The Ice Age 

The Pleistocene Epoch is the most recent Ice Age – a time when glaciers (slowly moving masses or rivers of ice formed by the accumulation and compaction of snow on mountains or near the poles) covered huge areas of the Earth’s surface. The Pleistocene began about 2.6 million years ago and lasted until roughly 11,700 years ago, making it the only Ice Age in which humans lived. At its height (known as Glacial Maxima), glaciers covered all of Antarctica, large parts of Europe, North America, South America, and small areas in Asia. By this time, the continents had drifted into their modern positions. There is a common misconception that the Earth was completely covered in ice during the Pleistocene. The climate, in general, was cooler and drier than it is today. However, this was not a period of continuous glaciation, meaning the glaciers were cycling through periods of advancing (moving forwards) and retreating (melting back). There were about 20 cycles, which corresponded with periods of warmer weather. Many plants and animals lived and even flourished during this time. Ohio, for example, was extremely lush. Only about 2/3 of the state was covered periodically by ice. Species of plants that are common in Canada today were widespread; this included spruce, fir, tamarack, cedar, hemlock, and larch trees. Large animals, known as megafauna, roamed the landscape. The Ice Age was not consistently cool and there were several lengthy portions where temperatures warmed, then cooled again.

Megafauna literally means large (mega) animal (fauna). Scientists use this term to describe mammals that weigh more than 100 pounds. It was the extinction of the dinosaurs 65 million years ago that triggered this large growth spurt in mammals. Suddenly, there was a lot of vegetation available and no animals to consume it. Mammals, especially herbivores, continued to grow due to this abundance of food. Mammalian carnivores also grew large, but not as large as the plant eaters. For a predator, large size can be a disadvantage, considering it makes it easier for potential prey to see them. The size of megafauna continued to grow and plateaued around 30 million years ago during the Oligocene Epoch. The largest megafauna that ever walked the Earth was Indricotherium transouralicum – a hornless rhinoceros that stood 16 feet at the shoulder and weighed approximately 44,000 pounds. The megafauna that lived during the Pleistocene included mammoths, mastodons, saber-toothed cats, giant beavers, short-faced bears, giant ground sloths, dire wolves, and giant armadillos.

The megafauna of the Pleistocene started to decline around 80,000 years ago and most were extinct by 10,000 years ago. However, this extinction did not occur at the same time in all regions. In certain areas, megafauna continued to thrive. A small population of mammoths lived on Wrangel Island located off the northern coast of eastern Siberia until 1650 BC; these mammoths were protected due to their isolation. There is a long running debate over the causes of the Pleistocene megafauna’s extinction. Currently, there are three main theories: Over-Kill, Over-Ill, and Over-Chill. These theories are not exclusive and it is likely a combination of them is the true cause of the Pleistocene megafauna’s extinction. A recent hypothesis suggested that at the same time as the Younger Dryas (see Over-Chill Hypothesis below), a comet or meteor either exploded in the Earth’s atmosphere or impacted the surface. Archaeologists uncovered a layer of soil (known as the black-mat) dating to 12,900 years ago that contained charcoal, soot, microscopic diamonds, and other trace materials consistent with this hypothesis. Atmospheric explosions and/or impacts can cause wildfires, change ocean circulation, and create ash/dust that block the sun, resulting in mass extinctions. Critics of this theory question the lack of a crater associated with a large impact event as well as the black-mat layer. New evidence suggests that the layer does not in fact date to the Younger Dryas period.

• Over-Chill Hypothesis: The rapid extinction of the megafauna may have been the result of climate change as the Pleistocene ended. Temperatures began to warm around 17,000 years ago. This was followed by a brief return to cooler conditions between 12,900 and 11,500 years ago known as the Younger Dryas. These shifting and abrupt climatic conditions (from warm to cool to warm) may have stressed the megafauna to a point where they could not recover. Skeptics argue that megafauna successfully survived previous periods of warming during the Pleistocene without extinction. Many scientists are now considering the idea that it was a combination of over-hunting and climate change that caused megafauna populations to collapse.
• Over-Ill Hypothesis: This hypothesis states that disease caused the megafauna to go extinct and humans introduced diseases as they migrated into new regions. These diseases may have been carried by people or by the animals that they had with them, like dogs or rats. The native megafauna had no immunities to these diseases. Due to the size and distribution of the megafauna, diseases could likely spread quickly among them. Disease may also explain why there were differences in extinction rates between larger, slow reproducing species and smaller, fast reproducing species. However, there have yet to be any pathogens (disease-producing agents, especially a virus or bacterium) detected in preserved bones of megafauna that could have triggered a multi-species extinction.
• Over-Kill Hypothesis: Some scientists have suggested that humans hunted megafauna to extinction since many species abruptly went extinct after humans entered the region. They argue that hunting, taking eggs, and killing juveniles could have disrupted the reproduction of the megafauna. However, there is a lack of conclusive data. In North America, a few kill sites have been found where humans hunted mammoths, mastodons, sloths, horses, and camels, but there are none found for 30 other extinct megafauna species nor for smaller game animals. Skeptics argue that the total number of humans present was too small to cause extinction and point out that these animals were hunted for over 2,000 years before they went extinct. Archaeologists now agree that most early native people were probably not big-game hunters and were more complex than previously thought.

In 1966, Lowell Carter, a local farmer, decided to expand two bogs (or wetlands) on his property located roughly two miles west of Ansonia, Ohio.  Lowell loved fishing and he had big plans to build a new fishing area from himself.  Using a track hoe and a marl spreader, he scooped out the edges of the bogs and he found something amazing.  While spreading the nutrient-rich soil on his grassland, something went awry; he heard a loud crunch, signaling that something had jammed the spreader.  He shut down the machinery, looked inside and noticed a large object protruding from the machine.  He removed the broken object only to find an oddly shaped and rather large bone.  Lowell continued to find bones so he decided to notify staff from the Dayton Society of Natural.  Once they arrived on Lowell’s property, they were taken a barn full of bones of animals who lived during last Ice Age! 

Over the next three years, the Dayton Society of Natural History located and excavated over three thousand bones, representation at least 22 species.  The preservation on Lowell’s property was excellent because the bones were enclosed in a kettle bog.  A kettle forms when a block of stagnant ice detaches from a glacier.  Over time, the glacier sinks down and melts, leaving a pit.  In many cases, the remaining pit will fill with water to become a pond, lake, or bog.  A bog is wetland that contains a large amount of peat/decomposed plant material.  Bogs are excellent for preservation because they are extremely low in oxygen.  To better understand the age of the deposits on Lowell’s farm, two radiocarbon dates were obtained. One from a log of an ancient spruce tree found entangled with a partial skeleton of a giant sloth, and the other from the bone collagen of one of the mastodon bones. The two dates recovered were 11,500 and 12,000 years ago which dates both bogs to the last glacial maximum.  Today, this site is known as Carter Bog.

The wallpaper mural displayed in this gallery is an artist reconstruction of Carter Bog in the Ice Age.  If you look closely, you can see many species of animals (included humans).  The mural – titled “The Pleistocene Era of Ohio” – was painted by artist Emily Agnew.  She started the painting in November 1982 and finished it in March 1983.  It originally served as the backdrop for a diorama within Ice Age Ohio exhibition.  The diorama included miniature models of animals like the mastodon, giant beaver, and stag moose. It also contained little cattails, oak trees, and ash trees.  Emily Agnew attended the Dayton Art Institute where she earned a degree in Fine Arts. Her works included commissions with the Dayton Museum of Natural History, Cincinnati Zoo, and Cincinnati Museum Center.  She was a mother of 5 and often painted alongside her son, John. John went on to be a well-known wildlife artist and painted the murals in the Cincinnati Museum Center’s Ice Age Galley. John is described in an article from the DDN in 1990, which stated that he “started his career at the Dayton Museum of Natura History….where he learned most of what he knows about wildlife murals.”

Find these specimens on display!

1. Common Beaver

Scientific name: Castor canadensis

Composite skeleton and original prehistoric bones

There are many animal alive today that also lived during the Ice Park; for example, the common beaver.  The remains of 12 beavers were found during the excavations from 1971 through 1973. Some of their more notable traits are direct adaptations to swimming, such as webbed feet and a long and flat compressed tail, which they use as a threat display to warn away other animals.

2. Muskrat

Scientific name: Ondatra zibethicus

Muskrats are true masters of the lakes and streams in and around North America.  They are well adapted to swimming with webbed feet and a laterally flattened tail.  Some of their more notable traits are their ability to hold their breath for 20 minutes, can swim 3 miles per hour, and can even swim backward.  At Carter Bog, 143 individual muskrats were collected.

3. Mink

Scientific name: Neovison vison

A mink looks similar to a household ferret and belongs to a family that includes skunks.  They are small, weighing over 3.5 lbs. and are extremely adept in water as well as on land and trees. Only one mink was found during excavations at the Carter bog.  Here are the actual remains of this animal.

4. Fisher

Scientific name: Pekania pennanti

Paleontologists only recovered one fisher bone during the 1972 excavation.  This bone, a right jaw, was enough to tell us that they were there.  It is interesting to note that fishers have never historically been identified in Ohio until just recently when a pregnant female fisher was captured.  The lack of fishers in Ohio during historic times suggests that when the environment changed, their loss of suitable habitat caused them to move north into Canada.

5. Stag Moose

Scientific name: Cervalces scotti

The Stag Moose was a moose-like deer, which stood over 8 feet tall.  It lived in North America and went extinct approximately 11,700 years ago.  The neck vertebrae on display was found at Carter Bog and was the first Stag Moose bone ever found in the state of Ohio.  Three pieces of Stag Moose antler were also discovered at Carter Bog.  Male Stag Moose had elaborate, branched antlers that could grow up to six feet in length, making him appear larger than he was.

6. White-Tailed Deer

Scientific name: Odocoileus virginianus

Today, the white-tailed deer is one of the most well-known wildlife species in Ohio. Deer have lived in Ohio for a long time even during the Ice Age.  Their populations bombed after the megafauna, like mastodons and mammoths, went extinct.  During excavations at Carter Bog, the DSNH staff found the remains of two white-tailed deer.

7. Jefferson’s Ground Sloth

Scientific name: Megalonyx jeffersonii

The first Megalonyx bones were described by President Thomas Jefferson in 1799; this is where it got its name.  This animal was a large ground-dwelling sloth with big claws for digging, grabbing, and self-defense.  It was an herbivore, eating mostly leaves and low-lying shrubs.  The Megalonyx skeleton found at Carter Bog is roughly 40% and at the time it was discovered, it was the largest and most complete Jefferson’s Ground Sloth ever found.

8. Mallard Duck

Scientific name: Anas platyrhynchos

The mallard is also known as the wild duck.  It is considered to be the ancestor of nearly all ducks and are found today throughout the Americas, Europe, Asia, and North Africa.  They evolved during the Late Pleistocene.  At Carter Bog, they found one skull of a mallard duck.

9. Giant Beaver

Scientific name: Castoroides ohioensis

There were two known species of Giant Beavers: Castoroides ohioensis (found in the continental United States and Canada) and Castoroides leiseyorum (found only in Florida).  Giant Beavers were the largest rodents that ever lived in North America and the largest species of beaver in the world. They resembled the modern beaver.  It is thought that Giant Beavers were strong swimmers who spent most of their time in the water. They were likely clumsy walkers, which restricted their ability to move over land. The brain of a Giant Beaver was proportionally much smaller than that of a modern beaver, suggesting that the behavior of the Giant Beaver was much more limited.