Begin the lesson by getting students to make a list of as many mammals as they can think of that live in your area. Cats and dogs are easy, but what animals live in the woods, in an abandoned dwelling, near wetlands, or on the prairies? Are there mice, raccoons, or bears near you? Which are biggest? Have students research mammals that lived during the most recent ice age. Ask: How were these animals different from the ones today? What happened to them? Are any types of mammals still around that also lived during an ice age? How did they survive when so many others didn't?

On a windblown steppe some 11,000 years ago, a herd of mammoths stampeded up a hill as a vast fire set by Paleo­Indians burned toward them across the grasslands. The panicked giants, elephant­like creatures standing 11 to 13 feet (3.3 to 4 meters) high at the shoulder, reached the top of the rise, then fell 50 feet down into a ravine. Out of the drifting smoke appeared a dozen of the Paleo­Indians, carrying spears tipped with sharp Clovis points to finish off the mammoths that had survived the fall. Starting fires to stampede large animals over cliffs was one of the ways humans used to hunt. Mammoths, with large tusks and abundant meat, were highly prized.

Mammoths were members of the genus Mammuthus, a group of several species of prehistoric elephants that roamed the North American continent from about two million years ago until becoming extinct here about 11,000 years ago. Many scientists believe human hunting and climate change combined to kill off the mammoths.

Before human hunters arrived and the climate changed, mammoths thrived on the plentiful grasses and other vegetation of the tundra and steppe. There were several species of the creatures, including the Columbian mammoth, Jefferson's mammoth, the imperial mammoth, and the woolly mammoth. The Columbian, Jefferson's, and imperial mammoths were similar to modern elephants in that they had two large, curved tusks; a long trunk; and little hair. The adults stood about 9 to 15 feet (2.7 to 4.6 meters) tall and had a life span of about 50 years. The woolly mammoth, which lived in the colder arctic tundra, was covered with thick curls of wool overlaid with long, coarse protective hair.

Mammoths differed from mastodons, another elephant­like creature that roamed North America from about 4.5 million to 10,000 years ago. Mastodons were smaller, standing 8 to 10 feet (2.4Ð3 meters) tall at the shoulder and weighing four to six tons. The key difference between mastodons and mammoths was their teeth. Mammoths had flat teeth designed to grind grasses, while mastodons had cones on their teeth that enabled them to feed off shrubs and trees. As a result, mastodons lived in the tropical rain forest and spread into South America.

Mammoths have ancestral roots going back about 35 million years to a swamp­dwelling creature that resembled a small hippopotamus. During eons of evolution, an assortment of strange­looking creatures came and went ­ animals with two or fourtusks, curved up or down, some shaped like flat shovels or corkscrews. Mammoths evolved from this group about four million years ago, but elephants are the only modern survivors.

1. How could changes in the climate at the end of the last ice age push a species toward extinction?

2. What is the biggest threat to modern elephants ­ hunting or climate change? Why?

Vast herds of mammoths roamed the North American continent for more than a million years, surviving several ice ages. At the end of the last ice age, about 11,000 years ago, just after the arrival of human hunters, mammoths became extinct. While the changing climate certainly made life more difficult for mammoths, the added threat of human hunters may have been enough to cause the extinction.

In this activity students divide into small groups and play two games of survival to see how extinction might have occurred when the human hunters arrived.

Materials (for each group)

1. Each team begins with a herd of 20 mammoths, each animal being represented by a single die. The numbers on the dice represent the following events:

1 = Death by starvation
2 = Birth of a calf
3 = Falls into an ice crevasse of the permafrost
4 = Lives well for one year
5 = Killed by giant bears
6 = Lives well for one year

2. Each roll of all of the dice represents one year. For each 1, 3, or 5 rolled, subtract one mammoth from the herd. For each 2 rolled, add a mammoth. For each 4 or 6, don't change the number.

3. Roll the dice for 20 turns, representing 20 years. Keep track of the births and deaths

for each year, then graph the growth or shrinkage of the herd over time. Did any of the teams have a herd go extinct? Did the number of mammoths go up, down, or stay about the same?

4. Play the game again, but this time change the meaning of number 4 on the die to "Killed by Paleo­Indian hunter." Compare your graphs from both rounds of the game with those of the other teams.

Questions

1. Based on your results, would mammoths have become extinct if humans had not come to North America? Explain.

2. Suppose you replaced the meaning of both the "4" and the "1" with "Killed by Paleo­Indian hunter." How would that affect the herd? What other factors might affect the survival of the mammoths?

3. Are there any modern animals that are being threatened by changes to their ecosystem? Is the threat caused by nature, human hunting, or some other human activity?

Invite a geologist, archaeologist or paleontologist from a local college or state geological survey office to talk to the class about what the ice ages were like, why they happened, and if another one could happen. Read some books about the last ice age and try to find some geological evidence of an ice age in your local landscape.

Copy a picture of a mammoth onto a sheet of overhead transparency plastic. Then project this image onto a wall so that the mammoth appears 3m (10') tall. Trace the image onto strips of butcher paper. When the drawing is complete, cut out the animal's outline and assemble the strips into a complete life­size representation.