callaway 2011 the black death decoded.pdf

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s word of a brutal pestilence raging across Europe reached London,its residents started digging. In 1348, Ralph Stratford, Bishop ofLondon, dedicated acres of land that had been purchased to bury thelegions of Black Death victims who would overwhelm existing church-yard cemeteries. Within two years, one-third to one-half of the citys40,000100,000 residents succumbed, and many thousands were bur-

ied in two newly dug cemeteries at East and West Smithfield. At the height of the scourge,200 bodies were interred each day.

East Smithfield, originally called the Churchyard of the Holy Trinity, is one of a hand-ful of burial sites known to have been used only during the Black Death. In the 1980s,excavation of this plague pit turned up nearly a third of the 2,400 bodies estimated tobe buried there, some piled five deep. Despite the urgency of the time, the bodies wereplaced purposefully, oriented east to west, some with charcoal, possibly to absorb the

fluids released during putrefaction, and many with coins and trinkets of their formerlives. Such foresight not only helped keep corpses from piling up in the streets, but also,it seems, afforded some Black Death victims a dignified Christian burial. Six-and-a-halfcenturies later, it would also give scientists the opportunity to dissect the disease that laidwaste to Europe (see Death on the march).

This month, geneticists reported that they have reconstructed the genome of Yersinia pes-tis, the bacterium that causes bubonic plague , recovered from remains at East Smithfield1.

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By Ewen Callaway

660-year-old bacterium isrevealing secrets from one of

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The sequence the first from an ancientbacterial pathogen may help to explain howa disease could wreak so much havoc. It alsomarks a renaissance in genetic studies of ancientdiseases, a field that has suffered a controversialhistory but that is now being revitalized. Therewill be a race now for all the ancient pathogens,says Hendrik Poinar, a palaeogeneticist atMcMaster University in Hamilton, Canada,who co-led the sequencing efforts.

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When Alexandre Yersin linked Y. pestistobubonic plague in 1894, many scientistssurmised that the pathogen was behind notonly the Black Death, but also a spate of ear-lier mass die-offs. The sixth-century Justinianplague devastated Constantinople and killedmillions in Europe and the Near East. Plaguesreared their heads periodically for the next twocenturies. Black Death itself reappeared severaltimes, even into the nineteenth century.

Clues tying Y. pestisto these outbreaks camelargely from historical accounts of their symp-toms, such as Giovanni Boccaccios descriptionof the Black Death in TheDecameron, writtenaround 1350: It first betrayed itself by theemergence of certain tumours in the groin or

the armpits, some of which grew as large as acommon apple, others as an egg.

But some modern historians and scientistscame to doubt that Y. pestiscaused these ancientoutbreaks. Bubonic plague epidemics known tohave been caused by Y. pestis in the past cen-tury seemed too mild to have been caused bythe same culprit as the Black Death: they killedfewer people and spread more slowly. Someplague revisionists have argued that fleas,which spread Y. pestisto humans, would havestruggled to survive the cold temperaturesreported during the Black Death. And therewas the speed with which it killed Boccaccio

reported that death often occurred within three

days of the first symptoms appearing. Anthraxor a haemorrhagic-fever-causing virus similarto Ebola would be more likely than plague tocause such a rapid demise, say critics.

DNA evidence would seem to offer adefinitive answer. In 2000, a team led by DidierRaoult, a microbiologist at the University ofthe Mediterranean in Marseilles, France, saidit had proved the link between the bacteriumand the disease. The researchers reported2thatthey had successfully recoveredY. pestisDNAfrom the teeth of a child and two adults dug upfrom a fourteenth-century mass burial site inMontpellier. The team identified the bacteriumusing a sensitive technique called the polymer-ase chain reaction (PCR) to amplify a portion ofa gene from Y. pestiscalledpla. We believe thatwe can end the controversy, the team wrote2.Medieval Black Death was plague.

But several critics raised concerns aboutcontamination. The PCR might instead haveamplified DNA from modern Y. pestisusedpreviously in the lab, or possibly the sequencesfrom a closely related soil-dwelling bacte-rium. I could never, ever replicate it, saysThomas Gilbert, an evolutionary geneticist atthe University of Copenhagen in Denmark.In 2004, Gilbert and his colleagues reported

no trace of Y. pestisDNA in 108 teeth from 61individuals found in plague pits in France, Den-mark and England (including East Smithfield)3.

Raoult says that there was no contaminationand that Gilberts methods did not accuratelyreplicate his4. Still, those who were alreadysceptical of the suggestion that Y. pestiscausedthe Black Death latched on to Gilberts study.

Other studies of microbial DNA extractedfrom ancient human remains includingthose affected by tuberculosis, syphilis andmalaria were also being scrutinized. Inseveral cases, researchers could not replicateresults, or they found methodological short-

comings. Critics said that DNA from these

samples was too degraded by heat, moistureand time to detect, and the field soon dividedinto believers and sceptics.

There was a complete schism, says IanBarnes, a palaeogeneticist at Royal HollowayUniversity of London, who says he spent two-and-a-half years trying unsuccessfully tofind DNA evidence of syphilis or tuberculosisin bones dating from the nineteenth and earlytwentieth centuries5. People largely ignoredeach other, he says.

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Although Poinar was dubious of claims aboutancient microbial DNA, he was intrigued bythe bones from East Smithfield. Nearly all ofthe remains are from Black Death victims,many of whom were cut down during theprime of their lives.

In a bright ground-floor laboratory of theMuseum of London, a short walk from EastSmithfield, osteoarchaeologist Jelena Bekvalacexamines the nearly complete skeleton of oneof the plague pits former residents. Wearing ablack silk scarf dotted with white skull-prints,Bekvalac handles a pelvic bone and determinesthat it belonged to a man who died in his lateteens or early twenties. Apart from some plaque

on his teeth and a gash in his skull that showssome signs of healing, the mans skeleton offersno outward evidence of Black Death.

His remains, and those from hundreds ofothers, represent a snapshot of life and deathin London during the epidemic. Since the sitesexcavation, researchers have descended on thebones in search of information.

In the late 1990s, Poinar met SharonDeWitte, then a graduate student atPennsylvania State University in State College,who was working on a demographic analysisof the remains suggesting that Black Deathpreferentially killed those who were already

frail. The two considered drilling into teeth

Lond

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Path of the epidemic

D In the 1340s, a pestilence originating in Western Asia spreadrapidly across Europe. Before it overtook London in 1348, landwas set aside in East Smithfield to bury the dead.

EastSmithfield

In the late 1980s,large areas of the

East Smithfieldcemetery wereexcavated, revealingthe remains of 762individuals.

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TowerBridge

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The port of Caffawas the Black

Deaths gatewayfrom Asia intoEurope.

RoyalMintStreet

SOURCE:REF.

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