The Origin of Life

by

S. Blair Hedges

• LAST REVIEWED: 13 January 2014
• LAST MODIFIED: 13 January 2014
• DOI: 10.1093/obo/9780199941728-0045

Introduction

Biological evolution begins with the origin of life, but the subject is the perhaps the most interdisciplinary of any in science. Understanding how life began on Earth requires knowledge of the astronomical, geological, and atmospheric settings. However, those settings are in turn dependent on knowing the time period when life arose, which comes from the fossil and molecular records, including molecular clocks based on genetic mutations. Interrelated with the setting is the chemistry that generates the organic molecules used to assemble the first cells and carry the genetic information to successive generations of cells. But holding the chemical reactions and products together in a cell requires a membrane, and the assembly of that involves biophysics. Thus, we have all of the fields of science coming together to understand a single event that happened about four billion years ago and initiated the Tree of Life on Earth. Because little evidence of anything has remained from this early time, there have been enormous amounts of published speculation on this subject. Narratives on how life originated can be grouped by location (surface versus submarine hydrothermal vents), temperature (cold versus hot), source of energy (heterotrophic versus autotrophic), and evolutionary order (genetics-first versus metabolism-first). I use the last dichotomy here, only because it has a long history and renewed focus in recent years. Currently there is no consensus on any one theory for the origin of life, but this is an active field that has made great strides in recent decades.

General Overviews

There have been many general overviews of the origin of life but few that are updated, do not espouse one particular theory or another, and are written by someone with intimate knowledge of the material. Two works come closest to this ideal. Hazen 2012 is a short adaptation of Hazen 2005 and would be a good place to gain a quick overview. Lazcano 2011, with an emphasis on the history of the field, is another excellent starting place to gain an overview. Gesteland, et al. 2006 and Deamer and Szostak 2010 are edited books on the RNA World and Origins of Life, respectively. They are more technical and mostly written to be understood by graduate students or scientists with some background in the field. Among the shorter, technical reviews, Hedges 2009 takes the perspective of the molecular record, Zahnle, et al. 2007 addresses early Earth geology and atmosphere, and Szostak, et al. 2001 covers the polymerization of nucleotides and cell formation.

• Deamer, David W., and Jack W. Szostak, eds. 2010. The Origins of Life. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.

  This is a nicely integrated collection of separate articles written by experts in those areas, on cohesive themes rather than specific research projects.

• Gesteland, Raymond F., Thomas R. Cech, and John F. Atkins, eds. 2006. The RNA World. 3d ed. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.

  An edited volume of chapters written by experts on different aspects of RNA, biochemistry, and how RNA figures in the origin of life. It is not an overview of the origin of life but rather of RNA research bearing on the genetics-first theories.

• Hazen, Robert H. 2005. Gen-e-sis: The scientific quest for life’s origin. Washington, DC: Joseph Henry.

  A good, even-handed overview of research on the origin of life, written by an astrobiologist.

• Hazen, Robert H. 2012. Geochemical origins of life. In Fundamentals of geobiology. Edited by Andrew H. Knoll, Donald E. Canfield, and Kurt O. Konhauser, 315–332. Chichester, UK: Wiley.

  DOI: 10.1002/9781118280874

  A shortened adaptation of the author’s 2005 book Gen-e-sis: The Scientific Quest for Life’s Origin but with some new references. One of the best overall reviews of this field in concise form.

• Hedges, S. Blair. 2009. Life. In The timetree of life. Edited by S. Blair Hedges and Sudhir Kumar, 89–98. New York: Oxford Univ. Press.

  Reviews the origin and early evolution of life, including the astronomical and physical setting, with respect to organisms, relationships, rooting the tree, terminology, and especially the timing from molecular clocks.

• Lazcano, Antonio. 2011. Origin of life. In Encyclopedia of astrobiology. Edited by Muriel Gargaud, 1183–1190. Berlin: Springer-Verlag.

  DOI: 10.1007/978-3-642-11274-4

  An excellent general overview of the field, appropriate for undergraduates, graduate students, and scientists.

• Szostak, Jack W., David P. Bartel, and P. Luigi Luisi. 2001. Synthesizing life. Nature 409:387–390.

  DOI: 10.1038/35053176

  An essay on advances in membrane biophysics and cell formation, pointing out the importance of evolution and natural selection at an early stage in the origin of life.

• Zahnle, Kevin, Nick Arndt, Charles Cockell, et al. 2007. Emergence of a habitable planet. Space Science Reviews 129:35–78.

  DOI: 10.1007/s11214-007-9225-z

  A comprehensive treatment of the atmospheric, geological, and astronomical setting during the first 300 million years of Earth history.