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 labourer, 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 boring 21km of tunnels under the heart of the city. Archaeologists 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.

Scientists took one tooth from each of 12 skeletons, then extracted DNA from the teeth. They yesterday announced 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 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.

The Black Death is thought to have killed at least 75m people

Archaeologists are planning a dig this summer to learn how many bodies lie under the square. Carver says the number appears to be in the “low thousands”.