The co-evolution of life and Earth

It has long been recognized that deciphering the relationship between the history of life on Earth and the history of the planet is a profound task. Recent technological innovations in both the earth and life sciences have made this task more tractable than ever before, leading to the emergence of the discipline of geobiology — the study of how organisms have influenced, and been influenced by, the Earth’s environment. Along with enthusiasm for this new field, however, has come confusion, as geobiology combines highly specialized and historically separate fields. How does a sedimentologist communicate his/her problems to a cell biologist and vice versa? The fact that geobiology derives from two disparate scientific traditions — those of natural history and experimental science — can make identification of appropriate problems challenging. As C.P. Snow [1] recognized nearly a half century ago in his famous lecture ‘The Two Cultures’, communication between different disciplines often results in “a gulf of mutual incomprehension” that can be difficult to ford. Although Snow was referring to the divide that separates the humanities from the sciences, many of his insights can be applied to the divide that until recently has separated biology from geology. In this Primer, we shall attempt to illustrate the compelling nature of geobiology by highlighting two geobiological problems. Our goal is to introduce molecular and cell biologists to this discipline, and make it clear just how much their skills can contribute to it and their questions benefit from it. We begin with a brief review of what is known Primerabout the geochemical evolution of the Earth. From there, we provide What we do and do not know about the Earth’s geochemical evolution Geologists use sedimentary rocks as probes to study the environments in which the primary sediment was originally deposited. A sandstone may contain structures useful for inferring water depth or flow velocities, while a rock formed primarily by precipitation may contain minerals or elemental distributions useful for inferring the abundances of certain chemical species in the precipitating fluid. By studying relevant rocks deposited in different environments and at differen