A thousand years ago, a city rose on the banks of the
MississippiRiver, near what eventually became
Saint Louis. Over miles of rich farms,
public plazas and earthen mounds, the city — known today as Cahokia — was a
thriving hub of immigrants, lavish feasting and religious ceremony. At its peak
in the 1100s, Cahokia housed 20,000 people, greater than contemporaneous
Paris.
اضافة اعلان
By 1350, Cahokia had largely been abandoned, and why people left
the city is one of the greatest mysteries of North American archaeology.
Now, some scientists are arguing that one popular explanation —
Cahokia had committed ecocide by destroying its environment, and thus destroyed
itself — can be rejected out of hand. Recent excavations at Cahokia led by
Caitlin Rankin, an archaeologist at the University of Illinois at
Urbana-Champaign, show that there is no evidence at the site of human-caused
erosion or flooding in the city.
Her team’s research, published in the May/June issue of
Geoarchaeology suggests that stories of great civilizations seemingly laid low
by ecological hubris may say more about our current anxieties and assumptions
than the archaeological record.
In the 1990s, interpretations of archaeological research led to
the proposal that the Cahokians at the height of their city’s population had
cut down many trees in the area. This practice, they said, led to widespread
deforestation, erosion and increasingly severe and unpredictable local
flooding.
Rankin and her colleagues set out to discover more about how
Cahokia’s environment changed over the course of its development, which they
hoped would test whether that hypothesis was true. Excavating in Cahokia’s
North Plaza — a neighborhood in the city’s central precinct — they dug at the
edge of two separate mounds and along the local creek, using preserved soil
layers to reconstruct the landscape of 1,000 years ago. This area had the
lowest elevation, and they presumed it would have endured the worst of any
flooding.
Those soil layers showed that while flooding had occurred early
in the city’s development, after the construction of the mounds, the
surrounding flood plain was largely spared from major flooding until the
industrial era.
“We do see some negative consequences of land clearance early
on,” Rankin said, “but people deal with it somehow and keep investing their
time and energy into the space.”
Rather than ruining the landscape, she added, Cahokians seem to
have reengineered it into something more stable.
That finding is in keeping with our knowledge of Cahokian
agriculture, said Jane Mt. Pleasant, professor emeritus of agricultural science
at Cornell University, who was not involved in the study. While Cahokians
cleared some land in the uplands, Mt. Pleasant said, the amount of land used
remained stable. While heavy plow techniques quickly exhausted soil and led to
the clearing of forests for new farmland, hand tool-wielding Cahokians managed
their rich landscape carefully.
Mt. Pleasant, who is of Tuscarora ancestry, said that for most
academics, there was an assumption “that Indigenous peoples did everything
wrong.” But she said, “There’s just no indication that Cahokian farmers caused
any sort of environmental trauma.”
If anything, said John E. Kelly, an archaeologist at Washington
University in Saint Louis, the explanation of a Cahokia battered by denuded
bluffs and flooding actually reflects how later European settlers used the area’s
land. In the 1860s, bluffs upstream from Cahokia were cleared for coal mining,
causing enough localized flooding to bury some of the settlement’s sites.
European deforestation created a deep overlying layer of eroded sediment,
distinct from the soils of the precontact flood plain.
“What Caitlin has done in a very straightforward fashion is look
at the evidence, and there’s very little evidence to support the Western view
of what native people are doing,” Kelly said.
Why, then, did Cahokia disappear? Environmental factors, like
drought from the Little Ice Age (1303-1860), may have played a role in the city’s
slow abandonment. But changes in the inhabitants’ politics and culture shouldn’t
be overlooked, Mt. Pleasant said. By the 1300s, many of the great mounds of
Central Cahokia stood abandoned, and life in the city had seemingly shifted to
something more decentralized. Nor did the peoples of Cahokia vanish; some
eventually became the Osage Nation.
Outside of natural disasters like the volcanic eruption that
destroyed Pompeii, Rankin notes, the abandonment of a city tends not to happen
all at once. It’s more like a natural progression as people slowly ebb out of
an urban environment that stops meeting their needs.
“It doesn’t mean that something terrible happened there,” Rankin
said. “It could be that people found other opportunities elsewhere, or decided
that some other way of life was better.”
The view of Cahokia as a place riven by self-inflicted natural
disasters speaks more to Western ideas about humanity’s relationship with
nature, Rankin said, one that typically casts humans as a separate blight on
the landscape and a source of endless, rapacious exploitation of resources. But
while that narrative resonates in a time of major deforestation, pollution and
climate change, she said it was a mistake to assume that such practices were
universal.
“We’re not really thinking about how we can learn from people
who had conservation strategies built into their culture and land use
practices,” Rankin said. “We shouldn’t project our own problems onto the past.
Just because this is how we are, doesn’t mean this is how everyone was or is.”
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