I’ve read that there were up to 100 million natives living in the Americas when the Euorpeans arrived. Within 200 years, 90% of them had been killed by smallpox etc. My question is, why did European diseases kill the native Americans but native American diseases not kill Europeans. Did the native Americans not have diseases? Were the Europeans already somehow immune to them?
There were no significant New World diseases (except maybe syphilis). Even in the Central and South American empires there was not the population density for killer diseases to develop. When a virulent strain did develop, the few persons the carriers came in touch with die and the spread is halted. In a more populous area, the disease can spread to many more people, running for a much longer time, with the all the associated chances of mutating into a more virulent plague or a more benign form.
And, as we see today with the various strains of influenza that are first seen in domestic fowls, many of the microbes that cause deadly diseases are mutations of animal diseases. There were very few domestic animals in the pre-Columbian Americas, so there was a proportionately lower pool of potential diseases.
If you are really interested in this, Jared Diamond’s Guns, Germs, and Steel gives a pretty good overview.
Oh, and remember, these Europeans were the descendants of the survivors of the Black Death only a few generations before. Given their exposure to the bubonic plague, smallpox, measles, and Ghu only knows what in their festering stinkholes of cities, there wasn’t a New World germ made that could get through their immune system. Their antibodies had more practice before they were weaned than most Native Americans had in their entire lives…
Complex question, but in simple terms Indians didn’t have any novel contagious diseases. That doesn’t mean they didn’t have any disease, but whatever diseases they did have were either found in Europe already, or else they weren’t very contagious.
Remember that a person won’t readily die from a disease they have already caught, which is why you normally only get chickenpox once, and is also the basis of vaccination. Just as importantly a person who dies from a disease can’t have any more kids. As a result the children in every generation are mostly from parents who were resistant to that disease and eventually an entire city, country or continent will become populated by people who are able to fight off a disease just because of their genetics. They are born with some resistance to that disease.
The flipside of that is that a person who has never been exposed to a disease is very likely to catch the disease, and a person whose ancestors never caught the disease is very likely to die from it.
Because Europeans already had ‘Indian’ diseases they were largely immune and little effected. But Europeans had lots of diseases the Indians had never been exposed to and the Indians caught them and died very frequently.
So why did the Europeans have all these novel diseases that the Indians had never seen? Farm animals. Indians probably reached the Americas before animals were domesticated, and they certainly never brought any animals with them except possibly wolves. And very few American animals were ever domesticated so Indians ended up with relatively few animals, just a couple of camels, dogs, turkeys and guinea pigs really. Moreover most Indians would only have seen at most two of these, so someone in South America might have seen dogs and guinea pigs but never turkeys. In contrast the average European village probably had dogs, cats, rabbits, chickens, pigs, ducks, cattle, donkeys, goats, sheep and horses at least. And over the whole of Eurasia we can add a couple of camels, buffalo, yaks, reindeer and several other species.
With all those people living close to lots of different animal species (and often keeping tem in their huts during the winter months) Eurasians contracted lots of animal diseases. That’s because diseases won’t jump species all that easily as we are finding with bird flu. They need lots of time and ideal conditions to do it, and spending 6months in a straw hut with two pigs and a cow is ideal conditions. In contrast Indians didn’t usually live with their animals and never kept large herds so very few diseases jumped species.
Indians also tended to be isolated from each other so disease soften didn’t spread. Because of trade routes plagues in India or Egypt could be in London within weeks and so when a disease did jump species all Europeans got it. Those who were resistant survived to have kids, those who didn’t left no descendants and as a result all of Europe was resistant to all diseases. Even when diseases did jump species in the Americas they tended to affect one town or at most one nation and then burn out, so most people aren’t descendants of resistant individuals.
Add to that the fact that all Indians are descendants fairly recently of a small band of travelers. They are all fairly closely related. That means that the chance of having genetic resistance to a range a novel diseases is low. In contrast Eurasians were genetically drawing from all of North Africa, Asia and Europe at the very least. They had a huge potential gene pool so it was highly likely that at least some people in any town would survive any given disease.
So what happened was that a closely related population with few endemic animal diseases and little chance for continent-wide exposure was suddenly exposed to a population with a continental resistance to multiple animal diseases. The result was as it was seen: decimation. Those few people who were genetically resistant to one disease such as smallpox were very rapidly subjected to another disease such as influenza which they had almost no chance of being resistant to, and the handful who survived both were then immediately hit with measles. The disease load was unevenly distributed and there was no real chance for resistance to even develop.
The Europeans in contrast only had to face a small number of American diseases and they had thousands of years of ancestors who had been selected to be resistant to a wide variety of diseases. As a result they escaped largely unharmed. The only disease that I know of that went the other way was syphilis, and that is still open to dispute.
Hmmm . . . so how come Europeans with their mighty-man immune systems dropped like flies when exposed to African-originated diseases such as Yellow Fever and malaria?
Because the African diseases had had even longer to “learn” how to be deadly. The African pathogens had been practicing on humans since before we were even plains chimps.
Do you mean practicing on hominids?
Here is a good article by Jared Diamond: The Arrow of Disease.
One thing I didn’t see mentioned yet, that I actually just read recently, talked about the climate early settlers in the americas encountered as the moved from far north down to more temperate climes. The book basically suggested that a good portion of diseases did not fare well in the colder environment, so that by the time they had reached the more termperate zones, those infections were basically no longer carried in any of the populace that had survived the trip over however many thousand years.
So by the same logic that Europeans have “better” immune systems because they were exposed to deadly diseases that Native Americans were not, then tropical Africans should have “super-duper” immune systems compared to Europeans, right?
I’m not trying to be a smartass, I’m just taking a little issue with the contention that Europeans had better resistance to Native American diseases because European’s historic exposure to other contagious diseases had given them “better” immune systems. Certainly natural selection would have made Europeans more resistant to those contagions that Europe had been previously exposed to, but any pathogen they encountered in North America would have evolved separately from European diseases for tens of thousands of years.
Would resistance to smallpox and plague translate into resistance to a new, totally alien disease? My understanding is that antibodies are pretty specific in terms of the pathogens they recognize, so an individual’s resistance to those pathogens does not confer any benefit at all in terms of resistance to diseases that work differently.
Except humans have not been in N.A. that long.
Picture it this way: Ten, maybe fifteen thousand years ago a relatively small group of people exited the frozen north and found a huge empty continent. These people carried few if any pathogens, since germs don’t do well in the arctic environment, especially since population was sparse. The humans and their descendants dispersed, rarely settling into large groups or anything like the crowded urban centers of Europe. Throughout both North and South America, they had few domesticated animals and never shared close quarters with animals, as was common in Europe. They remained relatively disease-free, and there was no particular advantage in having a strong immune system.
In contrast, the Europeans who invaded were the end result of many, many generations of surviving powerful pathogens since they had been living in close proximity to each other and to domesticated animals under prime conditions for the spread of disease. ONLY those with strong immune systems survived. The Europeans not only had existing defenses against things like TB, measles, etc., but their immune systems had the capability of recognizing and fighting off any new challenges encountered.
Analogy: If you’re already strong from stacking oak logs, you can also stack maple.
A log is a log, but smallpox and malaria are spread through different vectors, attack different body systems, in different ways, with different symptoms and generate different immune responses. I don’t think the analogy holds.
My point is, did the Europeans have “better” immune systems, or merely immune systems better adapted to resisting certain contagious diseases? Is there any evidence that exposure to Eurasian disease not only made Europeans more resistant to those diseases, but also other, entirely unrelated conditions? I mentioned tropical diseases, to which Europeans were in fact more suceptible than the native populations who evolved alongside those pathogens. If their immune systems were somehow inherently “better”, wouldn’t Europeans also be less likely to die of, say, infected wounds than other populations? Is there any evidence this is the case?
I am not a doctor, so I would greatly appreciate any medically informed input. But my understanding is that populations evolve specific resistance to the pathogens they are periodically exposed to, not generalized “iron man” immune systems.
I would agree with you. Europeans immune systems would be no different than any others when exposed to a copletely new disease or strain, all things (malnutrition etc) being equal. Black Death, Spanish Flu, AIDS etc have cut swathes through all populations exposed.
I’m a complete convert to Jared Diamond’s views on this subject.
By the way, I think that Diamond would agree that Europeans did not have “stronger” immune systems in general, just against epidemic disease.
Native Americans had no empidemic disesases to speak of.
The key to epidemics is population.
In small, separated hunter-gatherer populations, an empidemic type disease would kill some people and make the survivors resistant – and it would die out. These diseases only evolved in high population density herd animals. Part of the herd could hold the disease while another part lost resistance, and the disease could migrate back and forth.
Eurasians (for reasons Diamond analyzes in the aforementioned Guns, Germs, & Steel) domesticated herd animals, and raised their own population to sufficient levels (through farming) to support epidemics. The germs leaped over from animals, and then the Native Americans were in for a rude shock one day.
Sailboat
While Diamond covers this adroitly, William McNeill’s Plauges and Peoples goes into greater detail on the topic. Essentially, the diseases we now refer to as “childhood diseases” (chicken pox, various measles, rubella, et cetera) are highly virulent diseaes that winnowed out most Euopeans, leaving those and their descendants who were capable of resisting the viruses. High population concentrations combined with close proximity to domestic animals resulted in epidemics that in these epidemics. Because people on continents other than the Eurasian land mass didn’t live in dense populations and didn’t engage in animal husbandry to the extent of the Eurasians, and because travel and commerce were not as widely practiced (because of geology, levels of industry, et cetera) as they were between the states of Europe and Asia, African and American diseases never came to the same sort of equilibrium with human populations as they did in Eurasia.
The notion that Europeans are some how more generally resistant to disease, based upon their experience in the temperate North America, is belied by their exploration elsewhere, where they were beset by malaria, cholera, and other tropical diseases from which their heritage provided no defense.
Stranger
I can’t believe I’m the first to link to the definitive article on the topic (or at least, on this particular forum, it would be uncouth to dispute the author’s omniscience):
Actually, plenty of Europeans had genetic resistance to these two diseases. Malaria was endemic to southern Europe until the 20th century, and the genes that cause thalassemia also provide malaria resistance for carriers, much like sickle-cell. Likewise, cholera ravaged Europe for centuries, and the genes that cause cystic fibrosis also provide resistance to cholera.