Research raises doubts about whether modern humans and Neanderthals interbred
Findings point to common ancestry to explain genetic similarities
Public release date: 13-Aug-2012
Contact: Genevieve Maul
University of Cambridge
New research raises questions about the theory that modern humans and Neanderthals at some point interbred, known as hybridisation. The findings of a study by researchers at the University of Cambridge suggests that common ancestry, not hybridisation, better explains the average 1-4 per cent DNA that those of European and Asian descent (Eurasians) share with Neanderthals. It was published today, 13 August, in the journal PNAS.
In the last two years, a number of studies have suggested that modern humans and Neanderthals had at some point interbred. Genetic evidence shows that on average Eurasians and Neanderthals share between 1-4 per cent of their DNA. In contrast, Africans have almost none of the Neanderthal genome. The previous studies concluded that these differences could be explained by hybridisation which occurred as modern humans exited Africa and bred with the Neanderthals who already inhabited Europe.
However, a new study funded by the BBSRC and the Leverhulme Trust has provided an alternative explanation for the genetic similarities. The scientists found that common ancestry, without any hybridisation, explains the genetic similarities between Neanderthals and modern humans. In other words, the DNA that Neanderthal and modern humans share can all be attributed to their common origin, without any recent influx of Neanderthal DNA into modern humans.
Dr Andrea Manica, from the University of Cambridge, who led the study said: "Our work shows clearly that the patterns currently seen in the Neanderthal genome are not exceptional, and are in line with our expectations of what we would see without hybridisation. So, if any hybridisation happened - it's difficult to conclusively prove it never happened - then it would have been minimal and much less than what people are claiming now."
Neanderthals and modern humans once shared a common ancestor who is thought to have spanned Africa and Europe about half a million years ago. Just as there are very different populations across Europe today, populations of that common ancestor would not have been completely mixed across continents, but rather closer populations would have been more genetically similar to each other than populations further apart. (There is extensive genetic and archaeological evidence that population in Africa were 'structured'; in other words, different populations in Africa only had limited exchange through migration, allowing them to remain distinct from each other both in terms of genetics and morphology.)
Then, about 350-300 thousand years ago, the European range and the African range became separated. The European range evolved into Neanderthal, the African range eventually turned into modern humans. However, because the populations within each continent were not freely mixing, the DNA of the modern human population in Africa that were ancestrally closer to Europe would have retained more of the ancestral DNA (specifically, genetic variants) that is also shared with Neanderthals.
On this basis, the scientists created a model to determine whether the differences in genetic similarities with Neanderthal among modern human populations, which had been attributed to hybridisation, could be down to the proximity of modern humans in northern Africa (who would have later gone on to populate Europe) to Neanderthals.
By examining the different genetic makeup among modern human populations, the scientists' model was able to infer how much genetic similarity there would have been between distinct populations within a continent. The researchers then simulated a large number of populations representing Africa and Eurasia over the last half a million years, and estimated how much similarity would be expected between a random Neanderthal individual and modern humans in Africa and Eurasia.
The scientists concluded that when modern humans expanded out of Africa 60-70K years ago, they would have brought out that additional genetic similarity with them, making Europeans and Asians more similar to Neanderthals than Africans are on average – undermining the theory that hybridization, and not common ancestry, explained these differences.
Dr Manica added: "Thus, based on common ancestry and geographic differences among populations within each continent, we would predict out of Africa populations to be more similar to Neanderthals than their African counterparts - exactly the patterns that were observed when the Neanderthal genome was sequenced; but this pattern was attributed to hybridisation. Hopefully, everyone will become more cautious before invoking hybridisation, and start taking into account that ancient populations differed from each other probably as much as modern populations do."
For additional information please contact:
Genevieve Maul, Office of Communications, University of Cambridge
Tel: direct, +44 (0) 1223 765542, +44 (0) 1223 332300
Mob: +44 (0) 7774 017464
Notes to editors:
1. The paper 'Effect of ancient population structure on the degree of polymorphism shared between modern human populations and ancient hominins' will be published in the 13 August 2012 edition of PNAS.
2. The Leverhulme Trust was established in 1925 under the Will of the first Viscount Leverhulme. It is one of the largest all-subject providers of research funding in the UK, distributing funds of some £60 million every year. For further information about the schemes that the Leverhulme Trust fund visit their website at www.leverhulme.ac.uk / www.twitter.com/LeverhulmeTrust
3. About BBSRC - BBSRC is the UK funding agency for research in the life sciences and the largest single public funder of agriculture and food-related research. Sponsored by Government, in 2010/11 BBSRC is investing around £470 million in a wide range of research that makes a significant contribution to the quality of life in the UK and beyond and supports a number of important industrial stakeholders, including the agriculture, food, chemical, healthcare and pharmaceutical sectors.
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Study casts doubt on human-Neanderthal interbreeding theory
Cambridge scientists claim DNA overlap between Neanderthals and modern humans is a remnant of a common ancestor
Alok Jha, science correspondent
The Guardian, Tuesday 14 August 2012
When scientists discovered a few years ago that modern humans shared swaths of DNA with long-extinct Neanderthals, their best explanation was that at some point the two species must have interbred.
Now a study by scientists at the University of Cambridge has questioned this conclusion, hypothesising instead that the DNA overlap is a remnant of a common ancestor of both Neanderthals and modern humans.
When the genetic sequence of Homo neanderthalensis was published in 2010, one of the headline findings was that most people outside Africa could trace up to 4% of their DNA to Neanderthals. This was widely interpreted as an indication of interbreeding between Neanderthals and early Homo sapiens just as the latter were leaving Africa. The two species would have lived in the same regions around modern-day Europe, until Neanderthals died out about 30,000 years ago.
But Andrea Manica said the analysis had over-estimated the amount of shared DNA between Neanderthals and humans that could be explained by interbreeding. The analysis had not taken into account the genetic variation already present between different populations of the ancestors of modern humans in Africa.
"The idea is that our African ancestors would not have been a homogeneous, well-mixed population but made of several populations in Africa with some level of differentiation, in the way right now you can tell a northern and southern European from their looks. The mixing is not complete within continents."
Taking these population differences, known as "substructuring", into account for early humans living in Africa, Manica and his colleague Anders Eriksson worked out that modern humans and Neanderthals must have shared a common ancestor some 500,000 years ago and that the subsequent evolution of this species was enough to account for the DNA crossover.
"There was an ancestor of both Neanderthal and modern humans – some archaeologists would call that Homo heidelbergensis – that would have covered Africa and Europe about half a million years ago," he said. "It wouldn't have been a single well-mixed population, it would have been like modern humans – populations that are closer to each other are more similar."
The results are published in the Proceedings of the National Academy of Sciences.
About 350,000 years ago, the European and African ranges of this last common ancestor became separate: the European range would later evolve into Neanderthals and the African range into anatomically modern humans, who left the continent 70,000 years ago to cover the world.
Prof Svante Pääbo, at the Max Planck Institute for Evolutionary Anthropology in Leipzig, who led the sequencing of the Neanderthal genome in 2010 and has championed the idea that modern humans interbred with Neanderthals, said he was surprised that Manica's work had been published, since his original paper had admitted a role for substructuring in Africa in the sharing of DNA between humans and Neanderthals. "But we regard this as a less parsimonious explanation," he said.
Pääbo has co-authored a paper, which is yet to undergo peer-review, to further support his thesis that humans and Neanderthals did in fact interbreed. "We find that the last gene flow from Neanderthals (or their relatives) into Europeans likely occurred 37,000-86,000 years before the present, and most likely 47,000-65,000 years ago," he writes. "This supports the recent interbreeding hypothesis, and suggests that interbreeding may have occurred when modern humans carrying Upper Paleolithic technologies encountered Neanderthals as they expanded out of Africa."
MACABRE FINDS IN THE BOG AT ALKEN ENGE
August 14, 2012 by HeritageDaily in Archaeology News, Europe
A FRACTURED SKULL AND A THIGH BONE HACKED IN HALF — FINDS OF DAMAGED HUMAN BONES ALONG WITH AXES, SPEARS, CLUBS AND SHIELDS CONFIRM THAT THE BOG AT ALKEN ENGE WAS THE SITE OF VIOLENT CONFLICT.
‘It’s clear that this must have been a quite far-reaching and dramatic event that must have had profound effect on the society of the time,’ explains Project Manager Mads Kähler Holst, professor of archaeology at Aarhus University.
For almost two months now, Dr Holst and a team of fifteen archaeologists and geologists have been working to excavate the remains of a large army that was sacrificed at the site around the time of the birth of Christ. The skeletal remains of hundreds of warriors lie buried in the Alken Enge wetlands near Lake Mossø in East Jutland, Denmark.
The remains will be exhumed from the excavation site over the coming days. Then an international team of researchers will attempt to discover who these warriors were and where they came from by performing detailed analyses of the remains.
‘The dig has produced a large quantity of skeletal remains, and we believe that they will give us the answers to some of our questions about what kind of events led up to the army ending up here,’ explains Dr Holst.
FORTY HECTARES OF REMAINS
The archaeological investigation of the site is nearing its conclusion for this year. But there are many indications that the find is much larger than the area archaeologists have excavated thus far.
‘We’ve done small test digs at different places in the 40 hectare Alken Enge wetlands area, and new finds keep emerging,’ says Field Director Ejvind Hertz of Scanderborg Museum, who is directing the dig.
In fact, the find is so massive that researchers aren’t counting on being able to excavate all of it. Instead, they will focus on recreating the general outlines of the events that took place at the site by performing smaller digs at different spots across the bog and reconstructing what the landscape might have looked like at the time of the birth of Christ.
NEW GEOLOGICAL INSIGHTS
At the same time as the archaeological dig, geologists from the Department of Geoscience at AU have been investigating the development of the bog.
‘The geological survey indicates that the archaeological finds were deposited in a lake at a point in time when there was a a smaller basin at the east end of Lake Mossø created by a tongue of land jutting into the lake,’ explains Professor Bent Vad Odgaard, Aarhus University.
This smaller basin became the Alken Enge bog of today. The geologists’ analyses also indicate that the water level in the area has changed several times. Mapping these periods of high and low water levels chronologically using geological techniques will tell researchers what the precise conditions were on the site at the time of the mass sacrifice.
The archaeological excavation at the Alken Enge site will continue until 23 August. There are guided tours for the general public on Thursdays at 13.00 and 17.00.
The excavation is a cooperation between Skanderborg Museum, Moesgård Museum and Aarhus University.
The project ‘The army and post-war rituals in the Iron Age: warriors sacrificed in the bog in the Alken meadows in the Illerup river valley’ is supported by a DKK 1.5m grant from the Carlsberg Foundation.
Roman 'curse tablet' found in Kent
15 August 2012 Last updated at 16:13
If you were called Sacratus, Constitutus or Memorianus, and had some bad luck in Roman Kent, archaeologists may have discovered why.
A "curse tablet" made of lead and buried in a Roman farmstead has been unearthed in East Farleigh.
Inscribed in capital letters are the names of 14 people, which experts believe were intended to have bad spells cast upon them.
The tablet is being examined by a specialist from Oxford University.
It was discovered by the Maidstone Area Archaeological Group during a dig and has undergone a detailed series of tests.
Measuring 6cm (2.3in) by 10cm (3.9in) and 1mm thick, the tablet is extremely fragile.
Experts believe it would have been used by Romans to cast spells on people accused of theft and other misdeeds.
The tablets, which have been found throughout Europe, were rolled up to conceal their inscriptions, then hidden in places considered to be close to the underworld, such as graves, springs or wells.
'Suspected of theft'
Dr Roger Tomlin, lecturer in late Roman history at Wolfson College, Oxford, and an authority on Roman inscriptions, spent four days examining the scroll.
He said it is difficult to date the tablet but believes it was made in the third century AD.
Dr Roger Tomlin said the tablet is likely to date from the third century AD
"Lists of names are quite often found on lead tablets," he said. "Sometimes they accompany a complaint of theft addressed to a god, and name persons suspected of the theft.
"In one case, a tablet found in Germany, the names were explicitly those of enemies."
The tablet's significance also lies in the fact that Romans were the first inhabitants of Britain who could read or write.
This means the tablet, along with other similar items, are among the earliest written records of British life.
Only six of the 14 names are legible. The Roman names of Sacratus, Constitutus, Constan and Memorianus can be seen.
There are also two Celtic names - Atrectus and Atidenus - written on the tablet.
Dr Tomlin said the eight other names are incomplete, but further cleaning and testing could lead to them being transcribed.
He added: "If this is a curse tablet, which it seems to be, it is presumably a product of its local community - so it is a reasonable guess that the persons named on it lived there."
The Sittingbourne-based Conservation Science Investigations (CSI) is being funded by the Kent Archaeological Society to conserve the tablet.
It is hoped that visitors to its offices will be able to watch some of the work take place.
Since 2005, the site has been slowly excavated with finds such as painted wall plaster and an underfloor heating system being discovered.
Other notable artefacts have included broken copper bracelets found scattered on the kitchen floor and a ring, decorated with snakes.
Bornais finds shed light on Iron Age and Viking life
19 August 2012 Last updated at 09:20
By Steven McKenzie
BBC Scotland Highlands and Islands reporter
Powerful figures from the late Iron Age through to the end of the Vikings were drawn to a sandy plain on South Uist, according to archaeologists.
Bornais, on the west side of the island, has the remains of a large farmstead and a major Norse settlement.
The area has produced large numbers of finds, including what have been described as exotic items from abroad.
Green marble from Greece, ivory from Greenland and bronze pins from Ireland have been among the finds.
A piece of bone marked with an ogham inscription, an ancient text that arrived in Scotland from Ireland, was also found.
Archaeologists said the items provided a detailed picture of life in the first millennium AD.
The universities of Cardiff and Sheffield have been involved in a long-term project to record South Uist's history, from the initial prehistoric colonisation through to the Clearances of the 17th and 18th centuries.
A complex of mounds on the wide sweep of machair at Bornais was excavated between 1994 and 2004.
What was uncovered is now being explained in a series of books.
The latest published by Oxbow Books for Cardiff University details the late Iron Age history of Bornais. A later volume will explore the area's Viking past.
“Bornais is the largest Viking settlement known in Scotland, certainly outside of the towns”
Prof Niall Sharples, head of archaeology and conservation at Cardiff, said Bornais had provided the island's best record of settlement activity from the 5th and 6th centuries to the 13th and 14th centuries.
He edited the new book, A Late Iron Age farmstead in the Outer Hebrides: Excavations at Mound 1, Bornais, South Uist.
Prof Sharples said the large sizes of the area's settlements, and the quality of the finds recovered, suggested that people of significance had lived there.
He said: "From the late Iron Age there are the remains of what is called a wheelhouse.
"This is not uncommon, but what is interesting is the house burned down and a new home was built over the top of the collapsed roof, preserving the carbonised roof timbers and items on the floor beneath it."
The relics from this house included a decorated animal bone called an astragalus and a bone dice which had been pushed into the floor of the rebuilt house.
Prof Sharples said: "These bones are thought to have been used in gaming and the dice is marked with numbers one, four, six and three.
"But they may also have been used in trying to predict the future.
"After the fire, they may have been used to help the occupiers to decide whether the fire was a bad omen, or if the house's future was safe."
Cattle bones found decorating the hearth in the rebuilt house may suggest the residents later went on to host a large feast to celebrate the rebuilding.
Prof Sharples said: "Between seven and 12 cattle would have been needed to provide the foot bones used, suggesting whoever occupied the house could afford to lose that number of livestock."
The Vikings later occupied Bornais, on a site a little distance away from where the Iron Age dwellers had lived in the 5th and 6th centuries.
Clues that a Norse of high status lived in the later settlement include a piece of green marble thought to have been quarried on a Greek island.
The same marble was used as building stone in Rome.
Prof Sharples said the fragment from Bornais was shaped as a slab and possibly brought as a Christian relic from Rome.
He added: "Bornais is the largest Viking settlement known in Scotland, certainly outside of the towns, and someone very important in the hierarchy of the Kingdom of Man and Isles is likely to have lived here."
17th century shipwreck to be freeze-dried, rebuilt
By By MICHAEL GRACZYK | Associated Press – Wed, Aug 15, 2012
BRYAN, Texas (AP)
More than three centuries ago, a French explorer's ship sank in the Gulf of Mexico, taking with it France's hopes of colonizing a vast piece of the New World — modern-day Texas.
Like La Salle in 1685, researchers at Texas A&M University are in uncharted waters as they try to reconstruct his vessel with a gigantic freeze-dryer, the first undertaking of its size.
By placing the ship — La Belle — in a constant environment of up to 60 degrees below zero, more than 300 years of moisture will be safely removed from hundreds of European oak and pine timbers and planks. The freeze-dryer, located at the old Bryan Air Force base several miles northwest of College Station, is 40 feet long and 8 feet wide — the biggest such machine on the continent devoted to archaeology.
Researchers will then rebuild the 54 ½-foot vessel, which will become the centerpiece of the Bob Bullock Texas State History Museum in Austin.
From a historical perspective, it's "an icon of a small event that dramatically changed the course of Texas history," said Jim Bruseth, who led the Texas Historical Commission effort to recover the remains.
The supply ship was built in 1684 and sank two years later in a storm on Matagorda Bay, about midway between Galveston and Corpus Christi.
"When La Belle sank, that doomed La Salle's colony and opened up the door for Spain to come in and occupy Texas," Bruseth said. "People can see firsthand how history can turn on a dime."
"It's an important piece in ship architecture," said Peter Fix, conservator at the school's Center for Maritime Archaeology and Conservation. Researchers have determined that unlike earlier vessels, the frames on La Belle were marked specifically by the French craftsmen so the wood comprising the hull could follow the complex curve of the ship.
"This was the age of Enlightenment when math was coming into more play," Fix said.
After a more than decade-long hunt, Texas Historical Commission archaeologists found it in 1995 in 12 feet of murky water. Then began the tedious recovery that involved constructing a dam around the site.
After the water was pumped out, teams dug through up to 6 feet of mud in the Gulf of Mexico seabed to retrieve the nearly intact ship and some 700,000 items, from swords, cannons and ammunition to beads and mirrors intended for trade. Archaeologists also found one skeleton, believed to be a crew member or settler among the some 40 people aboard.
The ship was then transferred to the Texas A&M lab, where the water-logged wood has been immersed in a chemical solution to keep it solid.
Initially, the ship was being reassembled in a two-stage chemical process, but as oil prices rose, so did the cost of the key chemical, polyethylene glycol. They decided the freeze-dry process was more economical and would shorten the preservation timeframe. So, the hull was disassembled and the wood was categorized and digitally scanned so that they could make molds of its original shape.
A New York-based firm that specializes in scientific equipment built the submarine-like freeze dryer.
"If we were to take any piece of wood, say it's been in the water for 300 years, and pull it out, it would shrink, crack, warp within a couple of days," Fix said. "The physical stress on wood would essentially cause it to fall apart and crumble and powder into pieces."
But scientists know that at the right temperature and pressure, water can go from being solid to gas and skip the liquid phase.
"It's a slow, controlled process and depending on the thickness of material, over four to six or seven months, we know that timber has lost most of its bound water and it's safe to bring out," Fix said, noting that they're experimenting with smaller pieces to "make sure nothing goes wrong."
A similar preservation using freeze-dryer technology is planned for a medieval ship discovered in 2002 in Newport, South Wales. That vessel is about twice the length of La Belle.
The La Belle rebuilding will start late next year at the Bullock Museum.
"I can't wait," said Bruseth, who is serving as guest curator for the exhibit. "It's just fantastic to see this project reach the point where we'll actually be reassembling the ship as a permanent installation."
Rene-Robert Cavelier Sieur de La Salle was the first European to travel the Mississippi River south to the Gulf, claiming all the land along the Mississippi and its tributaries for France in 1682. In 1685, he sailed from France with more than 300 colonists aboard four ships, La Belle among them, to establish a settlement at the mouth of the Mississippi.
Maps of the time show he believed the river was closer to Mexico, and his expedition missed the Mississippi by hundreds of miles.
"They were guessing," Bruseth said.
His team established a colony near Matagorda Bay, but it was ravaged by disease, rattlesnakes and Indians. Three years later, La Salle led a handful of survivors inland in search of the Mississippi. The explorer didn't make it out of Texas; he was murdered by his own men.
Solved: the 17 year mystery of the ship under the floorboards
August 17, 2012 By Carly Hilts Filed Under: News
In 1995 archaeologists made a surprising discovery beneath the floorboards of the Georgian wheelwright’s workshop at Chatham Historic Dockyard – the remains of an 18th-century flagship.
Now after almost two decades of research, the mystery vessel has been named as the Namur, a second-rate ship of the line that played a key role in the battle that eliminated the threat of French invasion and left Britain ruling the waves.
Described as ‘the single most important warship discovery in Northern Europe since the Mary Rose’, the Namur was launched at the Kent dockyard in 1756, and served with the Royal Navy for 47 years, taking part in nine fleet actions, including three major worldwide conflicts.
The Namur was identified after archaeological detective work focussing on her structure and fittings.
Archaeologists knew she had to be have been a second or third-rate ship of the line, built at Chatham between 1750-1775, and broken up at the same dockyard after 1786 – but the crucial clue was in her innovative ’round bow’, a new design adapted when shipwrights were piloting the use of iron in ships, which showed that she was still in use after 1803.
Her identity was announced today (17 August) on the eve of the 253rd anniversary of one of her most important engagements, the Battle of Lagos.
In 1759 Britain was in the middle of the Seven Years’ War and success at sea was a distant dream. A series of disastrous defeats had left the Royal Navy in a desperate state, and worse, the French were amassing troops in the mouth of the Loire for a planned invasion.
But the Battle of Lagos, which took place over 18-19 August off the coast of Portugal, saw the destruction of the French Mediterranean fleet, leaving invasion plans in tatters. At the head of the British forces was Admiral Edward Boscawen, and his flagship, the Namur.
With the destruction of the French Atlantic fleet at the battle of Quiberon Bay that November, the Royal Navy gained almost total supremacy of the seas, which it would retain for more than a century and a half – and 1759 became known in Britain as the Annus Mirabilis, the ‘Year of Miracles’.
Scott's wrecked ship Terra Nova found off Greenland
16 August 2012 Last updated at 15:52
By Paul Rincon
Science editor, BBC News website
The wreck of the ship that carried Captain Robert Scott on his doomed expedition to the Antarctic a century ago has been discovered off Greenland.
The SS Terra Nova was found by a team from a US research company.
Scott and his party set off from Cardiff aboard the Terra Nova in 1910 with the aim of becoming the first expedition to reach the South Pole.
The ship had a life after the polar trek, sinking off Greenland's south coast in 1943.
It had been on a journey to deliver supplies to base stations in the Arctic when it was damaged by ice. The Terra Nova's crew was saved by the US Coast Guard cutter Southwind.
On arriving at the geographical South Pole in January 1912, Scott and his party discovered they had been beaten to it by a Norwegian team led by Roald Amundsen.
The polar team led by Scott died on their return journey from the pole; their bodies were found by a search party eight months later.
Their endeavour became popularly known as the Terra Nova expedition.
A crew from the Schmidt Ocean Institute discovered the Terra Nova whilst testing echo-sounding equipment aboard its flagship vessel - the R/V Falkor.
One of the scientists noticed an unidentified feature during sonar mapping of the sea bed.
Team members then noted that the 57m length of the feature matched the reported length of the Terra Nova.
Technicians dropped a camera package called Shrimp to just above the presumed wreck to film it.
Camera tows across the top of the target showed the remains of a wooden wreck lying on the seabed.
Footage from the Shrimp also identified a funnel lying next to the ship.
Taken together, the features of the wreck closely matched historical photos of the Terra Nova, leading to the identification.
Brian Kelly, an education officer from the Discovery Point museum in Dundee, where the ship was built, told the Daily Record newspaper: "The Terra Nova has such a story.
"She went through a lot in her lengthy history and really was the pinnacle of Scottish wooden shipbuilding.
"It is incredible that one of the most famous ships in history has been found 100 years after the race for the pole and in the year commemorating the event."