Black Death was the first plague pandemic in human history, no previous bug or virus wiping out a greater proportion of humanity in a single epidemic.
The disease that ravaged 14th-century Europe, the Black Death was not just a more dangerous form of an illness already occurring disease, but in fact a harmless bacteria that had newly evolved, yet today remains much the same, undergoing no major genetic changes over a 600 year period.
Mediaeval cadavers from a London cemetery yielded those old plague germs, shedding light on why the Black Death bacterium was so deadly, spawning waves of epidemics as it progressed. Dubbed Yersinia pestis, the bacterial DNA shows it to have been a germ to which humanity in those times had no immunity.
According to a study in the British journal Nature, in evolutionary terms, the Black Death was the first plague pandemic in human history, no previous bug or virus wiping out a greater proportion of humanity in a single epidemic.
From China, the disease was introduced to Europe, mowing down, across the continent between 1347 and 1351, somewhere in the region of thirty million people, around 9% of world population and 33% of Europe's at that time in history.
Remarkably, based on the reconstructed genome, researchers feel certain that the mediaeval plague lies at the heart of all modern human pathogenic plague strains, not carrying a single position not found in modern varieties, this amazing similarity calling into question the assumption that mutations are what made the Middle Ages Y. pestis so deadly.
Europeans had never been exposed to the bacterium, just as native American Indians had no immunity to smallpox, so the plague proved to be among the strongest sources of human population in the last few millennia, less susceptible humans passing on their resistance.
The terrible social conditions of those far-off days could well have worsened the Black Death's toll, with poverty and malnutrition rampant, and even hygiene almost non-existent for the average citizen. Add to that the fact of many pathogens travelling more quickly in cold climes, and the onset of the so-called Little Ice Age at that time could also have favoured the spread of the disease.
Whilst that infamous Spanish flu pandemic of 1918-19 killed 50 million people, in real terms it was not the deadliest pandemic in human history, because in a world population of two billion, the toll was far smaller than the Black Death, when humans numbered only hundreds of millions, in real terms.
Plague was first recorded breaking out in China over 2,600 years ago before reaching Europe via the so-called Silk Road trade route, before spreading to Africa in the 15th century, in the late 19th century reaching the United States.
Though this disease is now eminently treatable, the recently released film Contagion, which explores the topic of how a global pandemic might affect the world today, goes to demonstrate just how deadly the most microscopic of inhabitants of the earth can be, and how unprepared we often are for what are nothing more than evolutionary events in nature, truth be told.