Smallpox And Salmonella Did More To Wipe Out Native Americans Than Genocide

Something like 95% of Native Americans died when Europeans arrived in the New World.

But, in North America, at least, the leading cause of death was an epidemic of smallpox from 1775 to 1782 that raced ahead of European colonists from the Atlantic Coast to the Pacific Coast. 

This epidemic was not intended by the colonists as a means of destroying the existing population, nor was it even really well understood. While the germ theory of disease had been proposed at that point, it was not widely accepted.

This isn't to say that Europeans did right by Native Americans before or after this epidemic. But, the bulk of the Native American deaths caused by the Europeans in North America were due to the inadvertent spread of diseases to which Native American populations never exposed to them were far more vulnerable than Europeans who had 8,000 years or so of natural selection at work building their immune systems' ability to defend against these diseases. And, the military superiority of Europeans in the century or so of conquest called "the Indian Wars" that followed, had as much to do with the residual impacts of this devastating loss of life due to new infectious diseases as it did to do with weapons or tactics.

According to the linked Wikipedia article:

The 2010 census found 2,932,248 Americans who identified themselves as being Native American (or Alaskan Native), about 0.9% of the U.S. population. No consensus exists on how many native people lived in the Americas before the arrival of Columbus, but extensive research has been and continues to be conducted. Estimates on the population of pre-Colombus North America range from a low of 2.1 million (Ubelaker 1976) to 7 million people (Russell Thornton) to 18 million (Dobyns 1983).

As the direct result of infectious diseases, conflict with Europeans, wars between tribes, assimilation, migration to Canada and Mexico, declining birth rates, the numbers of Native Americans dropped to below half a million in the 19th century. Scholars believe that the overwhelming main causes were new infectious diseases carried by European explorers and traders. Native Americans had no acquired immunity to such diseases, which had been chronic in Eurasian populations for over five centuries. For instance, some estimates indicate case fatality rates of 80–98% in Native American populations during smallpox epidemics.

The United States Census Bureau (1894) provided their estimate of deaths due specifically to war during the 102 years between 1789 and 1891, including 8,500 natives and 5,000 whites killed in "individual affairs": 

The Indian wars under the government of the United States have been more than 40 in number. They have cost the lives of about 19,000 white men, women and children, including those killed in individual combats, and the lives of about 30,000 Indians. The actual number of killed and wounded Indians must be very much higher than the number given... Fifty percent additional would be a safe estimate.

One important matter attributable to neither combat death nor disease that none of the sources above address is the loss of life, loss of land, loss of culture, and general privation associated with the relocation of Native Americans to reservations far less desirable to them than their ancestral lands, mostly during the 19th century. Such as the relocation of the Cherokee Nation by Andrew Jackson in 1838 and 1839 known as the Trail of Tears.

In a similar vein, another European disease spread long before the germ theory of disease was understood probably causes massive deaths among the people of what is now Mexico. According to Scientific American magazine, hard evidence now linked the collapse of Aztec society following first contact with Spanish conquistadors with an outbreak of Salmonella, to which that society was not adapted either in food preparation methods or in their immune systems.

One of the worst epidemics in human history, a sixteenth-century pestilence that devastated Mexico’s native population, may have been caused by a deadly form of salmonella from Europe, a pair of studies suggest. 

In one study, researchers say they have recovered DNA of the stomach bacterium from burials in Mexico linked to a 1540s epidemic that killed up to 80% of the country's native inhabitants. The team reports its findings in a preprint posted on the bioRxiv server on February 8. . . .

In 1519, when forces led by Spanish conquistador Hernando Cortés arrived in Mexico, the native population was estimated at about 25 million. A century later, after a Spanish victory and a series of epidemics, numbers had plunged to around 1 million. The largest of these disease outbreaks were known as cocoliztli (from the word for ‘pestilence’ in Nahuatl, the Aztec language). Two major cocoliztli, beginning in 1545 and 1576, killed an estimated 7 million to 18 million people living in Mexico’s highland regions. 

“In the cities and large towns, big ditches were dug, and from morning to sunset the priests did nothing else but carry the dead bodies and throw them into the ditches,” noted a Franciscan historian who witnessed the 1576 outbreak. 

There has been little consensus on the cause of cocoliztli—although measles, smallpox and typhus have all been mooted. In 2002, researchers at the National Autonomous University of Mexico (UNAM) in Mexico City proposed that a viral haemorrhagic fever, exacerbated by a catastrophic drought, was behind the carnage. They compared the magnitude of the 1545 outbreak to that of the Black Death in fourteenth-century Europe.

In an attempt to settle the question, a team led by evolutionary geneticist Johannes Krause at the Max Planck Institute for the Science of Human History in Jena, Germany, extracted and sequenced DNA from the teeth of 29 people buried in the Oaxacan highlands of southern Mexico. All but five were linked to a cocoliztli that researchers think ran from 1545 to 1550. 

Ancient bacterial DNA recovered from several of the people matched that of Salmonella, . . . Further sequencing of short, damaged DNA fragments from the remains allowed the team to reconstruct two genomes of a Salmonella enterica strain known as Paratyphi C. Today, this bacterium causes enteric fever, a typhus-like illness, that occurs mostly in developing countries. If left untreated, it kills 10–15% of infected people. . . . 

Krause and his colleagues’ proposal is helped by another study posted on bioRxiv . . . which raises the possibility that Salmonella Paratyphi C arrived in Mexico from Europe. A team . . . collected and sequenced the genome of the bacterial strain from the remains of a young woman buried around 1200 in a cemetery in Trondheim, Norway. It is the earliest evidence for the now-rare Salmonella strain, and proof that it was circulating in Europe . . . 

The existence of Salmonella Paratyphi C in Norway 300 years before it appeared in Mexico doesn’t prove that Europeans spread enteric fever to native Mexicans, says Schroeder, but that hypothesis is reasonable. A small percentage of people infected with Salmonella Paratyphi C carry the bacterium without falling ill, so apparently healthy Spaniards could have infected Mexicans who lacked natural resistance. Paratyphi C is transmitted through faecal material, and a collapse of social order during the Spanish conquest might have led to the poor sanitary conditions that are ripe for Salmonella spread, Krause and his team note in the paper. 

Even in modern times, mass deaths on this scale usually accompanies first contact experiences of "uncontacted peoples" such as certain remaining Amazonian tribes.