Tracking Early Migrants to North America
Fire and Feces would be an excellent
name for a Guns 'n' Roses cover band.
But it's also how early human presence in North America can be traced.
A recent study describes "direct evidence of both human fecal presence
and sustained burning of Arctic Alaskan landscapes as early as
32,000 years ago."
People moved from today's Siberia to Alaska through
Beringia, the area submerged
today beneath the Bering Stait.
The traditional theory, based on archaeology and study of the
ancient environmental conditions,
has been that there was a swift movement and settlement from Asia
through Beringia and on south through the Americas.
However, recent studies of traces of the earliest inhabitants' fires and feces
support the "Beringian standstill" hypothesis.
It appears that a population migrated from Asia during, or even before,
the Last Glacial Maximum and then lived in Beringia for thousands of
years before continuing south.
from the U.S. National Park Service
show today's exposed land in dark brown.
The two shades of light brown show the land that was also exposed
when water was frozen in glaciers, dropping sea level.
That land, plus the nearby land exposed today, is Beringia.
Central and Northern Alaska
The paper is:
Evidence of Ice Age humans in eastern Beringia
suggests early migration to North America,
Quaternary Science Reviews,
Volume 205, 1 February 2019, pp 35-44.
In it, the scientific team describes what they found in sediment cores
from a lake prosaicly called Lake E5.
That small lake lies just off the Dalton Highway
connecting Fairbanks to Prudhoe Bay on the north coast of Alaska.
It's in what's called the North Slope of Alaska,
on the north side of the Brooks Range that runs east–west
across the state.
The road north from Fairbanks is paved as far as the settlement of Livengood.
The paved part, about 80 miles long, is called the Elliott Highway.
The study area is just north of the "R" in "Range" in the below map.
At Livengood the road becomes the Dalton Highway,
also called "the Haul Road".
The Dalton Highway is all gravel and mud, much of it in pretty bad shape.
I've been as far as Livengood and the first few miles of the Dalton Highway.
I was doing a Linux job at the Arctic Region Supercomputing Center
at the University of Alaska Fairbanks.
About 120 miles up the gravel Dalton highway you would cross the Arctic Circle.
The lake where they did this study is another 200 miles or more
further north from the Arctic Circle.
The haul road was built as the Alaska Pipeline was built in the mid 1970s.
Originally, it belonged to the oil companies and only they could drive on it.
Now us "normals" as they call us are allowed to drive on it,
at least until you get close to the north end.
The last 10 miles is off-limits to everyone but the oil companies.
You're not supposed to take a rental car off pavement.
Of course, everyone drives a few miles onto the very southern end
of the Dalton.
But you quickly turn around and get off of it, as what little traffic exists
is almost entirely high-speed semi tractor-trailer rigs spraying gravel
and larger rocks.
The Study Area
Lake E5 is a small lake at
68.641667° N 149.457706° W,
in the northern foothills of the Brooks Range.
This map shows the area in 1956, before the Dalton Highway was constructed.
Lake E5 is one of the cluster of lakes toward left center.
The foothills leading up into the Brooks Range rise toward the south.
The Sagavanirktok, Toolik, Kuparuk, and Itkillik rivers flow north,
emptying into the Arctic Ocean.
There were glaciers in this area during the Quaternary period.
Lake E5 is in the Sagavanirktok area, named for that river.
It's an older glacial landscape from about 125,000 years ago.
E5 is one of the few lakes in northeastern Beringia that has persisted
through the cold and arid conditions of the Last Glacial Maximum.
So, its sediments are a rare archive of the area's history.
Now the Dalton highway passes just north of Lake E5,
near where the pipeline crosses the road running to the south-west,
south of the lake.
which was from Brown University, Woods Hole Oceanographic Institution,
Rice University, and the University of Massachusetts Amherst,
collected core samples.
They analyzed charcoal, pollen, organic chemicals, and lipids
they found in the lake sediment cores.
They used carbon-14 and lead-210, 14C and 210Pb,
to calibrate the ages of the layers in the cores.
Climate models tell us there was little cloud coverage, and thus very
little thunderstorm and lightning activity, from the Glacial period to today.
Lightning frequency north of the Brooks Range today
is among the lowest observed on Earth.
There are tundra fires today, especially in lower latitudes,
but very few in the North Slope foothills and on to the north.
So, almost all fires creating charcoal would have been made by human settlers,
not by the weather.
What They Found
Charcoal deposits show that fires most frequently occured in the region
between 32,000 to 30,000 years ago,
and again from 29,000 to 27,000 years ago,
and then mostly stopped 19,000 years ago.
In parallel with that, the amounts of PAHs or polycyclic aromatic hydrocarbons
were greatest from 32,000 to 19,000 years ago,
at which time they largely disappear.
PAHs are created when organic material burns.
Then there's the gold standard for detecting ancient human poop:
It's very diagnostic of human feces,
and it's stable enough to be detected in soil after millennia.
All living creatures excrete sterols.
That's a class of chemical of which cholesterol is one example.
Various sterols are excreted in feces.
The precise mixture of sterols in feces depends some on what the
But it depends more on what their body synthesizes,
and how their specific gut flora transforms that combination.
A high percentage of
also known as 5β-cholestan-3β-ol, indicates feces
"of predominantly human origin".
It is produced by the bacteria typically found in a human host,
acting on cholesterol ingested or biosynthesized by the host.
Human feces are clearly disguishable from, say, mammoth feces
by their much higher ratio of coprostanol to stigmastanol.
Coprostanol, or 5β-cholestan-3β-ol.
We eat some cholesterol, we synthesize much more,
and then our gut bacteria turn it into coprostanol.
Centuries or millennia later, scientists track our presence
by the coprostanol we leave behind in our feces.
The scientists found coprostanol in human ratios
in the sediments all through the
period since the Last Glacial Maximum,
especially during the times of greatest fire activity.
There is still some human fecal input into Lake E5,
although at lower amounts than during the Glacial.
There's no human settlement in the lake's watershed,
so it isn't flowing in from local residents.
However, scientists frequently visit from the nearby Toolik Field Station.
And, seasonal caribou hunters pass through.
As the book says,
Or, as these scientists say in their paper:
This offers insight into the taphonomy of fecal sterols;
humans need not settle within the watershed of a lake to be recorded
in its sediments, they only need to visit and defecate regularly.
They speculate that these early human settlers may have burned landscapes
as part of their hunting practices.
Maybe to drive the megafauna, maybe to lead to increased growth of the
grasses and similar plants upon which the animals fed.
Drive them now, or attract them later.
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