If we add to this a potted history of China and the importance of the Silk Road, as well as the life cycle of another history-altering insect, the mulberry leaf-eating moth Bombyx mori (commonly known in its larval stage as the silkworm), then we begin to see the scope of Rosen's ambition.Īt the core of the book, however, is a splendid biography of the emperor Justinian (482-565). It discusses how the Roman empire's collapse gave birth to the proto-nations within it, and how the rise of Islam helped to shape the identity of the European superstate of Christendom. But this book also contains a detailed account of the evolution of the bubonic plague and how it weakened the empire's resistance to the conquering armies of Muhammad. It is a history of the eastern Roman empire and its many enemies, as well as a survey of the great city of Constantinople, a new Rome straddling seven hills and smelling strongly of fermented fish sauce. Justinian's Flea is a massively ambitious work that covers a great deal of ground. In this eccentric and erudite book, in which a flea looms as large as an emperor, Rosen sets out to establish the forces that transformed the Mediterranean world of late antiquity into medieval Europe, and in his view the major force was the bubonic plague.

History's first pandemic killed at least 25 million people, depopulating entire cities and depressing birth rates for generations. At first the hospitals were full, then the burial grounds. Carried by the Mediterranean black rat, the plague migrated westwards from Pelusium to Alexandria, from whence it was exported - aboard ships - across the trade routes of the Mediterranean to Constantinople, the capital of the eastern Roman empire, in the spring of 542. pestis was Xenopsylla cheopsis, whose preferred host was the rat. However, its distinctive effects - grapefruit-sized swellings (buboes) in the armpits and groin - were first recorded in AD540 in the city of Pelusium on the Nile delta. pestis, the bacterium of the bubonic plague, probably evolved in the fertile region of the Great Lakes of East Africa. From that moment on, says Rosen, a 'demon' was unleashed on an unsuspecting world.

As William Rosen explains in this impressive study of the bubonic plague and its impact on history, while trying to turn off the flea's defences the bacterium evolved into the far more deadly Yersinia pestis. Yersinia pseudotuberculosis was a fairly benign bacterium, causing mild flu-like symptoms, until it happened upon a superior method of transportation: the flea.

Justinian's Flea by William Rosen