or even your whole country were wiped out.

城市或國家一半的居民消失

It might sound like something out of an apocalyptic horror film,

就像末日災難電影的場景

but it actually happened in the 14th century

這就是14世紀時

during a disease outbreak known as the Black Death.

「黑死病」大流行的樣子

Spreading from China through Asia, the Middle East, Africa and Europe,

從中國、西亞、中東、非洲 最後到歐洲

the devastating epidemic destroyed as much as 1/5 of the world's population,

冷血無情的瘟疫 奪走全球1/5的人命

killing nearly 50% of Europeans in just four years.

4年內歐洲人口因此減少近50%

One of the most fascinating and puzzling things abut the Black Death

但「黑死病」最令人好奇也不解的是

is that the illness itself was not a new phenomenon

它不是突然出現的新疾病

but one that has affected humans for centuries.

而是早已在人類身上 流轉好幾世紀的病

DNA analysis of bone and tooth samples from this period,

從早期的遺骸骨骼、牙齒做DNA分析

as well as an earlier epidemic known as the Plague of Justinian in 541 CE,

發現黑死病跟西元541年爆發的 「查士丁尼大瘟疫」

has revealed that both were caused by Yersinia pestis,

都是由「鼠疫桿菌」引起的

the same bacterium that causes bubonic plague today.

同樣的這種細菌 現代稱為「腺鼠疫」

What this means is that the same disease caused by the same pathogen

也就是說 同一種病原引發的同一種疾病

can behave and spread very differently throughout history.

在不同時期 有不同的徵狀和傳染途徑

Even before the use of antibiotics, the deadliest oubreaks in modern times,

在使用抗生素前 現代死亡人數最多的一次流行

such as the ones that occurred in early 20th century India,

例如在20世紀早期的印度

killed no more than 3% of the population.

也只害死不到3%的人口

Modern instances of plague also tend to remain localized,

現在的黑死病 也多具地域性或散佈緩慢

or travel slowly, as they are spread by rodent fleas.

取決於做為媒介的老鼠跳蚤

But the medieval Black Death, which spread like wildfire,

但中世紀像野火蔓延的黑死病

was most likely communicated directly from one person to another.

反而是在人之間直接傳染

And because genetic comparisons of ancient to modern strains of Yersinia pestis

而且比較古今的「鼠疫桿菌」發現

have not revealed any significantly functional genetic differences,

他們沒什麼基因功能上的不同

the key to why the earlier outbreak was so much deadlier

早期會這麼致命的原因

must lie not in the parasite but the host.

應該和「病原」無關 而是「宿主」

For about 300 years during the High Middle Ages,

在中世紀中期的300年間

a warmer climate and agricultural improvements

溫暖的氣候和農業進步

had led to explosive population growth throughout Europe.

造成歐洲人口爆炸性成長

But with so many new mouths to feed,

糧食需求快速增加

the end of this warm period spelled disaster.

隨後氣溫的下降 導致了悲劇

High fertility rates combined with reduced harvest,

出生率高和糧食生產下降

meant the land could no longer support its population,

代表土地不堪負荷龐大人口

while the abundant supply of labor kept wages low.

而充沛的勞動力拉低整體薪資

As a result, most Europeans in the early 14th century

結果就是 14世紀早期的歐洲人

experienced a steady decline in living standards,

大多開始經歷 逐漸下降的生活水準：

marked by famine, poverty and poor health, leaving them vulnerable to infection.

飢荒、貧困、病痛

And indeed, the skeletal remains of Black Death victims found in London

讓他們對傳染病喪失抵抗力

show telltale signs of malnutrition and prior illness.

在倫敦地底 發現的黑死病患者骨骸

The destruction caused by the Black Death changed humanity in two important ways.

都有營養不良 和患有其他疾病的跡象

On a societal level, the rapid loss of population

黑死病的肆虐 為人類帶來兩項重要影響

led to important changes in Europe's economic conditions.

社會層面

With more food to go around,

人口大量減少 改變了歐洲的經濟情況

as well as more land and better pay for the surviving farmers and workers,

有相對多的糧食、 土地和較高的薪資

people began to eat better and live longer as studies of London cemeteries have shown.

提供給倖存者

Higher living standards also brought an increase in social mobility,

人們開始吃得好也活得長

weakening feudalism, and eventually leading to political reforms.

如同倫敦公墓裡的遺骸所顯示

But the plague also had an important biological impact.

生活水準提高帶動更多社會流動

The sudden death of so many of the most frail and vulnerable people

削弱封建制度 最後導致政治改革

left behind a population with a significantly different gene pool,

同時黑死病也有重要的演化意義

including genes that may have helped survivors resist the disease.

大量無法抵禦疾病的人口 迅速死亡

And because such mutations often confer immunities

留下最適生存的人類基因庫

to multiple pathogens that work in similar ways,

也留下那些能抵抗黑死病的基因

research to discover the genetic consequences of the Black Death

遺傳過程中的些許變異 可能也讓我們對類似的病原免疫

has the potential to be hugely beneficial.

黑死病過後的基因研究

Today, the threat of an epidemic on the scale of the Black Death

洽好能證明這一點

has been largely eliminated thanks to antibiotics.

現在黑死病疫情的威脅

But the bubonic plague continues to kill a few thousand people worldwide every year,

歸功於抗生素已經有效控制

and the recent emergence of a drug-resistant strain

但「腺鼠疫」每年 還是奪走全球數千條人命

threatens the return of darker times.

而病原最近開始出現的抗藥性

Learning more about the causes and effects of the Black Death is important,

為我們帶來新一波威脅

not just for understanding how our world has been shaped by the past.

了解黑死病的起因和影響很重要

It may also help save us from a similar nightmare in the future.

不只能了解現在的世界 如何被過去影響