parts of North America is very well sampled, but if you looked at this alone then you might think that they were struggling, while they were actually flourishing in other regions. Their extinction really was a chance event and not an inevitable outcome.”

To find out what was responsible for the continued success of ammonites through the Late Cretaceous, the team looked at potential factors might have caused their diversity to change through time. They were particularly interested in whether their speciation and extinction rates were driven mainly by environmental conditions like ocean temperature and sea level (the Court Jester Hypothesis), or by biological processes like pressure from predators and competition between ammonites themselves (the Red Queen Hypothesis).

“What we found was that the causes of ammonite speciation and extinction were as geographically varied as the rates themselves,” said co-author Dr Corinne Myers of the University of New Mexico. “You couldn’t just look at their total fossil record and say that their diversity was driven entirely by changing temperature, for example. It was more complex than that and depended on where in the world they were living.”

“Palaeontologists are frequently fans of silver bullet narratives for what drove changes in a group’s fossil diversity, but our work shows that things are not always so straightforward,” Dr Flannery Sutherland concluded. “We can’t necessarily trust global fossil datasets and need to analyse them at regional scales. This way we can capture a much more nuanced picture of how diversity changed across space and through time, which also shows how variation in the balance of Red Queen versus Court Jester effects shaped these changes.”

Ammonites basking under the Late Cretaceous sun. Artwork by Callum Pursall (@cpursall on X)

The paper:

‘Late Cretaceous ammonoids show that drivers of diversification are regionally heterogeneous’ by Joseph Flannery-Sutherland, Cameron Crossan, Corinne Myers, Austin Hendy, Neil Landman and James Witts in Nature Communications.

JOURNAL

Nature Communications

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Late Cretaceous ammonoids show that drivers of diversification are regionally heterogeneous

ARTICLE PUBLICATION DATE

27-Jun-2024

Prehistoric Pompeii discovered: Most pristine trilobite fossils ever found shake up scientific understanding of the long extinct group

UNIVERSITY OF BRISTOL

Researchers have described some of the best-preserved three-dimensional trilobite fossils ever discovered. The fossils, which are more than 500 million years old, were collected in the High Atlas of Morocco and are being referred to by scientists as “Pompeii” trilobites due to their remarkable preservation in ash.

The trilobites, from the Cambrian period, have been the subject of research by an international team of scientists, led by Prof Abderrazak El Albani, a geologist based at University of Poitiers and originally from Morocco. The team included Dr Greg Edgecombe, a palaeontologist at the Natural History Museum.

Dr Greg Edgecombe comments: “I’ve been studying trilobites for nearly 40 years, but I never felt like I was looking at live animals as much as I have with these ones. I’ve seen a lot of soft anatomy of trilobites, but it’s the 3D preservation here that is truly astounding.

“An unexpected outcome of our work is discovering that volcanic ash in shallow marine settings could be a bonanza for exceptional fossil preservation.”

Due to their hard, calcified exoskeleton often being well-preserved in the fossil record, trilobites are some of the best studied fossil marine animals. Over 20,000 species have been described by palaeontologists over the past two centuries.

However, until now, comprehensive scientific understanding of this phenomenally diverse group has been limited by the relative scarcity of soft tissue preservation. Owing to the fact the Moroccan trilobites were encased in hot ash in sea water, their bodies fossilised very quickly as the ash transformed to rock – meeting a similar end to the inhabitants of Pompeii following the eruption of Mount Vesuvius.

The ash moulds preserved each segment of their bodies, their legs and even the hair-like structures that ran along the appendages. The trilobites’ digestive tract was also preserved after it filled with ash. Even small “lamp shells” attached to the trilobites’ exoskeleton remained attached by fleshy stalks as they were in life.

Lead author, Prof Abderrazak El Albani, comments: “As a scientist who has worked on fossils from different ages and locations, discovering fossils in such a remarkable state of preservation within a volcanic setting was a profoundly exhilarating experience for me.

“I think pyroclastic deposits should become new targets for study, given their exceptional potential for trapping and preserving biological remains, including delicate soft tissues.

“These findings are anticipated to lead to significant discoveries about the evolution of life on our planet Earth.”

Using CT scanning and computer modelling of virtual X-ray slices, the researchers discovered that appendages found at the edge of the mouth had curved spoon-like bases but were so small they had gone undetected in less perfectly preserved fossils. In fact, it had previously been thought that trilobites had three pairs of head appendages behind their long antennae but both Moroccan species in this study showed that there were four pairs.

A fleshy lobe covering the mouth, called a labrum, was documented for the first time in trilobites.

Co-author Harry Berks, from the University of Bristol, added: “The results revealed in exquisite detail a clustering of specialised leg pairs around the mouth, giving us a clearer picture of how trilobites fed. The head and body appendages were found to have an inward-facing battery of dense spines, like those of today’s horseshoe crabs.”

The paper, Rapid volcanic ash entombment reveals the 3D anatomy of Cambrian trilobites, will be published online in the journal, Science, on Thursday 27 June, 19:00 BST, and in print on Friday 28 June. The paper can be accessed from that time here.

Notes to editors

Assets

Images are available here.

Microtomographic reconstruction of the head and anterior trunk (“body”) limbs of the trilobite Protolenus (Hupeolenus) in ventral view.

CREDIT

Microtomographic reconstruction of the trilobite Gigoutella mauretanica in ventral view.

CREDIT

Fig 4 [VIDEO]

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JOURNAL

Science

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Rapid volcanic ash entombment reveals the 3D anatomy of Cambrian trilobites

ARTICLE PUBLICATION DATE

27-Jun-2024

From a Pompeii-like ash burial in Morrocco: Pristine 3D anatomy of Cambrian trilobites

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)

Thanks to being rapidly entombed in volcanic ash – in a “Pompeii-like” process – Cambrian-age trilobites’ anatomy is more discernable than ever, via exquisitely preserved fossils. The fossils uncovered in Morrocco are reported in a new study that reveals microscopic details including of trilobite appendages and the trilobite digestive system. Trilobites are perhaps the most well-known creatures that lived during the Cambrian Period. These extinct marine arthropods’ hard exoskeleton lends itself to high fossilization potential, facilitating the identification of more than 22,000 trilobite species and a robust fossil record spanning the early Cambrian to the Permian extinction. While this bounty of fossils has led to great insight into the external morphology of these animals, knowledge of their anatomy, particularly their rarely preserved soft tissue appendages and internal organs, is greatly limited. Here, Abderrazak El Albani and colleagues report several exceptionally well-preserved and anatomically complete Cambrian-age trilobite fossils from the Tatelt formation in Morrocco. According to El Albani et al., the trilobites were fossilized through rapid ash burial from a single pyroclastic flow event that swept through a shallow marine environment. This scenario led to their instantaneous burial and pristine, 3D preservations of both the exoskeleton and soft anatomy contained therein. Using microtomographic x-ray imaging, the authors were able to observe anatomical features, including the trilobites’ articulated and undistorted exoskeleton, antennae, post-antennal appendages, digestive system, and other soft tissues. El Albani et al. also describe previously unknown anatomical features, such as their novel feeding structures, a slit-like mouth opening, and specialized head appendages that form a complex feeding apparatus around the mouth. Moreover, the findings suggest that other volcanic ash deposits in marine settings, such as that entombed the Tatelt trilobites, may have significant potential for preserving soft-bodied creatures or anatomy with fine details, highlighting the potential for further discoveries in similar deposits.

JOURNAL

Science

DOI

10.1126/science.adl4540

ARTICLE TITLE

Rapid volcanic ash entombment reveals the 3D anatomy of Cambrian trilobites

ARTICLE PUBLICATION DATE

28-Jun-2024

Last surviving woolly mammoths were inbred but not doomed to extinction

CELL PRESS

Wrangel Island tusk — IMAGE:
WRANGEL ISLAND TUSK
view more
CREDIT: LOVE DALÉN

The last population of woolly mammoths was isolated on Wrangel Island off the coast of Siberia 10,000 years ago, when sea levels rose and cut the mountainous island off from the mainland. A new genomic analysis reveals that the isolated mammoths, who lived on the island for the subsequent 6,000 years, originated from at most 8 individuals but grew to 200–300 individuals within 20 generations. The researchers report June 27 in the journal Cell that the Wrangel Island mammoths’ genomes showed signs of inbreeding and low genetic diversity but not to the extent that it can explain their ultimate (and mysterious) extinction.

“We can now confidently reject the idea that the population was simply too small and that they were doomed to go extinct for genetic reasons,” says senior author Love Dalén (@love_dalen), an evolutionary geneticist at the Centre for Palaeogenetics, a joint collaboration between the Swedish Museum of Natural History and Stockholm University. “This means it was probably just some random event that killed them off, and if that random event hadn't happened, then we would still have mammoths today.”

In addition to shedding light on woolly mammoth population dynamics, this analysis of Wrangel Island mammoths could help inform conservation strategies for present-day endangered animals.

“Mammoths are an excellent system for understanding the ongoing biodiversity crisis and what happens from a genetic point of view when a species goes through a population bottleneck because they mirror the fate of a lot of present-day populations,” says first author Marianne Dehasque (@MariDehasque) of the Centre for Palaeogenetics.

To understand the genomic consequences of the Wrangel Island bottleneck on the mammoth population, the team analyzed the genomes of 21 woolly mammoths—14 from Wrangel Island, and 7 from the mainland population that predated the bottleneck. Altogether, the samples spanned the last 50,000 years of the woolly mammoth’s existence, providing a window into how mammoth genetic diversity changed through time.

Compared to their mainland ancestors, the Wrangel Island mammoth genomes showed signs of inbreeding and low genetic diversity. In addition to overall low genetic diversity, they showed reduced diversity in the major histocompatibility complex, a group of genes known to play a critical role in the vertebrate immune response.

The researchers showed that the population’s genetic diversity continued to decline throughout the 6,000 years that the mammoths inhabited Wrangel Island, though at a very slow pace, suggesting that the population size was stable up until the very end. And although the island’s mammoth population gradually accumulated moderately harmful mutations throughout its 6,000-year tenure, the researchers showed that the population was slowly purging the most harmful mutations.

“If an individual has an extremely harmful mutation, it's basically not viable, so those mutations gradually disappeared from the population over time, but on the other hand, we see that the mammoths were accumulating mildly harmful mutations almost up until they went extinct,” says Dehasque. “It’s important for present day conservation programs to keep in mind that it’s not enough to get the population up to a decent size again; you also have to actively and genetically monitor it because these genomic effects can last for over 6,000 years.”

Though the mammoth genomes analyzed in this study straddle a large timespan, they do not include the final 300 years of the species’ existence. However, the researchers have unearthed fossils from the mammoth’s final period and plan to conduct genomic sequencing in the future.

“What happened at the end is a bit of a mystery still—we don't know why they went extinct after having been more or less fine for 6,000 years, but we think it was something sudden,” says Dalén. “I would say there is still hope to figure out why they went extinct, but no promises.”

###

This research was supported by the Swedish Research Council, the Science for Life Laboratory, the National Genomics Infrastructure, and UPPMAX.

Cell, Dehasque et al. “Temporal dynamics of woolly mammoth genome erosion prior to extinction” https://cell.com/cell/fulltext/S0092-8674(24)00577-4

Cell (@CellCellPress), the flagship journal of Cell Press, is a bimonthly journal that publishes findings of unusual significance in any area of experimental biology, including but not limited to cell biology, molecular biology, neuroscience, immunology, virology and microbiology, cancer, human genetics, systems biology, signaling, and disease mechanisms and therapeutics. Visit http://www.cell.com/cell. To receive Cell Press media alerts, contact press@cell.com.

JOURNAL

Cell

DOI

10.1016/j.cell.2024.05.033

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Temporal dynamics of woolly mammoth genome erosion prior to extinction

ARTICLE PUBLICATION DATE

27-Jun-2024

New twists on tornadoes: Earth scientist studies why U.S. has so many tornadoes

PURDUE UNIVERSITY

WEST LAFAYETTE, Ind. — Across the Midwest during the warmer months, studying the sky for signs of storms and tornadoes becomes one of the most popular pastimes.

Dan Chavas, an associate professor in the Department of Earth, Atmospheric, and Planetary Sciences at Purdue University’s College of Science, takes it further: All day every day, he studies what makes tornadoes tick. Working at the intersection of climate science and meteorology, he looks at the big picture of what causes severe storms and tornadoes — and what dictates where they occur.

“I study both the climate and extreme weather,” Chavas says. “My research asks, ‘Why do we have severe thunderstorms or tornadoes at all?’ There are specific regions on Earth that have more storms, more tornadoes than other places. What creates these stormy regions?”

The central and eastern regions of the United States are among the top spots for severe thunderstorms and form the hot spot for the Earth’s most damaging and frequent tornadoes. Chavas uses real-world computer models to conduct experiments to determine what contributes to the formation of these storms.

“We have had these decades-old assumptions about what causes storms,” he says. “We’re validating those hypotheses and figuring out what makes North America such a hot spot.”

ADDITIONAL INFORMATION

Moving heaven and earth

Chavas isn’t a storm chaser. He’s not out there in a weather van topped with satellite wires hunting down individual storms for the insights they might yield. Nor can he grow storms in his lab or unleash tornadoes to understand their anatomy or behavior.

Instead, he harnesses decades of rich, detailed historical data and complex computer models to imagine and test what-if scenarios. He’s a storm tester.

“We use weather and climate models, as well as extensive databases of thunderstorms, lightning strikes, atmospheric data and more, to ask, ‘What if the world was different?’” Chavas says. “We can use these models as laboratories to ask questions like ‘What happens to the weather if you flatten the Rocky Mountains? What about if you fill in the Gulf of Mexico? What aspects of the modern continental and mountain configurations really matter? Let’s actually test this prevailing, conventional wisdom.’”

Both of those hypotheticals — flattening the Rockies and filling in the Gulf of Mexico — are the focus of studies Chavas and his team have conducted.

For more than 50 years, established wisdom said that the Gulf of Mexico, a source of warm, wet air flowing inland to the east of the Rocky Mountains, plays a major role in the formation of North America’s tornadoes. But no one knew for sure.

“It was a very reasonable hypothesis,” Chavas says. “There were a lot of very reasonable explanations. But no one had been able to test these 50-year-old ideas because they came about when there weren’t climate models with the necessary computational power. Now we can really start to understand the physics of the situation.”

When his team virtually filled in the Gulf of Mexico with land, they found that a dry Gulf of Mexico affected the frequency and severity of storms far less than they had expected. Without the Gulf of Mexico, severe thunderstorms shifted eastward from the central Great Plains into Illinois, although they were reduced over southern Texas.

“Severe thunderstorms and tornadoes form in environments with specific ingredients for how temperature, moisture, and especially wind speed and direction change with height in the atmosphere,” Chavas says. “The climate determines where and when those ingredients can be found together to produce these types of storms. Computer models let us understand why the ingredients are there in the first place and what role they each play in the weather we see.”

In his most recent study with graduate student Funing Li, just published in the Proceedings of the National Academy of Sciences, the team compared severe weather potential in North America, famous for tornadoes, with South America, which has a geography similar to North America’s and also many severe thunderstorms, but far fewer tornadoes. Their research has been funded by the National Science Foundation and NASA.

They found that the rough texture of the land surface east of the Andes mountains, its roughness determined in part by the hills and tall trees of the Amazon region, may play a large role in preventing tornadoes over central South America. In contrast, in North America many tornadoes form east of the Rockies, where air flows in from the much smoother ocean surface of the Gulf of Mexico. The team first used climate model experiments in which equatorial South America was smoothed to be similar to an ocean surface, which drastically increased central South America’s tornado potential. They also performed experiments in which the Gulf of Mexico region was roughened to be similar to a forested land surface, which strongly suppressed North American tornado potential.

“A rough surface upstream means that downstream the wind is no longer changing speed and direction with height very strongly near the surface, which we refer to as ‘wind shear,’” Chavas says. “It doesn’t change ingredients for severe thunderstorms, but the wind shear in the 1 kilometer of air above the ground is a critical ingredient for tornadoes.”

Storm warning

Real weather and real-world applications fascinate Chavas, a fascination born after a storm-torn tree fell on his house in Wisconsin when he was 4 years old.

The real-world implications of his research — what will the weather be like next week, next month, next year and next century — are what drives him.

“If we want to understand how climate change will affect weather in the future, we need to understand how climate determines weather in the first place,” Chavas says. “We don’t have a very good understanding of how climate controls the severe weather we have.”

Understanding how surface roughness and land use changes weather, for example, may enable future humans to better predict — and even partially affect — weather patterns. If the rough land of the Amazon, including a component from the trees of the Amazon, protects South America from tornadoes, could the regrowth of the United States’ eastern forests affect tornadoes, too?

Climate change affects the flow patterns of the atmosphere and moisture distribution on land, Chavas says.

“If we change the land surface and the trajectory of air flowing inland from the Gulf of Mexico, it may have a direct impact on these ingredients that give rise to tornadoes farther inland. When we think about climate change, we think about it getting hotter and the land getting drier. But if the jet stream changes where and how quickly air flows inland, it can change where and how tornadoes form. Places that didn’t see them before may see them more, and places that had more may see fewer,” he says. “We need to understand the weather now to help us better predict the weather of the future.”

About Purdue University

Purdue University is a public research institution demonstrating excellence at scale. Ranked among top 10 public universities and with two colleges in the top four in the United States, Purdue discovers and disseminates knowledge with a quality and at a scale second to none. More than 105,000 students study at Purdue across modalities and locations, including nearly 50,000 in person on the West Lafayette campus. Committed to affordability and accessibility, Purdue’s main campus has frozen tuition 13 years in a row. See how Purdue never stops in the persistent pursuit of the next giant leap — including its first comprehensive urban campus in Indianapolis, the Mitchell E. Daniels, Jr. School of Business, Purdue Computes and the One Health initiative — at https://www.purdue.edu/president/strategic-initiatives.

Writer/Media contact: Brittany Steff, bsteff@purdue.edu

Source: Dan Chavas, dchavas@purdue.edu

JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2315425121

ARTICLE TITLE

Upstream surface roughness and terrain are strong drivers of contrast in tornado potential between North and South America

ARTICLE PUBLICATION DATE

18-Jun-2024

Archaeology: Occupational hazards for ancient Egyptian scribes

Peer-Reviewed Publication

SCIENTIFIC REPORTS

Repetitive tasks carried out by ancient Egyptian scribes — high status men with the ability to write who performed administrative tasks — and the positions they sat in while working may have led to degenerative skeletal changes, according to a study published in Scientific Reports.

Petra Brukner Havelková and colleagues examined the skeletal remains of 69 adult males — 30 of whom were scribes — who were buried in the necropolis at Abusir, Egypt between 2700 and 2180 BCE. They identified degenerative joint changes that were more common among scribes compared to men with other occupations. These were in the joints connecting the lower jaw to the skull, the right collarbone, the top of the right humerus (where it meets the shoulder), the first metacarpal bone in the right thumb, the bottom of the thigh (where it meets the knee), and throughout the spine, but particularly at the top. The authors also identified bone changes that could be indicative of physical stress caused by repeated use in the humerus and left hip bone, which were more common among scribes than men with other occupations. Other skeletal features that were more common among scribes were an indentation on both kneecaps and a flattened surface on a bone in the lower part of the right ankle.

The authors suggest that the degenerative changes observed in the spines and shoulders of scribes could result from them sitting for prolonged periods in a cross-legged position with the head bent forwards, the spine flexed, and their arms unsupported. However, changes to knees, hips, and ankles could indicate that scribes may have preferred to sit with the left leg in a kneeling or cross-legged position and the right leg bent with the knee pointing upwards (in a squatting or crouching position). The authors note that statues and wall decorations in tombs have depicted scribes sitting in both positions, in addition to standing, while working. Degeneration to the jaw joints could have resulted from scribes chewing the ends of rush stems to form brush-like heads they could write with, while degeneration to the right thumb could have been caused by repeatedly pinching their pens.

The findings provide greater insight into the lives of scribes in ancient Egypt during the third millennium BCE.

###

Article details

Ancient Egyptian scribes and specific skeletal occupational risk markers (Abusir, Old Kingdom)

DOI: 10.1038/s41598-024-63549-z

Corresponding Author:

Petra Brukner Havelková
National Museum in Prague, Prague, Czech Republic
Charles University, Prague, Czech Republic
Email: petra.havelkova@nm.cz

JOURNAL

Scientific Reports

DOI

10.1038/s41598-024-63549-z

ARTICLE TITLE

Ancient Egyptian scribes and specific skeletal occupational risk markers (Abusir, Old Kingdom)

ARTICLE PUBLICATION DATE

27-Jun-2024

NIST researchers identify a cheaper, more convenient method to detect asbestos

The scientists found that scanning electron microscopy (SEM) can serve as a replacement for more labor-intensive, costly techniques used in construction.

Peer-Reviewed Publication

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST)

Image of asbestos fibers — IMAGE:
IMAGES OF ASBESTOS FIBERS TAKEN BY SCANNING ELECTRON MICROSCOPY (SEM).
view more
CREDIT: J. HOLM/NIST

For decades, a laboratory procedure known as transmission electron microscopy (TEM) has been used to test for asbestos in samples taken at construction sites.

In 1989, the U.S. Environmental Protection Agency (EPA) required most schools undergoing asbestos abatement to use TEM to test for the presence of asbestos fibers in air samples before reopening. Several states require or recommend using TEM for testing as part of asbestos removal in commercial buildings.

But TEM must be carried out in a specialized lab by highly trained staff and can be expensive. Another approach, phase contrast microscopy, is easier and cheaper but less precise.

Now, researchers at the National Institute of Standards and Technology (NIST) have determined that a third option, scanning electron microscopy (SEM), can achieve results roughly comparable to TEM. SEM is a “viable alternative to the current regulatory methods for asbestos identification and classification,” the NIST researchers Jason Holm and Elisabeth Mansfield wrote in a new paper published in Analytical Methods.

Since SEM is, in many cases, cheaper and more convenient than TEM, the finding could potentially speed up and reduce the expense of asbestos remediation in the United States, which costs an estimated $3 billion every year.

Asbestos is a naturally occurring mineral whose fibers were used for insulation, weather- and fire-proofing and reinforcing building materials. Its use began declining in the 1970s as researchers became aware of its health risks, including its link to cancer. In March, the EPA banned the last form of asbestos still in use.

As their names suggest, both TEM and SEM are types of electron microscopy. In both methods, technicians focus electron beams on a microscopic amount of material. Electrons interact with the material to produce highly detailed information on the material’s composition, structure and shape.

With TEM, the electrons pass through the sample, whereas with conventional SEM, they are reflected off the surface. This enables TEM to produce more detailed images and probe the surface’s interior. TEM also offers much better spatial resolution — the ability to distinguish between objects very close together — than SEM.

But in recent years, SEM manufacturers have improved the technology’s imaging power and other capabilities. Several companies now produce tabletop SEMs, making it possible to use the technology in the field, while TEM must still be done in a lab. Holm said training to use and operate SEM equipment can be completed in several months, while “expertise in TEM can take years to establish.”

“There are some capabilities TEM has which SEM doesn’t, but we think SEM is good enough” for use in asbestos abatement, said Holm.

To test SEM on asbestos, Holm and Mansfield used NIST Standard Reference Material (SRM) 1866, a sample of asbestos fibers the agency produces for labs to benchmark their equipment and testing procedures. The SRM comes with extensive data characterizing the properties of the material.

Using SEM, the researchers analyzed SRM 1866. Their results closely agreed with those listed in the SRM’s documentation, indicating the method’s accuracy.

Holm and Mansfield summarized SEM’s potential advantages by writing that it could result in “lower equipment cost, less stringent operator training requirements, increased sample throughput and greater field of view compared to TEM.”

JOURNAL

Analytical Methods

DOI

10.1039/D4AY00555D

ARTICLE TITLE

Transmission electron imaging and diffraction of asbestos fibers in a scanning electron microscope

ARTICLE PUBLICATION DATE

24-Jun-2024