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CHAPTER ONE
Coming to the Americas: 50,000
B.C. to 1492 A.D.--The Humans
My grandparents sailed to America from
Austria and Galicia in the 1880s, swept up in the wave of
nineteenth-century immigration. Neglectful of family history, I
can't trace my origins back more than a century. Still, even
that small fragment of history pleases me. We take comfort in
knowing where we come from and the historical causes that
ultimately brought us here. I mention this bit of autobiography
because on occasion I visit my two young grandsons in Florida
and grandfathers of all societies have a ritualistic obligation to
(1) bring toys and (2) pass down the mysteries and genealogy
of the tribe. The problem is, my grandsons have the privilege
of being part American Indian, and there is still some
uncertainty as to their deepest roots. There are some clues,
some speculations. And that's how it should be; grandfather
stories should never precisely cleave to facts.
It might also be that my grandchildren will eventually want
to know what baggage of pathogens their ancestors brought
with them from the Old World and what microbial dangers
they faced in the New.
A speculative look at Amerindians and their diseases prior
to 1492 presents scenes of shifting complexity. Let us first
consider the weather.
Actually, there are two "weathers," inside weather and
outside weather. Its always summer in our insides, 37 [degrees] C
(96.8 [degrees] F)--the humid tropical heat of the
metabolically regulated healthy human body. Worms and
germs flourish in that milieu. The problem for the worms and
germs is that of going from host to host to perpetuate their
species since they do not enjoy, as we mammals do, the
uninterrupted heat of sex and gestation. The microbe's and the
parasite's journey of perpetuation could expose them to the
harsher climate and conditions of the outside world. Of course,
the sexually transmitted pathogens have solved their
perpetuation problem in a most rational way, and other
microbes have developed other strategies such as forming
resistant spore stages. But for many of the pathogens it can be
bitterly cold and hostile on the outside. Thus, the weather in
America at the times of successive human migrations would
certainly have dominated disease epidemiology.
A (hypothetical) wormy, malarious Asian immigrant comes
to America, circa 20,000 B.C. (or earlier, depending on which
evidence you accept). He arrives in Alaska and he defecates.
Frozen feces. Put an egg in the refrigerator and the embryo
won't develop. That's true whether the egg is chicken or
parasitic worm; all eggs need warmth to develop. The
migration maven paleoparasitologists have used this basic
biological fact in sleuthing the human colonization of the
Americas. Their train of logic begins with the fact that humans
in Africa, Asia, and Europe have been massively parasitized by
intestinal worms for many thousands of years. The common
great triad of gut worms are the roundworm (Ascaris
lumbricoides), the whipworm (Trichuris trichiura), and the
hookworms (Ancylostoma duodenale, Necator americanus).
All three worms are strictly parasites of humans; animals can't
become infected--no humans, no worms. So where did these
Old World parasites come from when they parasitized the Amerinds?
All have a life cycle in which the eggs embryonate to the
infective stage (or hatch in the case of hookworm) while in the
soil. They require a minimum balmy temperature of 20
[degrees] C (68 [degrees] F) to 25 [degrees] C (77 [degrees] F)
for them to do so. Only after they have embryonated, that
is, incubated to contain larval worms, are the eggs infective,
transmittable to a new human who will ingest these ova in
contaminated soil or food. The hookworm is a little different;
its larva develops rapidly within the egg and under optimum
conditions hatches from the egg and then dwells in the soil.
Along comes our barefoot pilgrim and the hookworm larva
penetrates the skin and, after a complex migration through the
body, comes to its home in the small intestine where it sucks
blood assiduously from the vessels of the intestinal mucosa. If
our hypothetical scenario holds true, all the original Amerind
migrants would have been "cold sterilized" of their intestinal
parasites by the time they moved south to the more parasite
equable climes. Thus any pre-Columbian worms in Amerinds
would signify that there were contacts and introductions
before Columbus and his wormy crew reached our shores.
Another example is the mother of fevers, malaria. This
disease, exquisitely dependent on temperature for its
perpetuation by transmission through the mosquito, eventually
became a major scourge of North and South Americans.
Human malaria is a constellation of four protozoan parasites of
the genus Plasmodium, all of which have an obligatory cycle
of development in Anopheline mosquitoes and only
anophelines, not the little brown nuisances (Culicines) that bite
you at night or the spotted ones that bite you in the shade of
late afternoon (Aedines). Those transmit some nasty viral
diseases that devastated the Americas, but they don't transmit
the malaria parasites. The malaria parasites require a certain
minimum temperature, 20 [degrees] C (68 [degrees] F) to 24 [degrees] C
(75 [degrees] F)
depending on the species of the malaria, to undergo their
complex cycle of transformation to the infective form in the
anopheline. Many mosquito species can live in temperatures
below the malaria parasite's life limits. Indeed some
anophelines, as well as other mosquitoes, can winter over to
await spring's warmth. However, an anopheline without
malaria is just another damned nuisance.
Today's climate doesn't gauge yesteryear's weather.
Throughout the hundreds of millions of years that the Earth has
been a planet of the living, climate has been a sometime thing.
The table on the following pages illustrates how climate has
bounced around these last 400 million years and how it is
expected to change again during the next century. Numerous
causes are responsible for these climatic changes. For one
thing, our Earth is not cemented in its heaven; it wobbles.
Sometimes it is closer to the sun and sometimes it is farther
away. Thus solar energy increases and decreases, possibly in a
cyclical fashion every 100,000 years or so. Then there are
natural and cataclysmic climate-altering events, like the impact
of an asteroid. Nor is the greenhouse effect novel to our time.
In the very ancient past, long periods of volcanism spewed
massive amounts of carbon dioxide into the atmosphere. The
industrial age has led to the well-publicized discharge of carbon
dioxide, fluorocarbons, and other greenhouse, or
ozone-depleting, gases. Meat and milk for the millions has led
to the great expansion of the cattle industry. The collective
flatulence of cows brings great amounts of methane into the
air--more greenhouse. And so when we speak of migrations
and pathogens, the climate of the times is always an
influencing presence.
When and where: If we throw caution to the winds of
hypotheses, the first Americans arrived 50,000 years ago, give
or take 5,000 years. The more accepted scenario is that sometime
around 20,000 B.C. they crossed from Siberia to Alaska,
island hopping or land bridging by way of the Bering Straits.
They were northern mongoloids with type O blood and the
identifiable bits of genetic markers that characterize the
Amerind or northern mongoloid. Theirs was a cold crossing
during the last glacial age when the ice extended from the
Polar caps. The Amerinds rapidly fanned out to the east and
south; by 16,000 B.C. they had reached our East Coast and
northern South America. A few thousand years later the
Indians were everywhere, from Alaska to Tierra del Fuego.
The latecomers were the Eskimos, the Inuits who arrived in
Alaska from the Kamchatka peninsula about 10,000 years ago.
Theirs was a lateral spread across the frozen North and forest
tundra to Greenland. Still later, about 4,000 to 5,000 years ago
a third immigration wave flowed from the Siberian forests. The
immigrants came to the American Northwest Coast and stayed
there to become the Tlingit, Athapaskan, Haida, and Eyak
tribes. From the evidence of linguistic and genetic homologies it
appears that one group wandered from the Northwest Coast to
the Southwest. These were the Navajo. That is the textbook
account of how humans first came to the Americas, although
from textbook to textbook there is controversy over the
details.
So what were people doing in northeastern Brazil 50,000
years ago?
In a remote region of northeastern Brazil, a landscape of
high sandstone cliffs and scrub bush, caves, and rock shelters
are adorned with spectacular Lascaux-like paintings. It had
been assumed, for many years, that this was the art of an
Amerind tribe who lived there 7,000 to 8,000 years ago. In
1986 a French anthropologist, Dr. Niede Guidon, upset that
applecart, and virtually every other specialist in New World
prehistory, by declaring that the oldest paintings dated to 32,000
B.C. She had the laboratory evidence, carbon 14 dating of
charcoal from domestic fires, to back up her claim!
In 1993 a doctoral candidate who had been "dissertation
digging" at Pedra Furada since 1984 sat in Paris before his
committee to defend his thesis that human habitation went
back not to 32,000 B.C. but to 50,000 years B.C. or more. That
committee had reviewed the monster four-volume, 15-pound
thesis and sat for four hours to hear the student
paleoanthropologist, Fabrio Parenti, make his defense. Parenti
argued that he had found assemblages of quartz pebbles at the
50,000 years B.C. sediment stratum in front of the rock shelter
that were not randomly dispersed in natural fashion but were
arranged in the collected fashion of humans.
Parenti's jury accepted his thesis, but for others the jury is
still out. The sceptics have a problem in accepting the pebble
proof of human habitation in 50,000 years B.C. Brazil. Then too,
there is the problem of discontinuity. There are no discovered
signs of human habitation that early anywhere in North
America. Thus, those early putative Brazilians conflict with the
historical orthodoxy that the human occupation of the Americas
was by a southward expansion from the Bering Strait
"beachhead."
One obvious catch to all this is the implication that if there
were 50,000-year-old Brazilian Amerinds who came from
Bering Strait transmigrations, then there would have to
be 50,000+-year-old Siberians and no one knows whether
humans had colonized Siberia that early or earlier.
The first human occupation of Siberia has been thought to
have been between 20,000 and 30,000 years ago--a time
which didn't jibe with the Pedra Furada advocates. That notion
persisted unchallenged until a Russian husband and wife team
of archaeologists, Yuri A. Mochanov and Svetlana Fedoseena,
found a collection of chipped rocks at a site along Siberia's
Lena River. To the untutored eye they didn't look like much of
anything more than broken rocks. But the Mochanovs
maintained that they were of human manufacture, simple tools
made by smashing one rock against another. And what's more,
the Mochanovs dated them at 3,000,000 years B.C.! New
dating analyses by a technique called thermoluminescence
date the artifacts at 500,000 years B.C. That is still very, very
old--a time when our immediate ancestor, Homo erectus, is
believed to have dispersed from Africa. And if true, as Dennis
Stanford of the Smithsonian Institute has noted, "... if people
were dealing with the cold that far north in Siberia 500,000
years ago, then a little bitty ice age like the Wisconsin (the
name given to the ice age of that period) isn't going to stop you
from getting to America." Thus if we can accept the specious
factor, the Mochanov assertion, then the Pedra Furadan as a
Siberian descendent becomes a logical possibility.
