Monthly Archives: April 2019


Global Climate Change, Disease and European contact, the “Germs” part of “GUNS, GERMS AND STEEL” (the PBS series and book by Jared Diamond)


4 December 2018


Alexander Koch a, *, Chris Brierley a, Mark M. Maslin a, Simon L. Lewis a, b

a Geography, University College London, London, WC1E6BT, United Kingdom
b School of Geography, University of Leeds, Leeds, LS29JT, United Kingdom

Abs t r a c t
Human impacts prior to the Industrial Revolution are not well constrained. We investigate whether the
decline in global atmospheric CO2 concentration by 7e10 ppm in the late 1500s and early 1600s which
globally lowered surface air temperatures by 0.15+C, were generated by natural forcing or were a result of
the large-scale depopulation of the Americas after European arrival, subsequent land use change and
secondary succession. We quantitatively review the evidence for (i) the pre-Columbian population size,
(ii) their per capita land use, (iii) the post-1492 population loss, (iv) the resulting carbon uptake of the
abandoned anthropogenic landscapes, and then compare these to potential natural drivers of global
carbon declines of 7e10 ppm. From 119 published regional population estimates we calculate a

           pre-1492 CE population of 60.5 million

(interquartile range, IQR 44.8e78.2 million), utilizing 1.04 ha land per
capita (IQR 0.98e1.11).

European epidemics removed 90% (IQR 87e92%) of the indigenous population over the next century.

This resulted in secondary succession of 55.8 Mha (IQR 39.0e78.4 Mha) of
abandoned land, sequestering 7.4 Pg C (IQR 4.9e10.8 Pg C), equivalent to a decline in atmospheric CO2 of
3.5 ppm (IQR 2.3e5.1 ppm CO2). Accounting for carbon cycle feedbacks plus LUC outside the Americas
gives a total 5 ppm CO2 additional uptake into the land surface in the 1500s compared to the 1400s, 47
e67% of the atmospheric CO2 decline. Furthermore, we show that the global carbon budget of the 1500s
cannot be balanced until large-scale vegetation regeneration in the Americas is included.

Global climate change graph

YELLOW BOX IS THE “GREAT DYING” TIMESPAN, BLACK IS “CARBON UPTAKE” due to reforestation, BLUE and GREY are ice cores showing atmospheric CO2 levels




Amerindians in North America

Once, North America was full of Amerindian nations, populations of people ancestrally indigenous to the continent. Researchers estimate population numbers in the millions prior to the arrival of Europeans, but today Amerindians make up only about 1% of the total population. So, what happened? Well, the arrival of Europeans introduced many new things to North America. Some of those things were invisible bacteria and viruses that caused pandemic-level outbreaks amongst Amerindian populations. Now, off the bat it should be acknowledged that diseases did not single-handedly destroy Amerindian civilizations. However, when coupled with slavery, oppression and forced dietary/social changes that came from colonialism, these diseases did have an absolutely lethal impact. One of the most notorious of these diseases was smallpox, a vicious virus that even today cannot be treated except to manage its symptoms and prevent its spread. Of all the colonial empires to touch Amerindian nations, smallpox may have been the most aggressive.

Introduction of Smallpox

Smallpox found its way into the Americas basically in tandem with the first major colonial expeditions. The Spanish started setting up colonies in the Caribbean in the late 15th century, and by the first decade of the 16th century the region was already experiencing widespread mortality amongst Amerindian populations. Now, the obvious question here is why smallpox affected Amerindians so harshly. Smallpox as a disease first transferred to humans around 10,000 BCE. It appeared first in agricultural societies as humans were exposed to diseases carried by animals, and spread across Africa and Europe. But, over thousands of years they built up immunities. This doesn’t mean they were completely safe; a smallpox outbreak in Rome is believed to have killed roughly 7 million people in 108 CE. However, when smallpox appeared in the Caribbean, it encountered a people with absolutely no previous exposure, and therefore no genetic immunities to the disease.


Europeans landing in the Caribbean unknowingly introduced new diseases

The people of the Caribbean, called the Taíno, were the first to really have to deal with smallpox, and they were entirely wiped out. When Europeans first arrived in the Caribbean, they often enslaved the Taíno and forced them into hard labor. Exhaustion and starvation weakened their immune systems, reducing the little ability they had to fight off new diseases like smallpox. Of the many populations to be decimated by smallpox, the Taíno are amongst the only ones considered to have experienced nearly a 100% mortality rate. In fact, it was because the Taíno had all succumbed to the disease that Europeans started importing new slaves from Africa. This actually made the smallpox problem worse, as African slaves unknowingly carried new strains of the disease.

Impact on European Colonialism

Smallpox ended up being one of the most dramatic factors in the colonial wars that would emerge between Amerindians and European empires across the next several centuries. When Hernán Cortés and the Spanish Conquistadores took on the Aztec Empire, many parts of that empire had already been ravaged by smallpox. Since the virus passes from person-to-person and can hide within a host for almost two weeks before that person shows any symptoms, smallpox worked its way into the continental Americas long before the Europeans got there. In fact, the Aztec capital of Tenochtitlán was ravaged by smallpox while the Spanish weren’t in the city, and the Aztec emperor himself was killed. The loss of warriors and political disunity caused by the disease was part of the reasons the Aztec Empire fell.


Smallpox depicted in Aztec illustrations
Aztec smallpox art

This trend would continue across the Americas. When European traders first made it to what is now Oregon and Washington, they noted that there were already members of the tribal nations there who were sick with smallpox. Researchers estimate that a smallpox outbreak in a community who has never seen the disease before can impact their population for 100 to 150 years. Those who survive are still carriers of the disease, and with each generation the virus can reappear, wreaking havoc.

In 1517 the Spanish conquistadors, led by Hernán Cortés, arrived in Tenochtitlan, the capital of the Aztec Empire. The ruler of the Aztecs, Motecuhzoma II, made the Spanish welcome and things were friendly between the Spanish and the Aztecs initially.


Tenochtitlan before Cortes–250,000 people, compulsory public education for all




Two years later the conquistadors began their conquest of Mexico, and by August 1521 Tenochtitlan had been destroyed. The Spanish colony of New Spain was established and the Aztec Empire had ended. The reasons for this rapid and dramatic destruction of such a mighty Empire were multi-factorial. The superior weaponry and more sophisticated military tactics of the Spanish, the religious beliefs of the Aztecs, and the long history of ritual sacrifice and persecution of the other peoples living in Mexico all played essential roles. There are a large number of detailed resources available on this subject, and I highly recommend the History on Fire podcast series by Daniele Bolleli if you are interested in the topic.

In addition to these factors, smallpox undoubtedly played a huge part in the fall of the Aztec Empire. When Cortés and his army began their campaign against the Aztecs in 1519, over 30 million people were living in Mexico. One hundred years later, after a series of smallpox epidemics had decimated the local population, it is estimated only around 1.5-3 million natives had survived.

Native Americans Helped the Europeans when they Suffered Disease

Updated on May 9, 2013

Native Americans became exposed to many new diseases when the Europeans arrived in North America. Native American communities were isolated from disease until the arrival of the Europeans. The Europeans had built up immunity to many diseases while living in the Old World. Native Americans had never been exposed to these diseases before and their traditional cures did not work. The transmission of the diseases caused more devastation in the New World than the Black Death had done in Europe. Hundreds of thousands of Natives died from these diseases. Well established trade routes helped spread the diseases very quickly. Diseases that the Europeans brought over were smallpox, measles, malaria, yellow fever, influenza, chicken pox, and many others. Diseases that were spread to the Europeans from the Natives were syphilis, polio, hepatitis, and encephalitis.

Christopher Columbus

Christopher Columbus and his crew landed in Hispaniola, an island in the Caribbean Sea, in the year 1492, and by the year 1600 most of the Natives were dead from disease. The reason they died so quickly is because the Europeans brought over livestock with them. The Natives were hunters and gatherers. The Europeans lived in tight settlements with their livestock, which helped diseases spread faster. Cattle pass measles, tuberculosis, and smallpox to people. Pigs pass influenza and pertussis to people. Chickens pass malaria to people. The Natives did not have these animals until the Europeans arrived, and did not have the antibodies to fight the diseases as well as the Europeans had. Trading with one another helped spread the diseases quickly. Alfred Crosby writes about some of these diseases in his article The Columbian Exchange, Smallpox was the worst and the most spectacular of the infectious diseases mowing down the Native Americans. The first recorded pandemic of that disease in British North America detonated among the Algonquin of Massachusetts in the early 1630s: William Bradford of Plymouth Plantation wrote that the victims “fell down so generally of this disease as they were in the end not able to help one another, no not to make a fire nor fetch a little water to drink, nor any to bury the dead.” European explorers encountered distinctively American illnesses such as Chagas Disease, but these did not have much effect on Old World populations. Venereal syphilis has also been called American, but that accusation is far from proven. Even if we add all the Old World deaths blamed on American diseases together, including those ascribed to syphilis, the total is insignificant compared to Native American losses to smallpox alone.”


The Europeans not only brought disease to the New World, but also brought disease with them back to the Old World. European sailors on their way back to Europe brought syphilis with them. “The origin of venereal syphilis is referred to as the “Columbian hypothesis”, it asserts that the disease causing agent Treponema pallidum originated in the New World and was spread in 1493 by Christopher Columbus and his crew, who acquired it from the Natives of Hispaniola through sexual contact. Upon return to Spain, some of these men joined the military campaign of Charles VIII of France and laid siege to Naples in 1495. Encamped soldiers exposed the local populations of prostitutes, which amplified disease transmission. Infected and disbanding mercenaries then spread the disease throughout Europe when they returned home. Within five years of its arrival, the disease was an epidemic in Europe. Syphilis reached Hungary and Russia by 1497; Africa, the Middle East and India by 1498; China by 1505; Australia by 1515; and Japan by 1569.” The most common remedies for syphilis were mercury and guaiacum.

Native Americans

The Native Americans did help the Europeans when they suffered disease. One example is when the French explorer Jacques Cartier and his crew were trapped in the St. Lawrence River near Montreal. The ships were frozen in the ice from November to March during the winter of 1535 to 1536. As a result, disease broke out on the ships and twenty-five men died. (The disease is what we now call scurvy.) The local Natives saw the Frenchmen’s plight and showed them how to take bark and leaves of a certain tree (either white pine or hemlock) boil them down and drink it every other day. Native American healers, many of them women, knew where to find natural plant remedies. Europeans would have rather received natural healing then the alternative European healing, such as purging and bleeding. Natives would treat wounds with crushed bark of Chionanthus; use Spirea as a purgative like ipecac; apply the pulverized roots and leaves of Dracontium (skunk or polecat-weed) after attacks of asthma; use a decoction of Aralia spinosa to treat rheumatic pains; apply the bark of witch hazel to tumors and inflammations and make a poultice from the inside bark as a remedy for burning eyes; relieve coughs with a decoction of Adiantum; and use the resin from the buds of the tacamahac tree for various illnesses. They also used bayberry roots for toothaches and petroleum to relieve rheumatism and aches and pains.


The Europeans also helped the Native Americans when they were suffering. Traditional Native healing practices, such as fasting, taking sweat baths, and plunging into an icy river, did not help them fight the diseases, but made it worse. The Europeans had sought the aid of the Natives for cures for snakebites and other ailments, now the Natives were seeking help from the Europeans. The Huron Natives accepted Baptism from Jesuit priests in hopes that they would be healed. The Europeans had some medical knowledge and supplies and helped them the best they could. Alvar Nunez Cabeza de Vaca writes in Relacions how he helped cure Natives of illnesses. “We remained with the Avavares Indians for eight months, according to our reckoning of the moons. During that time they came for us from many places and said that verily we were children of the sun. Until then Dorantes and the negro had not made any cures, but we found ourselves so pressed by the Indians coming from all sides, that all of us had to become medicine men. I was the most daring and reckless of all in undertaking cures. We never treated anyone that did not afterwards say he was well, and they had such confidence in our skill as to believe that none of them would die as long as we were among them.” In his writings, Cabeza de Vaca tells that the only thing that they did for the Indians was to pray for them. “Every one of the patients offered him his bow and arrows, which he accepted, and by sunset he made the sign of the cross over each of the sick, recommending them to God, Our Lord, and we all prayed to Him as well as we could to restore them to health.”



Native American cultures saw illness as a sign of imbalance in the spirit world. They did not believe that disease was spread person to person. Staying in harmony with others through rituals was very important for a good mind in the natural and spirit world. Illnesses could be caused by violated taboos, witchcraft, or unfulfilled dreams, but could be cured by rituals. Some tribes believe that there are three kinds of diseases. Some are natural and can be cured with natural remedies. Some are caused by the soul of the sick person and are cured by giving what the soul desires. And then some are caused by a spell that a sorcerer has cast upon the person and is cured by drawing out the spell that is making the person sick.

Interestingly, the Europeans thought that the illnesses that were killing the Native Americans were a divine act of God. “According to John Winthrop, God was killing Indians and their supporters to ensure “our title to this place.” And as the “instruments of Providence, divinely appointed to claim the New World from its ‘godless’ peoples,” the colonists felt it was their duty to destroy the “godless savage.” In the words of Captain John Underhill, “We had sufficient light from the word of God for our proceedings” — he refers to the massacre of five hundred Pequot men, women, and children at a village along the Mystic River.”

Helped Modern Medicine

The diseases that affected early American people are very extensive. The treatments varied depending on what part of the country and what culture lived there. As you can see in my research, there are many differences on who helped who and what treatment they received. The Native Americans were natural healers and the Europeans used advanced medical technology. The two groups did not always get along and work together, but when they did it was very advantageous for all involved. The Natives specialized in ways that the Europeans did not, and vice versa. The diseases helped modern medicine and doctors gain more knowledge as time went on.



Hence, the carbon uptake that is thought to have occurred
following the arrival of epidemics in the Americas may have
reduced atmospheric CO2 levels and led to a decline in radiative
forcing that may then have contributed to the coldest part of the
Little Ice Age

Though scientists don’t agree on what caused the Little Ice Age, most agree the climate cooled from the 15th century to the middle of the 19th century, with the greatest intensity between 1550 and 1700. Some scientists peg the coldest period even more narrowly, between 1645 and 1715. During that period the average winter temperatures in North America fell two degrees Celsius.

The NASA Earth Observatory blames diminished solar activity for the Little Ice Age, though scientists offer competing theories.

Historians, on the other hand, agree that the Little Ice Age altered the course of history. It froze rivers and canals in Northern Europe, wiped out cereal production in Iceland and caused famine in France, Norway and Sweden. Colder winters meant denser wood, which contributed to the superior tone of the Stradivarius violin.

little-ice-age-great-snowThe Little Ice Age brought cool summers and bitterly cold winters to New England.  During the Great Snow of 1717, for example, a series of snowstorms buried houses and got search parties lost looking for them.

The Cold Friday of 1810 also belonged to the Little Ice Age. People died in their homes when the temperature suddenly plummeted more than 60 degrees in less than a day. Years later, Henry David Thoreau’s mother remembered how dishes froze as fast as they were washed – right next to the fire

In conclusion, a pre-industrial event such as the “Great Dying”, which was thought to trigger both the reduction in CO2 and increase in carboniferous plant residues captured in ice cores inverts the usual understanding of global climate change due to human activities which, when you think about it, provides unique confirmation of the hypothesis.




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