Mesomerican turquoise may have different origin than previously thought

New research published today in the journal Science Advances overturns more than a century of thought about the source of turquoise used by ancient civilizations in Mesoamerica, the vast region that extends from Central Mexico to Central America. For more than 150 years, scholars have argued that the Aztec and Mixtec civilizations, which revered the precious, blue-green mineral, acquired it through import from the American Southwest. However, extensive geochemical analyses reveal that the true geologic source of Aztec and Mixtec turquoise lies within Mesoamerica.

Geochemist Alyson Thibodeau, assistant professor of earth sciences at Dickinson College, and a team of researchers from the University of Arizona, California State University at San Bernardino, and the Museo del Templo Mayor in Mexico City, measured the isotopic signatures of Mesoamerican turquoise artifacts associated with both the Aztecs and Mixtecs. These isotopic signatures function like fingerprints that can be used to determine the geologic origins of the turquoise.

Specifically, Thibodeau and her research team carried out analyses of lead and strontium isotopes on fragments of turquoise-encrusted mosaics, which are one of the most iconic forms of ancient Mesoamerican art. Their samples include dozens of turquoise mosaic tiles excavated from offerings within the Templo Mayor, the ceremonial and ritual center of the Aztec empire, and which is located in present-day Mexico City. They also analyzed five tiles associated with Mixteca-style objects held by the Smithsonian's National Museum of the American Indian. The analyses revealed that turquoise artifacts had isotopic signatures consistent with geology of Mesoamerica, not the Southwestern United States.

"This work revises our understanding of these relatively rare objects and provides a new perspective on the availability of turquoise, which was a highly valued luxury resource in ancient Mesoamerica," said Thibodeau. The work is the result of a decade-long collaboration between archaeologists and isotope geochemists to understand the nature of turquoise circulation and trade across southwestern North America. In earlier published research, Thibodeau showed that isotopic signatures could distinguish among turquoise deposits across the southwestern U.S. and identified the geologic sources of turquoise artifacts from archaeological sites in Arizona and New Mexico.

Thibodeau said that long-standing assumption that Mesoamerican civilizations imported turquoise from the Southwest had not been fully substantiated with evidence and that the new geochemical measurements unveil a different story. "These findings potentially re-shape our understanding of both the nature and extent of long-distance contacts between Mesoamerican and Southwestern societies, said Thibodeau. "I hope this inspires people to be skeptical of claims."


Though scholars have long assumed that Aztec and Mixtec turquoise artifacts uncovered in Mesoamerica were imported from the American Southwest, a new isotopic analysis suggests these artifacts likely derived from Mesoamerican sources. The results provide insights into the origin and circulation of turquoise across Southwestern North America. Artifacts made of turquoise - a blue-green mineral extremely valued by prehispanic societies, including the Aztecs and Mixtecs - have been uncovered in Mesoamerica, a region of the Americas that spans from central Mexico to parts of South America.

Experts have hypothesized that turquoise was brought to Mesoamerica from prehistoric mines of the Greater Southwest (present-day American southwest and northwestern Mexico), in part because no remnants of turquoise mines have been discovered in Mesoamerica and also because goods were known to be exchanged between the two cultures. Yet, some have questioned this hypothesis, particularly as geochemical data from Southwestern turquoise mines have not been fully published.

Taking advantage of the way turquoise deposits harbor distinct isotopic characteristics depending on surrounding rock, Alyson M. Thibodeau et al. analyzed the lead (Pb) and strontium (Sr) isotopic ratios in 43 Mesoamerican turquoise mosaic tiles (tesserae) from the Sacred Precinct of Tenochtitlan, most of which date to the late 15th century, as well as five tesserae associated with Mixtec turquoise mosaics. They were able to collect both Pb and Sr isotopic data for 31 samples, and out of those, 29 fall outside the distribution of ratios for turquoise deposits in the Southwest. What is more, these turquoise deposits match well with copper deposits and crustal rocks of Mesoamerica, suggesting that Mesoamerica was the source of this Aztec and Mixtec turquoise.

Large-scale whaling in north Scandinavia may date back to 6th century Uppsala University

IMAGE: Left: a board-game piece made from whalebone at the end of the 6th century CE, found in Gnistahögen near Uppsala, Sweden (photograph by Bengt Backlund, Uppland County Museum). Right: the... view more 

Credit: Bengt Backlund/Rudolf Gustavsson

The intensive whaling that has pushed many species to the brink of extinction today may be several centuries older than previously assumed. This view is held by archaeologists from Uppsala and York whose findings are presented in the European Journal of Archaeology.

Museum collections in Sweden contain thousands of Iron Age board-game pieces. New studies of the raw material composing them show that most were made of whalebone from the mid-6th century CE. They were produced in large volumes and standardised forms. The researchers therefore believe that a regular supply of whalebone was needed. Since the producers would hardly have found the carcasses of beached whales a reliable source, the gaming pieces are interpreted as evidence for whaling.

Apart from an osteological survey, species origin has been determined for a small number of game pieces, using ZooMS (short for Zooarchaeology by Mass Spectrometer). The method shows that all the pieces analysed were derived from the North Atlantic right whale (Eubalaena glacialis), a massive whale weighing 50-80 tonnes. It got the name because it was the right whale to hunt: it swam slowly, close to shore, and contained so much blubber as to float after being killed.

Whalebone gaming pieces appear at the same time as production features for blubber and large boathouses were multiplying in northern Norway. The gaming pieces were probably made in this region, from where they were transported south and ultimately used as burial gifts in Sweden.
The origins of large-scale whaling in northern Europe have long been shrouded in mystery. Written sources refer to whaling on a large scale during periods corresponding to the Viking Age in Scandinavia. Ninth-century sagas about the Norwegian merchant Ohthere/Ottar (a guest and informant at the court of King Alfred the Great) mention his extensive hunt for large whales, but these stories have long been controversial as factual sources.

The gaming pieces not only indicate early whaling. To the archaeologists, they are an important component in research on extensive early trading networks. These were well-functioning several centuries before the formation of towns in Viking times. The new study, along with several other archaeological studies over the past few years, shows increasingly substantial exploitation of marine resources, and also of inland resources in northern Scandinavia. In a supplementary in-depth study, the results will also be used to study human influence on the marine ecosystems in relation to whale population trends, since it is now realised that the inception of large-scale whaling took place further back in time than was previously known.

On the origins of agriculture

The invention of agriculture changed humans and the environment forever, and over several thousand years, the practice originated independently in a least a dozen different places. But why did agriculture begin in those places, at those particular times in human history?

Using a new methodological approach, researchers at Colorado State University and Washington University in St. Louis have uncovered evidence that underscores one long-debated theory: that agriculture arose out of moments of surplus, when environmental conditions were improving, and populations lived in greater densities.

The first-of-its-kind study, "Hindcasting global population densities reveals forces enabling the origin of agriculture," published in Nature Human Behaviour, lends support to existing ideas about the origins of human agriculture. In contrast, they found little support for two other, longstanding theories: One, that during desperate times, when environmental conditions worsened and populations lived at lower densities, agriculture was born out of necessity, as people needed a new way of getting food. And two, that no general pattern exists, but instead the story of agriculture's origins is tied to unique social and environmental conditions in each place.

Senior author Michael Gavin, an associate professor in CSU's Department of Human Dimensions of Natural Resources, said the findings and the general methodological approach may help explain other watershed events in human history.

"There have been several key threshold events in our history that changed the entire course of our species," Gavin said. "Agriculture is a link to so many other components for what the world is like today for billions of people. This begins to help us explain a key moment in human history."

Predicting into the past
Studying the depths of human history is challenging, as little data are available when looking back tens of thousands of years. Scientists typically rely on archeological evidence, but getting a broad picture is difficult, since archeological digs cover relatively small areas.

To overcome these limitations, the researchers modeled correlations between the environment, cultural traits and population densities of relatively recent foraging societies, which used hunting, fishing and gathering to obtain food.

Among the factors they considered as possible predictors of population density: environmental productivity; environmental stability; the average distance travelled when people in a community moved to a new location; whether people owned land or other resources; and distance to the nearest coast.

This model, the team found, did a remarkably good job at predicting recent population densities, which led the researchers to pair the model with data on past climate. In doing so, they could hindcast, or predict into the past, the potential population density of the entire globe dating back thousands of years.

Population maps
This study was the first to produce maps of potential population densities dating back as far as 21,000 years. The researchers used these maps to examine conditions that existed in each of the 12 centers of origin, at the point in time agricultural practices began.

Patrick Kavanagh, a CSU postdoctoral scientist and one of the study's lead authors, said the different centers of origin for agriculture all showed improving environmental conditions and increasing population densities.

"All regions that developed agriculture showed the same pattern," he said.

Researchers believe that improving environmental conditions may have allowed people the luxury of tinkering with new ideas, and that having more people living in one place would allow ideas to be shared and honed, with sparks of innovation following.

While the researchers found commonalities in the surplus aspect of what was occurring in different locations, that doesn't mean the exact same conditions existed in each center of origin. Socially, the places and people studied were probably very different. In addition, the timing of when agriculture began in these major centers varied over thousands of years, and the species of plants they were working with was different.

But, amazingly, although the centers of origin varied in time by thousands of years and ranged from the New Guinea Highlands to Central America and the Middle East, they all had one thing in common: improving environmental conditions, and the potential for higher population densities.

"In all of these major origin centers of agriculture, there were some critical environmental changes that needed to occur," Kavanagh added. "Environmental conditions needed to improve -- which we saw in all 12 centers of origin -- despite variation in the timing and the diverse geographic locations in which they occurred."

The research team is now exploring other applications for the maps they produced.

"It is amazing to examine these maps of the potential population density of the world dating back tens of thousands of years," said Gavin. "We could potentially create them going back to the dawn of our species. This provides a new tool to explore many unanswered questions about human history."

Hats on for Easter Island statues

IMAGE: Restored statue platform with standing moai on the south coast of Rapa Nui. Note that one of the moai is adorned with a red scoria pukao. view more 

Credit: Sean Hixon

How do you put a 13-ton hat on a giant statue? That's what a team of researchers is trying to figure out with their study of Easter Island statues and the red hats that sit atop some of them.
"Lots of people have come up with ideas, but we are the first to come up with an idea that uses archaeological evidence," said Sean W. Hixon, graduate student in anthropology, Penn State.

Rapa Nui --Easter Island, Chile -- sits in the Southern Pacific Ocean more than 2,000 miles from Chile in South America. The island is about 15 miles long and 7.6 miles wide at its widest with an area of about 63 square miles. According to the researchers, the island was first inhabited in the 13th century by Polynesian travelers.

The statues, carved from volcanic tuff, came from one quarry on the island, while the hats, made of red scoria, came from a different quarry 7.5 miles away on the other side of the island.

Previous research by Carl P. Lipo, professor of anthropology, Binghamton University, and Terry Hunt, professor of anthropology and dean of the Honors College, University of Arizona, determined that the statues, which can be up to 33 feet tall and weigh 81 tons, were moved into place along well-prepared roads using a walking/rocking motion, similar to the way a refrigerator is moved.

"The statues were moved in a fashion using simple physics-based processes in a way that was elegant and remarkably effective," said Lipo. Not all statues made it to their final locations, and the fallen and/or broken ones showed that, to move them, the statues were carved so they leaned forward and were later leveled off for final placement.

The hats, with diameters up to 6.5 feet and weighing 13 tons, might have been rolled across the island, but once they arrived at their intended statues, they still needed to be lifted onto the statues' heads. The islanders probably carved the hats cylindrically and rolled them to the statues before further carving the hats to attain the final shapes, which vary from cylindrical to conical and which usually have a smaller cylindrical projection on the top. Chips of red scoria are found in the platform of some of the statue hat combinations.

"We were interested in figuring out the method of hat transport and placement of the hats that best agrees with the archaeological record," said Hixon.

The researchers took multiple photographs of many Rapa Nui hats to see what attributes of the hats were the same throughout. Using photogrammetry and 3-D imaging, they created images of the hats with all their details.

"We assumed they were all transported and placed in the same way," said Hixon. "So we looked for features that were the same on all the hats and all the statues."

The only features they found the same were indentations at the bases of the hats, and these indentations fit the tops of the statues' heads. If the hats had been slid in place on top of the statues, then the soft stone ridges on the margin of the indentations would have been destroyed. So the islanders must have used some other method.

Previous researchers suggested that the statues and the hats were united before they were lifted in place, but the remnants of broken or abandoned statues, and other evidence for walking the statues, indicates this was not the approach used and that the hats were most likely raised to the top of standing statues.

Many of the hats left around the island are much larger than those placed on statues.

"The best explanation for the transport of the pukao (hats) from the quarry is by rolling the raw material to the location of the moai (statues)," said Lipo. "Once at the moai, the pukao were rolled up large ramps to the top of a standing statue using a parbuckling technique." Parbuckling is a simple and efficient technique for rolling objects and is often used to right ships that have capsized. The center of a long rope is fixed to the top of a ramp and the two trailing ends are wrapped around the cylinder to be moved. The rope ends are then brought to the top where workers pull on the ropes to move the cylinder up the ramp.

Besides reducing the force needed to move the hats, this arrangement also makes it easier to stabilize the hat on the trip up because the hat typically will not roll back down the slope. The researchers report in the current issue of the Journal of Archaeological Science, that 15 or fewer workers could move the largest preform hats up the ramps.

Once the hat was at the top of the ramp, it could not simply be pushed into place because of the ridges on the margin of the hat base indentation. Rather, the researchers believe that the hats were tipped up onto the statues.

First the hat would be modified to its final form, some including a second, smaller cylindrical piece on top.

The hats could be rotated 90 degrees and then levered up with small wooden levers to sit on the statue tops, or the ramp could be slightly to the side, so that rotation in the small space at the top of the ramp would be unnecessary. Then the hat would simply be levered and pivoted on edge and into place.

The ramps were then disassembled and became the wings of the platform surrounding the statues.

"This is the first time anyone has systematically explored the evidence for how the giant hats were placed on the top of the heads of the massive statues of Easter Island," said Lipo. "Our work combines cutting-edge 3-D modeling with artifact analysis and models drawn from physics to arrive at the best answer."

Earliest European evidence of lead pollution uncovered in the Balkans

New research from Northumbria University has revealed that metal-related pollution began in the Balkans more than 500 years before it appeared in western Europe, and persisted throughout the Dark Ages and Medieval Period, meaning the region played a far bigger role in mineral exploitation than previously believed.

The study provides a new perspective on both the timing and extent of metallurgy - the technique of extracting metal from ores prior to heating or working with metals to give them a desired shape - in the Balkans, and the associated economic change this brought to the region, such as the inception of the Metal Ages.

The findings are published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) Monday 28 May 2018.

The exploitation of mineral resources has a broad range of environmental impacts, including metal-contaminated wastewater and the release of microscopic chemical particles into the atmosphere from mining and smelting. As these particles settle on to the surface of a peat bog, an environment in which the sediment develops year on year, a clear history of the bog's development may be established.

Samples recovered from the Crveni Potok peat bog, located on the Serbia/Montenegro border, were geochemically examined by researchers from Northumbria's Department of Geography and Environmental Sciences alongside colleagues from the University of Montpellier and the Romanian Academy. They found the first clear evidence of metal pollution originating from lead in the region dating back to approximately 3600 BC.

The evidence is supported by a concurrent rise in charcoal concentration, which suggests an increase in biomass burning which is potentially related to a broad range of economic activities, including fuel production for metal smelting.

Previously, the oldest European environmental pollution dating to circa 3000 BC had been found in southern Spain, but the new data from Crveni Potok show that metal pollution was evident in this region of eastern Europe more than 500 years earlier. This evidence is the earliest documented in European environmental records and indicates environmental pollution from metallurgy at a time when Britons were still in the Stone Age. This confirms that the Balkans were not only the birthplace of metallurgy in Europe, but also of metallic pollution.

Furthermore, levels of lead pollution decreased dramatically in western Europe after the collapse of the Roman Empire, a feature not observed in this Balkan record. This suggests that the region - which is metal rich - should be considered more of a major player in environmental metal pollution through Dark and Middle Ages than previously thought.

This contrast between eastern and western Europe indicates that while western Europe was in the 'Dark Ages' there was significant economic development in the Balkan area with high levels of metal environmental pollution throughout the Medieval period. This confirms the large extent and size of the metalworking industry in the Balkans during this era.

As part of his PhD research Jack Longman uncovered these findings supervised by Dr Vasile Ersek, Senior Lecturer in Physical Geography in the University's Department of Geography and Environmental Sciences.

Dr Ersek explained:

 "Much of the focus in determining sources of ancient pollution has been on established sources such as the Romans or ancient Greeks, but these findings highlight the crucial role that the Balkan metallurgy has played in the economic development of the area.

"Metallurgy and mining is intimately linked to socioeconomic development, therefore improving our knowledge of how these resources were exploited in the past can help us understand better how societies developed over time. In this respect, the peat bog record from Crveni Potok provides a fascinating history of pollution from the early Bronze Age through to the Industrial Revolution."

Dr Longman added:

"What is most interesting is that after the Roman Empire falls in the third and fourth centuries AD, lead pollution continues and even increases, indicating that the strong mining and smelting culture developed by the Romans was continued by the local population. This goes against the long-held view of barbaric hordes with little technological know-how ousting the Romans leading to the Dark Ages - as we term the 1,000 years following the Roman period. These Dark Ages may well have been true in much of western Europe, but in the Balkans, it seems that this period was, in fact, rather 'well-lit'."

Two ancient populations that diverged later 'reconverged' in the Americas

A new genetic study of ancient individuals in the Americas and their contemporary descendants finds that two populations that diverged from one another 18,000 to 15,000 years ago remained apart for millennia before mixing again. This historic "reconvergence" occurred before or during their expansion to the southern continent.

The study, reported in the journal Science, challenges previous research suggesting that the first people in the Americas split into northern and southern branches, and that the southern branch alone gave rise to all ancient populations in Central and South America.

The study shows for the first time that, deep in their genetic history, many Indigenous people in the southern continent retain at least some DNA from the "northerners" who are the direct ancestors of many Native communities living today in the Canadian east.

"It was previously thought that Indigenous South Americans, and indeed most Native Americans, derived from one ancestry related to the Clovis people, who lived about 13,000 years ago," said Cambridge University archaeology professor Toomas Kivisild, who co-led the research with University of Illinois anthropology professor Ripan Malhi

"We now find that all Native populations in North, Central and South America also draw genetic ancestry from a northern branch most closely related to Indigenous peoples of eastern Canada," Kivisild said. "This cannot be explained by activity in the last few thousand years. It is something altogether more ancient." "We are starting to see that previous models of ancient populations were unrealistically simple," Malhi said.

The researchers analyzed 91 ancient genomes from sites in California and Canada, along with 45 mitochondrial genomes from present-day Native individuals. The work adds to the evidence that two populations diverged 18,000 to 15,000 years ago. This would have been during or after their migration across the now-submerged land bridge from Siberia along what is now coastal Alaska, the researchers report.

Ancient genomes from southwest Ontario show that after the split, Indigenous ancestors representing the northern branch migrated to the Great Lakes region. They may have followed the retreating glacial edges as the most recent ice age began to thaw, the researchers said.

Populations representing the southern branch likely continued down the Pacific coast, inhabiting islands along the way, the researchers found.

"The ancient Anzick child from Montana also represents the southern branch and is associated with the Clovis culture, which was once thought to be ancestral to all Native Americans," Malhi said. "The analysis of genomes from ancient peoples from Ontario and California allowed us to identify components of the northern and southern branches in contemporary Central and South American genomes. These components were likely the result of a 'reconvergence' of the two branches deep in time."

"The blending of lineages occurred either in North America, prior to the expansion south, or as people migrated deeper into the southern continent, most likely following the western coast," said Christiana Scheib, the first author of the study who conducted the work while at the University of Cambridge. "We don't have ancient DNA to corroborate how early this northern ancestral branch arrived."

Ancient tooth shows Mesolithic ancestors were fish and plant eaters

IMAGE: The Mesolithic tooth had evidence of fish scales and fish tissue. view more 

Credit: Sapienza University of Rome

Previous analysis of Mesolithic skeletal remains in this region has suggested a more varied Medittaranrrean diet consisting of terrestrial, freshwater and marine food resources, not too dissimilar to what modern humans eat today.
Although this recent find is the only example of a skeleton that provides evidence of both fish and plants in the diet of early people in this region, the researchers argue that the discovery provides a significant insight into the lifestyle of Adriatic and Mediterranean foragers.
The team found microfossils entombed in the dental calculus, commonly known as tooth plaque or tartar, of the young male skeleton, revealing fish scale fragments and fish muscle fibres.
Analysis also showed microfossils of plants in the dental calculus, which has not been identified in skeletal remains in this part of the Mediterranean before. The researchers point out that finding both ancient plant and fish deposits in the teeth further demonstrates the value of dental remains in the understanding of human evolution.
Dr Harry Robson, from the University of York's Department of Archaeology, said: "Whilst fishing during the Mesolithic period has been demonstrated by fish remains as well as fishing related technologies in the past, here, for the first time we have direct evidence that humans consumed these resources, or used their teeth for de-scaling activities, which is very unique.
"The skeleton, which has been dated to the late eighth millennium BC, is also significant in terms of its bone chemistry. Using carbon and nitrogen stable isotope analysis we were able to demonstrate that marine resources were a major component of the diet of this individual over a sustained period of time."
The team were unable to identify the fish scales, although they are thought to be very similar to tuna, mackeral, and gilthead sea bream.
Despite the lack of a grave, the male who was between 30 and 40 years-of-age, was probably purposefully buried there. Although long-term consumption of marine resources is a rare find for this period and region, dental analysis of more skeletal finds could help reveal if it was common to early human diets.
Lead researcher, Professor Emanuela Cristiani, from Sapienza University of Rome, said: "This is an exciting, but surprising finding. We only have three skeletal remains from this period that demonstrate the long-term consumption of marine-resources, so when you can identify microfossils of this kind, it can provide a great leap forward in our understanding.
"Our data provides a novel perspective on forager diet in the Mediterranean region by revealing the role of marine organisms during the Mesolithic.
"The recovery of starch granules from two wild grass groups in the dental calculus of the analysed individual, suggests that energy-rich plants were a part of the Holocene forager dietary habits in the region.