Image copyright Crossrail Image caption The plague victims' bones reveal clues to their harsh lives in medieval London 
 
 Skeletons unearthed in London Crossrail excavations are Black Death victims from the great pandemic of the 14th Century, forensic tests indicate. 
 
 Their teeth contain DNA from the plague bacterium Yersinia pestis and their graves have been dated to 1348-50. 
 
 Records say thousands of Londoners perished and their corpses were dumped in a mass grave outside the City, but its exact location was a mystery. 
 
 This discovery solves a 660-year-old mystery. It's a hugely important step forward Jay Carver , Lead archaeologist, Crossrail 
 
 Archaeologists now believe it is under Charterhouse Square near the Barbican. 
 
 They plan to expand their search for victims across the square - guided by underground radar scans, which have picked up signs of many more graves. 
 
 Crossrail's lead archaeologist Jay Carver says the find "solves a 660-year-old mystery". 
 
 "This discovery is a hugely important step forward in documenting and understanding Europe's most devastating pandemic," he said. 
 
 "Further excavations will follow to see if - as we expect - we are coming across a much bigger mass burial trench." 
 
 Media playback is unsupported on your device Media caption The teeth of the skeletons contain plague bacterial DNA 
 
 Between 1347 and 1351 the "Great Pestilence" swept westward across Europe killing millions of people. It later became known as the Black Death. 
 
 The plague The plague is one of the oldest identifiable diseases known to man 
 
 Plague is spread from one rodent to another by fleas, and to humans either by the bite of infected fleas or when handling infected hosts 
 
 Recent outbreaks have shown that plague may reappear in areas that have long been free of the disease 
 
 Plague can be treated with antibiotics such as streptomycin and tetracycline 
 
 Source: World Health Organization 
 
 It arrived on Britain's shores in 1348 and is believed to have wiped out up to 60% of the population at the time. 
 
 In London, two emergency burial grounds were dug outside the walls of the City. One has been found at East Smithfield, while the other is known to lie somewhere in Farringdon. 
 
 In March 2013, Crossrail engineers uncovered 25 skeletons in a 5.5m-wide shaft - alongside pottery dated to the mid-14th Century. 
 
 Samples from 12 of the corpses were taken for forensic analysis. In at least four cases, scientists found traces of the DNA of the Yersinia pestis, confirming they had contact with the plague prior to their death. 
 
 To pinpoint which historical plague outbreak the "Charterhouse 25" could have fallen victim to, the researchers used radio carbon dating. 
 
 They determined the burial ground was used in at least two distinct periods - the earliest within the Black Death in 1348-50, followed by a later outbreak in the 1430s. 
 
 Image copyright Crossrail Image caption The bodies were found in a Crossrail shaft 
 
 In a bid to understand just how far the grave extends across the square, Crossrail approached the University of Keele to undertake a forensic geophysics survey - using ground-penetrating radar. 
 
 The initial scan detected signs of further burials across Charterhouse Square and also the foundations of a building - possibly a chapel. 
 
 Image copyright crossrail Image caption Traces of plague bacteria were found in the teeth of the skeletons 
 
 "We will undertake further excavations in Charterhouse Square later this year to confirm some of the results," said Mr Carver. 
 
 The skeletons provide a rare opportunity to study the medieval population of London, according to osteologist Don Walker, of the Museum of London Archaeology. 
 
 He said: "We can start to answer questions like: where did they come from and what were their lives like? 
 
 "I'm amazed how much you can learn about a person who died more than 600 years ago." 
 
 Analysis of the skeletons' bones and teeth indicates that: 
 
 Many of the skeletons appear to suffer signs of malnutrition and 16% had rickets. 
 
 There is a high rate of back damage and strain indicating heavy manual labour. 
 
 The later skeletons from the 1400s had a high rate of upper body injury consistent with being involved in violent altercations. 
 
 13 of the skeletons were male, three female, two children, the gender was undetermined in the other seven skeletons. 
 
 40% grew up outside London, possibly as far north as Scotland - showing that 14th Century London attracted people from across Britain just as it does today. 
 
 Mr Carver said: "We can see from the people here that Londoners weren't living an easy life. 
 
 "The combination of a poor diet and generally a struggle means they were very susceptible to the plague at that time and that's possibly one of the explanations for why the Black Death was so devastating." 
 
 Image copyright Crossrail Image caption Archaeologist Jay Carver hopes to explore more of the burial site 
 
 By sequencing the ancient bacterial DNA, researchers hope to understand how the plague has evolved and spread over the centuries. 
 
 Globally the infection still kills 2,000 people a year, including countries like Madagascar. Antibiotics are available, but if untreated the disease kills within four days. 
 
 Scientists hope to confirm whether the 14th Century strain was the grandmother of all plague that exists today. 
 
 The £14.8bn Crossrail project aims to establish a 118km-long (73-mile) rail link with 37 stations across London, and is due to open in 2018. 
 
 The excavations have already unearthed Roman skulls washed down a lost river, a Bronze-Age transport route, and the largest piece of amber ever found in the UK. 
 
 The latest announcement comes ahead of a Channel 4 documentary, Return of the Black Death: Secret History, on 6 April, which follows the Charterhouse Square discovery. ||||| In this Wednesday, March 26, 2014 photo, some of the skeletons found by construction workers under central London's Charterhouse Square are pictured. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) You can learn a lot from a tooth. Molars taken from skeletons unearthed by work on a new London railway line are revealing secrets of the medieval Black Death—and of its victims. 
 
 This week, Don Walker, an osteologist with the Museum of London, outlined the biography of one man whose ancient bones were found by construction workers under London's Charterhouse Square: He was breast-fed as a baby, moved to London from another part of England, had bad tooth decay in childhood, grew up to work as a laborer, and died in early adulthood from the bubonic plague that ravaged Europe in the 14th century. 
 
 The poor man's life was nasty, brutish and short, but his afterlife is long and illuminating. 
 
 "It's fantastic we can look in such detail at an individual who died 600 years ago," Walker said. "It's incredible, really." 
 
 The 25 skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for plague victims. The location, outside the walls of the medieval city, chimes with historical accounts. The square, once home to a monastery, is one of the few spots in the city to stay undisturbed for centuries. 
 
 To test their theory, scientists took one tooth from each of 12 skeletons, then extracted DNA from the teeth. They announced Sunday that tests had found the presence of the plague bacterium, Yersinia pestis, in several of the teeth, meaning the individuals had been exposed to—and likely died from—the Black Death. 
 
 The findings didn't stop there. Archaeologists, historians, microbiologists and physicists worked together to apply techniques from several scientific disciplines to the discovery. 
 
 In this Wednesday, March 26, 2014 photo, Don Walker, a human osteologist with the Museum of London, poses for photographers, with one of the skeletons found by construction workers under central London's Charterhouse Square. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 Radiocarbon dating and analysis of pottery shards helped determine when the burials took place. Forensic geophysics—more commonly used in murder and war-crimes investigations—helped locate more graves under the square. Studying oxygen and strontium isotopes in the bones revealed details of diet and health. 
 
 These were, by and large, poor people. Many of the skeletons showed signs of malnutrition consistent with the "Great Famine" that struck Europe 30 years before the Black Death. Many had back injuries suggesting lives of hard labor. One man became a vegetarian late in life, indicating he may have entered an order of monks. 
 
 Archaeologists were surprised to discover that the skeletons lay in layers and appeared to come from three different periods: the original Black Death epidemic in 1348-1350, and later outbreaks in 1361 and the early 15th century. 
 
 In this Wednesday, March 26, 2014 photo, some of the skeletons found by construction workers under central London's Charterhouse Square are pictured. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 "It suggests that the burial ground was used again and again for the burial of plague victims," said Jay Carver, Crossrail's lead archaeologist. 
 
 The Black Death is thought to have killed at least 75 million people, including more than half of Britain's population, yet the burials suggest a surprisingly high degree of social order—at first. As the plague ravaged continental Europe—borne westward by fleas on rats—city fathers leased land for an emergency burial ground. The burials were simple but orderly, the bodies wrapped in shrouds and laid out in neat rows, sealed with a layer of clay. 
 
 The later skeletons, however, show more signs of upper-body injuries, consistent with a period of lawlessness and social breakdown. 
 
 Archaeologists are planning a new dig this summer to learn how many bodies lie under the square. Carver says the number appears to be in the "low thousands." 
 
 In this Wednesday, March 26, 2014 photo, Don Walker, a human osteologist with the Museum of London, poses for photographers, with one of the skeletons found by construction workers under central London's Charterhouse Square. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 And the teeth may not have yielded all their secrets. Experts in ancient DNA at McMaster University in Canada are working to sequence the plague genome found in the teeth, in order to learn more about a disease that still infects several thousand people a year around the world. Most patients recover if treated early with antibiotics. 
 
 Scientists want to know if the 14th-century disease is the same as the modern version, or whether the disease has evolved. Study of DNA from the teeth of skeletons discovered in the 1980s at another London plague cemetery suggested the bug was largely unchanged, but the scientific jury is still out. 
 
 Brendan Wren, a professor of molecular biology at the London School of Hygiene and Tropical Medicine, said the new information could help scientists "understand how the plague bacillus—and other nasty bugs—become so virulent to humans." 
 
 "It is useful information that could warn and avert potential epidemics and pandemics," he said. 
 
 In this Wednesday, March 26, 2014 photo, Don Walker, a human osteologist with the Museum of London, poses for photographers, with one of the skeletons found by construction workers under central London's Charterhouse Square. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 
 
 In this Wednesday, March 26, 2014 photo, one of the skeletons found by construction workers under central London's Charterhouse Square is pictured. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 In this Wednesday, March 26, 2014 photo, one of the skeletons found by construction workers under central London's Charterhouse Square is pictured. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 In this Wednesday, March 26, 2014 photo, members of the media film one of the skeletons found by construction workers under central London's Charterhouse Square. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 In this Wednesday, March 26, 2014 photo, Don Walker, a human osteologist with the Museum of London, holds the scull of one of the skeletons found by construction workers under central London's Charterhouse Square, as he poses for photographers. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 In this Wednesday, March 26, 2014 photo, some of the skeletons found by construction workers under central London's Charterhouse Square are pictured. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plague was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 In this Wednesday, March 26, 2014 photo, Don Walker, a human osteologist with the Museum of London, holds the scull of one of the skeletons found by construction workers under central London's Charterhouse Square, while posing for photographers. Twenty-five skeletons were uncovered last year during work on Crossrail, a new rail line that's boring 13 miles (21 kilometers) of tunnels under the heart of the city. Archaeologists immediately suspected the bones came from a cemetery for victims of the bubonic plague that ravaged Europe in the 14th century. The Black Death, as the plauge was called, is thought to have killed at least 75 million people, including more than half of Britain's population. (AP Photo/Lefteris Pitarakis) 
 
 Explore further: Ancient skeletons dug up at Florence's Uffizi
– Skeletons dug up in London last year are indeed the remains of people who died from the Black Plague—and who suffered a tough life before falling ill, the BBC reports. Forensic analysis shows that teeth taken from at least four of the 12 corpses discovered during excavation for a rail line contained trace amounts of plague DNA, indicating exposure. Early burials found at the site, from the late 1340s, are nice and orderly, with bodies wrapped in white shrouds, but skeletons from a second outbreak in the 1430s are tossed in with what appear to be upper-body injuries—evidence of "a period of lawlessness and social breakdown," Phys.org reports. Among other significant details: Several skeletons suffered from malnutrition and 16% had rickets. Many had back damage, signalling stressful manual labor. Analysis of one victim is amazingly detailed: He was born outside of London, breastfed, had bad tooth decay as a boy, and worked in manual labor before dying as a young man of the Black Death. Archaeologists suspect that thousands more Black Death victims lie nearby, and a dig is planned for this summer. DNA experts are analyzing the plague genome in victims' teeth in case there's more to learn about the disease, which still kills 2,000 people per year (when antibiotics aren't applied within four days). "It is useful information that could warn and avert potential epidemics and pandemics," says a London scientist. In a similar vein, see why it's bad news that the Plague and Black Death were quite different.