10 September, 1996. Copyright, 1996, Graphic News. All rights reserved

WHAT TRIGGERED THE BLACK DEATH?
By Laura Spinney, Science Editor

EMBARGOED UNTIL 10.30 TUESDAY 10 SEPTEMBER

LONDON, Graphic News, 10 September - Comets could have triggered the devastating plagues of the sixth and fourteenth centuries, a scientist claimed at the British AssociationÕs annual science meeting in Birmingham today.

Both the Justinian plague, which arrived in Europe in AD 542, and the Black Death which struck in AD 1347, were pandemics of bubonic plague. Outbreaks of this disease, which is caused by a bacterium transmitted by rat fleas, are thought to be triggered when infected rats move into contact with human populations that have no natural immunity to the disease. But according to Professor Mike Baillie of the School of Geosciences at Queens University, Belfast, we should look to space to find what really triggered the two plagues.

It is most unlikely that the bacteria were brought to Earth from outer space by a comet, says Baillie. But it is possible that dust trails and debris left by comets could have contaminated the atmosphere and brought about climate changes which led to crop failures. Faced by famine, human communities may have been forced to move, perhaps into areas where the disease was endemic. In the case of the sixth century plague, climate changes could have been caused by five comets recorded in the historical literature between 530 and 542. Another five comets were recorded in the decade leading up to the beginning of the Black Death in 1347. And it is also possible, says Baillie, that volcanic eruptions contributed to fourteenth century climate changes.

In order to find evidence to support his hypothesis, Baillie has studied records of growth rings in trees to get a picture of how environmental conditions have changed over the last 2000 years. Only recently, he says, has it been possible to compare such records with similar ones from other countries. ÔIn both cases the tree rings have gone narrow before the plague arrived,Õ he says. A narrowing of rings suggests a reduction in growth, and that in turn implies an Ôenvironmental downturnÕ, probably a slight drop in temperature. ÔIf the trees are recording environmental changes, then the implication has to be that these environmental changes were somehow involved in the effects on humans.Õ


Sources: British Association Annual Festival of Science