In his preface to this novel, Harry Turtledove reveals that the idea for it came from an article by Stephen Jay Gould speculating about how humanity’s distant cousin, Australopithecus, would be treated if that species had survived. Turtledove decided to use a nearer cousin, Homo erectus, in his story. The short answer that he provides to the above question is “not very well.”
The story begins with an entry from a fictional reference work that establishes that the novel takes place in an alternate reality, with the difference that the New World, when discovered by Europeans, was populated by Homo erectus, dubbed “sims” by their discoverers. Living in bands of hunter-gatherers but lacking the neocortex, spoken language, and superior reasoning skills of Homo sapiens, sims were less efficient hunters than the denizens of the Old World. Consequently, species hunted to extinction in Europe and Asia still flourish in the New World. Among these are saber-toothed tigers and woolly mammoths.
Subsequent historical entries describe the settlement of the New World, the development of a rail system powered by woolly mammoths (later replaced by steam engines), the rise of plantation agriculture sustained through the enslavement of sims, and the development of a growing sims-rights movement. Each of these entries is followed by an expository episode that gives the details of the changes described.
(The entire section is 406 words.)