- Around 11,200 years ago in what is now Carter County,
the first Montanans made their living by slaughtering giant bison, now
extinct. They left their tools and butchered animal bones for
archaeologists
to discover at what is now called the Mill Iron Site.
-
- The earliest Montanans go as far back in prehistory as
Paleo-Indians almost anywhere in the Great Plains. They appeared as the
last ice age began to recede and thrived here, following large herds that
fed on abundant vegetation. Evidence of their presence can be found in
distinctive spear points and tools scattered in various layers of time
all over Eastern Montana prairies.
-
- Then about 8,000 to 7,500 years ago, something
happened.
-
- In the archaeological record, evidence of human
habitation
disappears, and it doesn't reappear for another 3,000 years.
-
- "We just don't find sites of that age out on the
plains in Montana," said archaeologist Steve Aaberg of Billings.
"I
can't think of one site from that period."
-
- Scientists think that what depopulated Eastern Montana
and much of the Great Plains was drought--drought more severe than we can
imagine today and of much longer duration. Sand dunes formed in parts of
Montana during that long age. Much of the West became desert.
-
- "The era is known today at the 'altithermal'.
Analysis
of pollen samples from the time suggests that vegetation changed to more
drought-resistant plants and sagebrush," Aaberg said.
-
- Responding to the inhospitable conditions, the human
population disappeared from the plains.
-
- "The archaeological record tells us there were lots
of sites of that (altithermal) age once you get into the foothills and
mountains," Aaberg said. "They were a much more attractive place
to live then. Maybe some of the big river valleys, too, although
we haven't seen any evidence of that in Montana.
-
- The Black Hills of South Dakota and the Cypress Hills
in Canada have sites from that age, indicating that people displaced by
the climate change may have found refuge there. Aaberg said
archaeologists
like to think that some of Eastern Montana's island mountain ranges could
have served the same purpose, but so far no evidence has turned up.
-
- "What we think happened was the grass cover was
so reduced, the bison population were reduced and people basically left
the plains," he said.
-
- There probably were periods during the altithermal when
the weather broke, allowing for a few years or decades of green vegetation.
But the bottom line is that the drought persisted over the Great Plains
for three millennia.
-
- In the grand scheme of things, Montana has seen climate
variations that dwarf a mere three-year drought. Long before man
appeared here, Montana's landscape experienced everything from ices ages
millions of years long to lush, warm periods where dinosaurs wallowed in
swamps. In geologic time, our modern climate is a short, warmer
period
within a glacial age that began less than 3 million years ago. More
recently,
ice sheets have expanded into the Midwest eight major times in the last
750,000 years.
-
- Research compiled by the National Oceanic and Atmospheric
Administration (NOAA) suggests that 20th century droughts, even the one
extending now into the 21st century, actually may have been fairly
mild.
-
- Since the time of human habitation, things have been
much worse.
-
- Prolonged drought may account for the disappearance of
the Anasazi from the Southwest during the 12th and 13th centuries.
-
- Tree-ring studies show that about the time British
colonists
made their second attempt to settle on Roanoke Island off the Virginia
coast (now part of North Carolina) in 1587, a three-year period of extreme
drought had begun. According to NOAA, tree rings indicate "that
the most severe growing-season drought and the most severe three-year
period
of drought in 800 years coincided with the disappearance of the Roanoke
Island colonists.
-
- A few years after the Roanoke experiment, colonists at
Jamestown struggled through a longer, though less severe drought, between
1606 and 1612. Malnutrition carried off colonists by the
hundreds.
-
- Reconstruction of drought indexes for the last 300 years
still puts the 1930s at the top of the heap for droughts dating back to
1700. There were many of similar magnitude to that of the 1950s,
the other major drought of the 20th century. NOAA lists examples
in the 1860s, 1820s and the 1730s.
-
- NOAA warns that droughts similar to those of the 1930s
and 1950s can be expected once or twice each century, and the historical
record holds evidence for even longer, more severe periods of
drought.
The difference now, of course, is that there are more people here to
experience
the consequences.
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