Meet the Mammoth

 

Mammoth: Witness to Change

The close of the great Ice Age brought many changes to the upper Midwest. It was an ending time and a beginning time. The mighty surges of ice sheets and glaciers from the north had ended. Great rivers, vegetation, animals, and the landscape itself changed as the climate warmed. With these changes came human habitation.

The great beasts that had lived during the Pleistocene epoch watched as their world and their dominance disappeared. Among these huge beasts were the largest of them all—the mammoths.

Once monarchs of their realm, mammoths now relinquished dominance to humans. Once protected in their long, woolly coats, they now faced warming temperatures and a changing environment.

Two particular mammoths, separated by a few hundred miles and a few hundred years, witnessed their world changing. Their deaths, in what are now Iowa and Wisconsin, preserved those particular moments in time.

The Hebior Mammoth

The Hebior mammoth died about 15,000 years ago in a small depression or pond not far from Lake Michigan in southeastern Wisconsin. Over time its body decomposed. Wetland sediment settled over it.

In 1994, farmer John Hebior discovered bones when he was digging a drainage ditch across the old pond. A team of archeologists led by David Overstreet excavated the site.

What they found startled many archeologists. Here was the most complete mammoth skeleton found to date in the Upper Midwest. Ninety percent of the bones were still there. Even more astounding was the discovery of stone tools and butchering marks on some of the bones, making this one of the earliest known butchering sites in North America.

Here was a rare glimpse of the time when mammoths and humans crossed paths. On path led to extinction. The other, to dominance.

The bones of the Hebior mammoth were discovered in two adjacent areas. The main cluster occupied the bottom of the ancient pond. A second cluster, of butchered bones of the right foreleg, were a short distance away, up the pond bank.

The dotted line through the site (above) marks the area cut out for a drainage tile project in 1994.

The Butchers' Tools
Chipped-stone tools made of chert were found around and under the mammoth's bones. These along with cut marks on the bones of the right leg indicated butchering activities.

One stone knife (1-1) was found next to a pile of ribs and vertebrae. A second stone knife (1-2) was located in another cluster of bones. A flake (1-3) was found under the pelvis, and a dolomite chopper (1-4) was nearby.

Carnivore Marks

A large carnivore, possible the dire wolf, Canis dirus, might have made the teeth marks on the Hebior mammoth's right ulna, the lower foreleg. A large tooth furrow is also visible on the lower end of the bone. In addition the beast is believed to have gnawed off the end of the bone.

Marks of Butchering

As the mammoth lay on its left side, the right foreleg was removed and transported up the side of the depression. Here it was skinned, disarticulated, and the meat removed. The foot would have been of special interest because of its meaty pad.

Chipped-stone tools left marks on the bone as they cut through joints and removed meat. The shaft of the humerus and several toe bones also show marks characteristic of cutting.

The Allied Mammoth

In preparation for building the new Allied Insurance and Farmland Insurance parking ramp in downtown Des Moines, a large number of support pillars were formed by drilling down to bedrock and pouring reinforced columns of concrete.

On August 14, 2001, an enormous auger, with a bit 6.5 feet wide, bore down through old building rubble, then through yards and yards of sand and gravel. At 10:30 in the morning, 55 feet below the surface, the auger struck bedrock—and bone. The auger had cut through the skeleton of a mammoth lying on the very floor of the Raccoon River valley.

The construction workers recognized the significance of this find and notified the executives of Allied Insurance. They, in turn, contacted the State Historical Society of Iowa for assistance and later donated the bones to the museum.

A small sample of the bone was sent to Stafford Research Laboratories, Inc., in Colorado, for radiocarbon dating. The bones were dated at 16,500 BP (before present).

When the auger cut through a part of the skeleton, it broke the bones into pieces. Not all the pieces were brought to the surface in the slurry. Some of the fragments form a portion of the right shoulder region. They include vertebrae, a scapula, and parts of the front leg.

The American Mastodon

The American mastodon, Mammut americanum, first appears in the fossil record about 3.5 million years ago throughout North America. Although the mastodon was similar to the mammoth in form and size, they were only distant relatives. The mastodon was shorter, about ten feet tall, and its head lacked the characteristic high dome of the mammoths. The greatest difference, however, was in their teeth. This meant that mastodons and mammoths did not compete for exactly the same foods. both lived in Iowa about the same time.

Each mastodon tooth had several heavy, rounded cones covered with enamel. These were will suited for crushing and eating a variety of plant material including grasses, twigs and leaves, the kinds of plants found in conifer forests, woodlands , and on the edges of grasslands. (The flat planes of mammoth teeth were best suited for eating grasses.)

Both mastodons and mammoths became became extinct about 10,000 years ago.

Mammoth History

The woolly mammoth has come to symbolize the last Ice Age and the arrival of humans in the Western Hemisphere. Here in Iowa, mammoth bones have been unearthed in the daily activities of Iowans tilling the land, excavating for buildings and bridges, or merely walking along creeks and streams. Finding mammoth bones reminds us that change is ever present.

Remains of both woolly mammoths and Columbian mammoths have been found in Iowa, but sometimes it's difficult to tell which is which. Bones and teeth of the two species are similar, and of course there are individual variations within each species.

The Ears
Mammoths had small ears, about 15 inches long and 10 inches wide—much smaller than the ears of a modern African elephant. Small ears reduced heat loss.

Skin
The skin of a mammoth was an inch thick over most of its body. Around the eyes and mouth it was only half an inch thick. A thick layer of fat under the skin helped to insulate the body from the cold.

What's in a Trunk?
The trunk functioned as nose, hand, and straw to the mammoth. Combining the upper lip and nose, the trunk was both sensitive and muscular. A mammoth used its trunk to lift, entwine, grasp, and drink, and to make sounds, communicate by touch, and distinguish scents. Like modern elephants, mammoths had better senses of smell than of eyesight. There were no bones within the trunk, only tissue, cartilage at the tip to divide the nostrils, and thousands of muscles.

The modern Asian elephant has a single finger at the top side of the trunks' tip, which grasps and holds an object so the trunk can twist around it.

The African elephant has two fingers, at top and bottom. They act like a finger and thumb to grasp an object or a bundle of grass.

The mammoth had a single finger at the top and a wide flap at the bottom. Its ability to grasp short grasses or small items may have been enhanced by this arrangement.

Mammoth Steps
Each foot had five toes. Though it seems unlikely for such a huge animal, the mammoth walked slightly tiptoed. Behind the foot bones was a large pad of fatty, fibrous tissue. These springy pads cushioned each step and gave the animal agility and balance. Thick, rough skin covered the pads and helped the animal from slipping on ice and snow.

When a mammoth stepped upon the snow, each step had to support a portion of its total weight, sometimes nearly 16,000 pounds. It is no surprise that the footprint was large—very large, about two feet across. The large area dispersed its weight so that the mammoth could walk upon the snow rather than breaking through at every step.

How fast could a mammoth walk? A modern elephant can walk 30 miles a day at four miles an hour, or a shorter distance at nearly 15 miles an hour. A mammoth probably could do about the same.

Hair
Mammoths had two protective layers of hair. The inner layer of short hair served as an insulating blanket to protect the mammoth in the winter and was shed yearly. The coarse outer layer of guard hairs protected the animal year round and grew as long as two feet.

Mammoth hair was probably originally black to dark brown. Over the thousands of years that mammoth remains have been frozen, the color has faded.

The Lower Jaw
The lower jaw of the mammoth was short and deep. Its teeth developed in the rear of the jaw and moved forward to replace worn-down teeth in the front. A worn tooth was expelled as the next tooth moved forward to replace it. Only six sets of teeth were produced during a mature mammoth's lifetime. Each set had four teeth, two in the upper jaw, and two in the lower. Once the last tooth was worn away, the mammoth would starve to death.

Mammoth Teeth
Mammoth teeth were huge! A single tooth of a mature mammoth was as big as a shoe box and weighed about ten pounds. Mammoth teeth were also specially adapted to tear, grind, and chew up grasses and other plants—a few hundred pounds of plants a day! Chewing silica-rich vegetation slowly wore down the teeth, each layer at a slightly different rate. This caused ridges in each tooth, which helped crush the food. The three layers were made of enamel, dentin, and cementum.

Aged By Their Teeth
We humans have two sets of teeth during our lifetime, baby teeth and permanent teeth. Mammoths had six sets, and each set had four teeth, two in the top jaw and two in the bottom jaw.

As in modern elephants, as one set of mammoth teeth was wearing out, the next set was slowly forming and moving forward into position to replace the old set. Each new set of four teeth was larger and had more plates than the set before. Scientists can determine the age of a mammoth by the age of its teeth, because the sets of teeth were replaced about the same time in all mammoths.

Tusks
The tusks of a mammoth were simply oversized incisors, or upper front teeth, which had become specialized for particular uses. They continued to grow throughout the mammoth's life. Tusks could grow as long as nine feet on the male woolly mammoth and 16 feet on the male Columbian mammoth.

How Old?
A mammoth could live 80 years or more. Scientists an determine its age by its teeth and bones.

Reproduction
Today's elephants did not evolve from mammoths. But because mammoths and elephants were close relatives, scientists have determined that in some ways mammoths probably looked and acted like elephants. About modern elephants, we know that a female must be at least 12 years old to reproduce. A pregnancy lasts about 22 months, a newborn elephant weights about 270 pounds, and the calf will nurse for about two years. Scientists think that mammoths were much the same.

Social Structure
Mammoths, like their close relatives the elephants, probably had a complex social structure with a matriarch leading the group. The matriarch is the female elephant with the most experience, knowledge, and status. If hunting, disease, or climatic change kills the matriarch before others have gained knowledge and status, the family herd may be in jeopardy.

 

© State Historical Society of Iowa