Violence... The story so far

Life Ascending By Nick Lane, Research Fellow, University College London.

Extended book Review

In the beginning the earth was null and void of life. But certain precursors were there. As the earth grew by accretion from hot gases left over by second generation supernova, they became trapped by their common gravity. The light and heavy elements segregated in response. The denser materials sank to the center, forming a core of nickel and iron that still exists as the core of our planet. The less-dense outer layers formed a thickening shell about the core. These layers, comprised of mixtures of heavy and light elements found comfortable arrangements by forming minerals of this composition and that, peridotite and pyoxene being prominent members. Antigorite happens to incorporate water into its structure. With the passage of time, these minerals reacted to one another at high temperatures and pressures to form the various varieties of serpentine. The outermost layer is made up of the lightest elements, hydrogen, oxygen, nitrogen and the noble gases—that do not react to form dense compounds. Earth atmosphere and oceans are comprised mostly of just the four light gases. In-fall from space included methane, and water as well as other organic substances that include amino acids. From this odd random mixture of minerals, organics, liquids and gases, life arose spontaneously, given the impetus of a thermal gradient conveniently provided by the central star of this new solar system as well as the volcanism of the new earth, life arose. What happened from there is the subject Lane develops so admirably and vividly, that we could not put the book down until we had devoured it.

The early atmosphere was composed mostly of carbon dioxide, methane, ammonia, and small amounts of water vapor, quite unsuitable to life as we experience it. That was not to change much for some four billion years. But early on, oceans existed. Residual heat from the infall along with new heat from radioactive decay led to hydrothermal-steam vents arising from the earth’s interior.

There were two basic types, black smokers—new vents driven by potential volcanoes—and the far more delicate non-smokers akin to present earth-surface hot springs, usually driven by residual heat left over from volcanic activity. These two extremes of vent features differ in their acidity, or pH, and other elements and compounds such as such as hydrogen and hydrogen sulfide. This is where the key presence of the mineral serpentine comes in. It acts as a catalyst that enables or speeds chemical reactions that provide the brick in the wall of life.

Now, when free hydrogen and carbon dioxide atoms meet, they can form a hydrocarbon, and by doing so they release heat. In Lane’s words: “… from a thermodynamic point of view, the reaction is a free lunch.” It happens spontaneously. Life at the bacteria and archaea levels are thus a given from nature. There is of course much more to all this as Lane takes great pains to explain, but our time and space are limited. There is much reason to believe that Bacteria and Achaea arose separately.

The next and most interesting of the stepping stones to humanity comes with the advent of the eukaria, the third great domain of life. Since eukaryotes are complex cells that contain genes from each of the prior forms, they likely arose from a union of the earlier two. Exactly how that came about is still a subject of research. A second way eukaria might have evolved is by splitting off from the archaea. That idea relates to the fact eukarya share more genes with the archaea than with the bacteria. This also implies that bacteria came first. It may have taken as long as a billion years or more, but happen it did. Eukariotes comprise all the visible flora and fauna, plants and animals, of life as we know it. In short, we have more in common with earthworms, fish, birds and pine trees than we have with either bacteria or archaea. And that is a marvelous fact to contemplate, as it affects virtually every human activity.

The full story is long and fascinating. But Lane is up to the task. Drama at every turn, and scientific as well. It beautifully augments Natural History and Laws of Nature

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For more see

• Archaea
• Biodiversity
• Lane’s book
• Space Daily
• The Phylogeny of Life