Transcript New World Encounters

New World Encounters
Setting the scene
• Early humans who had migrated to what is now the Americas were
cut off from Eurasia around 14,000 years ago – effectively isolating
themselves from the disease cycle of the ‘Old World’
• Recall that the cycle of infectious disease in the ‘Old World’ was the
result of the creation of mass civilizations (of about half a million
people) and the domestication of animals
• While the ‘New World’ did create mass civilizations it did not have the
same number or type of domesticated animals – thus there was no
opportunity for zoonotic diseases like smallpox, measles, influenza
and others to jump from animals to humans
Civilization in South America
• Farming in South America stretches back to around 3000 B.C., and the
first mass civilization dates to between 900 and 200 BC
• In the Andes the Chimu empire came to prominence around 900 AD
in the coastal region, and the Tiahuanaco empire in the region of Lake
Titicaca
• Both empires were characterized by having large cities and complex
irrigation systems to grow crops to feed a growing population
• Farming potatoes gave their society a high caloric sources of food
relative to the amount of space and labour they required
North and Meso America
• The earliest civilization in Mexico was founded around 1,400 BC, the
Olmecs, which were followed by the Maya and Teoihuacan empires
• The hybrid Toltec empire emerged around 900 AD in Meso America
• They built massive cities and relied on long-distance trade to fuel
their economy
• They traded with many people, stretching from the Great Lakes in the
north to the Gulf of Mexico in the south
• Their main crop and source of food was corn
Eve of the Spanish conquest
• In the two centuries before the arrival of the Spanish, powerful
empires, built on the foundations of earlier ones, were ruling in
Mexico and in Peru
• The Aztec Empire emerged in 1426 as an alliance of three city states
that ruled over the Mexico Valley – Tenochtitlan, Texocco, and
Tlacopan – they were wealthy and powerful
• The Inca Empire originated the thirteenth century, and by the
fifteenth century the empire witnessed an incredible expansion
• These empires were similar to the types of empires we have seen in
Eurasia – with the exception of infectious diseases
• During the century preceding the
arrival of the Spaniards, the Inca
Empire was experiencing a
significant burst of conquest itself
• Thus it created a massive empire
that mirrored the types of
empires that were known in the
Old World
The Conquest of Mexico
• In 1519 the Spanish explorer and adventurer Hernán Cortés arrived in
Mexico for the purpose of colonial expansion
• In November of the year he arrived at the capital, Tenochtitlan, a city
of nearly 100,000 people
• Cortés was welcomed by the ruler Montezuma, who very quickly took
Montezuma captive for the next six months
• While Cortés was called away from the city, his mex massacred
several noble men in Tenochtitlan, and Aztec troops had risen up
against the Spaniards and drove them from the city, killing
Montezuma in the process
• Having been driven from the city,
Cortes retreated and gather his
troops, returning in 1520 to lay siege
to Tenochtitlan
• The siege lasted for eight months,
during which time the city was
almost completely destroyed by fire
and canons
• One of the decisive reasons for the
Spanish victory was an outbreak of
smallpox in Sept. 1520 that lasted for
70 days and killed many Aztecs,
including their new leader
Conquest of Peru
• A group of Spanish conquistadores led by Francisco Pizarro reached
Inca territory by 1526; he returned in 1532 armed with a commission
to conquer the territory for Spain
• The Incas had lot of gold and silver, which they offered to the Spanish
as a ransom for their leader Atahualpa, but the Spaniards deceived
them, eventually executing him
• Not only did the Spaniards have technological advantages, but again
smallpox worked to their advantage, killing upwards of 70 per cent of
their population within a few years of contact with Europeans
• The Inca had a very extensive and wellmaintained road system that stretched
from one end of the empire to the other
• It was probably the efficient travel along
these highways that allowed the
infectious diseases that Europeans
brought with them to have such a
devastating effect on the population
Smallpox
• The first infectious disease to make its presence known was smallpox,
caused by a virus, transmitted through airborne droplets from nose,
mouth or through mucous
• For Europeans (as for all Afro-Eurasians) smallpox had long been
endemic (it probably emerged around 10,000 BC, likely jumping from
rodents to humans) thus it afflicted mainly children as adults had built
up a natural immunity
• For indigenous inhabitants of the Americas, however, it was brand
new, and thus they had built up no immunity to it (they were
”biologically naïve”), and the results were catastrophic
This illustration shows a contemporary drawing in the Florentine Codex of Nahuas of central Mexico suffering
from smallpox
Other infectious diseases from Eurasia
• Along with smallpox, Europeans introduced
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Measles
Typhus
Influenza
Diptheria
Mumps
• Once the transatlantic slave trade became established, Africans also
brought to the tropical and subtropical areas of America:
• Malaria
• Yellow
Death toll of infectious diseases
• Scholars estimate that the population of pre-contact America was just
over 60 million people (though there is some debate) – about 25-30
million in Mexico, roughly the same in Peru, and others scattered
across the continent
• By 1650, that population had shrunk to less than six million people
• Disease was by far the the primary cause of mortality of native people
in the Americas
• For many smaller tribes and island populations, disease wiped them
out completely
Globalization of infectious disease pools
• The spread of diseases from Eurasia to the Americas marks a
watershed in disease history because it marks the first time in history
that a disease has gone global
• Who knows what that will mean for the co-evolution of pathogens
and human beings … will it mean the balancing out of infectious
disease across the world resulting in less virulence, or the
development of new super-pathogens that can spread more quickly
than humans can develop (scientifically) vaccines to stop them in
their tracks?
Looking ahead
• In next week’s seminar we will discuss an article that proposes a more
biological direction and a new model for the study of Native American
disease
• In next week’s lecture we will be discuss the spread of sextually
transmitted infections