The co-evolution of life and Earth

Abstract

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 about the geochemical evolution of the Earth. From there, we provide two examples of problems relevant to the co-evolution of life and Earth. The first example illustrates how a better understanding of biology — specifically, the distribution and function of sterol-like molecules in bacterial membranes — will inform our understanding of the rise of oxygen, arguably the most important event in the geochemical evolution of the Earth. The second example illustrates the counterpoint: how a better understanding of changes in the Earth's geochemistry over time can affect our interpretations of organelle evolution, specifically, the relationship between hydrogenosomes and mitochondria.

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