Would a Pre-Columbian America with its own plagues still be vulnerable to Old World diseases?

Question

Most of the Native Americans in our history were killed by smallpox, measles, etcetera, and this video makes a good case for why: though the Americas had cities of their own, they lacked many options for domesticable animals, hence they did not come into contact with the beasts continuously in poorly-sanitised places, hence there was little opportunity for animal diseases to jump over to humans, hence the Americans never had their own Bubonic Plague and similar poxes.

Let's change some of that. The video leaves some details out and its arguments have been contested, but let's just suppose that for whatever reason (more domesticable animals, denser and less sanitary cities) the Americas are just as disease-ridden as Europe and Asia. It is a second Europe, in essence, but it still developed separately for ten thousand years.

Would diseases still have killed 90% of Americans but few Europeans? I am considering the following possible outcomes:

• Hardened by their own plagues, the Americans would not lose nearly as many people to European diseases. Europeans would get their own plagues. In effect both sides of the Atlantic would take a hit after first contact, but no cultures are eradicated (except for whatever results from subsequent colonisation, which is out of the scope of this question).
• Both continents now have deadly plagues that the other continent is vulnerable to. Each side of the Atlantic loses 75%-90% of its respective population.
• For some reason the loss of life is still asymmetrical.

What's more likely?

The focus is purely on the disease side. I am not interested in how colonisation would go in this scenario (this question already pretty much covers that), the long-term consequences of a different powerbase in an urbanised Iroquois Confederacy, etcetera etcetera. The essential question is: does having plagues of your own make you hardened against plagues from a different continent?

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It is safe to say that this has been a very interesting - and extremely confusing - response.

I would still be curious if someone could enlighten me (because frankly the answers all seem to be answering a different question than what I was trying to ask) with simple yes/no answers to the following steps in my reasoning.

1. Were or weren't Native Americans killed in greater numbers to Old World diseases, measured as the mortality rate for specific diseases, than the people from the Old World with whom that disease originated? Mortality rate does not include those who were already immune and never contracted the disease during a specific outbreak.
2. If they were, is this difference explained fully and entirely by societal, cultural, environmental differences with the Old World?
3. If not, is there is in fact a 'hereditary resistance' (however you want to call it) component resultant from the disease having been endemic in a population for centuries? Something biological that makes a person from one population more resistant to a disease than someone from another population, even if they never personally contracted the disease?
4. If so, is that component broad, a contributor to the base immune system, or is it just as narrow as regular immune system which will not protect against a virus/bacteria only slightly different from one it has encountered?

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It's probably pointless, but before I get even more people telling me to pick up a biology textbook, I want to try phrasing it one more different way.

It's not about whether having had one plague makes you immune to the other plague. That's not the case on several counts; first because I'm talking about resistance in general (difference can be tiny), and second because I'm talking about plagues, plural.

Does a population that has had (for centuries) many different plagues fare any better against a new plague than a population that never had any plagues?

Analogy: two children, one raised in a sterile bubble and the other grew up playing in a forest. As adults, both get the common cold (new to both since that virus changes every year): does the one who grew up sterile not suffer far more from that disease than the one who was raised in the woods?*

My question is whether there is an analogous mechanism in to human populations. Yes yes in the macro scale, over multiple generations, we're not really talking about the immune system specifically any more, but I had held it self-evident that populations do have some form of hereditary resistance to specific diseases endemic to them, as evidenced by e.g. measles which has a different mortality rate in Eurasians and Native Americans. Turns out there's strong, conflicting opinions about whether this exists or not.

But to finish my analogy: if you take two populations, and one has suffered and survived many epidemics because it lived in insanitary cities with livestock, whereas the other has largely lived in less urbanised areas, and even in the greatest cities there were less domesticated animals walking around. Is the first population more resistant (by some amount however small) to a fresh disease than the second population?

Back to my scenario: does giving the Native Americans denser cities and more animals give them an edge (however small) in resistance to fresh diseases, after they have been suffering many diseases of their own? Yes or no. That's my question: that is not a theory that I thought up out of thin air and wholeheartedly believe in.

*Yes yes I know very well that the sterile child would not develop any immune system in this scenario: it is only an analogy.

Answer 1

In humans, genetic resistance to disease does exist for specific diseases but not in general

I have not seen any studies identifying human genes that make one more resistant to all disease in general. There are plenty of cases where a specific gene causes resistance or susceptibility to a specific disease.

Lets assume that such genes appear due to a mutation in an individual. In that case they spread locally within a population over several generations thereby creating populations of people with resistance to a specific disease.

People with genes for Sickle Cell can be resistant to Malaria.
https://www.cdc.gov/malaria/about/biology/index.html

Genes for Cystic fibrosis appear to cause cholera resistance.
https://pubmed.ncbi.nlm.nih.gov/26527495/

Some people appear to have a genetic resistance to Tuberculosis causing bacteria.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6170664/

The NIH has a whole list of other genetic traits that cause disease resistance.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6150079/

Europe wasn't even immune to their own plagues

Its my understanding that plagues in Europe routinely wiped out large sections of the European population. So even the Europeans weren't really that immune to even their own plagues. So we wouldn't expect a more densely populated America to be any different. It wasn't until they learned about proper sanitation that things got better.

Plagues develop according to the living conditions present in the populations they infect. If both continents contain similar living conditions then we would expect that a plague from one continent might spread well on another. But because the plagues developed in isolation, neither side would have immunity. The likely scenario is that plagues would hit both continents hard.

Answer 2

does having plagues of your own make you hardened against plagues from a different continent?

I would answer looking at the fresh case of Covid19. No matter where the virus hit, the local variety of infections doesn't seem to affect how well or bad the population answers.

I would expect the same to apply also in this case.

Answer 3

One word: syphilis. Of which the great virulence among Europeans for the first two or three centuries after it came from the Americas shows that it doesn't matter if they had contagious diseases in general, only that they didn't have that particular disease or that class of diseases.

Answer 4

Yes. Immune systems aren't the only thing that needs practice dealing with outbreaks.

How good one countries zoonanautic outbreaks inoculated them for an introduced outbreak from another country will be a bit hit and miss. American Cow pox could protect against european smallpox, but maybe some other disease might not be protected. Who knows exactly how the immune systems play out and what new stuff infects Americans in this world.

What will help;

• Quarintine procedures in force from last outbreak.
• recognising it's a medical issue and not a religious one.
• practice at locking down cities.
• symptom checking incoming people.
• isolating those who display certain symptoms.
• Doctors knowing how to treat respiratory problems.
• First aid training
• Sanitary lessons from the last plaque.

A case study for this is Asian countries that were hard hit by SARS doing better than expected with covid. An example is Vietnam. (That article is to the latest in a series on what Vietnam is doing against covid, I'd recommend reading all the series).

Singapore also showed some very early promising results as a result of what they learnt from SARS, however their later figures declined as they lost control of workplace dorm infections.

Answer 5

Yes and No...

It is unlikely that the Natives would have a natural herd immunity when dealing with diseases that would have evolved in such isolation, but they would still fare much better. One of the biggest reasons that the Natives lost so many people to European plagues was culture. In Europe where plagues were common, they knew to isolate the sick, burn the bodies, lock down travel etc. Smallpox, for example, was nearly as deadly to Europeans as Americans, but among Indigenous Americans, when a person got sick, it was generally their culture for everyone to come and visit them to take care of them until they got better. If America had had its own history of plagues, then they simply would not have done this as a standard practice; so, even if Europe brought in some really deadly diseases, they would not have been able to spread nearly as much.

You might have still seen a big die off, but probably no worse than the black death which killed 1/3 Europeans in the 14th century rather than the 9/10 that they actually experienced.

That said, even the figures for the black death were only that high because they did not understand that it passed through fleas; so, many normal precautions like masks and social distancing did not work. In all likelihood, the outcomes would have been much less severe than that since Smallpox spreads more like a normal disease (person to person). As for how well Europe would fair... well as it turns out the natives did give Europe a few pretty nasty diseases in exchange. Both syphilis and tuberculosis most likely originated in the Americas. Either one of these diseases could have ravaged Europe nearly as badly as European diseases did to America, but because the Europeans responded to outbreaks better, they never spread to critical levels.

Answer 6

I don't think it's because it's from different continents. A completely new plague would affect all in the same way unless there is a situation like cowpox and smallpox, where people who have had one cannot contract the other in a severe form.

Measles and suchlike affect populations differently only because of built up resistance.

Measles has been around some areas for a long long time. So it was survived by some who had natural resistance. Their descendants inherited some resistance and there were multiple cycles strengthening this until it's not even deemed life threatening except to an unlucky few in some locales.

In Polynesia, measles all but depopulated some Islands, the survivors resistance carried on in the people today but it's only a couple of generations. So while I'm half European and can consider measles more inconvenient than a danger with a lot of generations of survivors reinforcing the resistance, 85 kids here died of it during the last outbreak and thousands were seriously ill, it's no coincidence that these were almost all full-blooded natives.

Answer 7

Let's talk about how a plague can wipe out a civilization. Assume a generic disease hits a generic pre-industrial village. It's not even that bad of a disease; everyone will just be knocked out for a couple weeks. It can still kill everyone in the village. Why? Because everyone gets sick at the same time. In this situation, there's nobody who can help treat the sick, nobody to cook, nobody to gather wood for fires, and nobody to draw water, because everyone is sick. (That last one can be the deadliest if the illness includes diarrhea.) If one person from the village at a time got sick, someone else could care for them, and there would be few or even no deaths. Even if only one person happens to be immune, the death rate drops like a rock.

There is no particular reason to say that Europeans have "better" resistance to any diseases, they just had already been exposed enough to European diseases that this particular effect didn't hit them. If Native Americans had livestock kept in the same conditions Europeans had, they would not have been more resistant to European diseases. The only change would be that Europe would probably have caught something nasty from America.

With this in mind:

1. Were or weren't Native Americans killed in greater numbers to Old World diseases, measured as the mortality rate for specific diseases, than the people from the Old World with whom that disease originated? Yes, mostly because of this factor.
2. If they were, is this difference explained fully and entirely by societal, cultural, environmental differences with the Old World? No; the difference is because everyone got sick at the same time.
3. If not, is there is in fact a 'hereditary resistance' (however you want to call it) component resultant from the disease having been endemic in a population for centuries? Something biological that makes a person from one population more resistant to a disease than someone from another population, even if they never personally contracted the disease? No.
4. If so, is that component broad, a contributor to the base immune system, or is it just as narrow as regular immune system which will not protect against a virus/bacteria only slightly different from one it has encountered? Not relevant.

Answer 8

Yes

Yes, they would still be vulnerable.

My doctor just admonished me to get this year's flu shot. I've never had one and I've never had the flu. He and I talked about the science literally because too many people think as you do.

Immunity from one disease does not make you in any way immune to a disease your body hasn't encountered before. All it does is protect you from becoming ill from that first disease, which is good, because if you catch it your body's immune system becomes compromised, making it easier to catch another disease.

That is, in fact, how influenzas tend to kill — by compromising the immune system so that another disease (often bacteriological rather than viral) can set in. In the case of influenza, the most common secondary disease (and the one that almost always kills the patient) is pneumonia.

Consequently, where a virus originated is factually irrelevant. Whether or not an individual (an individual, not a geographic location) has been exposed to it is all that matters. When such an individual contracts a disease they've not been exposed to before (any disease, from COVID-19 down to the measles) their body begins developing antibodies. And a race begins. If the body can develop antibodies fast enough, the patient survives and with that new capability becomes fundamentally immune from further infection from that one disease (this isn't 100% true, but statistically it's close enough to 100% that we can leave the details for another day).

The reason diseases like mumps, small pox, measles, etc. have been declared eradicated is because humanity developed vaccines to help individuals build antibodies without having to actually become infected by the disease. So long as enough people are immunized (herd immunity), the whole of society is functionally protected.

The problem with your scenario is that you believe that immunity from one set of diseases grants immunity to another set and, for some reason, you think that geography is involved.

It's not.

The reality is that if the Native Americans had immunity to all sorts of diseases but no immunity to measles, then when the Europeans exposed them to measles, they'd contract it.

However

What all that immunity would do is keep the body from catching those diseases, reducing the liklihood of the body contracting the new diseases. A healthy body can fight a new disease better than an unhealthy body (that should be obvious).

My belief is that the plagues that swept the Native Americans would have still happened. At best, the number of deaths would have dropped. If 90% can be believed, maybe only 70% would have happened.

But they would still happen.

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Edit

There is no such thing as a "base immunity." This means there is no combination of diseases which, once survived, produce any level of immunity against another disease. Even influenzas, which one might think are of a "general class" that could create an immunity that protects against new influenzas, don't enjoy this benefit. Each and every disease is a threat to anyone, anywhere, who hasn't been exposed to it.

To reiterate my original answer, the benefit of having been infected by many diseases is that your body will remain healthy, giving it the best chance of survival should it be exposed to a new disease.

There are two ways immunity to a specific disease can be inherited.

(1) A population is infected. Again and again. People die — a lot of them. The survivors have a natural immunity. To intone the indomitable Morgan Freeman from the movie War of the Worlds (2005):

From the moment the invaders arrived, breathed our air, ate, and drank, they were doomed. They were undone, destroyed, after all of man's weapons and devices had failed, by the tiniest creatures that God in His wisdom had put upon this Earth. By the toll of a billion deaths Man had earned his immunity, his right to survive among this planet's infinite organisms. And that right is ours against all challengers, for neither do men live, or die, in vain.

(2) By birth, the antibodies in a survivor mother can be passed to her children. However, this process is imperfect and only temporary because the baby's body has not learned how to build those antibodies.

For example, if the mother has had chickenpox, she'll have developed immunity against the condition and some of the chickenpox antibodies will be passed to the baby.

But if the mother hasn't had chickenpox, the baby won't be protected.

Immunity in newborn babies is only temporary and starts to decrease after the first few weeks or months.

Breast milk also contains antibodies, which means that babies who are breastfed have passive immunity for longer. (Source)

Neither solution guarantees protection from that one disease. They only reduce the likelihood of infection. Regrettably, there are only two ways to actually protect an individual from future infection (no matter who it is and no matter what the disease is):

(a) They can become infected by the disease and survive (their body learns to create its own antibodies).

(b) They can be artificially inoculated with a vaccine (forcing the body to learn how to create antibodies without threatening, or with less threat, to the body).

To reiterate my answer...

Yes, they would still be vulnerable

Answer 9

does having plagues of your own make you hardened against plagues from a different continent?

Not all of them. Possibly some (don't count on it).

That's a bit like asking whether having risked being maimed by lions offers any protection against being maimed by leopards or crocodiles. Obviously it does not.

There is a very tiny possibility that the pathogen from across the sea actually targets some vulnerability that had been independently exploited by a local plague, which wiped out most potential victims. Survivors are now much more resistant to the local plague, and coincidentally immune to the new one.

This happened in humans when the Black Death came to Europe in 1348. The mortality was much higher among those Europeans who had a specific chemokine genetic marker; as a consequence, the survivors that got to reproduce more had, more often than not, the mutated form (dubbed CCR5-delta-32). Five centuries later, a zoonotic virus arose from a different continent, Africa, causing AIDS - and the European mutants turned out to be significantly more resistant.

Answer 10

This is sort of like asking if a nation that had become resistant/immune to cholera would then be resistant/immune to small pox. There is a fairly low limit to the overall resistance an immune system can create, beyond which it develops countermeasures to specific maladies that it had encountered before. It doesn't matter how strong an immune system your body has due to evolution or exposure when you're dealing with an infection that your body has never seen before. (It is able to fend off generic diseases or other invading foreign entities that are either limited in scale or unaggressive in attacking the host cells, but we aren't talking about those.)

The only thing that might have changed with the Native Americans is that they maybe would have had better precautions in place to deal with plague outbreaks, but the contagiousness and severity of the infections themselves would not have been lessened whatsoever.

Answer 11

If you preserve the asymmetry of travel, with more people travling from Europe to the Americas than the other way, the problem persists. The incubation period for disesases is shorter than the time to cross the Atlantic. Healthy carriers are traveling from Europe to America. Europeans who contract illnesses in the Americas:

1. Die in America, so do not spread the disease to Europe
2. Die on board ship, and are buried at sea, so may or may not spread the disease further
3. Catch the disease on the ship from a dying person and survive to reach Europe

I believe that the magnitude of the disease vectors pointing from Europe to America are much greater than in the other direction. The Americas will be disproportionately affected.

From https://thesouthern.com/progress/section3/searching-for-clues-in-the-disappearance-of-the-mississippians/article_d6c13308-f414-11e0-b052-001cc4c03286.html

When Father Jacques Marquette led an expedition down the Mississippi River in 1673, becoming the first European to penetrate into the Southern Illinois wilderness, his party met with a scene fit for a ghost story.

The group saw massive mounds at intervals within sight of the river obviously built by inhabitants of the region, and yet there was no sign of human life. Marquette had floated into what archaeologists now call the "vacant quarter" of North America. The mound-building Mississippians of Southern Illinois, southeastern Missouri, Tennessee and along the Ohio River into Southern Indiana and Kentucky had suddenly and without warning vanished after 1450.

No one knows what wiped out the Mississippian civilization, but disease is a good bet, and it happened before Columbus arrived. North America started off at a great disadvantage.

(More recent research suggests climate change causing flooding and other problems: https://news.berkeley.edu/2020/01/27/new-study-debunks-myth-of-cahokias-native-american-lost-civilization/ )

Answer 12

Were or weren't Native Americans killed in greater numbers to Old World diseases, measured as the mortality rate for specific diseases, then the people from the Old World with whom that disease originated? Mortality rate does not include those who were already immune and never contracted the disease during a specific outbreak.

They were. By a lot. To the point where europeans/Americans (as in citizens of the USA) thought North America was some sort of garden paradise because of all the seemingly-random well husbanded land. It wasn't random, the previous owners just died in huge numbers and abandoned many areas. Syphilis et al that were imported from the Americans to Europe were bad and killed boatloads of people, but nowhere near the average fatality rate the Native Americans suffered. Smallpox, on the other hand, is deadly to adults and more importantly spreads rapidly. Europeans survived because they tend to catch it early AND they have immune people to care for the sick. Meanwhile the native americans in any given village essentially all got sick at once and had nobody healthy to look after the sick. So even IF (as some argue) smallpox wasn't really more deadly to native americans, a case that a european would survive with care would kill a native american, because they had no healthy caregivers.

If they were, is this difference explained fully and entirely by societal, cultural, geographical differences with the Old World?

Almost. Syphilis, being an STD, is harder to transmit that, say, smallpox. It also doesn't kill as fast. Same goes (more or less) for the other New World diseases. If tuberculosis transmitted a bit better, or killed quicker, that might have changed the numbers. The delayed-deadliness of New World diseases could be a factor of less cramped livestock co-habitation, but mutations are also somewhat of a crapshoot.

If not, is there is in fact a 'hereditary resistance' (however you want to call it) component resultant from the disease having been endemic in a population for centuries? Something genetic that makes a person from one population more resistant to a disease than someone from another population, even if they never personally contracted the disease?

Yes, but not quite how you may be imagining. For example, Sickle cell anemia (common in people of african descent), is considered bad for a whole host of reasons such as increased risk of stroke, but also gives a genetic advantage against malaria. It's not so much that your resistance to maleria is passed down via some sort of inherited immunity, but your genetics may dispose you to better resist the effects of certain diseases. Which is why Native Africans do just fine in central africa, but white people died their in droves there from malaria. It wasn't that Africans were born with malaria antibodies or had different/better immune systems, they had a genetic predisposition to make the disease survivable.

If so, is that component broad, a contributor to the base immune system, or is it just as narrow as regular immune system which will not protect against a virus/bacteria only slightly different from one it has encountered?

The contributions which gives "hereditary resistance" to disease are genetic in nature and have little or nothing to do with a given person's immune system.

Answer 13

To summarise the findings of all the answers, as I understand them:

• People of a local population may or may not be more resistant to a disease that's been with them for a number of centuries (the answers disagree).
• Any such endemic resistance would be in the form of genetic traits - like Sickle cell anemia in African people that happens to make them more resistant to Malaria - not in the form of a general immune system booster.
• Antibodies to one disease may in some cases give immunity to different, related diseases, but that mechanism cannot be relied upon.
• A local population is more often resistant to a disease that's endemic to them because a fraction of the population will have had it and be immune to it, thereby preventing that they all get it at once and lose people because they cannot spare the manpower to treat them.
• For dealing with a foreign disease, the more important factor is that a Native American population familiar with plagues would be culturally better equipped to deal with the new Old World diseases they would still suffer from; for example, they would know to burn bodies and prevent contact with the ill.

Feel free to edit if I have once again misunderstood everything.

Answer 14

I'm posting this as an answer instead of a comment due to its length, but I want to emphasize the point @user3757614 made above: a major factor in the die-off of Native Americans exposed to European diseases wasn't the disease itself, but lack of care for the sick.

There is evidence for this. A similar situation occurred in the late 19th century: isolated communities of indigenous people were exposed to foreign diseases which in many instances effectively wiped out the populations. However, where there was someone to tend to the sick -- often white missionaries -- to tend to their fires, provide food & water, empty their chamber pots -- the local communities suffered much fewer deaths. (I don't remember the study that documented this, but a skilled researcher ought to be able to find the paper the published this finding.)

Many times having European cultural practices forced on natives peoples was what killed them, not the diseases. One example of this was the Yaghan of Tierra del Fuego, who were accustomed to wearing few clothes that could be kept dry by the small, carefully controlled fires they had in their canoes. When Western missionaries convinced them to wear "more appropriate" clothing made of thicker material, these could not be kept dry by their fires, which led to the natives dying of pneumonia. (The effects of the Tierra del Fuego Gold Rush in the late 19th century also didn't help them.)