Re: diseases and immunity

Joel and Lynn Gazis-Sax (gazissax@best.com)
Wed, 03 Jul 1996 18:01:49 -0800

Setting aside the now fashionable "turn-about-is-fair-play" tactic of calling
Domingo, Mary Beth Williams, and Eric Brunner "ethnocentric" which
certain nonprofessionals and demogogues are using in an attempt to rebut
the main argument about the value of statistics which show that the
continent was empty at the time of contact, let me turn to some findings
that I've turned up by examining several historical chronologies.

* Strangely enough, Phillip Deitiker is probably right about the population
of Rome at the time of the Empire. These figures have been known since
the time of Montesquieu and Robert Wallace who noted that the ancient
population probably exceeded that of early 18th century Europe.

* Between the high point of the Roman Empire and the time of Montesquieu
and Wallace, Europe was overrun by several varieties of disease such
as typhus, various "sweating sicknesses", measles, and the ever-popular
Black Death. These had a tendency to wipe out populations.

* One can see a pattern in these deaths: they aren't all over Europe,
but hit specific areas. Other areas are spared, until later. When
the big plagues hit again, they hit towns that have not suffered yet
or cities, like London, which are receiving steady streams of fresh
blood from the countryside. These people didn't bring the plague
with them: they caught it when they arrived because their genes
made them more susceptible. The less movement of a population, the more
resistance it develops to these diseases.

* The "superior hygiene" of the Europeans has been brought up as an
explanation for the differences in immunity levels. The opposite may
be the case. First, inferior hygiene made the Europeans susceptible
to more diseases than the Native Americans during these many centuries.
The general slovenliness of Europeans (note I am of European descent)
definately hurt in the short run, but helped them in the long run by
weeding out the weaker people. If I am not mistaken, the Black Death
never really killed people in America like it did in Europe.

* Another hygienic factor that was apparently not the fault of the
Europeans themselves was a shift in what kind of rats infested their
houses. During the Middle Ages, the black rat was endemic to Europe.
These rats carried the fleas that were the source of the Black Death.
Later, in about the 16th century, brown rats began pushing the black
rats out of their niche. Brown rats were less likely to carry the kind
of flea that carried the Black Death. Finally, the house rat replaced
the brown rat and incidents of plague declined even more.

* Even as incidents of plague continued to hit cities throughout Europe,
the numbers of those dying dropped. In one of the last cases of plague,
in Marseilles (18th century), 50,000 people died. The plague failed to
spread over Europe as it had before. Fatalities in Italian outbreaks also
dropped as Italians apparently began to be composed more and more of people
who possessed greater resistance to the disease.

* Another interesting statistic that comes out in looking over several
chronologies is that in 1505, the population of New Spain was over
11 million people. Ten years later, it had around 6 million and ten
years later only one million people. Reports of epidemics were rife
during this period, which matched the period of first contact and
conquest of Mexico.

Conclusions? The chronologies tend to support the following conclusions:

* That there were more people alive in the Roman Empire than there were
in subsequent periods of time up to the mid-18th century.

* That Europeans were exposed to many infectious diseases at an earlier
period than the peoples of the Americas.

* That this exposure weeded out those less able to withstand the diseases
and caused European populations to become more resistant to them.

* That improvement of hygiene (a product of the germ theory of disease --
not popular until the late 19th century) was less a factor than a
switch in the variety of rat which infested European households.

* That populations in the Americas dropped up to 90% or more when Europeans
brought their diseases with them. (Note that African slaves also brought
diseases with them -- things like Yellow Fever and Malaria which decimated
American cities from time to time until the mosquito link was found!)

We see nothing more than an evolutionary process at work. Good science
requires that we measure only that which can be measured and not try
to invent explanations which suit our personal whims and prejudices. And
most of us will be fine until a new infectious disease appears, one for
which the majority of us have no resistance for.

Regards,

Joel GAzis-SAx

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