来源：《BBC历史》2023年6月刊
In 1521, Hernán Cortés and his army of about a thousand Spaniards achieved one of the most remarkable feats of conquest in history. They captured Tenochtitlan, a city home to a quarter of a million people – four times the size of Seville, then the biggest city in Spain – that ruled over a vast empire stretching from the Atlantic to the Pacific.
1521年，埃尔南·科尔特斯和他的约1000名西班牙人的军队取得了历史上最非凡的征服壮举之一。他们占领了特诺奇蒂特兰，这是一座拥有25万人口的城市，面积是当时西班牙最大城市塞维利亚的四倍，统治着一个从大西洋延伸到太平洋的庞大帝国。
Then, in 1532, Francisco Pizarro managed something even more implausible: he conquered the Inca, the largest and most advanced empire in the Americas, with a force comprising just 106 foot soldiers and 62 horsemen. These victories were just the beginning. The Spanish ruled much of South and Central America for the next 300 years. Their language, religion and culture still dominate the region today.
然后，在1532年，弗朗西斯科·皮萨罗完成了一件更令人难以置信的事情：他用一支仅由106名步兵和62名骑兵组成的部队征服了美洲最大、最先进的帝国印加。这些胜利仅仅是个开始。在接下来的300年里，西班牙人统治了南美洲和中美洲的大部分地区。他们的语言、宗教和文化至今仍主导着该地区。
The Spanish conquest of the Americas was possible only because they were unwittingly aided by infectious diseases. After Europeans started settling in the New World, it was just a matter of time before pathogens that had evolved in the Old World made the jump across the Atlantic.
西班牙人之所以能够征服美洲，只是因为他们在不知不觉中得到了传染病的帮助。欧洲人开始在新大陆定居之后，在旧大陆进化而来的病原体跨越大西洋来到新大陆只是时间问题。
Smallpox hit Tenochtitlan in 1520, the year after Cortés first landed in Mexico, killing between one-third and half of the population in the region in just a few months. The Spanish, who would have been exposed to the virus in childhood, were unaffected. Without this seemingly miraculous intervention, Cortés would never have defeated the Mexica.
1520年，也就是科尔特斯首次登陆墨西哥的第二年，天花袭击了特诺奇蒂特兰，在短短几个月内导致该地区三分之一至一半的人口死亡。西班牙人儿童时期就接触过这种病毒，所以没有受到影响。如果没有这种看似不可思议的干预，科尔特斯永远不会击败墨西哥人。
Smallpox raced ahead of the Conquistadors. In 1524, it killed a similar proportion of the Inca population – including the emperor, his designated heir and most of the nobility. A war of succession then further weakened the empire. This death and disruption made Pizarro’s victory possible.
天花跑在了西班牙征服者的前面。1524年，天花杀死了差不多同样比例的印加人——包括皇帝、他指定的继承人和大部分贵族。一场继承战争进一步削弱了帝国。这种死亡和混乱使皮萨罗的胜利成为可能。
Smallpox was just the beginning. The Americas were hit by wave after wave of infectious diseases, resulting in a 90 per cent fall in the population, from about 60.5 million in 1500 to 6 million a century later. The decline in slash and burn agriculture that followed this fall in population resulted in a marked fall in atmospheric carbon dioxide levels, and the global surface air temperature cooled by 0.15°C.
天花只是一个开始。美洲受到一波又一波传染病的袭击，导致人口减少90%，从1500年的6050万人减少到一个世纪后的600万人。随着人口的减少，刀耕火种农业的减少导致大气中二氧化碳含量显著下降，全球地表气温下降了0.15摄氏度。