Pliocene

The Pliocene is a deep-time epoch whose traces in the novel make geological history tangible and unsettle the assumed separation between humanity and prehistoric life. Its fossil evidence links the travelers’ underground landscape to contemporary debates about how far back human existence might reach: the narrative describes Pliocene animal remains bearing signs of human workmanship, and presents these discoveries as a reason to imagine people preceding the mastodon by more than one hundred thousand years.

Geological Setting and Fossil Traces

As the travelers cross the plains of the Hardwigg Ocean, the ground itself records a vanished marine world. They tread on layers of stony relics resembling flints worn smooth by waves, while enormous shells—some more than fifteen feet across—are identified as the carapaces of Pliocene Glyptodons. The modern turtle, by comparison, is only a minute specimen. These remains make the epoch legible through scale and accumulation: the sea has withdrawn, but its former reach persists in the rocks and fossils far inland.

The landscape prompts the narrator to theorize about the underground ocean. He suggests that water may seep down from the ocean above through minute fissures, while the subterranean fires may vaporize some of it, helping to account for clouds and storms over the cavernous sea. This is offered as his conjecture, not established geological fact; the fossil shoreline gives the theory a material point of departure without resolving the mystery.

Human Antiquity and Scientific Debate

The Pliocene also enters the narrative through the nineteenth-century controversy over human antiquity. The account recalls the 1863 discovery of a human jawbone fourteen feet beneath the soil at Moulin-Quignon, near Abbeville, alongside stone hatchets and carved flints. Its authenticity and geological age became contentious. Professor Hardwigg supported the view that the jawbone belonged to the Quaternary, while Elie de Beaumont argued that the deposit was less ancient and rejected the idea that humans had lived alongside Quaternary animals.

Further finds in caves in France, Switzerland, and Belgium—including other jawbones, tools, and human remains—are described as strengthening the case for Quaternary humanity. More provocative still were Pliocene deposits containing fossil animal shinbones and thighbones that appeared deliberately hollowed and sculpted. The narrator distinguishes these artifacts from human bones: they were not themselves the remains of people, but objects he takes to bear unmistakable signs of human workmanship. On that basis, the account presents some scholars as assigning humanity an antiquity exceeding one hundred thousand years and placing humans before the mastodon, alongside the southern elephant.

Deep Time as Narrative Discovery

The travelers’ fossil discoveries give physical force to the scientific dispute introduced in retrospect. When Professor Hardwigg encounters a recognizable human skull in the underground cemetery, the discovery appears to bring the question of prehistoric humanity into immediate view. The narrative’s movement from a reported jawbone controversy to fossilized evidence encountered underground makes deep time more than an abstract chronology: it becomes a landscape through which the characters travel and a challenge to the limits of accepted knowledge.

The epoch therefore has two connected roles. It names the ancient world suggested by the Glyptodons and the sea-worn terrain, and it marks the boldest reach of the period’s debate over human origins. The novel stages these claims through competing scientific positions and the explorers’ startling finds; its Pliocene chronology belongs to that nineteenth-century intellectual setting and imaginative journey, not to present-day scientific consensus.