Clemens L Weiß Michael Dannemann Kay Prüfer Hernán A Burbano
Max Planck Institute for Developmental Biology, Germany; Max Planck Institute for Evolutionary Anthropology, Germany
DOI: http://dx.doi.org/10.7554/eLife.10005
Published November 3, 2015
Abstract
Contamination with exogenous DNA is a constant hazard to ancient DNA studies, since their validity greatly depend on the ancient origin of the retrieved sequences. Since contamination occurs sporadically, it is fundamental to show positive evidence for the authenticity of ancient DNA sequences even when preventive measures to avoid contamination are implemented. Recently the presence of wheat in the United Kingdom 8000 years before the present has been reported based on an analysis of sedimentary ancient DNA (Smith et al. 2015). Smith et al. did not present any positive evidence for the authenticity of their results due to the small number of sequencing reads that were confidently assigned to wheat. We developed a computational method that compares postmortem damage patterns of a test dataset with bona fide ancient and modern DNA. We applied this test to the putative wheat DNA and find that these reads are most likely not of ancient origin.
Wheat has been found in a settlement on England’s south coast dating back to 6000BC – 2000 years before farming reached Britain. This finding overturns many cherished archaeological beliefs – or myths – about the era. Though they were once patronised as simplistic hunter-gatherers, it turns out early Britons must have been active traders with the agricultural superpowers of their day in France and the Balkans. It’s time to reassess Mesolithic man.
The introduction of farming is usually regarded as a defining historic moment for human societies. Agriculture creates the conditions for permanent settlement, urbanisation and complex societies.
The positive impact and significance of farming, starting during the period known as the Neolithic, is often contrasted harshly with preceding hunter gatherer cultures. These societies, associated with a period entitled the Mesolithic in Britain (c. 10,000-4000 BC), were relatively mobile and the passage of time has been unforgiving in respect of the survival of their material culture.
This has meant a tendency to presume the peoples of pre-farming Britain were socially simple and geographically isolated. The recent TV show 10,000 BC, which approximates this period, perpetuates the view that life at this time was simply “nasty, brutish and short” with little for people to do other than eat hazelnuts as they waited patiently for wiser peoples from the East to arrive along with the lifestyle benefits of the new technology – farming.
Mesolithic northern Europe had lots of extra land (light green). Eleanor Ramsey, CC BY-NC-SA
Yet Mesolithic societies were as complex as any other. For instance, the earliest built ritual monuments in Britain, usually associated with farming societies, emerged as early as 9000BC near Stonehenge and one structure in Scotland may represent a calendrical device nearly 5000 years older than the first historical calendars. The first permanent homes and domestication of animals including the dog also occurred before the introduction of farming.
Yet, the use of grain and specifically wheat, remained essentially absent and a key indicator of farming in regions far from south west Asia, where grain was domesticated 12000 years ago. Consequently, a debate continues as to whether farming was introduced following colonisation by groups already practising agriculture or the new technology was adopted by indigenous hunter gatherer populations. Was farming a movement of people or ideas?
Farming is thought to have been introduced to Britain in around 4000BC, perhaps held back by the island’s new isolation following sea level rises at the end of the ice age. The same processes, however, also provide an opportunity to preserve evidence and Britain’s continental shelf has exceptional archaeological potential.
Under the sea
To investigate whether early traces of farming might be preserved in sediments on the sea bed, we gathered a team from the Universities of Birmingham, Bradford and Warwick, together with the Maritime Archaeology Trust.
Our results, just published in the journal Science, suggest that grain, rather than indicating the onset of farming, was actually present in Mesolithic settlements in Britain 2000 years before local agriculture.
We found evidence of grain after analysing DNA recovered from the uniquely preserved Bouldnor Cliff off the south coast of Britain. In the past ancient DNA has most commonly been obtained from anatomically intact material, such as hair, bones and teeth. It has only recently become clear that DNA can also be retrieved from other materials, including sediments, or SedaDNA – a discovery which has the potential to revolutionise the field.
The sedaDNA sequences at Bouldnor Cliff suggested a mixed habitat of oak forest and herbaceous plants, much as we would expect. We found traces of animals that could indicate human activity – lots of dogs, for instance, and aurochs (ancestors of the modern cow), as well as deer, grouse and rodents.
Garry Momber of Maritime Archaeology Trust with 8,000 year old Bouldnor Cliff flints. Author provided
However, in later sediments, dated to 6000 BC, the results revealed the presence of Einkorn wheat. This was 2000 years earlier than expected and at a time when the cutting edge of agriculture may have lain in the northern Balkans or possibly on the Mediterranean coast of France.
Mesolithic marketplace
What does this mean? In the absence of direct evidence for cultivation, it seems likely that wheat was imported rather than grown locally. If so the implications are considerable.
The presence of wheat suggests the existence of a web of social networks stretching between Mesolithic Britain and the advancing Neolithic front far to the south and east. Far from being simple or isolated, the Mesolithic peoples of southern Britain were probably engaged in trading or gifting exotic foodstuffs across much of continental Europe – it seems absolutely unreasonable to imply that hunter gatherer groups were passive recipients in such an exchange.
The results also indicate that key historical events, including the arrival of people in the Americas and agricultural development of Southeast Asia, may also be best explored through investigating the extensive land masses that were lost to the seas as a consequence of global warming. The results of the work at Bouldnor Cliff now suggests that that such landscapes also retain caches of genetic material that may not be preserved or even represented on land. If so the analysis of marine sediments may be an archaeological “game-changer”.
Contesting the presence of wheat in the British Isles 8,000 years ago by assessing ancient DNA authenticity from low-coverage data
Clemens L Weiß Michael Dannemann Kay Prüfer Hernán A Burbano
Max Planck Institute for Developmental Biology, Germany; Max Planck Institute for Evolutionary Anthropology, Germany
DOI: http://dx.doi.org/10.7554/eLife.10005
Published November 3, 2015
A recent discovery could radically change our views of one of the world’s most famous archaeological sites, Tutankhamun’s tomb. Scans of the complex in Egypt’s Valley of the Kings revealed it may still include undiscovered chambers – perhaps even the resting place of Queen Nefertiti – even though we have been studying the tomb for almost 100 years.
It’s common to get excited about high-profile archaeological discoveries, but it’s the slower, ongoing research that shows the real potential of new technology to change our understanding of history.
The latest findings touch on the mystery and conjecture around the tomb of the Egyptian queen consort Nefertiti, who died around 1330 BC. Some scholars believe that she was buried in a chamber in her stepson Tutankhamun’s tomb (known as KV62), although others have urged caution over this hypothesis.
Nefertiti is a pivotal figure in Egyptology. She and her husband Pharaoh Akhenaten helped bring about a religious revolution in ancient Egypt, and she may have even briefly ruled the country after his death. But we have little solid information about her life or death and her remains have never been found.
So the discovery of her tomb could be instrumental in revealing more about this critical period in history, and even change our views on how powerful and important she was. Nicholas Reeves, the director of the research, believes that the size and layout of KV62 means that it may have originally been designed for a queen. He has also used a ground-penetrating radar (GPR) survey to look for possible hidden antechambers that may contain Nefertiti’s remains after reassessment of the relationship between Nefertiti and Tutankhamun led to renewed interest in the tomb.
Ground penetrating radar. University of Southampton, Author provided
Underground archaeology
The geophysical survey techniques used to study the tomb have been applied in archaeology since the 1970s. GPR involves emitting electromagnetic radar waves through a structure and measuring how long it takes for them to be reflected by the different objects and elements that comprise it. Different materials reflect the radar waves at different velocity so it’s possible to use this information to build a 3D map of the structure. For KV62, the map suggests there are spaces beyond the standing walls of the tomb, which could be undiscovered antechambers.
The problem with such surveys is that the high hopes of the initial conclusions released to the public may not match the reality of later findings. The data can often be interpreted in different ways. For example, natural breaks and fissures in the rock may produce responses similar to undiscovered chambers. Scanning the relatively small area of the walls of an individual chamber can make it difficult to place the results in a broader context.
By gathering a wider range of data, we can slowly build up a clearer picture of the history of a site. While not as dramatic as uncovering a forgotten tomb, the process of using technology to gradually study a site can, directly and indirectly, significantly change our view of it or the people associated with it.
Other geophysical techniques tend to be used to study more open sites or landscapes. Magnetometry measures the variations in the Earth’s magnetic field that are caused by many forms of buried archaeological material, from fired material such as kilns to building material and filled ditches. Earth resistance measures how easily electrical current passes through the ground. Features such as walls, paving and rubble have a high resistance to current, while filled ditches and pits tend to have a low resistance.
Putting such techniques to use at Stonehenge, for example, has completely transformed the way we think about how the landscape was used, and the forms of worship used by Neolithic society. Prior to the survey only a handful of ritual monuments were known around the impressive remains of Stonehenge, meaning that archaeologists could not easily evaluate the way in which the landscape was used.
The geophysical survey revealed hundreds of archaeological features, including 17 major ritual monuments. For the first time archaeologists were able to map every single possible buried monument in the landscape, including henges, pits, barrows and ditches. This means we can start to fully appreciate the way in which the ritual landscape was organised. For example, the new monuments reveal astronomical alignments that were previously unknown or only partly recognised.
Similar geophysical survey work at Ostia Antica in Italy has completely altered our theories about the layout of the city and its harbour. A magnetometer survey conducted across the area between Portus and Ostia between 2008 and 2011, discovered the presence of buried warehouses and associated structures. These were enclosed by the line of a defensive wall, showing that the extent of the ancient city included both banks of the river Tiber. This crucial fact changes the potential size of the city and alters our plan of its harbour area. This suggests much more of the city was used for storage, perhaps making it even more important as a port for nearby Rome than previously thought.
Sarum revealed. University of Southampton, Author provided
An ongoing survey at Old Sarum in Wiltshire in the UK has been studying the area surrounding the remains of the Iron-age hillfort and medieval town. Using GPR, magnetometry and earth resistance together has uncovered an unprecedented number of Roman and medieval structures, courtyards and other remains. This indicates that there was a much more substantial and complex settlement at Old Sarum much earlier than previously thought. Further work in 2016 may even prove claims of a late Saxon settlement and mint at the site.
These kinds of discoveries show that geophysical technology has a huge role to play in archaeology, both through investigation of sites and landscapes, and also of smaller monuments such as buildings and tombs. But we need to look beyond the more sensational aspects of such research and understand the role it plays in the bigger picture of uncovering the past.
The recent discoveries at Stonehenge, including ritual monuments, burial mounds and a long barrow, are wonderful examples of how archaeological geophysics can be used in areas where excavation is hard to justify.
Some dismiss the use of these techniques in archaeology, arguing the methods are old and demonstrate only evolutionary, rather than revolutionary, improvement. But Stonehenge is a World Heritage Site spread over a large area and while it has been intensively studied for decades, physical digs are now extremely restricted.
Instead, over the past four years, the Stonehenge Hidden Landscape Project (SHLP) – a collaboration between the universities of Birmingham, Vienna, Bradford, St Andrews, Nottingham and Ghent with the National Trust and English Heritage – used geophysical survey techniques such as earth resistance, magnetometry, ground-penetrating radar and electromagnetic induction.
It’s true that these have been standard issue in the geophysicist’s armoury for some time, so the sceptical observer may feel justified. But what is not apparent is the scale of the survey and the quantity and quality of data unearthed.
The new discoveries at Stonehenge and revealed in the survey data generated by geophysical technology. Stonehenge Hidden Landscape Project LBIArchPRO, Author provided
Digging up new data
The main technique used by the project was magnetometry. This reveals patterns by recording the magnetic properties of ferrous elements in soil or as left behind by human activity such as burning. More than 12km2 around Stonehenge was surveyed using magnetometry, accomplished by using arrays of up to 10 fluxgate sensors to detect the magnetic fields, mounted on a customised non-magnetic cart pulled by quad bikes fitted with navigation aids. Sampling information at a resolution of 10cm x 25cm, this process generated a lot of data.
By way of comparison, using ground-penetrating radar – which beams radio waves into the earth and records their reflections bouncing back from solid objects underground – the team covered a smaller area at much higher resolution, using a system of 16 sensors at a resolution of 8cm x 8cm. The key to the success of both techniques is the ability to accurately pinpoint and record the location of each of the millions of measurements. The use of real time GPS and robotic guidance has shown that computerised, software-controlled techniques like these can provide huge amounts of accurate data and reveal buried features.
Archaeology by quad bike (sheep not included). Stonehenge Hidden Landscape Project LBIArchPRO, Author provided
The data from the magnetometers is gathered as the sensor array is pulled at 20mph or more, while the ground radar sensors move at a fast walking pace. The difference in speed is due to the nature of the properties being measured. The first is a passive sensor which records the earth’s ambient magnetic field, while the second is an active system where radio energy is transmitted into the ground and a receiver waits to collect the energy reflected, which by necessity takes longer.
As a result magnetometer surveys will always be cheaper to conduct and this explains in part why they’re highly favoured by commercial surveyors. But for successful use of magnetometry there must be a measurable contrast in magnetic properties of the archaeological features being searched for, for example the backfill in pits or ditches, and the surrounding soil. Fortunately the chalk landscape at Stonehenge is blessed with a low magnetic background which provides the high contrast needed.
New discoveries, new context
The results of the magnetic survey are a great starting point to consider how technological changes have altered our perspective of Stonehenge. Within the magnetic map we can see debris from the modern free festival in the 1970s-80s, trenches dug for troop practice during World War I a century ago, and evidence left from the earliest uses of the landscape.
Images of the new monuments found at Stonehenge using geophysical techniques. Stonehenge Hidden Landscape Project LBIArchPRO, Author provided
These images show the variation in magnetic field. The mid range is based around zero, with black, positive values tending to show accumulations of magnetic soil. In these images we can see soil-filled ditches and pits, and the location of former timber posts that once made up henges or supports for barrows or buildings.
The surveying has revealed 17 entirely undiscovered monuments as well as radical new information about existing sites. The impression is that far from standing in splendid isolation, Stonehenge was really part of an complex, ordered, ritual landscape. It’s likely to have been peppered by small shrines that were part of the Stonehenge experience for the Neolithic Britons of the time.
Even if you were allowed to excavate freely at Stonehenge today it would be impossible to understand the site in its landscape context without the technology employed during the project. While the cynical observer may think that the geophysical techniques have only marginally improved with age, this underestimates the technological advances in how they are practically used, and the effect this has on the quality of data they can generate.
Stonehenge in the first archaeological aerial photo, taken by Lt Philip Sharpe of the Royal Engineers Balloon Section. Royal Society of Antiquaries
The classical historian Mary Beard recently suggested that archaeological discoveries are now more likely to be found by modern technology than by traditional excavation. Aerial photography was the first such technology, and in fact the first archaeological aerial picture, taken in 1906, was of Stonehenge, so perhaps it’s fitting that modern techniques continue to turn up discoveries at the same site. After all, why spend time (and money) digging down for the past when you make images of it from the surface?
I led the team of researchers that discovered that Stonehenge was most likely to have been originally built in Pembrokeshire, Wales, before it was taken apart and transported some 180 miles to Wiltshire, England. It may sound like an impossible task without modern technology, but it wouldn’t have been the first time prehistoric Europeans managed to move a monument.
Archaeologists are increasingly discovering megaliths across the continent – albeit a small number so far – that were previously put up in earlier monuments.
Other ‘second-hand’ monuments
The best example of such a structure outside the UK is La Table des Marchand, a Neolithic tomb in Brittany, France, built around 4000BC. The enormous, 65-ton capstone on top of its chamber is a broken fragment of a menhir, a standing stone, brought from 10km away. The original menhir may be 300 years (or more) older than the tomb. Another fragment of this same menhir was incorporated into a tomb at Gavrinis, 5km away. This menhir, originally weighing over 100 tons, is actually one of the largest blocks of stone that we know of to have been moved and set up by Neolithic people.
Another example of a standing stone reused in a megalithic monument is an anthropomorphic menhir – a standing stone carved in the form of a human figure - incorporated as the capstone of another tomb at Déhus on Guernsey. Another megalithic tomb, La Motte de la Jacquille in western France, is built of dressed stones that have been rearranged into a new tomb but it is not known if they came from a different location or were an earlier version of the tomb rebuilt on the same spot.
Archaeologists have known for many years that some of Stonehenge’s bluestones (the shorter stones in the monument) were reused. Two are lintels reused as standing stones, and two others have vertical grooves that show they were part of a wall of interlocking standing stones. Until now it was thought that these were evidence of reuse just within Stonehenge which was first built around 2900BC and rebuilt circa 2500BC (at this point, large local sandstones known as “sarsen” were erected). It was then rebuilt again in around 2400BC and 2200BC.
However, we identified the actual quarries in Pembrokeshire, Wales (around 3400BC and 3200BC) that the bluestones came from. This is a period before prehistoric people were building stone circles (normally dating from 3000BC onwards) so we also think it is very likely that the bluestones originally formed a rather different type of monument from a stone circle.
People in western Britain and Ireland at this time were building Neolithic stone tombs known as passage tombs – Newgrange in Ireland is the best known example. So it is just possible that there is a dismantled passage tomb somewhere near the bluestone quarries. That’s what we will be looking for in 2016.
Stonehenge – an unusual distance
An interesting outcome from a recent conference in Redondo, Portugal, on prehistoric megaliths and “second-hand monuments” is that – while some megalithic stones for monuments in Portugal and elsewhere were brought as far as 8km from their sources – the vast majority of Neolithic stone monuments throughout Western Europe were built less than 2km to 3km away from their stone quarries. So Stonehenge is a major exception to this rule, as its bluestones were dragged around 290km. This makes it unique for prehistoric Europe.
How the stones were moved from Wales to Stonehenge is something of a mystery but our excavations at one of the Welsh quarries reveals that the trackway leading from the outcrop was too narrow for rollers to have been used. Instead, we think that monoliths were loaded onto wooden sledges and dragged over logs and branches laid rail-like in front of the sledge.
Some archaeologists have speculated that Stonehenge’s bluestones must have been thought to have had special properties – as musical “gongs” or healing stones – for them to have been sought out from so far away.
But we think it is far more likely that the bluestones were derived from quarries in close proximity to each other – within 2km to 3km – and brought together to build a local monument in Pembrokeshire. Scientific analysis of strontium isotopes in the teeth of people buried in the Stonehenge area reveals that many of them have values consistent with growing up in western Britain. So the stones may have been brought by people migrating from Wales, bringing their ancestral monument as a symbol of their history and identity. Strontium isotope analysis is currently being carried out on the people actually buried at Stonehenge when the bluestones were erected, and we await the results to see if they show a similar picture.
It’s also possible that the bluestones were put up somewhere on Salisbury Plain before they arrived at Stonehenge. For example, one of the bluestones never quite made it to Stonehenge and was dug out in 1801 from the top layer of a Neolithic burial mound called Boles Barrow, near Warminster, also in Wiltshire.
Although this tomb was first built around 3700BC, it seems to have gone through modifications, of which adding a layer of large stones (mostly local sarsen stones and this one bluestone) happened at the end of its use. So we don’t know precisely when it got there but it may have been set up as a burial marker before the rest of the bluestones were erected at Stonehenge.
Rebuilding tombs and other megalithic structures as second-hand monuments is only now turning out to be recognised in various parts of western Europe as archaeologists start to look more closely at the detailed aspects of construction. Simple expediency of finding suitable stone does not explain sites such as Stonehenge and the Table des Marchand – they were most likely incorporating aspects of the past which had rich historical resonance for them.
I have a copy of the 106 and Highways Agreement between Wiltshire Council and HBMCE (English Heritage) and others for the planning permission for the New Visitor Centre near Stonehenge.
I reproduce Paragraph 9 of Schedule 3 of Part 2 as it relates to the ongoing failure by English Heritage to provide a permissive path on the route of the old A344
Dated 23 JUNE 2010
WILTSHIRE COUNCIL (1 )
and
HISTORIC BUILDINGS AND MONUMENTS COMMISSION FOR ENGLAND (2)
and
SECRETARY OF STATE FOR CULTURE MEDIA AND SPORT (3)
and
ROBERT LIONEL TURNER (4)
and
THE HONOURABLE FINN BENJAMIN GUINNESS
THE HONOURABLE ERSKINE STUART RICHARD GUINNESS
THE HONOURABLE CATRIONA ROSE GUINNESS (5)
and
THE NATIONAL TRUST FOR PLACES OF HISTORIC INTEREST OR
NATURAL BEAUTY (6)
and
NATIONAL WESTMINSTER BANK PLC (7)
Agreement under Section 106 Town and Country Planning Act 1990
and
Section 278 of the Highways Act 1980
relating to-
THE STONEHENGE ENVIRONMENTAL IMPROVEMENTS PROJECT
STONEHENGE WORLD HERITAGE SITE, WILTSHIRE
PART 2 HIGHWAYS OBLIGATIONS AND ROAD TRAFFIC REGULATION AND HIGHWAYS ORDERS
SCHEDULE 3
Other Obligations
9 The National Trust and the Secretary of State as owners of the land
fronting that part of the A344 between its junction with Byway 12 and
the A303 to be stopped up and English Heritage covenant that as
from the date of such stopping up that part of the A344 may be used
at all times by cyclists and pedestrians until such time as an
alternative cycle route is available and has been provided in
accordance with a scheme which shall first have been approved by
the local planning authority in consultation with the local highway
authority and the Highways Agency
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In this new video researcher Tim Daw gets interviewed by the BBC and talks to Hugh Newman at Stonehenge about the Winter Solstice Sunrise and Sunset alignments, that are often overlooked due to the popularity of the Summer Solstice. He explains the significance and archaeological evidence for these astronomical achievements and how the ancients encoded it in to the monument, as well as giving an insight as to the use of the Bush Barrow Lozenge discovered nearby. Tim's websites: http://www.sarsen.org/ and http://thelongbarrow.com/
