March 23, 2005
* news@michigandaily. corn
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Prof claims the recently excavated tusk of the Ice Age mammal reveals that human hunting caused its extinction
By Scott Siglin
For the Daily
s it time to add yet another species to the list of
human-caused extinction? Mastodons, a once free-
ly roaming wooly mammoth-like mammal that lived
during the Ice Age, have been extinct for more than
10,00 years --an extinction that many scientists the-
orize was due to massive climate change.
But some say their tusks prove otherwise. Daniel
Fisher, Curator of Paleontology at the Universi-
ty's Exhibit Museum of Natural History, said
that by examining recently excavated mast-
odon tusks, he believes that human-hunting
instead of climate change played the
primary role in their extinction.
x As part of the Natural History
museum's series of titled "Mast-
odons and the Ice Age," Fisher,
The head of a fossil-
ized male mastodon in
the Exhibit Museum of Natu-
ral History. The ice Age mam-
mal dates back to more than
10,000 years ago.
who is also a professor of geology, will present his findings in a
lecture on May 20.
Fisher is currently researching the extinction of these elephant-
like creatures by studying the tusks of a mastodon that was
recently found in Fort Wayne,
Ind. Mastodons were common
in the Great Lakes area and
recently became the state fos-
of the bones sil of Michigan. The mastodon
found in Indiana will be shown
can show a in the exhibition in May.
The results of Fisher's
record of the research rely on the dissec-
lie tion of the tusks. The interior
animals life of the bones can show a record
of the animal's life and provide
and provide a a vast array of information of
vast aray of the animal and its surrounding
information on Mastodon tusks grow
throughout the animal's life
the animal. and are very responsive to
changes in the animal, Fisher
Growing up to nine feet in
length for males, the tusks are very similar to human teeth except
they have no enamel coating.
But Fisher said what makes the tusks grow in a fascinating way
is that they resemble ice cream cones stacked on top of each other
with a hollow center where blood vessels and nerves were.
Due to the special growth pattern of the tusks, a cross-sectional picture
of the bones is strikingly analogous to a cross sectional view of a tree;
both grow by forming concentric circles around the previous circle.
The sections of the tusk are grown in 14-day increments,
although Fisher said it was also common for mastodons to only
take a few days or even one night to a grow a new section to the
bone in their tusks.
"By analyzing material (in the tusk) that year, we can determine
the diet, climate, reproductive and health status of the animal,"
Fisher examines the tusk by subjecting the material of the tusk
to various experimental procedures, such as filing down and grind-
ing. These samples can then be used to examine certain minerals
and vitamins that could be present in the tusk.
Calcium levels can indicate bone growth in a certain period,
which could have possibly been a result of increased eating.
By researching the maturation of Mastodons, Fisher said he has
not only compiled more evidence against the climate theory, but
also evidence that supports the second theory of their extinction, in
which humans killed off the mastodons through hunting. Accord-
ing to the results from the tusk, the Mastodon that he examined
matured much earlier in life, Fisher said, evidence in support of
the human-hunting extinction theory.
"Increased predation would lead the animal to reproduce earlier
in life, therefore maturing earlier as well," he added. At the same
time, Fisher said earlier maturation and reproductive capabilities
would only occur in favorable environmental conditions, thus dis-
proving that climate change led to their extinction.
Side view of the mastodon currently being assembled by curators in
the Exhibit Museum of Natural History.
Man hunted these animals continuously for food and the ani-
mal's hide and bones, for heating purposes, he said.
"I think at least with my specimens of the Great Lakes region,
it seems to not be a climate or vegetation change, therefore it
becomes an obvious extrapolation that humans are the cause,"
Still, not all scientists agree with Fisher's evidence.
Kenneth Tankersley, an anthropologist at North Kentucky Uni-
versity, maintains the viability of the climate theory.
"The climate at the end of the Ice Age was unstable, and as it changed,
so did the distribution of plants and animals," Tankersley said.
Due to this climate shift, the abundance of certain plants and
animals decreased because of their lack of tolerance to these new
climatic conditions, he added.
Tankersley said he believes some animals migrated toward
more accommodating environments. This could account for the
growth of Fisher's tusk which suggest that the mastodon lived in a
"Would (mastodons) have gone extinct in the complete absence
of people. The paleoclimatic data suggests that the answer is an
absolute 'yes.' " Tankersley said.
The new exhibit of the mastodon from Indiana will join with the
Exhibit Museum's current display of a female mastodon.
The male mastodon is 20 percent larger than the female skel-
eton and stands at a height of nine feet, while the tusks extend to
seven feet long. The mastodon most likely weighed 6,000 pounds
and the skeleton of the exhibit are composed of a fiberglass cast
made from the molds of the real bones, which are currently being
studied by the museum.
sets sights on a return to
Mercury with NASA probe
NASA/JH U/APL/Carnegie Institution
Artist's interpretation of MESSENGER orbiting the planet Mercury
after completing its seven year journey.
By Eric Sweeney
For the Daily
More than 30 years ago, the Mariner 10 spacecraft shot past Mer-
cury three times, beaming back most of what we know today about this
"We got sort of a tantalizing glimpse," said Patrick Koehn, assistant
research scientist at the University's Space Physics Research Labora-
tory, of the first mission to Mercury.
Now scientists are venturing back to Mercury with NASA's MES-
SENGER spacecraft, which was launched last August, and will begin
a yearlong orbit of the planet in 2011. MESSENGER, which stands for
Mercury Surface, Space Environment, Geochemistry and Ranging,
will be the first spacecraft ever to orbit Mercury and study the planet
in detail. This time, scientists hope to finally crack some of Mercury's
mysteries through new technologies, particularly the Fast Imaging Plas-
ma Spectrometer developed by University researchers.
Mercury, the Earth's neighbor closest to the sun, basks in sunlight
11 times greater than that on Earth, scorching the planet with tempera-
"From that orbit, it will explore the planet and all its properties:
the interior, the surface, the environment of the planet." Zurbuchen
said. "We expect to learn where the planet came from, and how it is
part of the solar system."
Zurbuchen and Koehn, with the help of SPRL faculty and students, and
backed by a $3 million grant from NASA, built the small, three-pound
FIPS, a first-of-its-kind instrument that will take the first ever measure-
ments of the activity of charged particles in Mercury's environment.
As MESSENGER cruises through Mercury's magnetosphere - the
region surrounding the planet that contains charged particles controlling
Mercury's magnetic field - FIPS will function like a camera to detect
different types of these particles and their velocities. It is the most com-
pact instrument of this type ever developed, and, unlike previous narrow-
lensed models, provides scientist with a wider, "fish eye" view.
"It was a real innovation," said Zurbuchen. "We're going to go to
a place with an instrument that has never been there. We're going to
learn new science."
Data gathered by FIPS will provide new insight into how the solar wind
interacts with planetary magnetic fields. By having an unsubstantial atmo-
sphere and a magnetosphere, Koehn said, Mercury is perfect for studying
interaction between the solar wind and planetary magnetic fields.
While both Earth and Mercury each have a magnetosphere, Earth's
atmosphere is much thicker, while- Mercury's is very light, similar to
that of the Moon's. As Earth's magnetosphere is hit by the solar wind, it
responds by interacting with Earth's underlying atmosphere.
Mercury, having virtually no atmosphere, gives scientists the
opportunity to study the interaction between the solar wind and a
magnetosphere without interference from an
atmosphere. In effect, Mercury allows for a
controlled experiment that will test scientists'
general understanding of how the solar wind
interacts with planets.
"With the Mercury system we have one less
variable," Koehn said. "You can think of it as
a planetary laboratory."
But the overall goals of MESSENGER are
even more far-reaching.
According to NASA's website, surface com-
position measurements will reveal how Mer-
cury became the dense planet it is today. If the
surface is similar to other terrestrial planets,
then Mercury's density was caused simply by
an accumulation of dense particles as the solar
"We're going to go to a place
with an instrument that has
never been there. We're going
to learn new science."
- Thomas Zurbuchen
AOSS Professor and director of FIPS construction
oxygen, it would suggest that this crust was stripped of Mercury by
giant impacts soon after the planet formed.
Mercury's magnetic field will also be explored. For the most part,
planetary magnetic fields are generated by an active liquid interior, but
observations of Mercury's rotation indicate that it must have a solid iron
core, Zurbuchen said.
"So how can it have a magnetic field? All these things we use to
explain the Earth's magnetic field, or the sun's magnetic field, all these
theories can't apply." Zurbuchen said.
Before MESSENGER begins to orbit Mercury, it will have traveled
4.9 billion miles by conducting five deep space maneuvers, acclerating
the speed of the spacecraft in short bursts so that it can travel along the
gravitational pull of the planets to jump from the Earth to Venus and
then on to its final destination - Mercury.