A lot can be learned from a tooth. Molars taken from skeletons unearthed during work on a London railway line are revealing secrets of the medieval Black Death - and its victims.
Last week, Don Walker, an osteologist with the Museum of London, outlined the biography of one man whose 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 labourer, and died in early adulthood from the bubonic plague that ravaged Europe in the 14th century.
His life was nasty, brutish and short, but his after-life 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 railway that's boring 21km 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, matches 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 yesterday that tests had found the presence of the plague bacterium in several of the teeth, meaning the individuals had been exposed to, and were likely to have died from, the plague.
The findings didn't stop there. Archaeologists, historians, microbiologists and physicists worked together to apply techniques from several scientific disciplines to the discovery.
Radiocarbon dating and analysis of pottery shards helped determine when the burials took place. Forensic geophysics - more commonly used in murder investigations - helped locate more graves under the square. Studying oxygen and strontium isotopes in the bones revealed details of diet and health.
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.
"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.
Archaeologists are planning a new dig to learn how many bodies lie under the square.
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 there is some dispute.