Learn About the Mammoth


This page contains the text and images from all the topics on the "Learn" page, including The Ice Age, Paleo-Indians, Des Moines 16,000 Years Ago, How Do You Make a Mammoth?
The Bibliography and Lesson Plan can be printed separately.


The Ice Age

The Pleistocene, or Ice Age, began over 2.5 million years ago and ended a short 10,000 years ago. During this time, numerous ice sheets formed and moved south from Canada into the United States. Periodically the climate warmed and the glaciers receded, only to form and surge south again.

Why was there an Ice Age?
No single event or action caused the Ice Age. Instead, a number of conditions combined, including the following:

Large land masses near the poles created a surface upon which thick ice could form.

The formation of mountain ranges caused major climatic change by shifting global circulation patterns.

Decrease in atmospheric carbon dioxide reduces the insulating effect of the Earth's atmosphere, resulting in heat loss.

Changes in the position of the North Pole and the Earth's tilt and orbit around the sun affect how much solar radiation it received.

The Last Ice Age
The last Ice Age, the Wisconsinan, began about 50,000 years ago. As the environment cooled, a large ice sheet formed in the Hudson's Bay region, and began to spread south. One lobe entered central Iowa and moved as far south as Greene County. Then, as the climate warmed about 30,000 years ago, this lobe "retreated," or melted. Then as temperatures cooled again, another glacier, the Des Moines Lobe, entered Iowa and pushed down through the center of the state to reach Des Moines about 17,000 years ago. It finally retreated 14,000 years ago.

The Quaternary

Geologic Age

What Happened

Carbon 14 Dates


Development of modern soils and stream deposits and erosion.


Wisconsinan Glaciation

Wind-blown loess covers most of Iowa outside of the Des Moines Lobe.



The Des Moines Lobe reaches north-central Iowa and deposits its debris.



Early Wisconsinan glaciation is evident in northwestern Iowa under a blanket of loess.


Sangamonian Interglacial Stage

Development of a soil layer and erosion on older deposits. Evident across most of Iowa, covered by Wisconsinan tills and loess.


Illinoian Glaciation

Glacial tills deposited along the southeastern edge of Iowa.


Yarmouthian Interglacial Stage

Development of a soil layer and erosion on older deposits. Evident across most of Iowa, covered by Illinoian tills and Wisconsinan tills and loess.


Pre-Illinoian Glaciation

As many as 20 glacial advances may have crossed Iowa. Their evidence lies buried under more recent sediments and soil development. Evident across most of Iowa, covered by Illinoian and Wisconsinan tills and loess.



Links to the Iowa Department of Natural Resources' Geological Survey:

Geology of Iowa: Iowa's Earth History Shaped by Ice, Wind, Rivers, and Ancient Seas

Landscape Features of Iowa

Linked Depressions on the Des Moines Lobe

Glacier Landmarks Trail: Iowa's Heritage of Ice

Glacial Boulders in Iowa



They Came to North America
Humans came to North America near the end of the Wisconsinan glaciation, perhaps about 25,000 years ago. Scientists continue to debate when humans arrived. Discoveries of new evidence continue to push the possible dates of immigration back farther in time, perhaps to more than 40,000 years ago.

There was no single event or condition that allowed for human arrival and settlement in North America. Humans probably arrived here in small groups, and families soon spread across all of North America.

How Did They Get Here?
Scientists debate this, too. Here are some of their theories...

During Wisconsinan glaciation, so much water was locked up in ice that the sea level was about 300 feet lower than today. Today, Siberia and Alaska are separated by the waters of the Bering Straits. But during glaciation, when this land was exposed, grasslands a thousand miles wide connected the two continents. Many scientists believe that across these grasslands (called "Beringia") and down the exposed western coast of North America, plants animals, and humans slowly made their way into this new world.

The Ice-Free Corridor:
Many scientists believe that during Wisconsinan glaciation, an ice-free corridor existed from Beringia down the eastern side of the Rocky Mountains into the middle of the continent, making migration far easier than over glaciers.

Sea Coast Migration:
Proponents of this theory believe that some humans in boats followed the emergent seacoast from Asia down the west coast of North America.

The Atlantic Route:
Another theory holds that a maritime population from Europe traveled by boat, following the southern border of the North Atlantic ice to North America. Some scientists believe this theory because of similarities between the flaked-stone tools of early Paleo-Indians in North America and the Solutreans in Europe.

Evidence of Paleo-Indian Culture

The name Paleo-Indian refers to the earliest human inhabitants of North America. We know about them because the chipped-stone tools they made have been found on the surface of the land and from ancient campsites and butchering sites across the continent. Paleo-Indians were big-game hunters who hunted mammoths and giant bison.

This was a time of change in the environment. The climate warmed and the last glacier melted, or "retreated." Vegetation changed too, and the great Pleistocene megafauna (animals larger than 100 pounds) became extinct. With these environmental changes came changes in how humans lived and their technology—how they made and used things. Archeologists identify early people by their technologies, because the traditions of how they made and used things can be traced over periods of time.

Early Paleo-Indian Clovis
Older than 10,800 years

The typical Clovis projectile point is long with sharp edges and a central flute struck from both sides. The base is gently concave and smoothed. Clovis points have been found at kill and butchering sites for mammoth, mastodon, and bison across the continent. Although no butchering sites containing Clovis points have been found in Iowa, clovis points have been discovered on the surface to the land. The Runnels-Maske Site in Cedar County yielded 11 Clovis points.

10,900 to 10,500 years old

Within a short period, the Clovis Tradition gave way to the Folsom. In this tradition, the Paleo-Indians produced smaller projectile points. Folsom points are characterized by a long flute flaked from the base of each side, up the center. This technique creates a thin, easily hafted blade with pressure flaking on the sides. These points are associated with bison kill sites.

Throwing spears with atlatls (spear-throwing sticks) were probably also used during this time.

Evidence of the Folsom Tradition is found across North America. Although no butchering site with Folsom points have been found in Iowa, numerous Folsom points have been collected on the surface, especially in southwestern Iowa.

Atlatl and Spear
The Atlatl is a spear-thrower, which increases the range and power of the spear. It is a small, flat stick with a handhold at one end and a catch at the other. The spear is about six feet long and tipped with a chipped stone or bone point. The dart is placed on the end with the catch.

When the arm moves to throw the spear, the arc is increased by the length of the atlatl and imparts more energy to the spear. Experienced throwers can increase their force by two and a half times. With practice, a spear will travel more than 100 yards.


Des Moines 16,000 Years Ago

Des Moines 16,000 years ago was a place of contrasts. At times, the ice front of the Des Moines Lobe surged to the north edge of the Raccoon River Valley and then retreated. The ice stood hundreds of feet high. Sediment choked the Raccoon River, backing up the water and splitting the channel into interlacing braids. At other times the volume of melt waters increased and the current was deep, fast, and abrasive.

This area was a mix of grasslands and forests of spruce, aspen, and oak. Stretching north of Des Moines, in areas where the ice had melted, marshes and muskeg (or bogs) were common. This environment supported a variety of herbivores.

Fossils from the time reveal that the Des Moines region was home to mammoth, mastodon, giant ground sloth, musk ox, a variety of bison, and elk. We do not know for certain if humans walked the Raccoon River Valley at this time, but they may have. We do know that soon they would be in Iowa and surrounding states, hunting the mammoth, mastodon, and other game.

Within a few centuries, the temperatures warmed and the ice melted for the last time. New forests filled the river valleys, prairies stretched out to the west and south, and marshlands continued to the north. The subtle changes brought great change to the inhabitants—extinction for some, and opportunity for others.

Musk Oxen
Ovibos moschatus

Barren ground musk oxen became evident in the fossil record of North America nearly a half million years ago, and they remain active members of the arctic region today. Although once hunted to near extinction, the herds in Alaska, Canada, and Greenland now number about 100,000.

Musk Oxen
Symbos cavifrons (Bootherium bombifroms)

The woodland musk ox first appeared in North America before the expansion of the Wisconsinan ice sheet and remained into the early Holocene. It, like many other Pleistocene animals, became extinct about 10,000 years ago.


The ancestral bison, Bison priscus, entered North America through Beringia (the Bering Straits land bridge) during the Illinoian glaciation, 200,000 to 120,000 years ago. Descendants from this migration gave rise to a giant bison, Bison latifrons, standing more than eight feet at the shoulder and with horns spanning six feet, which survived into Wisconsinan time. Before the end of the Sangamon interglacial period, about 100,000 years ago, a new stock of Bison priscus moved south from Beringia. These developed, in stages, during the Wisconsinan time, into the two bison subspecies that still live in North America, the plains bison and the wood bison. This skull represents one of the large, intermediate stages of an extinct subspecies, Bison bison occidentalis.

Stag Moose
Cervalces scotti

This skull has been tentatively identified as belonging to a stag-moose, a large moose-like member of the deer family. Much like the modern moose, it inhabited muskegs (cool, wet, marshy areas).


How Do You Make a Mammoth?

The life-size cast of the Hebior mammoth was produced by PAST: Prehistoric Animal Structures, Inc., of East Coulee, Alberta, Canada. The molds for the cast were made from the original fossilized skeleton discovered in 1994 on the Hebior farm near Lake Michigan. Because the Hebior mammoth was 90 percent complete, some missing or damaged bones had to be created.

Candid shots show step by step how the skeleton was made and moved, from Canada to our museum.

1. The molds are "painted" with layers of fiberglass cloth and resin. These sections of the lower jaw and a tusk and lower jaw await the completion of additional parts before assembly.
image 1

2. Two leg bones are mounted together with a steel armature. The enormous size of a mammoth becomes evident.
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3. Freshly painted to look like a bone, the femur is placed into position in the hip socket.
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4. To test that all parts fit together properly, the skeleton is assembled. Then the mammoth is then taken apart for shipping and packed carefully into crates. Inside the crates, foam layers protect the skeletal segments.
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5. In late November 2003, the skeleton arrives at the State Historical Society of Iowa in Des Moines.
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6. Museum staff unload the five large crates and count the individual segments of the skeleton.
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7. The backbone is readied for installation.
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8. Museum staff lift the skull out of its foam protection and move it into position.
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9. The segmented tail is lifted into position.
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10. Finally, the last tusk is guided into place in the left alveoli.
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11. The test assembly of the mammoth is now complete. Everything fits together perfectly. Final measurements can now be taken so that the casework can be designed and built for the exhibit.
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© State Historical Society of Iowa