Category Archives: WORLD

EUROPE, WORLD

Black Death immunity came at a cost to modern-day health

Black Death immunity came at a cost to modern-day health

Black Death immunity came at a cost to modern-day health
Using DNA from the excavated remains of plague victims, including those buried in a London cemetery from 1348–1349, and from people who died earlier and later, researchers searched for evidence of how the Black Death pushed the immune system to evolve.

A genetic variant that appears to have boosted medieval Europeans’ ability to survive the Black Death centuries ago may contribute — albeit in a small way — to an inflammatory disease afflicting people today. 

Researchers used DNA collected from centuries-old remains to discern the fingerprints that the bubonic plague during the Black Death left on Europeans’ immune systems.

This devastating wave of disease tended to spare those who possessed a variant of a gene known as ERAP2, causing it to become more common, researchers report on October 19 in Nature. That variant is already known to scientists for slightly increasing the odds of developing Crohn’s disease, in which errant inflammation harms the digestive system.

The results show “how these studies on ancient DNA can help actually understand diseases even now,” says Mihai Netea, an infectious diseases specialist at Radboud University Medical Center in Nijmegen, Netherlands, who was not involved with the study. “And the trade-off is also very clear.”

Caused by the bacterium Yersinia pestis, bubonic plague once killed 60 per cent of those infected (SN: 6/15/22). In the ancient world, it caused successive waves of misery, the most devastating of which was the Black Death, often dated from 1346 to 1350, an episode thought to have wiped out at least 25 million people — about a third or more of the European population. 

By sparing individuals whose immune systems bear certain traits, pathogens such as Y. pestis have shaped the evolution of the human immune system. Studies are teasing out the ways the massive winnowing of the plague altered Europeans’ immune-related genetics. 

In this most recent study, population geneticist Luis Barreiro of the University of Chicago and colleagues collected samples containing DNA from the remains of 516 people in London and Denmark who died between 1000 and 1800, including those buried during the Black Death. The researchers examined stretches of DNA for immune-related genes and areas associated with autoimmune and inflammatory diseases.

Researchers collected DNA samples from burial sites in London, including the East Smithfield plague pits (shown here), and in Denmark.

Within those regions, the researchers identified four locations on chromosomes where they saw strong evidence of genetic changes that appeared to have been driven by the Black Death. In follow-up work, one change stood out: an increase in the frequency of a variant of ERAP2.

When infected with Y. pestis, immune cells from people with this version of ERAP2 more effectively killed the bacteria than cells lacking the variant. Studies of modern populations have linked that same variant to Crohn’s disease.

While the researchers calculate that the ERAP2 variant improved the odds of surviving the Black Death by as much as 40 per cent, it only slightly increases the risk for Crohn’s disease.

For complex disorders like Crohn’s, “you require probably hundreds, sometimes thousands of genetic variants to actually increase your risk in a significant manner,” Barreiro says.

For some time now, researchers in the field have theorized that adaptations that helped our ancestors fortify their immune systems against infectious diseases can contribute to excessive, damaging immune activity.

Earlier studies of plague offer support for this idea. A genetic analysis seeking traces of historical disease in modern Europeans and a study of DNA from the remains of 16th-century German plague victims both turned up what appear to be protective changes against the plague that, like the ERAP2 variant, are linked with inflammatory and autoimmune conditions.  

Likewise, this latest discovery suggests that genetic changes that have amped up the human immune response in the past, empowering it to better fight off ancient infections, can come at a cost. “If you turn the heat too much, that leads to disease,” Barreiro says.

EUROPE, SWEDEN, WORLD

Wreckage of 17th-Century Swedish Warship Identified

Wreckage of 17th-Century Swedish Warship Identified

Wreckage of 17th-Century Swedish Warship Identified
A diver approaches Äpplet’s wreck. Hansson said: ‘With Äpplet, we can add another key piece of the puzzle in the development of Swedish shipbuilding.’

Swedish maritime archaeologists have discovered the long-lost sister ship of the 17th-century warship Vasa, which sank on its maiden voyage, the Swedish Museum of Wrecks has said.

Launched in 1629, Äpplet (the Apple) was built by the same shipbuilder as the famed 69-metre Vasa, which was carrying 64 cannons when it sank on its maiden voyage outside Beckholmen, in the capital, Stockholm.

“Our pulses raced when we saw how similar the wreck was to Vasa,” said Jim Hansson, a maritime archaeologist at the museum.

Hansson said the construction and the dimensions seemed “very familiar”, raising hopes it could be one of Vasa’s sister ships. While parts of the vessel’s sides had fallen off, the hull was preserved up to the lower gundeck, and the parts that had dropped showed gunports on two levels.

A diver approaches the wreck. While parts of the ship’s sides had fallen off, the hull was preserved up to the lower gundeck.

The huge shipwreck was discovered in December 2021 in a strait off the island of Vaxholm, just outside Stockholm, according to the museum. A more thorough survey was carried out in the spring of 2022, which revealed details that had previously been seen only on Vasa.

The museum said technical details as well as measurements and wood samples confirmed that it was indeed Äpplet.

In 2019, the museum reported the discovery of two other warships in the same area.

Archaeologists at the time believed that one of them could have been Äpplet, but further investigations showed that those vessels were in fact two medium-sized warships from 1648 named Apollo and Maria.

“With Äpplet, we can add another key piece of the puzzle in the development of Swedish shipbuilding,” Hansson said, adding that this enabled researchers to study the differences between Äpplet and Vasa.

Named after the house of Vasa, the royal dynasty at the time, Vasa was meant to serve as a symbol of Sweden’s military might but capsized after sailing just over 1,000 metres.

It was salvaged in 1961 and is on display at the Vasa Museum in Stockholm, one of Sweden’s most popular tourist spots.

Three other ships were ordered from the same shipwright: Äpplet, Kronan (the Crown) and Scepter, and unlike their predecessor, they served in the Swedish navy and participated in naval battles.

The ships are believed to have been sunk on purpose after they were decommissioned, serving as underwater spike strips to snag enemy vessels.

ASIA, IRAQ, WORLD

Rare 2,700-Year-Old Stone Carvings Discovered in Iraq

Rare 2,700-Year-Old Stone Carvings Discovered in Iraq

Rare 2,700-Year-Old Stone Carvings Discovered in Iraq
An Iraqi worker excavates a rock-carving relief recently found at the Mashki Gate, one of the monumental gates to the ancient Assyrian city of Nineveh, on the outskirts of what is today the northern Iraqi city of Mosul.

Archaeologists in Iraq have unearthed 2,700-year-old stone carvings that were chiselled into a previously undiscovered section of the Mashki Gate, an iconic structure in what was once the ancient Assyrian capital city of Nineveh.

The eight intricately carved marble bas-reliefs, which depict war scenes, grapevines, palm trees and other motifs, were found in what is now Mosul, during a project to restore the gate after Islamic State group militants destroyed it.

Experts believe that the decorative gate dates back to King Sennacherib, who ruled the Assyrian empire from 705 B.C. to 681 B.C., according to a statement from the Iraqi Council of Antiquities and Heritage.

During his reign, King Sennacherib moved the Assyrian capital to Nineveh where he became well known for his vast military campaigns, according to BBC News. 

“We believe that these carvings were moved from the palace of Sennacherib and reused by the grandson of the king to renovate the gate of Mashki and to enlarge the guard room,” Fadel Mohammed Khodr, head of the Iraqi archaeological team, told Al Jazeera.

Because much of the gate was buried underground due to the way it was oriented during its original construction, the only portions that archaeologists could salvage were under the soil.

“Only the part buried underground has retained its carvings,” Khodr said.

In 2016, militants from IS (also called ISIS, ISIL or Daesh) destroyed the iconic gate with a bulldozer.

The Swiss-based International Alliance for the Protection of Heritage in Conflict Areas is working with Iraqi authorities as well as archaeologists from the University of Pennsylvania and Mosul University on the restoration of the gate.

EUROPE, GERMANY, WORLD

Archaeologists Just Unearthed 10,500-Year-Old Human Remains In A German Bog

Archaeologists Just Unearthed 10,500-Year-Old Human Remains In A German Bog

Archaeologists Just Unearthed 10,500-Year-Old Human Remains In A German Bog
Archaeologists think this was a temporary campsite on the shore of an ancient lake that has now silted up; it was used for roasting hazelnuts and for spearing fish, and the bones were probably from someone who died nearby.

Archaeologists in northern Germany have unearthed 10,000-year-old cremated bones at a Stone Age lakeside campsite that was once used for spearing fish and roasting hazelnuts, major food sources for groups of hunter-gatherers at that time.

The site is the earliest known burial in northern Germany, and the discovery marks the first time human remains have been found at Duvensee bog in the Schleswig-Holstein region, where dozens of campsites from the Mesolithic era or Middle Stone Age (roughly between 15,000 and 5,000 years ago) have been found.

Hazelnuts were a big attraction in the area because Mesolithic people could gather and roast them, Harald Lübke, an archaeologist at the Center for Baltic and Scandinavian Archaeology, an agency of the Schleswig-Holstein State Museums Foundation, told Live Science.

The campsites changed over time, the research shows. “In the beginning, we have only small hazelnut roasting hearths, and in the later sites, they become much bigger” — possibly a consequence of hazel trees becoming more widespread as the environment changed.

Archaeologists think Duvensee was a lake at that time, and that Mesolithic campsites on islands and the shore were used by hunter-gatherers who visited there in the fall to harvest hazelnuts.

The burial was found during excavations earlier this month at a site first identified in the late 1980s by archaeologist Klaus Bokelmann and his students, who found worked flints there not during a formal excavation, but during a barbecue at a house on the edge of a nearby village, Lübke said.

“Because the sausages were not ready, Bokelmann told his students that if they found anything [in the bog nearby], then he would give them a bottle of Champagne,” he said. “And when they came back, they had a lot of flint artefacts.” 

The cremated bones date from about 10,500 years ago, during the Mesolithic era. They are the first human remains found at any of the Mesolithic sites at the Duvensee bog.

Ancient lake

The burial site is near at least six Mesolithic campsites, which would have been on the shores of the ancient lake at Duvensee, Lübke said.

The first sites investigated by Bokelmann in the 1980s were on islands that would have been near the western shore of the lake, which has completely silted up over the last 8,000 years or so, and formed a peat bog, called a “moor” in Germany.

Archaeologists have discovered mats made of bark for sitting on the damp soil, pieces of worked flint, and the remains of many Mesolithic fireplaces for roasting hazelnuts, but they haven’t unearthed any burials at the island sites.

“Maybe they didn’t bury people on the islands but only at the sites on the lake border, which seem to have had a different kind of function,” Lübke said.

Unlike during the later Mesolithic era, when specific areas were set aside for the burial of the dead, at this time it seemed the dead were buried near where they died, he said. Significantly, the body was cremated before its burial at the Duvensee site, like other burials of approximately the same age near Hammelev in southern Denmark, which is about 120 miles (195 kilometres) to the north. 

Only pieces of the largest bones were left after the cremation, and it’s not clear if they were wrapped in hiding or bark before they were buried. In any case, “burning the body seems to be a central part of burial rituals at this time,” Lübke said.

The site where the cremated bones were found was identified in the 1980s when fragments of worked flints were found there, but it wasn’t excavated until this summer.

Changing landscape

As well as roasting hazelnuts and burning bodies — both of which are activities utilizing fire — Mesolithic people used the lakeside campgrounds for spearing fish, according to the discovery of several bone points crafted for that purpose that were found at the site.

Flint fragments also have been found throughout the area, although flint doesn’t occur naturally there, suggesting that Mesolithic people repaired their tools and hunting weapons in this place during the annual hazelnut harvest in the fall, Lübke said.

The Duvensee bog is among the most important archaeological regions in northern Europe; dozens of Mesolithic sites have been found there since 1923, and most of them since the 1980s.

The Mesolithic sites at Duvensee are about the same age as the Mesolithic site at Star Carr in North Yorkshire in the United Kingdom, and some of the artifacts found there are very similar, Lübke said.

From that time until about 8,000 years ago, the Schleswig-Holstein region and Britain were connected by a now-submerged region called Doggerland, and it’s likely that Mesolithic groups would have shared technologies, he said.

The researchers now plan to carry out further excavations at the site of the Mesolithic burial, to determine what other activities took place there. Ulf Ickerodt, head of Schleswig-Holstein’s State Archaeology Department, said the latest find at Duvensee is of global significance.

“It speaks to the long tradition of archaeological research in Schleswig-Holstein in the expiration of moors and wetlands,” he told Live Science in an email. “The present find advances itself and the landscape around it to something spectacular.”

But he noted that the preservation of organic finds in the Duvensee region is threatened by climatic changes that could result in heavy rain and flooding or dry periods.

Both types of changes could threaten archaeological features in the area, so archaeologists are working to recover any finds and to develop strategies for better managing the area in the face of a changing climate, Ickerodt said.

ASIA, IRAQ, WORLD

Drone photos reveal an early Mesopotamian city made of marsh islands

Drone photos reveal an early Mesopotamian city made of marsh islands

Drone photos reveal an early Mesopotamian city made of marsh islands
New remote-sensing studies at southern Iraq’s massive Tell al-Hiba site, shown here from the air, support an emerging view that an ancient city there largely consisted of four marsh islands.

A ground-penetrating eye in the sky has helped to rehydrate an ancient southern Mesopotamian city, tagging it as what amounted to a Venice of the Fertile Crescent. Identifying the watery nature of this early metropolis has important implications for how urban life flourished nearly 5,000 years ago between the Tigris and Euphrates rivers, where modern-day Iraq lies.

Remote-sensing data, mostly gathered by a specially equipped drone, indicate that a vast urban settlement called Lagash largely consisted of four marsh islands connected by waterways, says anthropological archaeologist Emily Hammer of the University of Pennsylvania. These findings add crucial details to an emerging view that southern Mesopotamian cities did not, as traditionally thought, expand outward from temple and administrative districts into irrigated farmlands that were encircled by a single city wall, Hammer reports in the December Journal of Anthropological Archaeology.

“There could have been multiple evolving ways for Lagash to be a city of marsh islands as human occupation and environmental change reshaped the landscape,” Hammer says.

Because Lagash had no geographical or ritual center, each city sector developed distinctive economic practices on an individual marsh island, much like the later Italian city of Venice, she suspects. For instance, waterways or canals crisscrossed one marsh island, where fishing and collection of reeds for construction may have predominated.

Two other Lagash marsh islands display evidence of having been bordered by gated walls that enclosed carefully laid out city streets and areas with large kilns, suggesting these sectors were built in stages and may have been the first to be settled. Crop growing and activities such as pottery making may have occurred there.

Drone photographs of what were probably harbors on each marsh island suggest that boat travel connected city sectors. Remains of what may have been footbridges appear in and adjacent to waterways between marsh islands, a possibility that further excavations can explore.

Lagash, which formed the core of one of the world’s earliest states, was founded between about 4,900 and 4,600 years ago. Residents abandoned the site, now known as Tell al-Hiba, around 3,600 years ago, past digs show. It was first excavated more than 40 years ago.

Hidden city

Drone photos taken across a massive site in southern Iraq revealed that buried structures, shown in yellow, from the ancient Mesopotamian city of Lagash clustered in four sectors that had probably been marsh islands. Walls, shown in red, surrounded two large sectors. Now-dry waterways, shown in dark blue, connected sectors and crisscrossed one sector, far right.

Composite map of Lagash based on remote-sensing data

E. HAMMER/J. ANTHROPOLOGICAL ARCHAEOLOGY 2022

Previous analyses of the timing of ancient wetlands expansions in southern Iraq conducted by anthropological archaeologist Jennifer Pournelle of the University of South Carolina in Columbia indicated that Lagash and other southern Mesopotamian cities were built on raised mounds in marshes. Based on satellite images, archaeologist Elizabeth Stone of Stony Brook University in New York has proposed that Lagash consisted of around 33 marsh islands, many of them quite small.

Drone photos provided a more detailed look at Lagash’s buried structures than possible with satellite images, Hammer says. Guided by initial remote-sensing data gathered from ground level, a drone spent six weeks in 2019 taking high-resolution photographs of much of the site’s surface. Soil moisture and salt absorption from recent heavy rains helped the drone’s technology detect remnants of buildings, walls, streets, waterways and other city features buried near ground level.

Drone data enabled Hammer to narrow down densely inhabited parts of the ancient city to three islands, she says. A possibility exists that those islands were part of delta channels extending toward the Persian Gulf. A smaller, fourth island was dominated by a large temple.

Hammer’s drone probe of Lagash “confirms the idea of settled islands interconnected by watercourses,” says University of Chicago archaeologist Augusta McMahon, one of three co–field directors of ongoing excavations at the site.

Drone evidence of contrasting neighborhoods on different marsh islands, some looking planned and others more haphazardly arranged, reflect waves of immigration into Lagash between around 4,600 and 4,350 years ago, McMahon suggests. Excavated material indicates that new arrivals included residents of nearby and distant villages, mobile herders looking to settle down and slave laborers captured from neighboring city-states.

Dense clusters of residences and other buildings across much of Lagash suggest that tens of thousands of people lived there during its heyday, Hammer says. At that time, the city covered an estimated 4 to 6 square kilometers, nearly the area of Chicago.

It’s unclear whether northern Mesopotamian cities from around 6,000 years ago, which were not located in marshes, contained separate city sectors (SN: 2/5/08). But Lagash and other southern Mesopotamian cities likely exploited water transport and trade among closely spaced settlements, enabling unprecedented growth, says archaeologist Guillermo Algaze of the University of California, San Diego.

Lagash stands out as an early southern Mesopotamian city frozen in time, Hammer says. Nearby cities continued to be inhabited for a thousand years or more after Lagash’s abandonment, when the region had become less watery and sectors of longer-lasting cities had expanded and merged. At Lagash, “we have a rare opportunity to see what other ancient cities in the region looked like earlier in time,” Hammer says.

EUROPE, SPAIN, WORLD

Neanderthals and humans co-existed in Europe for over 2,000 years: Study

Neanderthals, and humans co-existed in Europe for over 2,000 years: Study

Neanderthals, and humans co-existed in Europe for over 2,000 years: Study
Distinctive stone knives are thought to have been produced by the last Neanderthals in France and northern Spain. This specific and standardized technology is unknown in the preceding Neanderthal record and may indicate a diffusion of technological behaviours between Homo sapiens and Neanderthals immediately prior to their disappearance from the region.

Neanderthals and humans lived alongside each other in France and northern Spain for up to 2,900 years, modelling research suggested Thursday, giving them plenty of time to potentially learn from or even breed with each other.

While the study, published in the journal Scientific Reports, did not provide evidence that humans directly interacted with Neanderthals around 42,000 years ago, previous genetic research has shown that they must have at some point.

Research by Swedish paleogeneticist Svante Paabo, who won the medicine Nobel prize last week, helped reveal that people of European descent—and almost everyone worldwide—have a small percentage of Neanderthal DNA.

Igor Djakovic, a Ph.D. student at Leiden University in the Netherlands and lead author of the new study, said we know that humans and Neanderthals “met and integrated into Europe, but we have no idea in which specific regions this actually happened.”

Exactly when this happened has also proved elusive, though previous fossil evidence has suggested that modern humans and Neanderthals walked the Earth at the same time for thousands of years.

To find out more, the Leiden-led team looked at radiocarbon dating for 56 artifacts—28 each for Neanderthals and humans—from 17 sites across France and northern Spain.

The artifacts included bones as well as distinctive stone knives thought to have been made by some of the last Neanderthals in the region.

The researchers then used Bayesian modeling to narrow down the potential date ranges.

‘Never really went extinct’

Then they used optimal linear estimation, a new modeling technique they adapted from biological conservation sciences, to get the best estimate for when the region’s last Neanderthals lived.

Humans, neanderthals, Denisovan and mystery hominins.

Djakovic said the “underlying assumption” of this technique is that we are unlikely to ever discover the first or last members of an extinct species.

“For example, we’ll never find the last woolly rhino,” he told AFP, adding that “our understanding is always broken up into fragments.”

The modeling found that Neanderthals in the region went extinct between 40,870 and 40,457 years ago, while modern humans first appeared around 42,500 years ago.

This means the two species lived alongside each other in the region for between 1,400 and 2,900 years, the study said.

During this time there are indications of a great “diffusion of ideas” by both humans and Neanderthals, Djakovic said.

The period is “associated with substantial transformations in the way that people are producing material culture,” such as tools and ornaments, he said.

There was also a “quite severe” change in the artifacts produced by Neanderthals, which started to look much more like those made by humans, he added.

Given the changes in culture and the evidence in our own genes, the new timeline could further bolster a leading theory for the end of the Neanderthals: mating with humans.

Breeding with the larger human population could have meant that, over time, Neanderthals were “effectively swallowed into our gene pool,” Djakovic said.

“When you combine that with what we know now—that most people living on Earth have Neanderthal DNA—you could make the argument that they never really went extinct, in a certain sense.”

EUROPE, WORLD

Skeletons: Remains of 240 people under the Haverfordwest store

Skeletons: Remains of 240 people under the Haverfordwest store

The remains of more than 240 people, including children, have been unearthed by archaeologists working on the remnants of a medieval priory found beneath a former department store.

The “hugely significant” discovery was made under the old Ocky White building in Haverfordwest, Pembrokeshire. Archaeologists believe the ruins are from St Saviour’s Priory, founded by a Dominican order of monks in about 1256.

One expert said it offered a “window into medieval Haverfordwest”.

Ocky White was a popular store for more than a century before its riverside premises closed in 2013.

Skeletons: Remains of 240 people under the Haverfordwest store
Some skulls have been found with injuries consistent with having been in battle, according to the experts

Site supervisor Andrew Shobbrook, from Dyfed Archaeological Trust, described the priory as a significant complex of buildings with dormitories, scriptoriums – rooms devoted to writing and manuscripts – stables and a hospital.

“It’s quite a prestigious place to be buried. You have a range of people, from the wealthy to general townsfolk,” he said.

It is believed that the graveyard could have been used until the early 18th Century.

Archaeologists believe the ruins are from a 13th Century priory, including a hospital

About half of the remains are those of children, which is said to be a reflection of their high mortality rate at the time.

All the bones will be analysed by a specialist before being reburied on the consecrated ground nearby.

Some of the remains have been found with head injuries, consistent with having been in battle, and the wounds could have been caused by arrows or musket balls, according to Mr Shobbrook.

Hundreds of remains and artefacts have been unearthed
Tiles have also been found at the site
It is believed that the graveyard could have been used until the early 18th Century

One theory is that the victims could date from an attack led by Owain Glyndŵr, who was the last native Welsh person to hold the title Prince of Wales.

It was a joint assault by Welsh and French forces, who had united to battle the English occupation of Wales.

“We know that the town was besieged in 1405 by Owain Glyndŵr and they could be victims of that conflict,” said Mr Shobbrook.

The remains and other finds, including tiles, are being stored at a nearby disused shop after being cleaned and dried.

Archaeologists Andrew Shobbrook and Gaby Lester say the finds are significant

“Never in my wildest dreams did I think I would be involved in something so big,” said archaeologist Gaby Lester.

“The site is showing itself to be a massive part of the history of Haverfordwest and Pembrokeshire.

“It can be slightly overwhelming at times but it’s also quite humbling to be part of that person’s journey.”

The site is being redeveloped to become a food emporium, bar and rooftop terrace.

BELIZE, NORTH AMERICA, WORLD

Blue Fibers Found in Dental Calculus of Maya Sacrifice Victims

Blue Fibers Found in Dental Calculus of Maya Sacrifice Victims

More than 15 years after its discovery, Belize’s Midnight Terror Cave is still leaving clues about more than 100 people who were sacrificed to the Maya rain god there more than a millennium ago.

Blue Fibers Found in Dental Calculus of Maya Sacrifice Victims
The entrance to the Midnight Terror Cave in Belize.

Used for burial during the Maya Classic period (A.D. 250 to 925), the cave was named by locals who were called to rescue an injured looter in 2006. A three-year excavation project by California State University, Los Angeles (Cal State LA) professors and students concluded that the more than 10,000 bones uncovered in the cave represented at least 118 people, many of whom had evidence of trauma inflicted on them around the time of death. 

To dive deeper into the victims’ final moments, the latest research didn’t look at bones but instead at their mouths, investigating the calcified plaque from their teeth, known as dental calculus. The study, published Sept. 20 in the  International Journal of Osteoarchaeology(opens in new tab), describes curious blue fibres clinging to the teeth of at least two of the victims.

Study lead author Amy Chan, who’s now an archaeologist working in cultural resource management, started her analysis of the Midnight Terror Cave teeth as a graduate student at Cal State LA, where she was interested in learning more about the dental health of the victims, she told Live Science by email. 

“After finding minimal instances of dental pathology, I became interested in determining what foodstuffs the victims were consuming,” she said.

The blue fiber, likely made of cotton, is from Midnight Terror Cave in Belize.

Dental calculus can preserve microscopic pieces of food that someone ate — such as pollen grains, starches and phytoliths, which are mineralized parts of plants — so Chan scraped the gunk off six teeth and sent it to study co-author Linda Scott Cummings(opens in new tab), president and CEO of the PaleoResearch Institute in Golden, Colorado. Scott Cummings found that the samples contained primarily cotton fibres and that several of those were dyed bright blue.

“The discovery of blue cotton fibres in both samples was a surprise,” Chan said, because “blue is important in Maya ritual.” 

A unique “Maya blue” pigment has been found at other sites in Mesoamerica, where it seems to have been used in ceremonies — particularly to paint the bodies of sacrificial victims, Chan and colleagues wrote in their research paper. These blue fibres were also found in an agave-based alcoholic beverage at burials at Teotihuacan, an archaeological site in what is now Mexico. 

But Chan and her team offered another explanation for the fibres found on the teeth: Perhaps the victims had cotton cloths in their mouths, possibly from the use of gags leading up to their sacrifice. If victims were in custody for extended periods of time, their dental calculus could have incorporated the blue fibres.

The interior of the Midnight Terror Cave in Belize, with a person in blue for scale.

“It is interesting that they found coloured fibre in dental calculus,” Gabriel Wrobel(opens in new tab), a bioarchaeologist at Michigan State University who was not involved in the study, told Live Science by email. “Many researchers think that calculus only reflects diet, but this study is a great example of how much more information can be learned.”

Claire Ebert(opens in new tab), an environmental archaeologist at the University of Pittsburgh who was not involved in the study, told Live Science by email that she is “sceptical” that the blue fibres came from gags. However, she noted that dental calculus studies are important because they “can be used to look at other aspects of Maya life, ranging from ritual to domestic.” 

An expanded study including both elite and non-elite people would be worthwhile “to see if the pattern can also be detected” or if “other explanations for the presence of fibers may be more logical,” Ebert said.

Chan and her team agree that their study, while providing the first evidence of blue fibers in the dental calculus of Maya individuals, has some limitations. First, the rate at which plaque forms and hardens varies based on the type of food eaten and a person’s physiology, so the researchers cannot know for certain when the fibers were trapped. Additionally, very few teeth of Midnight Terror Cave victims had dental calculus, to begin with, limiting the team’s analysis. 

“Future studies will provide a more ample context for interpreting this data,” the researchers wrote in their study.