This documentary said about 37 huge mammals lived in North American thousands of years ago. Then, poof! They vanished. This work has great computer graphics. Those who liked "Ice Age" film may really like this.The problem is that they test their theory, which I'll try not to give away, by looking for a chemical element in ice and dirt. Yawn! Talk about a sexy intro with a frigid conclusion. This was dull. It just took the viewer along with the boring work that scientists do, not the cool summary that gives you info and allows you to move on.