Any tusks in your backyard?
By DARTMOUTH COLLEGE
Researchers trace the age of a rib
fragment of the Mount Holly mammoth.
Woolly mammoths may have walked the
landscape at the same time as the earliest humans in what is now New England,
according to a Dartmouth study published in Boreas.
Through the radiocarbon dating of a rib
fragment from the Mount Holly mammoth from Mount Holly, Vt., the researchers
learned that this mammoth existed approximately 12,800 years ago. This date may
overlap with the arrival of the first humans in the Northeast, who are thought
to have arrived around the same time.
“It has long been thought that megafauna and humans in New England did not overlap in time and space and that it was probably ultimately environmental change that led to the extinction of these animals in the region but our research provides some of the first evidence that they may have actually co-existed,” explains co-author Nathaniel R. Kitchel, the Robert A. 1925 and Catherine L. McKennan Postdoctoral Fellow in anthropology at Dartmouth.
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| Photograph showing the affixed tags and 3D model of the Mount Holly mammoth rib fragment housed at the Hood Museum of Art at Dartmouth. The rib was 3D surface scanned using a Creaform Go! SCAN50 at a resolution of 1.00 mm and has been digitally archived n .stl format at Morphosource.org. Credit: Image by Nathaniel R. Kitchel and Jeremy DeSilva |
The Mount Holly mammoth, Vermont’s state terrestrial fossil, was discovered in the summer of 1848 in the Green Mountains during the construction of the Burlington and Rutland railroad lines.
One molar, two tusks, and an unknown number of bones were excavated from a hilltop bog near Mount Holly.
Over time, the specimens became scattered across several repositories, as they transferred from one collection to the next.
A rib fragment from the Mount Holly mammoth became part of
the Hood Museum of Art’s collection and some of the other skeletal
materials are now housed at the Museum of Comparative Zoology at Harvard
University and the Mount Holly Historical Museum.
Kitchel stumbled across the Mount
Holly mammoth rib fragment last December at the Hood Museum’s offsite storage
facility, as curators had invited him to take a look at some of their artifacts
from New Hampshire and Vermont.
He came across a large bone
(approximately 30 cm. in length) that was stained brown in color from age. He
had a hunch that this was the remains of a mammoth and when he looked down at
the tag, it read, “Rib of fossil elephant. Mt. Holly R.R. cut. Presented by Wm.
A. Bacon Esq. Ludlow VT.”
This was rather serendipitous for
Kitchel, as he had recently delivered a talk at Mount Holly’s Historical Museum
for which he had read up on the Mount Holly mammoth.
To appreciate the significance of the
Mount Holly mammoth remains, including the rib fragment, it is helpful to
understand the paleontology of the Northeast.
During the Last Glacial Maximum
around 18,000 – 19,000 years ago when glaciers were at their maximum extent,
the ice began to retreat, gradually exposing what is now New England.
During that period, it is likely
that the glaciers probably sufficiently ripped up whatever soil might have been
preserving fossils, reducing the likelihood for fossils to remain intact. These
changes combined with the Northeast’s naturally acidic soils have created
inhospitable conditions for the preservation of fossils.
While Kitchel had discussed the
complicated paleontology of the Northeast in the past with colleague and
co-author Jeremy DeSilva, an associate professor of anthropology at
Dartmouth, he never thought that he would have much of an opportunity to work
on it.
After seeing this mammoth material
in the Hood’s collection, he and DeSilva decided to obtain a radiocarbon date
of the fragmentary rib bone. They took a 3D scan of the material prior to
taking a small (1 gram) sample from the broken end of the rib bone. The sample
was then sent out to the Center for Applied Isotope Studies at the University
of Georgia for radiocarbon dating and a stable istotopic analysis.
Radiocarbon dating enables
researchers to determine how long an organism has been dead based on its
concentration of carbon-14, a radioactive isotope that decays over time. Stable
isotopes however, are isotopes that do not decay over time, which provide a
snapshot of what was absorbed into the animal’s body when it was alive.
Nitrogen isotopes can be used to
analyze the protein composition of an animal’s diet. The nitrogen isotopes of
the Mount Holly mammoth revealed low values in comparison to that of other
recorded mammoths globally while also reflecting the lowest value recorded in
the Northeast for a mammoth.
The low nitrogen values could have
been the result of these mega-herbivores having to consume alder or lichens
(nitrogen fixing species) during the last glacial period when the landscape was
denser due to climate warming.
“The Mount Holly mammoth was one of
the last known occurring mammoths in the Northeast,” says DeSilva. “While our
findings show that there was a temporal overlap between mammoths and humans,
this doesn’t necessarily mean that people saw these animals or had anything to
do with their death but it raises the possibility now that maybe they did.”
The radiocarbon date for the Mount
Holly mammoth of 12,800 years old overlaps with the accepted age of when humans
may have initially settled in the region, which is thought to have occurred
during the start of the Younger Dryas, a final pulse of glacial cold before
temperatures warmed dramatically, marking the end of the Pleistocene (Ice Age).
While other research on mammoths in
the Midwest suggests that humans hunted and buried these animals in lakes and
bogs to preserve the meat, there’s little evidence that early humans in New
England hunted or scavenged these animals.
The researchers are intrigued by the
Mount Holly mammoth. The rest of its rib and other bones could be waiting to be
discovered. Or, through time, they could have broken apart, dissolved in the
acidic soil, or a scavenger could have run off with the bones.
There are still a lot of unknowns;
yet, the team has already begun further research using modern and more
sophisticated archaeological techniques to explore what may be underground at
Mount Holly.
Reference: 4 March 2021, Boreas.