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