[lit-ideas] How the Old World Conquered the New via infectious diseases
- From: "Lawrence Helm" <lawrencehelm@xxxxxxxxxxxxxx>
- To: <lit-ideas@xxxxxxxxxxxxx>
- Date: Sat, 10 May 2014 12:44:07 -0700
Here are a few paragraphs from Cochran and Harpending in regard to the ease
with which the Spanish conquered the Amerindians of America:
“The Amerindians migrated from Northeast Asia some 15,000 years ago. They did
not carry with them crowd diseases that arose after the birth of agriculture,
nor did they carry the genetic defenses that later developed against those
diseases. Since their path to the New World went through frigid landscapes like
Siberia and Alaska, they left behind some of the ancient infectious diseases
that were vectorborne or had complex life cycles—malaria and Guinea worm, for
example. . .”
“Although Amerindians did develop agriculture independently—a very effective
agriculture that included some of the world’s most important crops, such as
maize and potatoes—they domesticated few animals, mostly because they had
already wiped out most of the species suited to domestication. . .”
“. . . infectious disease was so unimportant among Amerindians, selection most
likely favored weaker immune systems, because people with weaker immune systems
would be better able to avoid autoimmune disorders, in which the immune system
misfires and attacks some organ or tissue. Type 1 diabetes, in which the immune
system attacks the pancreatic cells that make insulin, and multiple sclerosis,
where it attacks the myelin sheaths of the central nervous system, are
well-known examples—both are rare among Amerindians. A less vigorous immune
system would have been an advantage under those conditions.
This Amerindian vulnerability was a primary reason for European success in the
Americas. Epidemic disease, particularly smallpox, interfered with armed
resistance by Amerindians and thus played an important part in the early
Spanish conquests. In Mexico, where Hernán Cortés and his troops had made the
Aztec emperor their puppet, the Aztecs rose against them, killing Moctezuma II
and two-thirds of the Spanish force in the famous “Noche Triste.” The Aztecs
probably would have utterly destroyed the invaders, were it not for the
smallpox epidemic under way at the same time. The leader of the Aztec defense
died in the epidemic, and Cortés and his men conquered the Aztec Empire. It is
hard to see how Cortés could have won without those microscopic allies, since
he was trying to conquer an empire of millions with a few hundred men.
Cochran, Gregory; Henry Harpending (2009-01-27). The 10,000 Year Explosion: How
Civilization Accelerated Human Evolution . . .. Basic Books. Kindle Edition.
Comment: We’ve known about the conquering of the Amerindians by the
Conquistadors for a great many years, but what we didn’t know until scientists
began working with the human genome (completed in 2003) was that the
Amerindians didn’t have the diversified HLA systems. In the Old World with all
its years of agriculture since 8,000 BC, humans were subjected to a variety of
diseases from animals, poor hygiene, and the close proximity they were to each
other in cities. Having different HLA alleles expands the range of pathogens
that our immune systems can deal with. Amerindians didn’t have that diversity.
Many tribes had only a single HLA allele.
This also explains why the British had such an easy time colonizing North
America. The Amerindians had been decimated by disease. The New World was
largely empty.
Lawrence
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