Why is it that Native Americans died from diseases brought by the Europeans, but Europeans didn’t die in great numbers from Native American diseases? –Bob Kelso

There may have been at least one Native American bug that wiped out a few boatloads of Europeans; see below. But in general you’re right: percentagewise, and probably absolute numberswise, a lot more Native Americans died of European diseases than did Europeans of American diseases. The natives had no resistance to smallpox, influenza, or plague, or even to mild (to us) diseases like measles. Entire populations were virtually wiped out, with some Atlantic-coast tribes losing 90 percent of their adult members. Some historians go so far as to say European diseases reduced the precontact population of the New World as a whole by 90 percent or more. One says the population of central Mexico was reduced from 25 million in 1519 to 3 million by 1568 and only 750,000 by the early 1600s, 3 percent of the preconquest total.

Granted, some of these horrifying numbers may be arrived at by exaggerating the size of the original population. One researcher says there were 18 million people living north of Mexico before Columbus, but a more conservative estimate puts it at 4 million and some say only 1 million. Maybe there were only 12.5 million pre-Columbian Mexicans, not 25 million. Even so, we’re talking 94 percent mortality for central Mexico, maybe 87 percent for the Americas overall, reducing the population from 80 million in 1500 to 10 million 50 years later. One can make a good case that it was European germs rather than European military prowess that conquered the New World. One can also argue that disease led to the African slave trade. The conquistadores would have been happy to enslave local labor, except that it was dead.

Why were the natives so vulnerable? The best guess is that Europe had been a crossroads for war and commerce for millennia and so had encountered an extraordinary number of pestilences, while the Americas were isolated and had not. As a consequence Europeans had developed some resistance to disease, but Native Americans hadn’t.

That’s not to say Europeans were immune. While millions of Native Americans died of European diseases, millions of Europeans died of European diseases too. In fact, one reason the natives suffered such catastrophic mortality was that Europeans arriving in the New World were walking petri dishes. In some years 25 percent of European immigrants died at sea, often of diseases, such as typhus, that they’d picked up in the ports they’d just left. Epidemics were common in Europe. It was not unusual for a town to lose a third of its population to some new outbreak. Armies invariably lost more soldiers to disease than to combat. (Judging from U.S. figures, this remained true up until World War II.)

Compared to Europeans, historian Thomas Berger says, Native Americans were remarkably healthy. Most lived not in unsanitary cities but “in small, isolated bands and were therefore less likely to spread diseases over large geographical areas. They kept few domesticated animals to attract parasites.” Berger even claims that the few germs they carried with them during the original migration across the Bering land bridge didn’t survive the arctic “cold screen”–a little hard to believe since the humans made it through OK.

However Edenic the New World may have been, it may have harbored one bug that did kill a lot of Europeans: syphilis. The question remains controversial. The first known cases of syphilis showed up in Italy in 1494, and we know what happened in 1492. Many believe the Spanish contracted the disease on Hispaniola (now Haiti and the Dominican Republic) and gave it to the Italians and French at the siege of Naples. Bone damage characteristic of syphilis found at pre-Columbian New World archaeological sites supports this view. But others say syphilis was merely an old European disease that prior to 1500 had been improperly diagnosed. Even if it did originate in the Americas, syphilis was little enough payback for the disaster visited on the original inhabitants of the Americas by the subsequent ones.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.