The Old World transported a large number of diseases to the New World, but disease transmission was not bilateral. At least not in the same proportion (it is still debated whether syphilis, for example, came from America to Europe).
The fundamental reason for this asymmetry, however, lies in a factor that apparently could seem natural, ecological or even flower power: animals.
Domestication and zoonotic diseases
Most Old World diseases originated in animal livestock, especially domesticated animal farms. that were not present in America.
The Native Americans hardly had domesticated farm animals, and therefore there were not many zoonotic diseases (those spread by close contact between animals and humans). As explained Jeffrey D. Sachs in his book The ages of globalization:
The list of diseases that arrived from Europe was long and deadly, and included smallpox, influenza, typhus, measles, diphtheria, and whooping cough. Smallpox was the great mass murderer: it wiped out an alarming proportion of the native populations that encountered the newly arrived Europeans.
The exchange between the Old and New Worlds was very fruitful regarding agricultural products: America provided Europe with corn, potatoes and tomatoes; Europe provided America with wheat and rice. Sheep, goats and pigs also arrived there. And addictive products also flowed bidirectionally: tobacco or sugar cane. But the diseases were much more prevalent in the New World. simply because the natives were not so accustomed to domesticated animals.
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The news
Why were Europeans the ones who brought so many diseases to America and didn't the other way around?
was originally published in
Xataka Science
by
Sergio Parra
.