Megadrought and Megadeath in 16th Century Mexico

Megadrought and Megadeath in 16th Century Mexico


from Emerging Infectious Diseases
Rodolfo Acuna-Soto, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico, David W. Stahle, Malcolm K. Cleaveland, and Matthew D. Therrell, University of Arkansas, Fayetteville, Arkansas, USA



Abstract
The native population collapse in 16th century Mexico was a demographic catastrophe with one of the highest death rates in history. Recently developed tree-ring evidence has allowed the levels of precipitation to be reconstructed for north central Mexico, adding to the growing body of epidemiologic evidence and indicating that the 1545 and 1576 epidemics of cocoliztli (Nahuatl for "pest") were indigenous hemorrhagic fevers transmitted by rodent hosts and aggravated by extreme drought conditions.

Introduction
The native people of Mexico experienced an epidemic disease in the wake of European conquest (Figure 1), beginning with the smallpox epidemic of 1519 to 1520 when 5 million to 8 million people perished. The catastrophic epidemics that began in 1545 and 1576 subsequently killed an additional 7 million to 17 million people in the highlands of Mexico [1-3]. Recent epidemiologic research suggests that the events in 1545 and 1576, associated with a high death rate and referred to as cocoliztli (Nahuatl for "pest"), may have been due to indigenous hemorrhagic fevers [4,5]. Tree-ring evidence, allowing reconstructions of the levels precipitation, indicate that the worst drought to afflict North America in the past 500 years also occurred in the mid-16th century, when severe drought extended at times from Mexico to the boreal forest and from the Pacific to Atlantic coasts [6]. These droughts appear to have interacted with ecologic and sociologic conditions, magnifying the human impact of infectious disease in 16th-century Mexico.



Figure 1. (click image to zoom) The 16th-century population collapse in Mexico, based on estimates of Cook and Simpson [1]. The 1545 and 1576 cocoliztli epidemics appear to have been hemorrhagic fevers caused by an indigenous viral agent and aggravated by unusual climatic conditions. The Mexican population did not recover to pre-Hispanic levels until the 20th century.



The epidemic of cocoliztli from1545 to 1548 killed an estimated 5 million to 15 million people, or up to 80% of the native population of Mexico (Figure 1). In absolute and relative terms the 1545 epidemic was one of the worst demographic catastrophes in human history, approaching even the Black Death of bubonic plague, which killed approximately 25 million in western Europe from 1347 to 1351 or about 50% of the regional population.

The cocoliztli epidemic from 1576 to 1578 cocoliztli epidemic killed an additional 2 to 2.5 million people, or about 50% of the remaining native population. Newly introduced European and African diseases such as smallpox, measles, and typhus have long been the suspected cause of the population collapse in both 1545 and 1576 because both epidemics preferentially killed native people. But careful reanalysis of the 1545 and 1576 epidemics now indicates that they were probably hemorrhagic fevers, likely caused by an indigenous virus and carried by a rodent host. These infections appear to have been aggravated by the extreme climatic conditions of the time and by the poor living conditions and harsh treatment of the native people under the encomienda system of New Spain. The Mexican natives in the encomienda system were treated as virtual slaves, were poorly fed and clothed, and were greatly overworked as farm and mine laborers. This harsh treatment appears to have left them particularly vulnerable to epidemic disease.

Cocoliztli was a swift and highly lethal disease. Francisco Hernandez, the Proto-Medico of New Spain, former personal physician of King Phillip II and one of the most qualified physicians of the day, witnessed the symptoms of the 1576 cocoliztli infections. Hernandez described the gruesome cocoliztli symptoms with clinical accuracy [4,5]. The symptoms included high fever, severe headache, vertigo, black tongue, dark urine, dysentery, severe abdominal and thoracic pain, large nodules behind the ears that often invaded the neck and face, acute neurologic disorders, and profuse bleeding from the nose, eyes, and mouth with death frequently occurring in 3 to 4 days. These symptoms are not consistent with known European or African diseases present in Mexico during the 16th century.

The geography of the 16th century cocoliztli epidemics supports the notion that they may have been indigenous fevers carried by rodents or other hosts native to the highlands of Mexico. In 1545 the epidemic affected the northern and central high valleys of Mexico and ended in Chiapas and Guatemala [4]. In both the 1545 and 1576 epidemics, the infections were largely absent from the warm, low-lying coastal plains on the Gulf of Mexico and Pacific coasts [4]. This geography of disease is not consistent with the introduction of an Old World virus to Mexico, which should have effected both coastal and highland populations.

Tree-ring evidence, reconstructed rainfall over Durango, Mexico during the 16th century [6], adds support to the hypothesis that unusual climatic conditions may have interacted with host-population dynamics and the cocoliztli virus to aggravate the epidemics of 1545 and 1576. The tree-ring data indicate that both epidemics occurred during the 16th century megadrought, the most severe and sustained drought to impact north central Mexico in the past 600 years (Figure 2; [7]). The scenario for the climatic, ecologic, and sociologic mediation of the 16th-century cocoliztli epidemics is reminiscent of the rodent population dynamics involved in the outbreak of hantavirus pulmonary syndrome caused by Sin Nombre Virus on the Colorado Plateau in 1993 [8,9]. Cocoliztli was not pulmonary and may not have been a hantavirus but may have been spread by a rodent host. If true, then the prolonged drought before the 16th-century epidemics would have reduced the available water and food resources. The animal hosts would then tend to concentrate around the remnants of the resource base, where heightened aggressiveness would favor a spread of the viral agent among this residual rodent population. Following improved climatic conditions, the rodents may have invaded both farm fields and homes, where people were infected through aspiration of excreta, thereby initiating the cocoliztli epidemic. The native people of Mexico may have been preferentially infected because they worked the agricultural fields and facilities that were presumably infested with infected rodents.





Figure 2. (click image to zoom) Winter-spring precipitation reconstructed from tree ring data, Durango, Mexico (normalized and smoothed to highlight decennial variability). The tree-ring estimates explain 56% of the variance in precipitation for Durango and are consistent with independent precipitation data. This reconstruction is well correlated with the all-Mexico rainfall index (r = 0.76; p < 0.001) and with precipitation over north central Mexico, where the cocoliztli epidemics appear to have been most severe. Note the unprecedented 16th-century megadrought during both cocoliztli epidemics.



Ten lesser epidemics of cocoliztli began in the years 1559, 1566, 1587, 1592, 1601, 1604, 1606, 1613, 1624, and 1642 [10]. Nine of them began in years in which the tree-ring reconstructions of precipitation indicate winter-spring (November-March) and early summer (May-June) drought [8]. But the worst epidemic of cocoliztli ever witnessed, 1545-1548, actually began during a brief wet episode within the era of prolonged drought (Figure 3). This pattern of drought followed by wetness associated with the 1545 epidemic is very similar to the dry-then-wet conditions associated with the hantavirus outbreak in 1993 (Figure 3; [9]), when abundant rains after a long drought resulted in a tenfold increase in local deer mouse populations. Wet conditions during the year of epidemic outbreak in both 1545 and 1993 may have led to improved ecologic conditions and may also have resulted in a proliferation of rodents across the landscape and aggravated the cocoliztli epidemic of 1545-1548.





Figure 3. (click image to zoom) The winter-spring precipitation totals estimated for each year in Durango, 1540-1548 (top), 1571-1579 (middle), compared with the Palmer drought index, southwestern USA 1988-1995 (bottom). A tenfold increase in deer mice was witnessed in the southwestern USA during the 1993 outbreak, a year of abundant precipitation following a prolonged drought. The similar dry-wet pattern reconstructed for the 1545 epidemic of cocoliztli may have impacted the population dynamics of the suspected rodent host to aggravate the epidemic.



The disease described by Dr. Hernandez in 1576 is difficult to link to any specific etiologic agent or disease known today. Some aspects of cocoliztli epidemiology suggest that a native agent hosted in a rain-sensitive rodent reservoir was responsible for the disease. Many of the symptoms described by Dr. Hernandez occur to a degree in infections by rodent-borne South American arenaviruses, but no arenavirus has been positively identified in Mexico. Hantavirus is a less likely candidate for cocoliztli because epidemics of severe hantavirus hemorrhagic fevers with high death rates are unknown in the New World. The hypothesized viral agent responsible for cocoloztli remains to be identified, but several new arenaviruses and hantaviruses have recently been isolated from the Americas and perhaps more remain to be discovered [11]. If not extinct, the microorganism that caused cocoliztli may remain hidden in the highlands of Mexico and under favorable climatic conditions could reappear.



Acknowledgements
This research was funded by the National Science Foundation, Paleoclimatology Program Grant number ATM 9986074.

Reprint Address
Address for correspondence: David Stahle, Tree-Ring Laboratory, Department of Geosciences, Ozark Hall 113, University of Arkansas, Fayetteville, AR 72701 USA; fax: 479-575-3846; e-mail address: dstahle@mail.uark.edu.




Dr. Acuna-Soto is a professor of epidemiology on the Faculty of Medicine at Universidad Nacional Autonoma de Mexico. He is particularly interested in the history and environmental context of disease in Mexico.


sources:

http://www.medscape.com/viewarticle/432138?srcmp=id-051002

It's very interesting.

Yet I wonder how true it is that pre-colonial Mexican population was in the 22 millions. I think it's too high for a a Chalcolithic civilization, even one as rich as that of Mexico. I think that discussing the ancient demographics of Egypt (which can be comparable), never such a high figure was mentioned. Also, the Black Death didn't kill 80% of the population in Europe: just maybe 50% in the worst affected areas.

How do the authors justify that the population was so large before the conquest?

That doesn't seem like a good argumentation to me 300 thousand people is large but Tenochtitlan was by far the largest city of all Mesoamerica then and there weren't so many that could compare at all. When Mexico had 22 million at the start of 20th century, how many people lived in Mexico City? I bet that much more than just 300,000.

I can't make an estimate but consider please that we are talking about a warrying Chalcolithic civilization, nothing less but nothing more. The populaton of all Europe was between 50 and 70 millions at the middle of the 15th century. I just can't believe that Mexico, which was not just significatively smaller but also much less advanced in agricultural technologies and not having the rich deep soils of Atlantic Europe (that anyhow couldn't be effectively exploited with Chalcolthic tech) nor the manure produced by Eurasian cattle , could then support such a huge population.

That doesn't seem a good reply to me. True that maize and potato are great foods but the Eurasia had all the other types of cereal, plus large cattle to  fertilize and labour the fields and give milk, and it didn't make a diference. I still think that the figures are inflated. 

I would never try to justify the Spanish Empire unless I thought it was being unjustly treated, as it may be the case when the British and Nordamericans pretend theirs is better. For the rest I agree that the Spanish empire was a bureaucratic corrupt machine with very barbaric standards for the most part.

But I find hard to believe that there were 20 million people living in a not particularly rich region with Chalcolithic technology, when in the 16th century there were only between 50-70 millions in all Europe, which is a lot larger than Mexico, a lot more fertile (specially with Medieval tech that allowed the proper explotation of deep Atlantic soil) and was technologically far more advanced.

True that Medieval cities of Europe rarely had the size of Tenochtitlan (Constantinople in its good times, Cordoba surely too) but still Tenochtitlan was the largest city of all North America in that time with nothing that could compare in its context. It was the Constantinople of North America, a true megapolis.

I'm not questioning the existence of the epidemics at all, what I question is that Mexico could support so many people to start with. I am also a little skeptic about mortality rates of 80% or more, when not even the Black Death was able to do that in Europe, except in specific locations.


Edited by Maju

Just checked and Wikipedia only gives Tenochtitlan 60-130,000 people, smaller (according to the article) than Paris, Constantinople and Venice at the time of the conquest. 

On the other hand, the article on Aztecs, says that the Aztec empire produced the biggest demographic explosion in Mesoamerica: the population grew from an estimated 10 million to 15 million. That's almost half of the figures posted above.

Anyhow, it's all estimates. Just that. We don't have enough data to make good statistics.


Edited by Maju

An alternate theory to disease is famine.

The Spanish broke up the established agricultural system by slavery and seizing the best agriculeral lands from natives, taking away their capacity to feed themselves both in soil yield and labour. Mexican agriculture was based upon family units who lived above subsistence level, but evicting them from the best soil on to poorer land and removing the the fittest members of the families into slavery reduced most families to below subsistence level.

Later when the country had been plantationized so individual subsitance not possible but production efficient and enough to feed the whole populous, the deliberate exporting maize by the Spanish plantation owners for high profits overseas not leaving enough to feed the native populous, lead to many more deaths.

Both these have precidents in history. The famines in Ireland killed millions by the English appropriating lands and removing the capacity for subsistence from the locals. The great Indian famine of the 1940's in Bengal killed 8 million because the British were quite deliberately exporting too much grain and not leaving enough for the locals to eat.

 

In reality a disease was the major factor, but famine shouldn't be underestimated. Disease explains death, but famine explains lack of new births to replenish the deaths when by death so much new resources should become available to the survivors.

If we look at the black death in Europe, all countries went into an economic and population boom straight after, with huge opportunity land and wealth suddenly made available. This didn't happen in Mexico, the Spanish appropriating all the newly available wealth.

In Europe inheritance laws existed even for peasants. When a peasant's family, cousins ect, were devastated by plague, the peasant inherited their wealth. He could inherited 3-4 small hovels sell them and buy small holding, then with his new wealth have the resources to have a large family. Also the early stage of trade unionism began as shortage of labour meant established landowners were forced to pay premium rates for labour.

In Mexico as the natives died the Spanish overlords just appropriated the land and increased their estate size. The relatives of the dead continued starving at below-subsistence level. Slavery meant ensured no premium rates for labour.

 

I think the trouble with putting too much blame on disease is it gets the Spanish of the hook too easily for the annihilation of the population. Natural disaster killed the natives, but had done before, humans have evolved the capacity to replenish number quickly. It was the Spanish that destroyed them though. They removed any capacity for the natives to recover from the disease and in many cases deliberately killed the few that remained.

 

 

 

http://maize.agron.iastate.edu/maizearticle.html

...............When the Spaniards arrived in the central Valley of Mexico, land was measured by a unit (quahuitl) equivalent to 2.5 linear meters which was squared to express area (6.25 m2). Aboriginal records of parcels cultivated by individual family heads have survived, and these show that land was officially registered by area as well as soil type. Analyses by Barbara Williams of prehispanic codices show that a typical family unit of 6 individuals might cultivate 1.8 ha of land spread across 4 different parcels of varying soil quality, and that this land could produce an excess of 17% maize grain above the annual dietary needs of the family. This excess production was the family's buffer against poor production seasons, or a potential commodity for sale or barter. It clearly signified an economy beyond subsistence. In addition to each family's communal land, most heads of household contributed a minimal number of labor hours annually to maize production on parcels that supplied the needs of theocratic lords.

...................The Spanish conquest strongly impacted the social and agricultural systems of Mesoamerica. Initially, the ratio of Spaniards to aborigines in the region was small, and the Spanish population was focused on extracting mineral wealth for transport to Spain. This allowed for parallel economies to develop, where native production systems coexisted with those of the conquerors. Wheat, leavened breads, pork, mutton and Mediterranean fruits were produced and consumed by the Spaniards, while the natives continued to produce maize and beans in traditional ways. However, the interaction of the parallel economies was detrimental to the native Mesoamericans in that they were the primary source of forced labor for the Spanish mining industry, and increasingly for their agricultural enterprises. A number of legal structures were successively put in place by Spanish authorities to sanction the appropriation of native labor and property.

Several additional trends aggravated the precarious position of the native population. First, colonial Spaniards appropriated prime agricultural land surrounding major settlements for the production of their own introduced food crops, relegating the natives to marginal areas. The forced labor demands of the Spaniards during the early colonial period, as well as a series of epidemics, severely reduced the native population, impacting both general labor availability as well as the ability of the natives to produce enough to pay tributes, tithes and feed themselves. As the mining boom subsided in the 1580s and Spanish colonists looked for substitutes to generate capital they increasingly turned to agriculture. The form of agriculture they adopted was extensive (plantation agriculture, grazing), and by a number of devices (e.g., "congregations") they displaced natives and their agricultural systems into remote, mountainous hinterlands and other undesirable locations. The cumulative effect of these trends was to debase the aboriginal population and force its retrenchment to a sordid subsistence lifestyle. Economic depression in Spain during this time fueled an immigrant wave to Mexico (New Spain), and paired with the decimation of the native population the ratio of Spaniards to aboriginals increased dramatically. A famous estimate by Cook and Borah places the native population of Mexico at 1.4 million in 1595, compared with 25.2 million in 1518, when the Spanish arrived. Together with its cultivators, maize became a subsistence crop, identified with the poor and dispossessed (both rural and urban,) and used by the Spaniards primarily to feed their livestock.

....................During the colonial period Spain played an important part in the evolution of mercantile economies into global capitalist economies. The wealth Spaniards generated by extracting labor, land, agricultural produce and minerals from New Spain was cycled through an expanding trade web that embraced Asia, America, Africa and Asia. However, the boom and bust cycles characteristic of incipient capitalism raged throughout New Spain, with a disproportionally negative effect on the poor. Between 1560 and 1578 the "official" price of maize grain increased by more than 400%. In an attempt to stabilize prices colonial authorities devised a number of mechanisms, including requirement of payment of tributes in maize grain, in order to stimulate supply, but ultimately resulting in the creation of an "official granary" (alh�ndiga) in Mexico City. This was intended to buffer large fluctuations in supply and demand by becoming the central depository for all grain to be sold, and by selling this grain at controlled prices. By eliminating intermediaries and speculation the alh�ndiga was meant to eliminate fraud and sudden swings in prices. However, in order to work the official granary needed to pay top prices during scarcity and then sell the grain below market price. This operating deficit was made up by a royal subsidy. Though the scheme tended to work, it was opposed by large land owners.

Edited by Paul

Originally posted by Maju explosion in Mesoamerica: the population grew from an estimated 10 million to 15 million</span>. That's almost half of the figures posted above. Anyhow, it's all estimates. Just that. We don't have enough data to make good statistics.

Hi Maju: indeed really hard to get a good stats.
However, keep in mind that Mexico was not an aztec nation as many historians point out. Michoacan, Jalisco, the Yucatan peninsula, Zacatecas, Nayarit and the northern states were not part of the aztec empire.

Regards

Tobo: I agree that famine and over-explotaition can highly increase the death toll of disease, specially because they reduce the human natural defenses. A strong well-fed person can much better withstand a pandemic, at least statistically, while a deprived one will probably succumb. Yet, I still think we must be cautious about exaggerated figures.

Paul: What you say is very interesting. I guess, nevertheless, that the Spaniards took the land mostly for cattle herding, which is the only "industry" that can be exploited without aboundant workforce.

It seems quite clear that Spanish migration to Mexico was rather small, so they obviously didn't take the lands to work them for themselves (that would have been percieved as a joke by most Spanish colonists and even criollos, whose only aim was to make money quickly).

I found this genetic triangle which places US "Mexicans" as clearly native. This may be because creole Mexicans don't emigrate to the north but anyhow it seems like most Mexicans are hardcore native Americans in blood:



This seems to mean that Mexico has remained till today as mostly a native nation, with only traces of European blood, specially among the elites. This seems to partly contradict the hypothesis that Spaniards colonized the country at any significative level. The fact that they didn't bring African slaves either means also that, unlike in the Caribbean, there was no lack of workforce that needed to be supplied with such "imports".

Yet Moctezuma is described as having a beard by Diaz.