The Death of a Mastodon

Is it time to add yet another species to the list of human-caused extinction? Mastodons, a once freely roaming wooly mammoth-like mammal that lived during the Ice Age, have been extinct for more than 10,000 years — an extinction that many scientists theorize was due to massive climate change.

But some say their tusks prove otherwise. Daniel Fisher, Curator of Paleontology at the University’s Exhibit Museum of Natural History, said that by examining recently excavated mastodon tusks, he believes that human-hunting instead of climate change played the primary role in their extinction.

As part of the Natural History museum’s series of titled “Mastodons and the Ice Age,” Fisher, 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 fossil of Michigan. The mastodon found in Indiana will be shown in the exhibition in May.

The results of Fisher’s research rely on the dissection of the tusks. The interior of the bones can show a record of the animal’s life and provide a vast array of information of the animal and its surrounding environment.

Mastodon tusks grow throughout the animal’s life and are very responsive to changes in the animal, Fisher said.

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 said.

Fisher examines the tusk by subjecting the material of the tusk to various experimental procedures, such as filing down and grinding. 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. According 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 disproving that climate change led to their extinction.

Man hunted these animals continuously for food and the animal’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,” Fisher said.

Still, not all scientists agree with Fisher’s evidence.

Kenneth Tankersley, an anthropologist at North Kentucky University, 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 favorable environment.

“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 skeleton 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.