Devonian

The Devonian is invoked as a deep-time benchmark for biological survival. In Crowe’s argument, the persistence of Sharks across roughly four hundred million years makes them a model of evolutionary success—and gives the Yrr’s possible greater age an unsettling scale.

A measure of longevity

Crowe points to Sharks as a species group that has survived in unchanged form since the Devonian, dating that persistence to four hundred million years. The period matters here less as a setting than as a unit of comparison: it makes the length of evolutionary time tangible through an organism still present in the modern world.

The argument about success

The Devonian reference appears in Crowe’s challenge to the assumption that humanity represents the high point of life. Sharks, she argues, are a more successful species by virtue of their immense longevity; she also notes that there are three hundred and fifty different species. The comparison shifts the measure of success away from human intelligence and toward survival across deep time.

The Yrr in geological perspective

Crowe adds that the Yrr could be older than Sharks. Johanson later proposes that they may have gained consciousness at the beginning of the Jurassic, around two hundred million years ago, and explains that their DNA preserves knowledge across generations. The Devonian thus anchors a contrast between the known endurance of Sharks and the Yrr’s hypothesized history: their age is presented not as a settled fact, but as part of an argument about how far human ideas of evolutionary superiority may fall short.