According to Gary Paulsen, the main difference between animals and humans is that humans use fire.

Paulsen talks about the differences between people and animals to show the difference between how we used to live and how we live now. Before fire, almost no other things would be possible. For example, humans eat cooked meat while animals are able to digest raw meat. Without fire, we'd be stuck eating raw meat.

He says that there are other differences too, like certain inventions: airplanes and cars. But he says that controlled fire is what the biggest difference is.

Paulsen relates a story about being out with the dogs and starting a fire in a fire hole in the snow. The dogs became upset at the sight of it; he says that they'd never seen fire in the kennel. He calmed them, used the fire to warm their meat, and fed them. The mystery, he explains, is in the fear the dogs had of it automatically—and the curiosity they had about it once the fear waned.