LA Times article forwarded by Carolyn Weiss
THE AMERICAN MASTODON may not have
been hunted to extinction. Northern mastodons may have died off as
forests disappeared in the last glacial period.
Meat-hungry humanity has long been
suspected of hunting North American megafauna to extinction, but new
research suggests that Homo sapiens may have gotten a bum rap — at least
when it comes to the demise of the American mastodon.
Research published last week in the
Proceedings of the National Academy of Sciences argues that the ancient
beast started to disappear from what is now Alaska and Canada’s Yukon
Territory long before humans ever set foot on the continent.
One key reason for the confusion,
authors say, is that specimen contamination has rendered decades of
carbon-14 dating research potentially inaccurate.
“It’s a concern,” said Yukon
paleontologist Grant Zazula, lead author of the study. “A lot of the
radiocarbon dates that are out there in the literature are probably
problematic.”
Although it is still possible that
intensive hunting by humans may have played a role in the extinction of
Mammut americanum south of the continental ice sheets about 10,000 years
ago, study authors say the mastodon’s disappearance from the Arctic and
subarctic was a matter of “overchill” and not overkill.
“There was a massive die-off of a
good part of their population in the northern part of the continent
around 75,000 years ago,” Zazula said.
“We suspect that once the northern group died off,
the species was already heading
toward trouble,” Zazula said. “What ultimately pushed them over the
edge, though — hunters picking off the last of them or climate change at
the end of the ice age being just too much for them — is an unanswered
question. There isn’t a smoking gun.”
The mastodon belongs to the same
Proboscidean family as the woolly mammoth, but the two species differed
greatly in their diets and preferred habitat.
Shaggy mammoths grazed on the grasses and flowering plants commonly found on tree-less steppe tundras.
The mastodon, however, preferred warmer mixed woodlands and lowland swamps where it munched on trees and shrubs, authors say.
The mastodon’s favorite plants were
likely abundant in the Arctic and subarctic between 125,000 and 75,000
years ago, when Earth was as warm as it is today.
However, when things began to cool during the last glacial period, the forests gradually disappeared —
along with the mastodon, authors argue.
Zazula, along with UC Irvine physicist and carbon-14 dating expert John South-on, initially set out
to reconcile conflicting data regarding the mastodon’s disappearance in
the north.
Although vegetation reconstructions suggested that the animal’s habitat
had changed drastically 75,000 years ago, previous research suggested
the mammoth was still roaming the Arctic and subarctic as recently as
18,000 years ago — almost the height of the last ice age.
Zazula, Southon and their colleagues
radiocarbon-dated 36 mastodon fossils but were careful to filter the
samples to eliminate potential contamination.
Preservative varnishes and glues
painted onto fossils by well-meaning curators, as well as soil acids
that have interacted with remains over thousands of years, can confuse
dating results and make specimens appear much younger, Zazula said.
After eliminating these sources of
contamination, the researchers found that all of the high-latitude
fossils were older than the limits of carbon-14 dating — or more than
50,000 years old.
Zazula said that although the
researchers were unable to directly date the fossils, it made the most
ecological sense that they were at least 75,000 years old.
And though the disappearance of
mastodons in the warmer south may have overlapped with the presence of
humans, Zazula said there was still no clear evidence that they were
hunted to extinction.
“There really isn’t good evidence for hunting of mastodons,” Zazula said. “There’s mastodons at
archaeological sites in the Midwest and in the northeast United States,
but it’s not like there’s piles of dead mastodons everywhere with spear
points and arrows in them. There’s no evidence of slaughter, no evidence
of overkill.”
monte.morin@latimes.com
Painting by CHARLES R. KNIGHT American Museum of Natural History
been hunted to extinction. Northern mastodons may have died off as
forests disappeared in the last glacial period.
Meat-hungry humanity has long been
suspected of hunting North American megafauna to extinction, but new
research suggests that Homo sapiens may have gotten a bum rap — at least
when it comes to the demise of the American mastodon.
Research published last week in the
Proceedings of the National Academy of Sciences argues that the ancient
beast started to disappear from what is now Alaska and Canada’s Yukon
Territory long before humans ever set foot on the continent.
One key reason for the confusion,
authors say, is that specimen contamination has rendered decades of
carbon-14 dating research potentially inaccurate.
“It’s a concern,” said Yukon
paleontologist Grant Zazula, lead author of the study. “A lot of the
radiocarbon dates that are out there in the literature are probably
problematic.”
Although it is still possible that
intensive hunting by humans may have played a role in the extinction of
Mammut americanum south of the continental ice sheets about 10,000 years
ago, study authors say the mastodon’s disappearance from the Arctic and
subarctic was a matter of “overchill” and not overkill.
“There was a massive die-off of a
good part of their population in the northern part of the continent
around 75,000 years ago,” Zazula said.
“We suspect that once the northern group died off,
the species was already heading
toward trouble,” Zazula said. “What ultimately pushed them over the
edge, though — hunters picking off the last of them or climate change at
the end of the ice age being just too much for them — is an unanswered
question. There isn’t a smoking gun.”
The mastodon belongs to the same
Proboscidean family as the woolly mammoth, but the two species differed
greatly in their diets and preferred habitat.
Shaggy mammoths grazed on the grasses and flowering plants commonly found on tree-less steppe tundras.
The mastodon, however, preferred warmer mixed woodlands and lowland swamps where it munched on trees and shrubs, authors say.
The mastodon’s favorite plants were
likely abundant in the Arctic and subarctic between 125,000 and 75,000
years ago, when Earth was as warm as it is today.
However, when things began to cool during the last glacial period, the forests gradually disappeared —
along with the mastodon, authors argue.
Zazula, along with UC Irvine physicist and carbon-14 dating expert John South-on, initially set out
to reconcile conflicting data regarding the mastodon’s disappearance in
the north.
Although vegetation reconstructions suggested that the animal’s habitat
had changed drastically 75,000 years ago, previous research suggested
the mammoth was still roaming the Arctic and subarctic as recently as
18,000 years ago — almost the height of the last ice age.
Zazula, Southon and their colleagues
radiocarbon-dated 36 mastodon fossils but were careful to filter the
samples to eliminate potential contamination.
Preservative varnishes and glues
painted onto fossils by well-meaning curators, as well as soil acids
that have interacted with remains over thousands of years, can confuse
dating results and make specimens appear much younger, Zazula said.
After eliminating these sources of
contamination, the researchers found that all of the high-latitude
fossils were older than the limits of carbon-14 dating — or more than
50,000 years old.
Zazula said that although the
researchers were unable to directly date the fossils, it made the most
ecological sense that they were at least 75,000 years old.
And though the disappearance of
mastodons in the warmer south may have overlapped with the presence of
humans, Zazula said there was still no clear evidence that they were
hunted to extinction.
“There really isn’t good evidence for hunting of mastodons,” Zazula said. “There’s mastodons at
archaeological sites in the Midwest and in the northeast United States,
but it’s not like there’s piles of dead mastodons everywhere with spear
points and arrows in them. There’s no evidence of slaughter, no evidence
of overkill.”
monte.morin@latimes.com
Painting by CHARLES R. KNIGHT American Museum of Natural History
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