Characters who travel back in time take responsibility for not doing anything that might alter the future. Even the smallest change could have a multiplying effect that would render the future quite different from what it is. As Travis says,

A little error here would multiply in sixty million years, all out of proportion.

To behave responsibly, the people on the safari have to stay at all times on the special path the time travel company has built out of antigravity material so that it does not touch anything. They can't leave the path for any reason or so much as crush a blade of grass.

Unfortunately, Eckels panics when he sees the T. rex he came to hunt and leaves the path. He smashes a butterfly, and when the time travelers come home, history has been altered. A strongman dictator has been elected president of the United States.

Though Travis apparently shoots Eckels once they are back, it is not clear that either man takes full responsibility for what happened. Eckels, a very wealthy man used to buying his way out of trouble, is trying to avoid responsibility until the end. Travis's killing of Eckels—or possibly himself—in reality solves nothing.

The story cautions against using powerful technologies for frivolous reasons, such as taking people on a safari to the past for thrills. Technology should be taken seriously and treated with respect. Starting a company so that rich people can shoot dinosaurs is inherently irresponsible.