Off the Water photo/TERRI GORDON While fossils of giant, and extinct, animals exist, what they actually looked like is more of an educated guess. Here a large cat is reconstructed as best as can be.

Capturing the essence of the Ice Age, mystery and all, is the latest exhibit at the Priscilla U. Byrns Heritage Museum and Cultural Center, 601 Main St. in St. Joseph.

Dioramas allow visitors to imagine life amongst the giants.  Fossils from extinct animals such as saber tooth cats, woolly mammoths and giant beavers let folks see just how big the animals were.  Geologic charts plot climate changes and let people form their own ideas of what may have taken place.

To Tom Goodwin, a professor of paleobiology at Andrews University, plain old curiosity drives human interest in the ice age.

“We’re humans and we’re curious about our history,” he said. “But it may also have practical relevance: Better understanding the factors that lead to the demise of many species of large animals at the end of the Ice Age provides context to our understanding of the current, human-caused biodiversity crisis.”

Scientists say there was a time Earth was entirely covered in ice.  From that time to now, ice sheets, or glaciers, have retreated, slowly but surely, leaving the land available for the expansion of plant and mammal — including human — populations.

It is easy to think of this Ice Age as a desolate, lifeless era, but it isn’t that simple.

Evidence shows the process was more dynamic.  Glaciers retreated, only to advance again, and retreat again.  Scientists refer to periods of advancement as glacial periods, and times of retreat are considered interglacial periods.

It is generally accepted that over the past 60,000 years, in North America, much glacial activity has taken place, ending roughly 10,000 ago, in the current “lull.”

“Obviously, here in Michigan, it was pretty bleak.  There was ice,” said Goodwin, who studies animals of the era, “but over much of North America, life went on.  You had normal cycles of rain and snow.  You had more subtropical areas in the south.  So, it wasn’t like life was eradicated. It was just a different ecological context during the Ice Age.”

Scientists are convinced life flourished during this time. Evidence is found in the La Brea tar pits of southern California, where thousands of animals were trapped by the asphalt lakes.  Excavations have shown not only how many animals there might have been, but how wide a variety of animals existed.

Many of these species are now extinct, and many, including the mastodons whose fossils are found in Michigan, were gigantic.  What happened to these beasts is a mystery, but scientists agree they seem to disappear about the time North America was emerging from the most recent glacial episode.  Since they seem to have survived 50,000 years of glacial advance and retreat, the timing of their extinction seems strange.  There are many theories.

“One argument suggests that humans with more sophisticated hunting technology showed up in North America right at the end of the Ice Age,” said Goodwin, “and that over-hunting by these humans may have caused the collapse of these large mammal populations.

“There are models that suggest it may have been a combination of environmental change and hunting pressure.”