Evolution of consciousness: Phylogeny, ontogeny, and emergence from general anesthesia

Consciousness likely emerged early in vertebrate evolution, as the basic neural mechanisms supporting it are ancient and highly conserved across species. The stepwise emergence from general anesthesia can serve as a reproducible model to study consciousness across species. The neurobiological structure of the vertebrate central nervous system is evolutionarily ancient, and the neurophysiologic mechanisms supporting human consciousness are found at the earliest points of vertebrate brain evolution. Differences between species in the ability to experience the world are of degree, not kind, supporting Darwin's insight and the Cambridge Declaration on Consciousness in Non-Human Animals.

Study at a glance

Abstract

Are animals conscious? If so, when did consciousness evolve? We address these long-standing and essential questions using a modern neuroscientific approach that draws on diverse fields such as consciousness studies, evolutionary neurobiology, animal psychology, and anesthesiology. We propose that the stepwise emergence from general anesthesia can serve as a reproducible model to study the evolution of consciousness across various species and use current data from anesthesiology to shed light on the phylogeny of consciousness. Ultimately, we conclude that the neurobiological structure of the vertebrate central nervous system is evolutionarily ancient and highly conserved across species and that the basic neurophysiologic mechanisms supporting consciousness in humans are found at the earliest points of vertebrate brain evolution. Thus, in agreement with Darwin's insight and the recent "Cambridge Declaration on Consciousness in Non-Human Animals," a review of modern scientific data suggests that the differences between species in terms of the ability to experience the world is one of degree and not kind.