Abstract
<jats:title>Abstract</jats:title> <jats:p>The Earth’s past has seen periods of distinct states determined by new biological evolutionary innovations: the planet’s history consists of a dynamic between the evolution of its crust and atmosphere and that of biological evolution—there has been an interrelated co-evolution of life and planet. Further, each of these planetary states is separated by a critical transition that is ‘geologically’ brief (millions of years) compared with the length of these states’ duration (generally on the order of a billion years). All these critical transitions are driven by a major biological innovation and all have a distinct set of characteristics: other critical transitions do not have all these characteristics. That all these characteristics can be seen today suggests that the planet is about to cross a critical transition and enter a new state: the present day is part of an ongoing process stretching back billions of years. That all but one of the major biological evolutionary innovations driving these transitions have arisen multiple times suggests that not only are these common but also ‘easy’ evolutionary steps. That a technology-wielding species has arisen so late in the Earth’s habitable lifetime is less to do with it being a ‘difficult’ evolutionary step but that each of the previous evolutionary steps has to take place first and in sequential order. If this co-evolution of life and planet narrative has merit, then it should speak to the nature of life, and the exobiological probability, on other worlds. It might also explain the Fermi paradox.</jats:p>