Origins — Module 2

The Origin of Life

"To the honest man ... the origin of life appears ... to be almost a miracle, so many are the conditions which would have to be satisfied to get it going"

Francis Crick — Biochemist, discoverer of the structure of the DNA molecule

"Life is improbable, and it may be unique to this planet, but nevertheless it did begin and it is thus our task to discover how the miracle happened"

Euan Nisbet (The Young Earth, 1987)

Introduction

This module is about the origin of Life — one of the most fascinating of all subjects of enquiry. It is one of the most profound (and difficult) scientific questions that we can address. But it is much more than that, for the answers we find to this scientific question have a bearing on our own search for identity.

The module is in three parts. The first part sets the scene and explores theoretically the steps that we need to go through in order to create something living from something that is non-living. The second part of the module introduces the reader to 'what we know' — a discussion of the more fruitful lines of evidence which point towards the origin of life. These lines of evidence tend to be biased towards what is known from the Earth Sciences. Thirdly, the module examines what is currently a very popular hypothesis for the likely location of the origin of life on Earth: hydrothermal vents, forming today on the floor of the oceans, are thought to be a very likely environment within which the first life evolved.

Understanding the origin of life on Earth is but a part of a larger field of enquiry — that of the search for Life in the Universe. This is the major theme of NASA's astrobiology programme (sometimes the North Americans call this science 'exo-biology'). You will find a wealth of useful materials on their web site at http://astrobiology.arc.nasa.gov/. A good starting place for a search of this web site is the research goals which are described at http://astrobiology.arc.nasa.gov/roadmap/goals/index.html.

Other useful links are at:

• http://web99.arc.nasa.gov/~astrochm/originlinks.html
• http://www.geocities.com/CapeCanaveral/Lab/2948/originoflife.html
• http://www.resa.net/nasa/origins_life.htm#extreme

Printable versions of this module

Table of Contents

1. Steps to the Formation of Life
2. Step 1: A Biotic Synthesis
3. Step 2: Pre-biotic Synthesis
4. Step 3: Synthesis of Proteins and Nucleic Acids
5. Step 4: Synthesis of a Process of Replication
6. Step 5: Formation of a Single Cell
7. Step 6: Energy for Sustaining Unicellular Life
8. Post-script: The Cosmic Ancestry of Organic Matter
9. Evidences for the Earliest Life on Earth
10. The Earth's Oldest Fossils
11. Chemical Signals of Former Life on Earth
12. So When Did the First Life Appear on Earth?
13. Appendix:
14. Understanding Carbon Isotopes
15. Hydrothermal Vents — Where it all Began?
16. Evidence from the Family Tree of Bacteria
17. Protected from Impacting
18. A Source of Thermal Energy
19. A Source of Mineral-rich Solutions
20. A Source of Reducing Fluids
21. The Importance of Mineral Surfaces to Facilitate Chemical Reactions
22. An Environment in which the Cell Wall Could Evolve
23. Module 1: The Origin of the Earth
24. About the Author