IMAGE: AERIAL VIEW OF ALALAKH IN THE AMUQ PLAIN (TURKEY). view more
CREDIT: MURAT AKAR, TELL ATCHANA EXCAVATIONS
The Bronze Age in the eastern Mediterranean has long been considered by researchers to have been the 'first international age,' especially the period from 1600-1200 BC, when powerful empires from Anatolia, Mesopotamia, and Egypt set up large networks of subordinate client kingdoms in the Near East. These empires fought, traded, and corresponded with one another, and ancient texts from the period reveal rich economic and social networks that enabled the movement of people and goods.
A new study conducted by an interdisciplinary team of archaeologists, geneticists, and isotope experts, and published in PLOS ONE, investigated the movement of people in this period at a single regional center, a Bronze Age city-state called Alalakh in present-day southeastern Turkey. Their results indicate that the majority buried at Alalakh were raised locally and descended from people who lived in the region.
The team's goal was to see if the high levels of interregional connectivity evidenced by the architecture, texts, and artifacts found at the site during 20 years of excavations, sponsored by the Turkish Ministry of Culture and Tourism and Hatay Mustafa Kemal University, could be detected among the population buried at the city.
To do so, they conducted strontium and oxygen isotope analyses on tooth enamel, which can detect whether an individual grew up locally at Alalakh or moved there only during adulthood. The genetic data on the other hand can be used to determine where a person's recent ancestors came from.
The isotope analysis identified several non-local individuals. However, their DNA showed an ancestry that was local to Alalakh and neighbouring regions. "There are two possible explanations for our findings," said co-lead author Stefanie Eisenmann from the Max Planck Institute for the Science of Human History. "Either these individuals are short-distance migrants from the region or return-migrants, people whose parents or grandparents originally came from Alalakh."
Only one sampled individual, an adult woman, was not part of the local gene pool, instead showing ancestry that most closely matched groups in Central Asia. However, her isotopic signatures suggested a local upbringing. "We expected the isotope analysis to show that this person immigrated to Alalakh, since her genetic data was so different from the rest of the population, so we were surprised to see that she was likely native to Alalakh. It could have been her parents or grandparents who made the move, instead," explained Tara Ingman, the other lead-author of the study from Koç University.
While different types of mobility were identified, including short-distance, long-distance, and return migration, there were no complete foreigners in the dataset. Most people were born and raised at Alalakh and also their ancestors came from the region.
"There are several ways to explain this. It is possible that far less long-distance migrants were living at Alalakh than we had previously thought. Another possibility is that we haven't found their graves, yet. Perhaps most individuals that came from far away were not buried directly at Alalakh, or in a way we cannot trace," said Murat Akar, director of the excavations.
Working with environmental engineers, archaeologists at Newcastle University, UK, used modern air quality monitoring methods to assess the impact of domestic fuel burning inside buildings at Çatalhöyük, in Turkey, one of the world's earliest settlements.
A typical house at Çatalhöyük, a UNESCO World Heritage site, had a domed oven set against the south wall, located beneath an opening in the roof. In the 1990s, a replica of one of these houses was built at Çatalhöyük to show visitors what they may have looked like during the time of occupation.
Although previous studies have shown that burning biofuels has significant negative consequences on health, especially in enclosed spaces with poor ventilation, the relationship between fuel use and health in prehistory has never been explored.
The research team, which included experts from Northumbria, Durham and Copenhagen universities, burned different types of fuel in the hearth of the replica house and measured pollution levels to test how living in these buildings may have exposed the inhabitants to fine particulate matter and impacted on their respiratory health.
The research, which was funded by the Wellcome Trust, found that the average levels of fine particulate matter (PM2.5) over a two hour period were extremely high and that concentrations continued to remain high up to 40 minutes after the fires had burnt out afterwards.
The results indicated greater exposure directly in front of the oven although similar levels were also detected to the side of the hearth, suggesting that a person's position in relation to the fire would have had only a minimal impact on exposure.
Dr Lisa-Marie Shillito, Senior Lecturer in Landscape Archaeology, explained: "At Çatalhöyük, the lack of a proper chimney, and the fact that buildings consist of a single, small room that combined living space and the hearth, means that anyone inside the building would have been exposed to unsafe levels of particulates as a result of everyday domestic activities. This would almost certainly have had a negative health impact on these communities, due to a combination of an open fire and lack of ventilation."
Studying air pollution and respiratory health in the past can be challenging because human remains do not always provide clear signs due to inadequate preservation. Small particles of PM2.5 can travel deep into the lungs where they become embedded in the tissue and can even enter the blood stream, triggering an inflammatory response outside the lungs. The remains of many of the inhabitants of Çatalhöyük show signs of osteoperiostitis, or bone lesions, which can be response to infection, and the research team suggest that this may be explained by the chronic exposure to PM2.5 that this community would have had.
Professor Anil Namdeo, Professor of Air Quality Management, Northumbria University, said: "This work has important implications for the current era. Many communities all around the world still use biomass for cooking and heating, and in poorly ventilated houses, resulting in more than four million deaths each year associated with indoor air pollution. Our study highlights this issue and could pave the way for developing mitigation measures to minimise this."
IMAGE: FECAL RECORDS FROM LAKE SEDIMENT SHOW THAT MAYA LIVED IN THE AREA FOR LONGER THAN PREVIOUSLY BELIEVED. view more
CREDIT: ANDY BRECKENRIDGE
A McGill-led study has shown that the size of the Maya population in the lowland city of Itzan (in present-day Guatemala) varied over time in response to climate change. The findings, published recently in Quaternary Science Reviews, show that both droughts and very wet periods led to important population declines.
These results are based on using a relatively new technique involving looking at stanols (organic molecules found in human and animal faecal matter) taken from the bottom of a nearby lake. Measurements of stanols were used to estimate changes in population size and to examine how they align with information about climate variability and changes in vegetation drawn from other biological and archaeological sources.
By using the technique, the researchers were able to chart major Maya population changes in the area over a period starting 3,300 years before the present (BP). They were also able to identify shifts in settlement patterns that took place over the course of hundreds of years that are associated with changes in land use and agricultural practices.
They discovered, moreover, that the land had been settled earlier than previously suggested by archaeological evidence.
New tool provides surprising information about human presence in Maya lowlands
The evidence from faecal stanols suggests that humans were present on the Itzan escarpment about 650 years before the archaeological evidence confirms it. It also shows that that the Maya continued to occupy the area, albeit in smaller number, after the so-called "collapse" between 800-1000 AD, when it had previously been believed that drought or warfare caused the entire population to desert the area. There is further evidence of a large population spike around the same time as a historical record of refugees fleeing the Spanish attack of 1697 AD on the last Maya stronghold in the southern Maya lowlands (Nojpeten, or modern-day Flores in Guatemala) - something that had not been known before.
Estimates of ancient population size in the Maya lowlands have traditionally been obtained through ground inspection and excavation. To reconstruct population dynamics, archaeologists locate, map, and count residential structures, and they excavate them to establish dates of occupation. They compare population trends at the site and regional levels. And they then use techniques such as pollen analysis and indicators of soil erosion into lakes to reconstruct the ecological changes that took place at the same time.
"This research should help archaeologists by providing a new tool to look at changes that might not be seen in the archaeological evidence, because the evidence may never have existed or may have since been lost or destroyed," said Benjamin Keenan, a PhD candidate in the Department of Earth and Planetary Sciences at McGill, and the first author on the paper. "The Maya lowlands are not very good for preserving buildings and other records of human life because of the tropical forest environment."
Maya population size affected by both droughts and wet periods
The faecal stanol from the sediment in Laguna Itzan confirms that the Maya population in the area declined due to drought at three different periods; between 90-280 AD, between 730-900 AD and during the much less well studied drought between 1350-950 BC. The researchers also found that the population declined during a very wet period from 400--210 BC, something which has received little attention until now. The population decline in response to both dry and wet periods shows that there were climatic effects on population at both climate extremes, and not only during dry periods.
"It is important for society generally to know that there were civilisations before us that were affected by and adapted to climate change," said Peter Douglas, an assistant professor in the Department of Earth and Planetary Sciences and the senior author on the paper. "By linking evidence for climate and population change we can begin to see a clear link between precipitation and the ability of these ancient cities to sustain their population."
The research also suggests that the Maya people may have adapted to environmental issues such as soil degradation and nutrient loss by using techniques such as the application of human waste (also known as night soil) as a fertiliser for crops. This is suggested by a relatively low amount of fecal stanols in the lake sediment at a time when there is archaeological evidence for the highest human populations. One explanation for this is that human waste was applied to soils as fertilizer and therefore the stanols were not washed into the lake.
IMAGE: THIS IMAGE SHOWS THE SKULL BONES OF THE MAN BURIED IN RI??UKALNS, LATVIA, AROUND 5,000 YEARS AGO. view more
CREDIT: DOMINIK GÖLDNER, BGAEU, BERLIN
The oldest strain of Yersinia pestis--the bacteria behind the plague that caused the Black Death, which may have killed as much as half of Europe's population in the 1300s--has been found in the remains of a 5,000-year-old hunter-gatherer. A genetic analysis publishing June 29 in the journal Cell Reports reveals that this ancient strain was likely less contagious and not as deadly as its medieval version.
"What's most astonishing is that we can push back the appearance of Y. pestis 2,000 years farther than previously published studies suggested," says senior author Ben Krause-Kyora, head of the aDNA Laboratory at the University of Kiel in Germany. "It seems that we are really close to the origin of the bacteria."
The plague-carrying hunter-gatherer was a 20- to 30-year old man called "RV 2039." He was one of two people whose skeletons were excavated in the late 1800s in a region called Rinnukalns in present-day Latvia. Soon after, the remains of both vanished until 2011, when they reappeared as part of German anthropologist Rudolph Virchow's collection. After this re-discovery, two more burials were uncovered from the site for a total of four specimens, likely from the same group of hunter-fisher-gatherers.
Krause-Kyora and his team used samples from the teeth and bone of all four hunter-gatherers to sequence their genomes and then tested them for bacterial and viral pathogens. They were surprised to find evidence of Y. pestis in RV 2039--and after reconstructing the bacteria's genome and comparing it to other ancient strains, the researchers determined that the Y. pestis RV 2039 carried was indeed the oldest strain ever discovered. It was likely part of a lineage that emerged about 7,000 years ago, only a few hundred years after Y. pestis split from its predecessor, Yersinia pseudotuberculosis.
"What's so surprising is that we see already in this early strain more or less the complete genetic set of Y. pestis, and only a few genes are lacking. But even a small shift in genetic settings can have a dramatic influence on virulence," says Krause-Kyora.
In particular, this ancient strain lacked one crucial thing: the gene that first let fleas act as vectors to spread the plague. This gene was responsible for efficient transmission of the bacterium to human hosts, which resulted in the growth of the infamously grotesque pus-filled buboes in the sick associated with the medieval bubonic plague. Flea-based transmission also required the death of the human host, which means that the appearance of the gene could have driven the evolution of a deadlier disease.
From RV 2039, it likely took more than a thousand years for Y. pestis to acquire all the mutations needed for flea-based transmission. And it's not clear to what extent RV 2039 experienced the effects of the plague at all.
Y. pestis was found in his bloodstream, meaning he most likely died from the bacterial infection--although, the researchers think the course of the disease might have been fairly slow. They observed that he had a high number of bacteria in his bloodstream at his time of death, and in previous rodent studies, a high bacterial load of Y. pestis has been associated with less aggressive infections. Additionally, the people he was buried near were not infected and RV 2039 was carefully buried in his grave, which the authors say also makes a highly contagious respiratory version of the plague less likely.
Instead, this 5,000-year-old strain likely was transmitted directly via a bite from an infected rodent and probably didn't spread beyond the infected person. "Isolated cases of transmission from animals to people could explain the different social environments where these ancient diseased humans are discovered. We see it in societies that are herders in the steppe, hunter-gatherers who are fishing, and in farmer communities--totally different social settings but always spontaneous occurrence of Y. pestis cases," says Krause-Kyora.
These conclusions--that the early form of Y. pestis likely was a slow-moving disease and wasn't very transmissible--challenge many theories about the development of human civilization in Europe and Asia. For example, some historians have suggested that infectious diseases like Y. pestis evolved mostly in megacities of over 10,000 people near the Black Sea. However, 5,000 years ago--the age of RV 2039's strain--was long before the formation of large cities. Instead, agriculture was just beginning to appear in Central Europe, and populations were much sparser.
This timeline, plus the less contagious and deadly nature of this early Y. pestis strain, also contradicts the hypothesis that Y. pestis led to the large population declines in Western Europe at the end of the Neolithic Age.
The authors say that examining the history of Y. pestis could also potentially shed light on human genomic history. "Different pathogens and the human genome have always evolved together. We know Y. pestis most likely killed half of the European population in a short time frame, so it should have a big impact on the human genome," says Krause-Kyora. "But even before that, we see major turnover in our immune genes at the end of the Neolithic Age, and it could be that we were seeing a significant change in the pathogen landscape at that time as well."
Ancient Rome's emperors did some pretty bizarre stuff -- bursting into uncontrollable fits of laughter, appointing a horse as a priest, dressing in animal skins and attacking people ... the list goes on. Why were they acting that way? Well, it might have been lead poisoning. In this week's episode, we unwrap the possibility that lead caused the Roman Empire's collapse:
A cluster of comet fragments believed to have hit Earth nearly 13,000 years ago may have shaped the origins of human civilisation, research suggests.
Possibly the most devastating cosmic impact since the extinction of the dinosaurs, it appears to coincide with major shifts in how human societies organised themselves, researchers say.
Their analysis backs up claims that an impact occurred prior to start of the Neolithic period in the so-called Fertile Crescent of southwest Asia.
During that time, humans in the region -- which spans parts of modern-day countries such as Egypt, Iraq and Lebanon -- switched from hunter-gatherer lifestyles to ones centred on agriculture and the creation of permanent settlements.
It is thought that the comet strike -- known as the Younger Dryas impact -- also wiped out many large animal species and ushered in a mini ice age that lasted more than 1,000 years.
Since it was proposed in 2007, the theory about the catastrophic comet strike has been the subject of heated debate and much academic research. Now, researchers from the University of Edinburgh have reviewed evidence assessing the likelihood that an impact took place, and how the event may have unfolded.
The team says a large body of evidence supports the theory that a comet struck around 13,000 years ago. Researchers analysed geological data from four continents, particularly North America and Greenland, where the largest fragments are thought to have struck.
Their analysis highlights excess levels of platinum, signs of materials melted at extremely high temperatures and the detection of nanodiamonds known to exist inside comets and form during high-energy explosions. All of this evidence strongly supports the impact theory, researchers say.
The team says further research is needed to shed more light on how it may have affected global climate and associated changes in human populations or animal extinctions.
Dr Martin Sweatman, of the University of Edinburgh's School of Engineering, who led the study, said: "This major cosmic catastrophe seems to have been memorialised on the giant stone pillars of Göbekli Tepe, possibly the 'World's first temple', which is linked with the origin of civilisation in the Fertile Crescent of southwest Asia. Did civilisation, therefore, begin with a bang?"
A near-perfectly preserved ancient human fossil known as the Harbin cranium sits in the Geoscience Museum in Hebei GEO University. The largest of known Homo skulls, scientists now say this skull represents a newly discovered human species named Homo longi or "Dragon Man." Their findings, appearing in three papers publishing June 25 in the journal The Innovation, suggest that the Homo longi lineage may be our closest relatives--and has the potential to reshape our understanding of human evolution.
"The Harbin fossil is one of the most complete human cranial fossils in the world," says author Qiang Ji, a professor of paleontology of Hebei GEO University. "This fossil preserved many morphological details that are critical for understanding the evolution of the Homogenus and the origin of Homo sapiens."
The cranium was reportedly discovered in the 1930s in Harbin City of the Heilongjiang province of China. The massive skull could hold a brain comparable in size to modern humans' but had larger, almost square eye sockets, thick brow ridges, a wide mouth, and oversized teeth. "While it shows typical archaic human features, the Harbin cranium presents a mosaic combination of primitive and derived characters setting itself apart from all the other previously-named Homo species," says Ji, leading to its new species designation of Homo longi.
Scientists believe the cranium came from a male individual, approximately 50 years old, living in a forested, floodplain environment as part of a small community. "Like Homo sapiens, they hunted mammals and birds, and gathered fruits and vegetables, and perhaps even caught fish," remarks author Xijun Ni, a professor of primatology and paleoanthropology at the Chinese Academy of Sciences and Hebei GEO University. Given that the Harbin individual was likely very large in size as well as the location where the skull was found, researchers suggest H. longi may have been adapted for harsh environments, allowing them to disperse throughout Asia.
Using a series of geochemical analyses, Ji, Ni, and their team dated the Harbin fossil to at least 146,000 years, placing it in the Middle Pleistocene, a dynamic era of human species migration. They hypothesize that H. longi and H. sapiens could have encountered each other during this era.
"We see multiple evolutionary lineages of Homo species and populations co-existing in Asia, Africa, and Europe during that time. So, if Homo sapiens indeed got to East Asia that early, they could have a chance to interact with H. longi, and since we don't know when the Harbin group disappeared, there could have been later encounters as well," says author Chris Stringer, a paleoanthropologist at the Nature History Museum in London.
Looking farther back in time, the researchers also find that Homo longi is one of our closest hominin relatives, even more closely related to us than Neanderthals. "It is widely believed that the Neanderthal belongs to an extinct lineage that is the closest relative of our own species. However, our discovery suggests that the new lineage we identified that includes Homo longi is the actual sister group of H. sapiens," says Ni.
Their reconstruction of the human tree of life also suggests that the common ancestor we share with Neanderthals existed even further back in time. "The divergence time between H. sapiens and the Neanderthals may be even deeper in evolutionary history than generally believed, over one million years," says Ni. If true, we likely diverged from Neanderthals roughly 400,000 years earlier than scientists had thought.
The researchers say that findings gathered from the Harbin cranium have the potential to rewrite major elements of human evolution. Their analysis into the life history of Homo longisuggest they were strong, robust humans whose potential interactions with Homo sapiensmay have shaped our history in turn. "Altogether, the Harbin cranium provides more evidence for us to understand Homo diversity and evolutionary relationships among these diverse Homo species and populations," says Ni. "We found our long-lost sister lineage."
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Funding information for this research is available in the respective papers.
IMAGE: A PYRAMID AT TIKAL RISES FROM THE RAINFOREST IN GUATEMALA. view more
CREDIT: DAVID LENTZ
The ancient Maya city of Tikal was a bustling metropolis and home to tens of thousands of people.
The city comprised roads, paved plazas, towering pyramids, temples and palaces and thousands of homes for its residents, all supported by agriculture.
Now researchers at the University of Cincinnati say Tikal's reservoirs -- critical sources of city drinking water -- were lined with trees and wild vegetation that would have provided scenic natural beauty in the heart of the busy city.
UC researchers developed a novel system to analyze ancient plant DNA in the sediment of Tikal's temple and palace reservoirs to identify more than 30 species of trees, grasses, vines and flowering plants that lived along its banks more than 1,000 years ago. Their findings paint a picture of a lush, wild oasis.
"Almost all of the city center was paved. That would get pretty hot during the dry season," said paleoethnobotanist David Lentz, a professor of biology in UC's College of Arts and Sciences and lead author of the study.
"So it would make sense that they would have places that were nice and cool right along the reservoir," he said. "It must have been beautiful to look at with the water and trees and a welcome place for the kings and their families to go."
The study was published in the Nature journal Scientific Reports.
Lentz and his research team offered four hypotheses about what, if any, plants might have grown along the all-important reservoirs: Did the Maya grow crops such as maize or squash there? Or did they plant fruit trees like those found at a similar reservoir at Mexico's Purron Dam?
Maybe they lined the reservoirs with cattails in keeping with their nickname people of the reeds? Lentz noted that water lilies often adorn ancient Maya paintings.
"Throughout Maya iconography, water lilies represent continuity between the water world and the above world," Lentz said. "It was part of their mythology."
But researchers found little evidence to support any of these hypotheses. Instead, they found evidence bolstering a fourth idea: that the Maya allowed the embankments to remain undisturbed forest. This would have helped to prevent erosion and provided medicinal or edible plants and fruits.
Researchers found evidence of a variety of plants living along the aquifers, including trees like cabbage bark and ramón that tower 100 feet high. Lentz said ramón is a dominant rainforest species in Guatemala.
"Why you would find ramón around the reservoir is a curiosity. The answer is they left this forest intact," Lentz said. "Tikal has a harsh climate. It's pretty tough to survive when you don't get rain for five months of the year. This reservoir would have been the font of their lives. So they sometimes would protect these places by not cutting down the trees and preserving a sacred grove."
Among dozens of plants native to the region, they found evidence of wild onion, fig, wild cherry and two types of grasses. Lentz said grass seeds might have been introduced to the reservoir by visiting waterfowl. Grass would have proliferated at the edges of the reservoirs during dry seasons and droughts.
"Tikal had a series of devastating droughts. As the water levels dropped, they saw blue green algae blooms, which produces toxic substances," Lentz said. "The droughts were great for the grass but not so much for the forest plants that lived along the reservoir's banks."
Were these wild areas the equivalent of a park?
"I think they were. I don't know how public they would have been," Lentz said. "This was a sacred area of the city surrounded by temples and palaces. I don't know if the commoners would have been that welcome."
Tikal was a flourishing seat of power, religion and trade for Mesoamerica in what is now northern Guatemala, reaching its peak of influence more than 1,200 years ago. Today, the cultural and archaeological site is a scenic national park surrounded by primary rainforest.
But more than 1,000 years ago, the area would have looked dramatically different. Instead of rainforest, the city center would have been surrounded by homes and farm plots of corn, beans and squash needed to support 60,000 people or more. At its peak, Tikal was bigger in population than Wilkes-Barre, Pennsylvania; Atlantic City, New Jersey; or Pensacola, Florida.
Given the documented and widespread deforestation that occurred around Tikal during the city's rise and fall, the presence of an intact forest in the city would have stood out, said Nicholas Dunning, a UC geography professor and study co-author.
"It would not have been much of a park -- maybe 50 meters by 50 meters," Dunning said. "But it would have been in vivid contrast to the surrounding area of the city's central precinct, which was essentially entirely paved with plaster with many of the buildings colored red."
The reservoirs would have held significance beyond their value as an important source of water, he said.
"Given that the Maya were a forest culture whose cosmology included many forest elements (for example, certain sacred trees that held up the sky) having a sacred grove adjacent to the sacred spring and pool at the heart of the city was an extremely potent symbol -- kind of like parts of the cosmos in miniature," Dunning said. "On the other hand, ancient Maya cities as a whole were very green."
Tikal put today's urban gardens to shame.
"Away from the central precinct of Tikal, most of the land was either managed trees or crops," Dunning said. "Just about every household complex had significant gardens. A great deal of the food consumed by the residents of Maya cities was probably grown within the city itself or its immediate hinterland. Nothing much like a modern Western city."
Previously, researchers learned about the crops and wild plants that grew in ancient Tikal by studying ancient pollen or charcoal, Lentz said. For their study, UC turned to next-generation DNA sequencing that can identify plants and animals with even small strands of DNA.
"Typically, high-quality, high-concentration DNA is needed for next-gen work," UC botanist and study co-author Eric Tepe said. "The Tikal samples were both poor quality and very low concentration."
Microbiologists Alison Weiss, a professor in UC's College of Medicine, and Trinity Hamilton, now with the University of Minnesota, took up the task of analyzing ancient microbial DNA from the reservoir's sediment samples.
Weiss studies pathogenic E. coli and human microbiomes in her lab. Her latest work examined how chemotherapy in cancer patients impairs the protective lining of their digestive systems. But she likes all science, she said, and was eager to accept a new challenge.
"The DNA is ancient so it tends to be degraded with short little sequences," Weiss said.
With the help of the Florida company Rapid Genomics, UC's scientists developed a novel probe to select plant DNA in the sediment samples. And they were able to amplify small strands of DNA from chloroplasts, the plant structures where photosynthesis takes place. Then researchers could match the ancient Tikal samples with the DNA of known plant species in much the same way scientists amplify ribosomal DNA to identify species of bacteria.
"The analysis was quite challenging because we were the first to do this," Weiss said. "Bacterial ribosomal DNA has a database. There was no database for this. We had to take sequences one by one and search the general database to find the best match."
"This project was a bit of a shot in the dark," Tepe said. "We half-expected to get no results at all. The fact that we were able to get an idea of the vegetation surrounding the reservoirs at Tikal is, in my opinion, a spectacular success and a proof of concept that we hope to apply to other Mayan sites."
UC researchers can now study the ancient world in a promising new way.
"We're delighted we had success," Weiss said. "It took a long time to figure out how to do it and make sure it wasn't junk data in, junk data out. Now to be able to learn more about ancient people from these sediment studies is very exciting."
IMAGE: RESEARCHERS ZENOBIA JACOBS, BO LI AND KIERAN O'GORMAN COLLECTING SEDIMENT SAMPLES IN THE MAIN CHAMBER. view more
CREDIT: RICHARD G. ROBERTS
Denisova Cave is located in the Altai Mountains in southern Siberia and is famous for the discovery of Denisovans, an extinct form of archaic humans that is thought to have occupied large parts of central and eastern Asia. Neandertal remains have also been found at the site, as well as a bone from a child who had a Neandertal mother and Denisovan father, showing that both groups met in the region. However, only eight bone fragments and teeth of Neandertals and Denisovans have been recovered so far from the deposits in Denisova Cave, which cover a time span of over 300,000 years. These are too few fossils to reconstruct the occupational history of the site in detail, or to link the different types of stone tools and other artefacts found in Denisova Cave to specific hominin groups. For example, the discovery of jewelry and pendants typical of the so-called Initial Upper Palaeolithic culture in approximately 45,000-year-old layers has prompted debates as to whether Denisovans, Neandertals or modern humans were the creators of these artefacts.
Michael Shunkov of the Siberian Branch of the Russian Academy of Sciences, who leads the excavations at Denisova Cave, assembled an interdisciplinary team of archaeologists, geneticists, geochronologists and other scientists to study this unique site. The team has now performed the largest analysis ever of sediment DNA from a single excavation site. "The analysis of sediment DNA provides a wonderful opportunity to combine the dates that we previously determined for the deposits in Denisova Cave with molecular evidence for the presence of people and fauna", says Richard 'Bert' Roberts from the University of Wollongong in Australia. The team of geochronologists led by him and Zenobia Jacobs collected more than 700 sediment samples in a dense grid from the exposed sediment profiles in the cave. "Just collecting the samples from all three chambers in the cave, and documenting their precise locations, took us more than a week", Jacobs says.
When the samples arrived at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Elena Zavala, the lead author of the study, spent another two years in the lab to extract and sequence small traces of ancient hominin and animal mitochondrial DNA from this huge collection of samples. "These efforts paid off and we detected the DNA of Denisovans, Neandertals or ancient modern humans in 175 of the samples", Zavala says.
When matching the DNA profiles with the ages of the layers, the researchers found that the earliest hominin DNA belonged to Denisovans, indicating that they produced the oldest stone tools at the site between 250,000 and 170,000 years ago. The first Neandertals arrived towards the end of this time period, after which both Denisovans and Neandertals frequented the site - except between 130,000 and 100,000 years ago, when no Denisovan DNA was detected in the sediments. The Denisovans who came back after this time carried a different mitochondrial DNA, suggesting that a different population arrived in the region.
Modern human mitochondrial DNA first appears in the layers containing Initial Upper Palaeolithic tools and other objects, which are much more diverse than in the older layers. "This provides not only the first evidence of ancient modern humans at the site, but also suggests that they may have brought new technology into the region with them", says Zavala.
The scientists studied animal DNA and identified two time periods where changes occurred in both animal and hominin populations. The first, around 190,000 years ago, coincided with a shift from relatively warm (interglacial) conditions to a relatively cold (glacial) climate, when hyaena and bear populations changed and Neandertals first appeared in the cave. The second major change occurred between 130,000 and 100,000 years ago, along with a shift in climate from relatively cold to relatively warm conditions. During this period, Denisovans were absent and animal populations changed again.
"I believe that our Russian colleagues who excavate this amazing site have set the standards for many future archaeological excavations with their careful collection of many samples from each archaeological layer for DNA analysis", says Svante Pääbo who initiated the study with the Russian team. "Being able to generate such dense genetic data from an archaeological site is like a dream come true, and these are just the beginnings", says Matthias Meyer, the senior author on the study. "There is so much information hidden in sediments - it will keep us and many other geneticists busy for a lifetime."
IMAGE: THE FAMOUS ANGLO-SAXON SUTTON HOO HELMET FROM ABOUT 625 CE, PART OF THE BRITISH MUSEUM COLLECTION. PHOTO: ELISSA BLAKE/UNIVERSITY OF SYDNEY view more
CREDIT: PHOTO: ELISSA BLAKE/UNIVERSITY OF SYDNEY
A new study from archaeologists at University of Sydney and Simon Fraser University in Vancouver, has provided important new evidence to answer the question "Who exactly were the Anglo-Saxons?"
New findings based on studying skeletal remains clearly indicates the Anglo-Saxons were a melting pot of people from both migrant and local cultural groups and not one homogenous group from Western Europe.
Professor Keith Dobney at the University of Sydney said the team's results indicate that "the Anglo-Saxon kingdoms of early Medieval Britain were strikingly similar to contemporary Britain - full of people of different ancestries sharing a common language and culture".
The Anglo-Saxon (or early medieval) period in England runs from the 5th-11th centuries AD. Early Anglo-Saxon dates from around 410-660 AD - with migration occurring throughout all but the final 100 years (ie 410-560AD).
Studying ancient skulls
Published in PLOS ONE, the collaborative study by Professor Dobney at University of Sydney and Dr Kimberly Plomp and Professor Mark Collard at Simon Fraser University in Vancouver, looked at the three-dimensional shape of the base of the skull.
"Previous studies by palaeoanthropologists have shown that the base of the human skull holds a shape signature that can be used to track relationships among human populations in a similar way to ancient DNA," Dr Plomp said. "Based on this, we collected 3D data from suitably dated skeletal collections from Britain and Denmark, and then analysed the data to estimate the ancestry of the Anglo-Saxon individuals in the sample."
The researchers found that between two-thirds and three-quarters of early Anglo-Saxon individuals were of continental European ancestry, while between a quarter and one-third were of local ancestry.
When they looked at skeletons dated to the Middle Anglo-Saxon period (several hundred years after the original migrants arrived), they found that 50 to 70 percent of the individuals were of local ancestry, while 30 to 50 percent were of continental European ancestry, which probably indicates a change in the rate of migration and/or local adoption of culture over time.
"These findings tell us that being Anglo-Saxon was more likely a matter of language and culture, not genetics," Professor Collard said.
The debate about Anglo-Saxons
Although Anglo-Saxon origins can clearly be traced to a migration of Germanic-speaking people from mainland Europe between the 5th and 7th centuries AD, the number of individuals who settled in Britain is still contested, as is the nature of their relationship with the pre-existing inhabitants of the British Isles, most of whom were Romano-Celts.
The ongoing and unresolved argument is whether hordes of European invaders largely replaced the existing Romano-British inhabitants, or did smaller numbers of migrants settle and interact with the locals, who then rapidly adopted the new language and culture of the Anglo-Saxons?
"The reason for the ongoing confusion is the apparent contradiction between early historical texts (written sometime after the events that imply that the newcomers were both numerous and replaced the Romano-British population) and some recent biomolecular markers directly recovered from Anglo-Saxon skeletons that appears to suggest numbers of immigrants were few," said Professor Dobney.
"Our new data sits at the interface of this debate and implies that early Anglo-Saxon society was a mix of both newcomers and immigrants and, instead of wholesale population replacement, a process of acculturation resulted in Anglo-Saxon language and culture being adopted wholesale by the local population."
"It could be this new cultural package was attractive, filling a vacuum left at the end of the Roman occupation of Britain. Whatever the reason, it lit the fuse for the English nation we have today - still comprised of people of different origins who share the same language," Professor Dobney said.
