Evolution was a hot topic when Burroughs wrote The Land That Time Forgot in 1924. During the early part of the century, many states banned the teaching of scientific evolution, insisting on a biblical account of creation. In 1925, a high school teacher in Tennessee, John Thomas Scopes, was arrested and tried for teaching evolutionary theory, his case—referred to as the "Monkey Trial"—attracting worldwide attention.

Now, more than half a century later, the issue remains unsettled, although the law currently protects the teaching of Darwinian theory.

Burroughs's depiction of evolution in The Land That Time Forgot is in some ways a naive one. Evolution in Caspak is founded on the basic idea that primitive organisms evolved into fish, which evolved into reptiles, which evolved into mammals and birds—but the mechanism for this process is not described. Natural selection seems to have little...