The last time Utah weathered an Ice Age, around 12,000 years ago, our animals were as big and varied as the wildlife of Africa.

Utah was home to creatures much like elephants - mastodons and woolly mammoths. Roaming through the forests and savannas were saber-toothed cats, long-horned bison, dire wolves, giant deer, musk oxen, camels, ground sloths, lions and massive bears that could have eaten grizzlies for breakfast.The mammals were huge because of two factors, said Wade E. Miller, geology professor at Brigham Young University. First, herbivores grew larger so they wouldn't be such easy prey for predators, while the hunters enlarged to match their victims; also, massive bulk protected them against the cold.

Miller is working on a paper about Utah's wildlife during the Pleistocene era, the Ice Age that started about 1.8 million years ago and may have ended 10,000 years ago.

The climate was harsh and life was tough, judging by fossils he showed the Deseret News in a visit to his lab in the Pace School next to BYU's Earth Science Museum.

Saber-tooth cats - the genus name is Smilodon - probably had the strangest hunting tactic of any Ice Age carnivore. They did not bite and tear the way lions and other large cats do today.

The Smilodon had a pair of curving, sharp, scimitar-like upper fangs. They were so long that some experts have speculated they were just for show, maybe to scare off an enemy or attract a mate. But that's not the case, Miller said.

Holding a cast of a Smilodon skull from California (bones of the cats have been discovered in Utah, too, but not in such good condition), he showed how the edges of their teeth were serrated like steak knives. That helped them slice through flesh.

The lower jaw muscles were weak, biologists know from examining the small scooped-out places where muscles connected. However, the upper jaw had large muscle connections. The strong neck muscles anchored onto big shoulder bones.

The jaw hinge was an amazing piece of engineering, allowing the Smilodon to drop its lower jaw nearly onto its chest without dislocating.

Putting it all together, Miller said the saber-tooth would attack its prey by opening its mouth so wide that the slashing upper fangs stuck out like a pair of knives. It would rush onto a victim, stab it, rip downward, and jump out of the way while the animal bled to death.

"The mammoths we had here have a closer relationship with the Indian elephant than the Indian does to the African" elephant, Miller said. The extinct heavily winterized elephants stood 14 feet tall at the shoulder and had immense, curving tusks.

In a back room of the Earth Science Museum, Miller showed a mammoth skull that was recovered on Skyline Drive. It was almost the same size as a skull of a modern elephant, kept on the same shelf. But the mammoth's top vertebrae, which fit immediately behind the skull, was far thicker than the elephant's. The reason is that the mammoth was much bulkier and needed stronger bones to support it.

Another of Utah's huge Ice Age creatures was a ground sloth "bigger than a cow," he said.

The bones of one variety of camel have been recovered in Utah, and Miller said another species probably wandered through the state, too. So did two types of horses that are now extinct.

From a shelf back in the Page School, he picked up a cast of a bear's thigh bone. The top bulges were about as long as Miller's head and the whole bone was as long as his leg.

"There were bison, including this big extinct form that had a horn-spread of up to 10 feet," he said. Unlike the present-day bison, with its short upturned horns, the long-horned bison's weapons extended almost straight out on either side of its head. They were shaped much like the tusks of a modern elephant.

Mountain sheep and mountain goats thrived in the cold, wet climate.

Last week, Miller visited Brigham City, where a collector gave him a skull he had found in the bed of Bear Lake, exposed when the lake receded from the shore. It retains the prongs of a pair of horns that are shaped something like those on a mountain goat, but they are different from today's variety.

Miller is studying the remains of the skull, trying to identify it. The closest he has come is a drawing of an extinct mountain goat skull. But Miller said it will take more research before he's sure.

Earlier this month, Joe Miller, who works in a gravel pit at Point of the Mountain, brought him the shattered remains of a ground sloth fossil. It was only the third ground sloth ever found in the state, and "it's really important," Wade Miller said.

A front-end loader hit the fossil, breaking it, but Joe Miller rescued many of the pieces. Wade Miller, no relation, has been piecing together bits of its foot bones, which help to positively identify the animal.

During the Pleistocene, vast ice sheets locked up so much of the world's water that the level of oceans dropped, exposing land that had been seabed. A land bridge between Asia and North America allowed animals, such as bison and camels, to cross to this continent. Meanwhile, the Isthmus of Panama formed, letting South American creatures such as ground sloths move north.

"It's an interesting time," he said.

One of the interesting aspects of the Pleistocene is that it may not be over. Miller said some scientists believe that we are only living in a warmer period of the Ice Age.

"A lot of people don't understand that during the Ice Age there was ebb and flow of glaciation and deglaciation," Miller said. Four interglacial periods are known. We may be living in an interglacial time that is nearing its end.

"Some geologists feel that we're actually not warming, but we're going into a cooler situation," Miller said.

Despite the talk on TV about global warming and El Nino, those hotter trends might be nothing more than a momentary fluctuation, a blip in the overall scheme of things. Man's memory is too short to give much perspective.

If we're just in an interglacial period, how long do we have before the Ice Age returns in its full fury? Don't rush out to buy a homestead on the equator. "We're talking about probably a few thousand years," Wade Miller said.