Thursday, June 17, 2021

Bronze Age Scandinavia's trading networks for copper settled


Crossing the North Sea before crossing the Alps!

AARHUS UNIVERSITY

Research News

New research presents over 300 new analyses of bronze objects, raising the total number to 550 in 'the archaeological fingerprint project'. This is roughly two thirds of the entire metal inventory of the early Bronze Age in southern Scandinavia. For the first time, it was possible to map the trade networks for metals and to identify changes in the supply routes, coinciding with other socio-economic changes detectable in the rich metal-dependent societies of Bronze Age southern Scandinavia.

The magnificent Bronze Age in southern Scandinavia rose from copper traded from the British Isles and Slovakia 4000 years ago. 500 years later these established trade networks collapsed and fresh copper was then traded from the southern Alps, the so-called Italian Alps. This large-scale study could show that during the first 700 years of the Nordic Bronze Age the metal supplying networks and trade routes changed several times. These 700 years of establishment and change led to a highly specialised metalwork culture boasting beautiful artwork such as the Trundholm Sun wagon and spiral decorated belt plates branding high-ranking women; even depicted on today's Danish banknotes.

The study by H. Nørgaard, Moesgaard Museum and her colleagues H. Vandkilde from Aarhus University and E. Pernicka from the Curt-Engelhorn Centre in Mannheim built on the so far largest dataset of chemical and isotope data of ancient bronze artefacts. In total 550 objects were used to model the changes that took place: These changes correlate with major shifts in social organisation, settlements, housing, burial rites and long distance mobility.

"Now, this multi-disciplinary approach - based jointly on conventional archaeological methods and novel scientific methodologies processing large data quantities - allows us to detect these correlating changes and identify contemporaneity with societal changes recognised by colleague researchers", says Heide Nørgaard the project´s PI.

"It is highly likely that both people and technologies arrived to Scandinavia and that Scandinavians travelled abroad to acquire copper by means of the Nordic amber, highly valued by European trading partners".

New method could reveal what genes we might have inherited from Neanderthals


UNIVERSITY OF COPENHAGEN - THE FACULTY OF HEALTH AND MEDICAL SCIENCES

Research News

Thousands of years ago, archaic humans such as Neanderthals and Denisovans went extinct. But before that, they interbred with the ancestors of present-day humans, who still to this day carry genetic mutations from the extinct species.

Over 40 percent of the Neanderthal genome is thought to have survived in different present-day humans of non-African descent, but spread out so that any individual genome is only composed of up to two percent Neanderthal material. Some human populations also carry genetic material from Denisovans - a mysterious group of archaic humans that may have lived in Eastern Eurasia and Oceania thousands of years ago.

The introduction of beneficial genetic material into our gene pool, a process known as adaptive introgression, often happened because it was advantageous to humans after they expanded across the globe. To name a few examples, scientists believe some of the mutations affected skin development and metabolism. But many mutations are yet still undiscovered.

Now, researchers from GLOBE Institute at the University of Copenhagen have developed a new method using deep learning techniques to search the human genome for undiscovered mutations.

"We developed a deep learning method called 'genomatnn' that jointly models introgression, which is the transfer of genetic information between species, and natural selection. The model was developed in order to identify regions in the human genome where this introgression could have happened," says Associate Professor Fernando Racimo, GLOBE Institute, corresponding author of the new study.

"Our method is highly accurate and outcompetes previous approaches in power. We applied it to various human genomic datasets and found several candidate beneficial gene variants that were introduced into the human gene pool," he says.

The new method is based on a so-called convolutional neural network (CNN), which is a type of deep learning framework commonly used in image and video recognition.

Using hundreds of thousands of simulations, the researchers at the University of Copenhagen trained the CNN to identify patterns in images of the genome that would be produced by adaptive introgression with archaic humans.

Besides confirming already suggested genetic mutations from adaptive introgression, the researchers also discovered possible mutations that were not known to be introgressed.

"We recovered previously identified candidates for adaptive introgression in modern humans, as well as several candidates which have not previously been described," says postdoc Graham Gower, first author of the new study.

Some of the previously undescribed mutations are involved in core pathways in human metabolism and immunity.

"In European genomes, we found two strong candidates for adaptive introgression from Neanderthals in regions of the genome that affect phenotypes related to blood, including blood cell counts. In Melanesian genomes, we found candidate variants introgressed from Denisovans that potentially affected a wide range of traits, such as blood-related diseases, tumor suppression, skin development, metabolism, and various neurological diseases. It's not clear how such traits are affected in present-day carriers of the archaic variants, e.g. neutrally, positively or negatively, although historically the introgressed genetic material is assumed to have had a positive effect on those individuals carrying them," he explains.

The next stage for the research team is to adapt the method to more complex demographic and selection scenarios to understand the overall fate of Neanderthal genetic material. Graham Gower points out that the team aims to follow up on the function of the candidate variants in the genome that they found in this study.

Looking forward, it remains a challenge to search the human genome for genetic material from as yet unsampled populations, so-called ghost populations. However, the researchers are hopeful that they can further train the neural network to recognize mutations from these unsampled populations.

"Future work could also involve developing a CNN that can detect adaptive introgression from a ghost population, for cases in which genomic data from the source is unavailable," says Graham Gower.

First evidence that medieval plague victims were buried individually with 'considerable care'


UNIVERSITY OF CAMBRIDGE

Research News

IMAGE

IMAGE: RECONSTRUCTION OF PLAGUE VICTIM FROM ALL SAINTS, CAMBRIDGE view more 

CREDIT: MARK GRIDLEY

In the mid-14th century Europe was devastated by a major pandemic - the Black Death - which killed between 40 and 60 per cent of the population. Later waves of plague then continued to strike regularly over several centuries.

Plague kills so rapidly it leaves no visible traces on the skeleton, so archaeologists have previously been unable to identify individuals who died of plague unless they were buried in mass graves.

Whilst it has long been suspected that most plague victims received individual burial, this has been impossible to confirm until now.

By studying DNA from the teeth of individuals who died at this time, researchers from the After the Plague project, based at the Department of Archaeology, University of Cambridge, have identified the presence of Yersinia Pestis, the pathogen that causes plague.

These include people who received normal individual burials at a parish cemetery and friary in Cambridge and in the nearby village of Clopton.

Lead author Craig Cessford of the University of Cambridge said, "These individual burials show that even during plague outbreaks individual people were being buried with considerable care and attention. This is shown particularly at the friary where at least three such individuals were buried within the chapter house. Cambridge Archaeological Unit conducted excavations on this site on behalf of the University in 2017."

"The individual at the parish of All Saints by the Castle in Cambridge was also carefully buried; this contrasts with the apocalyptic language used to describe the abandonment of this church in 1365 when it was reported that the church was partly ruinous and 'the bones of dead bodies are exposed to beasts'."

The study also shows that some plague victims in Cambridge did, indeed, receive mass burials.

Yersinia Pestis was identified in several parishioners from St Bene't's, who were buried together in a large trench in the churchyard excavated by the Cambridge Archaeological Unit on behalf of Corpus Christi College.

This part of the churchyard was soon afterwards transferred to Corpus Christi College, which was founded by the St Bene't's parish guild to commemorate the dead including the victims of the Black Death. For centuries, the members of the College would walk over the mass burial every day on the way to the parish church.

Cessford concluded, "Our work demonstrates that it is now possible to identify individuals who died from plague and received individual burials. This greatly improves our understanding of the plague and shows that even in incredibly traumatic times during past pandemics people tried very hard to bury the deceased with as much care as possible."

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The study is published open access today in the European Journal of Archaeology.

Wednesday, June 16, 2021

Ten years of ancient genome analysis has taught scientists 'what it means to be human'

 A ball of 4,000-year-old hair frozen in time tangled around a whalebone comb led to the first ever reconstruction of an ancient human genome just over a decade ago.

The hair, which was preserved in arctic permafrost in Greenland, was collected in the 1980s and stored at a museum in Denmark. It wasn't until 2010 that evolutionary biologist Professor Eske Willerslev was able to use pioneering shotgun DNA sequencing to reconstruct the genetic history of the hair.

He found it came from a man from the earliest known people to settle in Greenland known as the Saqqaq culture. It was the first time scientists had recovered an entire ancient human genome.

Now a review of the first decade of ancient genomics of the Americas published in Naturetoday (June 16 2021) written by Professor Willerslev a Fellow of St John's College, University of Cambridge, and director of The Lundbeck Foundation GeoGenetics Centre, University of Copenhagen, with one of his longstanding collaborators Professor David Meltzer, an archaeologist based at Southern Methodist University, Texas, shows how the world's first analysis of an ancient genome sparked an incredible 'decade of discovery'.

Professor Willerslev said: "The last ten years has been full of surprises in the understanding of the peopling of the Americas - I often feel like a child at Christmas waiting to see what exciting DNA present I am about to unwrap! What has really blown my mind is how resilient and capable the early humans we have sequenced DNA from were - they occupied extremely different environments and often populated them in a short space of time.

"We were taught in school that people would stay put until the population grew to a level where the resources were exhausted. But we found people were spreading around the world just to explore, to discover, to have adventures.

"The last 10 years have shown us a lot about our history and what it means to be human. We won't ever see that depth of human experience on this planet again - people entered new areas with absolutely no idea of what was in front of them. It tells us a lot about human adaptability and how humans behave."

For decades, scientists relied on archaeological findings to reconstruct the past and theories weren't always accurate. It was previously thought, that there were early non-Native American people in the Americas but the ancient DNA analysis so far has shown that all of the ancient remains found are more closely related to contemporary Native Americans than to any other population anywhere else in the world.

Professor Meltzer, who worked on the review with Professor Willerslev while the former was at St John's College as a Beaufort Visiting Scholar added: "Genomic evidence has shown connections that we didn't know existed between different cultures and populations and the absence of connections that we thought did exist. Human population history been far more complex than previously thought.

"A lot of what has been discovered about the peopling of the Americas could not have been predicted. We have seen how rapidly people were moving around the world when they have a continent to themselves, there was nothing to hold them back. There was a selective advantage to seeing what was over the next hill."

In 2013, scientists mapped the genome of a four-year-old boy who died in south-central Siberia 24,000 years ago. The burial of an Upper Palaeolithic Siberian child was discovered in the 1920s by Russian archaeologists near the village of Mal'ta, along the Belaya river. Sequencing of the Mal'ta genome was key as it showed the existence of a previously unsampled population that contributed to the ancestry of Siberian and Native American populations.

Two years later, Professor Willerslev and his team published the first ancient Native American genome, sequenced from the remains of a baby boy ceremonially buried more than 12,000 years ago in Anzick, Montana.

In 2015, their ancient genomic analysis was able to solve the mystery of Kennewick Man, one of the oldest and most complete skeletons ever found in the Americas, and one of the most controversial.

The 9,000-year-old remains had been surrounded by a storm of controversy when legal jurisdiction over the skeleton became the focus of a decade of lawsuits between five Native American tribes, who claimed ownership of the man they called Ancient One, and the United States Army Corps of Engineers.

Professor Willerslev, who has rightly learnt to be mindful of cultural sensitivities when searching for ancient DNA, has spent much of the past decade talking to tribal community members to explain his work in detail and seek their support.

This meant he was able to agree with members of the Colville Tribe, based in Washington State where the remains were found, that they would donate some of their DNA to allow Professor Willerslev and his team to establish if there was a genetic link between them and Kennewick Man.

Jackie Cook, a descendant of the Colville Tribe and the repatriation specialist for the Confederated Tribes of the Colville Reservation, said: "We had spent nearly 20 years trying to have the Ancient One repatriated to us. There has been a long history of distrust between scientists and our Native American tribes but when Eske presented to us about his DNA work on the Anzick child, the hair on my arms stood up.

"We knew we shouldn't have to agree to DNA testing, and there were concerns that we would have to do it every time to prove cultural affiliation, but our Council members discussed it with the elders and it was agreed that any tribal member who wanted to provide DNA for the study could."

The Kennewick Man genome, like the Anzick baby, revealed the man was a direct ancestor of living Native Americans. The Ancient One was duly returned to the tribes and reburied.

Cook added: "We took a risk but it worked out. It was remarkable to work with Eske and we felt honoured, relieved and humbled to be able to resolve such an important case. We had oral stories that have passed down through the generations for thousands of years that we call coyote stories - teaching stories. These stories were from our ancestors about living alongside woolly mammoths and witnessing a series of floods and volcanoes erupting. As a tribe, we have always embraced science but not all history is discovered through science."

Work led by Professor Willerslev was also able to identify the origins of the world's oldest natural mummy called Spirit Cave. Scientists discovered the ancient human skeleton back in 1940 but it wasn't until 2018 that a striking discovery was made that unlocked the secrets of the Ice Age tribe in the Americas.

The revelation came as part of a study that genetically analysed the DNA of a series of famous and controversial ancient remains across North and South America including Spirit Cave, the Lovelock skeletons, the Lagoa Santa remains, an Inca mummy, and the oldest remains in Chilean Patagonia.

Scientists sequenced 15 ancient genomes spanning from Alaska to Patagonia and were able to track the movements of the first humans as they spread across the Americas at 'astonishing' speed during the Ice Age and also how they interacted with each other in the following millennia.

The team of academics not only discovered that the Spirit Cave remains was a Native American but they were able to dismiss a longstanding theory that a group called Paleoamericans existed in North America before Native Americans. Spirit Cave was returned to The Fallon Paiute-Shoshone Tribe, a group of Native Americans based in Nevada, for burial.

Professor Willerslev added: "Over the past decade human history has been fundamentally changed thanks to ancient genomic analysis - and the incredible findings have only just begun."


Monday, June 14, 2021

Early migrations of humans to the Americas from Siberia around 12,000 years ago have been traced using the bacteria they carried

 

Research News

  • International team used the stomach bacteria Helicobacter pylori as a biomarker for ancient human migrations
  • DNA sequences catalogued at University of Warwick in EnteroBase, a public genomes database, demonstrate that a migration of Siberians to the Americas occurred approximately 12,000 years ago
  • Project began in 2000s but new statistical techniques allowed researchers to reconstruct and date the migrations of Siberian Helicobacter pylori

Early migrations of humans to the Americas from Siberia around 12,000 years ago have been traced using the bacteria they carried by an international team including scientists at the University of Warwick.

Using samples of a stomach bacteria called Helicobacter pylori, which has shared a tight co-evolutionary relationship with humans for at least the past 100,000 years, analyses using new statistical techniques provide evidence that humans colonised the Americas through a pre-Holocene migration of evolutionarily ancient northern Eurasians across the Bering land bridge.

The study entitled "Helicobacter pylori's historical journey through Siberia and the Americas" is published this week (14 June) in the prestigious international journal Proceedings of the National Academy of Sciences of the USA (PNAS) by a team of researchers led by Professor Yoshan Moodley at the University of Venda, South Africa.

The research used genetic information on H. pylori catalogued in EnteroBase at the University of Warwick to trace the evolutionary history of the bacteria. H. pylori is a stomach bacteria that infects approximately half of individuals worldwide, but scientists have found that its genetic sequence also varies with the region that it is identified in.

Previous analyses had identified three populations of H. pylori from individuals in Eurasia and the Americas, and current data demonstrates that H. pylori from Siberia define additional previously unknown subpopulations of those groupings. The data also indicated one of these bacterial populations, which includes H. pylori from indigenous Americans, was distributed over the breadth of Siberia, suggesting that this population may have travelled with humans to the Americas at some point.

However, classical statistical analyses of the sequences were partially inconsistent with each other. To reconstruct the most likely evolutionary history for H. pylori in Siberia, researchers compared the most likely evolutionary models and timings using a technique called approximate Bayesian computation (ABC). The results showed that a tiny population of H. pylori colonised the Americas in a single migration event approximately 12,000 years ago.

Professor Mark Achtman of Warwick Medical School at the University of Warwick, senior co-author on the paper, said: "This project began in the early 2000s, when nothing was known about the genetic diversity of Helicobacter pylori in central Asia. By 2007, hundreds of Siberian H. pylori strains had been cultivated and selected genes had been sequenced. But repeated attempts by multiple talented population geneticists failed to shed light on their evolutionary history.

"This study now uses the powerful approach of ABC statistics to reconstruct and date the migrations of Siberian H. pylori (and their human hosts) across Siberia and to the Americas."

Originally, all modern humans came from Africa. About 60,000 years ago small groups of hunter-gatherers left Africa on foot and made their way into Eurasia where they settled. These were the world's first human immigrants. Astonishingly, by the end of the ice age some 50,000 years later, modern humans had already reached the American continent which, if travelling over land, is almost as far away from Africa as it is possible to get.

These ancient human migrations took place during the last glacial period, or ice age, which lasted from 115,000 to 11,700 years ago. At that time, most of northern Eurasia, also known as Siberia, would have been a frozen wasteland, and presumably inhospitable to long-term human settlement. So how then, did humans manage to migrate across this vast region and find their way to North America? This is one of the most important, and as yet unanswered, questions in human prehistory, because it would explain how humans were able to colonise the whole world from an African origin, in such a short space of time.

The team took the unusual approach of using the DNA of a human stomach bacterium named Helicobacter pylori as a biomarker for ancient human migrations. They successfully collected, sequenced and analysed bacterial strains from indigenous people across Siberia and the Americas. The bacterial DNA sequence database they generated suggested that, remarkably, some groups of humans, known as ancient northern Eurasians, did manage to reside in Siberia throughout the bitter ice age. Yet, other human groups who originally inhabited warmer latitudes in Asia, colonised Siberia after the end of the ice age, leading to the complex mix of human populations we see in that region today.

The team also used their bacterial data set to model human migration into the Americas. It is important to remember that during the ice age, much more water was frozen at the earth's poles, making the sea level at that time over 100 metres lower than the present-day sea level, thus exposing a land bridge between Eurasia and North America and allowing human migration. The team showed that one small group of ancient northern Eurasians managed to successfully cross this land bridge about 12,000 years ago, and this population subsequently expanded to give rise to the indigenous Americans we see today.

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Climate conditions during the migration of Homo sapiens out of Africa reconstructed


UNIVERSITY OF COLOGNE

Research News

An international research team led by Professor Dr Frank Schäbitz has published a climate reconstruction of the last 200,000 years for Ethiopia. This means that high-resolution data are now available for the period when early Homo sapiens, our ancestors, made their way from Africa to Europe and Asia. Schäbitz and his colleagues determined the dates using a drill core of lake sediments deposited in southern Ethiopia's Chew Bahir Basin, which lies near human fossil sites. Temporal resolution of the samples, reaching nearly 10 years, revealed that from 200,000 to 125,000 years before our time, the climate there was relatively wet, providing enough water and thus abundant plant and animal food resources in the lowlands of East Africa. From 125,000 to 60,000 years ago, it gradually became drier, and particularly dry between 60,000 to 14,000 years ago. The data now obtained fit well with genetic findings, according to which our direct genetic ancestors ('African Eve') left Africa 'successfully' during a wet phase about 70,000 to 50,000 years ago.

The article 'Hydroclimate changes in eastern Africa over the past 200,000 years may have influenced early human dispersal' has appeared in Nature Communications.

Scientists collect information about the environment from lake sediments because, in the best case, sediments are flushed into lakes relatively continuously from the catchment through erosion. In addition to mineral components, sediments include organic material and remains of organisms living in the lake. If lake sediments from suitable lakes can be drilled, these 'proxy data' can be used to draw conclusions about environmental conditions at the time, and thus help to reconstruct the climate.

From November to December 2014, the researchers recovered an approximately 300 metre long drill core from the Chew Bahir Basin in southern Ethiopia, which dries out during the dry season. In its entirety, the drill core dates back to about 620,000 years. 'This enables us to chronologically cover the entire evolutionary history of Homo sapiens in Africa. The work now published on the last 200,000 years of this drill core thus provides very good evidence of the environmental and climate history during the migration of our ancestors,' Schäbitz explained.

'Some of our proxies allow time resolution for specific decades in large sections of the core, which has not been done before for this part of Africa. That way we can capture very short-term climate changes representing less than a human lifetime,' he said. The drill core reveals that the climate of East Africa was largely influenced by changes in solar insolation, which led to either wet or dry climate conditions. From 200,000 to 125,000 years ago, the climate was generally relatively favourable, i.e., the lowlands provided enough water and thus abundant plant and animal food resources for our ancestors. Under such conditions, people could move relatively easily over long distances and even reach the Arabian Peninsula, as evidenced by the oldest fossil finds there (about 175,000 years ago). From 125,000 to 60,000 years ago, however, it gradually became drier, and then particularly dry between 60,000 to 14,000 years ago, with the lake drying up completely several times.

'However, during this period in particular, quite striking, short-term moisture fluctuations can also be observed, the temporal patterns of which are reminiscent of cold-warm climate fluctuations known from Greenland ice cores. So the people who lived in East Africa at that time were exposed to extreme changes in their environments,' Schäbitz said. 'It is interesting that just in the period from 60,000 to 14,000 years ago, when the lowlands of East Africa were repeatedly particularly dry, numerous archaeological findings in the high altitudes of the Ethiopian mountains bear witness to the presence of our ancestors there.' In addition, the weapons and tools of these people also evolved during this time period (transition from Middle to Late Paleolithic in Africa). 'We suspect that the greater "environmental stress" at lower elevations forced this development,' the scientist noted.

Furthermore, the scientists noted that the last major wet phase which we can see in the core fits well in time with the genetic findings: It shows that our direct genetic ancestors 'successfully' left Africa about 70,000 to 50,000 years ago. Their descendants probably reached southeastern Europe 50,000 to 40,000 years ago, where they encountered Neanderthals.

'We hypothesize that the evidence of dry-humid climate fluctuations in East Africa found in our drill core had a significant impact on the evolution and mobility of our ancestors,' said Schäbitz. 'Migration out of Africa was possible several times during the last 200,000 years, during periods when the climate was wetter, and has led to the spread of our ancestors as far as Europe. During the particularly dry phases of the recent past, starting around 60,000 years ago, Homo sapiens groups repeatedly managed to survive in the high altitudes of mountainous Ethiopia.'

Thursday, June 10, 2021

Researchers link ancient wooden structure to water ritual


Research News

The Noceto Vasca Votiva is a unique wood structure that was unearthed on a small hill in northern Italy in 2005. Built primarily of oak and slightly larger than a backyard swimming pool, the exact purpose of the in-ground structure has remained a mystery, as has the date of its construction. Italian researchers estimated its origins go back to the late Middle Bronze Age, sometime between 1600 and 1300 B.C.

While that gap might not seem huge, in archeological terms it's like comparing the culture that invented the steam engine with the one that produced the iPad.

A Cornell University team led by Sturt Manning, Distinguished Professor of Arts and Sciences in Classics and director of the Tree-Ring Laboratory, used dendrochronology and a form of radiocarbon dating called "wiggle-matching" to pinpoint, with 95% probability, the years in which the structure's two main components were created: a lower tank in 1444 B.C., and an upper tank in 1432 B.C. Each date has a margin of error of four years.

The finding confirms that the Noceto Vasca Votiva was built at a pivotal moment of societal change, and bolsters the Italian researchers' theory that the structure was used for a supernatural water ritual.

The team's paper, "Dating the Noceto Vasca Votiva, a Unique Wooden Structure of the 15th Century BCE, and the Timing of a Major Societal Change in the Bronze Age of Northern Italy," published June 9 in PLOS ONE.

Manning has led the Tree-Ring Laboratory since 2006, and his team has advanced a range of tools and techniques that have successfully challenged common assumptions about historical artifacts and timelines. Among the lab's specialties is tree-ring sequenced radiocarbon "wiggle-matching," in which ancient wooden objects are dated by matching the patterns of radiocarbon isotopes from their annual growth increments (i.e., tree rings) with patterns from datasets found elsewhere around the world. This enables ultra-precise dating even when a continuous tree-ring sequence for a particular species and geographic area is not yet available.

"Working at an archaeological site, you're often trying to do dendrochronology with relatively few samples, sometimes in less than ideal condition, because they've been falling apart for the last 3,500 years before you get to see them. It's not like a healthy tree that is growing out in the wild right now," Manning said. "We often measure the samples a number of times to extract as much signal as we can."

The Noceto Vasca Votiva is about 12 meters long, 7 meters across and roughly four meters deep - although the depth was a little ambiguous at first. When the site was fully excavated, the researchers found that the structure had a second tank beneath it, which had been built first but collapsed before it was finished. It was initially unclear how much time elapsed between the creation of the two tanks, which shared some of the same materials.

Judging by the size of the structure and the extensive labor that would have been required to excavate the earth and drag timber to the uphill location, the Italian researchers recognized that the Noceto Vasca Votiva was a major undertaking for its era and theorized its purpose. But they were unable to determine the precise date of its origins, and so turned to the Cornell Tree-Ring Laboratory.

Manning's team made multiple attempts with different samples. While the wood from the Noceto site was well-preserved - a rarity, given its age - there was an unexpected challenge when the samples did not seem to fit the international radiocarbon calibration curve that is used for matching tree-ring sequences. This suggested the curve needed revising for certain time periods, and in 2020 a new version was published. The Noceto data finally fit.

By combining radiocarbon dating calibrated via dendrochronologies from southern Germany, Ireland and North America, along with computer-intensive statistics, the Cornell team was able to establish a tree-ring record that spanned several hundred years. They pegged the construction of the lower and upper tanks at 1444 and 1432 B.C., respectively; and they determined the finished structure was in use for several decades before it was abandoned, for reasons that may never be known.

The new timeline is particularly significant because it synchs up with a period of enormous change in Italian prehistory.

"You've had one way of life in operation for hundreds of years, and then you seem to have a switch to fewer, larger settlements, more international trade, more specialization, such as textile manufacture, and a change in burial practices," Manning said. "There is something of a pattern all around the world. Nearly every time there's a major change in social organization, there tends often to be an episode of building what might be described as unnecessary monuments. So when you get the first states forming in Egypt, you get the pyramids. Stonehenge marks a major change in southern England. Noceto is not the scale of Stonehenge, but it has some similarities - an act of major place-making."

Because the structure was located atop a hill and not in the center of a village, it wasn't used as a reservoir or well. The smooth layers of sediment that filled in the structure, and the absence of channels, imply it wasn't used for irrigation. In addition, the researchers discovered a large set of objects deliberately deposited inside the tank, including numerous ceramic vessels, figurines and a range of stone, wood and organic items. All of that evidence indicates the structure was used in some kind of supernatural water ritual.

"It's tempting to think it was about creating a reflective surface that you can see into, and where you put some offerings, but you're also looking at the sky above and the linking of land, sky and water (rain)," Manning said.

Given the fact that nearby settlements in this southern edge of the Po Plain were built with dikes and terraces, and the region was agriculturally productive with much water management, water was clearly important for all aspects of the builders' lives. At least for a time.

"The collapse of the whole social and economic system in the area around 1200 B.C. seems to occur because it becomes much drier," Manning said.