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Grizzly bears, black bears, wolves, coyotes, cougars/ mountain lions,bobcats, wolverines, lynx, foxes, fishers and martens are the suite of carnivores that originally inhabited North America after the Pleistocene extinctions. This site invites research, commentary, point/counterpoint on that suite of native animals (predator and prey) that inhabited The Americas circa 1500-at the initial point of European exploration and subsequent colonization. Landscape ecology, journal accounts of explorers and frontiersmen, genetic evaluations of museum animals, peer reviewed 20th and 21st century research on various aspects of our "Wild America" as well as subjective commentary from expert and layman alike. All of the above being revealed and discussed with the underlying goal of one day seeing our Continent rewilded.....Where big enough swaths of open space exist with connective corridors to other large forest, meadow, mountain, valley, prairie, desert and chaparral wildlands.....Thereby enabling all of our historic fauna, including man, to live in a sustainable and healthy environment. - Blogger Rick

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Tuesday, August 16, 2016

Bison and people


One research team has examined layers of lake sediment in the ice-free corridor that was a migration route for humans thousands of years ago.CreditMikkel Winther Pedersen

About 23,000 years ago, in a period of intense
 cold that preceded the end of the last ice age,
glaciers from west and east merged to cut off
Alaska from North America. With so much of
 the world’s water locked up in ice, sea levels
 were much lower and a now-lost continent
, Beringia, stretched across what is now the
 Bering Strait to join Siberia to Alaska. But
people who had trekked across Beringia to
Alaska could go no further because of the
 ring of glaciers that blocked their way south.
Ten thousand years later, the glaciers started
 to retreat and an ice-free corridor, roughly
900 miles long, opened between Alaska and
the Americas. In the middle of the corridor
lay a body of water, 6,000 square miles in
area, fed by the melting glaciers and known
as Glacial Lake Peace. Not until the lake had
drained away, and plants and animals had
 recolonized the corridor, would early peoples
 have been able to support themselves as they
 traversed the corridor between the glaciers.
Using new methods for analyzing ancient
DNA, the two teams of scientists have each
developed ingenious ways to calculate the
 date at which the corridor first became fit
 for human travel. A group led by Peter D.
 Heintzman and Beth Shapiro of the
 University of California, Santa Cruz,
 regards bison as the ideal proxy for
 assessing human travel through the
 corridor, given that bison were a
 major prey of early hunters.
When the glaciers merged 23,000 years
 ago, the bison populations in Alaska and
North America were separated and started
 to evolve minor variations in their
 mitochondrial DNA, a genetic element
 that survives well in ancient bones. Dr.
Shapiro’s team collected ancient bison
 bones from up and down the corridor,
 analyzed their mitochondrial DNA and
 looked for Alaskan bison that had
 traveled south through the corridor
and American bison that had traveled


The corridor was “fully open” for bison
 traffic about 13,000 years ago, Dr.
Shapiro and colleagues reported on
June 6 in the Proceedings of the
National Academy of Science, and
human populations could have
traversed it at the same early date.
“Our chronology supports a habitable
and traversable corridor by at least
 13,000” years ago, “just before the
 first appearance of Clovis technology
in interior North America,” they write.
The Clovis culture was long thought
 to belong to the first people to reach
the Americas. But archaeologists have
 now detected human presence in the
 Americas as early as 14,700 years ago.
 Since the corridor was closed at that
 time, presumably those first
immigrants took a coastal route and
 arrived by boat. But the Clovis people
 could have arrived later through the
corridor. Also, Dr. Shapiro’s team
notes, people already in North
America could have used the
corridor to travel north.


The existing southward view of the area where retreating ice sheets created the ice-free corridor.CreditMikkel Winther Pedersen

A second team of researchers agrees
with Dr. Shapiro on the general
chronology of the corridor but puts
ts earliest possible opening some
500 years later, enough to tilt the
 scales against any significant use
of it by the Clovis people. A team led
 by Mikkel W. Pedersen and Eske
 Willerslev of the University of
Copenhagen has examined ancient
 DNA and pollen from sediments
of lakes thought to be the remnants
of Glacial Lake Peace.
DNA sequences from so many species
 have now been decoded that the snippets
 of ancient DNA can be identified by looking
for matches in DNA databanks.
The researchers infer that as the lake
shrank, grasses and sedges started growing
 around it, followed by sagebrush,
buttercups, birch and willow. About
 12,500 years ago, DNA from bison,
voles and jack rabbits appears in the
 lake sediments, Dr. Willerslev’s team
 reports in Wednesday’s issue of Nature

They say that 12,500 years ago is the first
date at which the corridor would have been
 able to supply bison for human travelers.
The corridor therefore “opened too late to
have served as an entry route for the
ancestors of Clovis,” who were present
in North America by 13,400 years ago,
the Willerslev team states. It prefers a
date 400 years earlier for the Clovis
 culture than that of the Shapiro team.
The two teams, though agreeing on
the general date for the opening of the
 corridor, have each found reason to
suppose the other is wrong on the
 issue of its use by the Clovis people.


A researcher drilling through ice to recover lake sediment.CreditMikkel Winther Pedersen

Dr. Willerslev argues that the Alaskan
 and American bison lineages analyzed
by the Shapiro team could have become
distinct before, not during, the merger of
 the glaciers 23,000 years ago. “If bison
could move north and south through the
 interior ice-free corridor, why should
they not also have been able to do so
before the ice caps completely blocked
the way?” he said. If so, the presence of
 northern bison in the south or vice
 versa cannot be used to date the
opening of the corridor.
A member of the Shapiro team, John
 W. Ives of the University of Alberta,
said its dating of the split in bison
lineages was more plausible. He also
 questioned whether the present-day
 lakes sampled by Dr. Willerslev were
true remnants of Lake Peace. They
could have formed many hundreds
 of years after Lake Peace disappeared
, in which case they would omit the
earliest sediment layers and evidence
 of an earlier opening of the corridor, Dr
. Ives said.
A recent genetic survey of Native
Americans concluded that their ancestors
 had arrived in the Americas as part of a
single migration but that this group had
split in two by around 13,000 years ago.
The Shapiro and Willerslev teams agree
 that this migration must have arrived by
 some route other than the corridor,
presumably along the coast. It remains
 to be seen what role, if any, the corridor
 played in the population split that occurred
 around the time of its opening.

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