Vital Question: Energy, Evolution, and the Origins of Complex Life

Biochemistry is in the midst of a golden age of discovery and Nick Lane is at the forefront, winning numerous awards in his contributions to the life sciences. In this work, he has identified the vital unsolved questions in the field of biology and has provided plausible solutions to these mysteries including: the enigma of why life emerged only once on this planet, why no evolutionary intermediaries exist between simple and complex life, and the most vital question of all, how life began. During the earth’s four billion year history, it appears that life emerged only once, just 500 million years after the earth’s formation. Early life consisted of prokaryotes (cells without a nucleus) in the form of bacteria and archaea, a third domain of life discovered by Carl Woese in the 1960s. Over billions of years through extreme environmental and ecological changes, these organisms have filled every conceivable niche on our planet. Photosynthetic bacteria have bioengineered our planet on a colossal scale, creating the oxygen we breathe, changing the chemistry of the atmosphere and oceans, building up continents with sedimentary rock and minerals as their bodies fall to the ocean floor, in short, creating Gaia, our living planet. Yet, after all this time, they have shown little change in form or complexity. Then, seemingly without any intermediate steps, the eukaryotes (cells with a nucleus) sprang into existence giving rise to all plants, animals, and fungi found today. According to the cherished standard model of evolution, evolutionary changes occur incrementally. With this in mind it is hard to understand how complex eukaryotic cells appeared virtually overnight. In 1967, Biologist Lynn Margulis proposed a modification to the standard model of evolution. Her astute analysis of paleontological history revealed that evolution rarely occurs in a Darwinian or Malthusian way in which species battle for limited resources. Instead, she discovered that most evolutionary advances occur as a result of cooperation and symbiotic relationships. Margulis went further when she proposed the radical idea that cells cooperated so closely that they merged by getting inside one another. It is now widely accepted that mitochondria in animals and chloroplasts in plants are the result of endosymbiosis between bacteria and archaea. Author Nick Lane believes that early on in the history of life on earth complex eukaryotic cells arose on just one occasion through a singular endosymbiosis between an archaeon host cell and a bacterial invader creating the precursor of eukaryotic cells. Lane says that this endosymbiotic event might have occurred more than once but those experiments never survived. Over time, all of the complex features of modern eukaryotes including straight chromosomes, a membrane-bound nucleus, mitochondria, specialized organelles, a dynamic cytoskeleton, and total organism replication and reproduction arose by standard Darwinian evolution. Evolutionary theory tells us how life begets life, but it tells us nothing about how life began in the first place. This was the vital question Lane set out to solve. All cells, both eukaryotic and prokaryotic, have one essential commonality involving the method of energy production by burning food in the process of respiration. All living cells power themselves through a process of pumping protons across a membrane creating a reservoir of electrical imbalance. The back-flow of these protons is used by cells to produce physical work such as turning the rotors of nanomachines, just as water through a dam turns a turbine. This process provided Lane a clue in his attempt to find geochemical processes that would mimic biological energy production. If he could discover this mechanism in the natural world, it would go a long way in solving the mystery as to how life emerged from geochemical processes. In this vein, Lane formulated his own recipe for the emergence of biological chemistry from geochemistry—rock, water, and carbon dioxide. These simple ingredients are not only abundant in our atmosphere but are abundant throughout the known universe. But one cannot simply put these ingredients in a bowl and stir. To begin the chain of chemical reactions leading to life, it is necessary for hydrogen gas (H2) and carbon dioxide (CO2) to react with one another to produce one of the simplest organic molecules—methane (C4). This reaction does not occur under normal conditions. In fact, it is very difficult for hydrogen to react with carbon dioxide and this was one of the problems that confronted Lane. All cells derive their energy from reduction/oxidation (redox) reactions in which electrons are transferred from a donor to an accepter molecule. Typically, the accepter is oxygen but any two molecules can perform redox reactions. The molecule that receives electrons is said to be reduced and the molecule that gives up electrons is said to be oxidized. In respiration, or in a fire, where carbon is burned, oxygen is reduced to water, in which oxygen atoms pick up two electrons (as well as two protons that make up the hydrogen atom) producing a final product of water and carbon dioxide. In the case of hydrogen gas (H2), an alkaline, and carbon dioxide (CO2), an acid, it is hydrogen gas that wants to give up its electrons and become oxidized. Carbon dioxide, on the other hand, wants to accept electrons and be reduced. Each has a reduction potential, which is the amount of energy released when the reaction occurs. If a molecule (in this case hydrogen gas) wants to give up electrons, it has a negative value (-414 at a neutral PH) for a reduction potential, and alternatively, a molecule that wants to accept electrons, in this case carbon dioxide, has a positive value. The reduction potential is dependent on the acidity of a solution. High acidity increases the reduction potential of carbon dioxide making it more positive and easier to accept electrons whereas alkaline solution increases the reduction potential of hydrogen gas making it more negative and more likely to give up its electrons. One would think that by changing the acidity of a solution it would be easier for hydrogen gas and carbon dioxide to readily react with each other, but changing the acidity of a solution affects all of the molecules in the solution in the same way, so hydrogen gas (H2) will tend to pass on its electrons to H+ to form CO2 and H2. Nothing is gained and we’re right back where we started. Simply changing the acidity of a solution won’t make it any more likely carbon dioxide and hydrogen gas will react to produce methane. Lane was not deterred, believing that if there really is a continuum between geochemical and biological processes there should be a way to react CO2 with H2 naturally. He turned his thoughts to the ocean depths. Alkaline hydrothermal vents seemed to Lane to be good candidate for the continuum between geochemical and biochemical processes. Alkaline vents are not volcanic, but originate from the sea floor and are a product of a chemical reaction between water and rocks rich in olivine. Olivine is rich in ferrous iron and magnesium and when mixed with water the ferrous iron is oxidized to ferric oxide releasing heat and generating hydrogen gas dissolved in warm alkaline fluids containing magnesium hydroxides. According to Lane, alkaline hydrothermal vents have the perfect physical and chemical environment to kick-start life. Alkaline vents have a microporous structure like a sponge with thin electrically conductive walls separating interconnected pores. Warm currents passing through these micropores concentrate organic molecules such as amino acids, fatty acids, and nucleotides. The interactions between these molecules often precipitate fatty acids into vesicles, the precursors of cell walls, and occasionally they will polymerize amino acids and nucleotides into proteins and RNA. These porous vent structures mimic the biological structures in mitochondria that pump protons across a gradient. But before it is possible to concentrate organic molecules, it is necessary to create them and this was only one of the problems facing Lane: If these alkaline hydrothermal vents create life, then why aren’t they incubating life today? It occurred to Lane that conditions three and one half billion years ago in Hadean times are far different than conditions now. Under today’s conditions, there is not enough carbon to incubate life; however, estimates suggest that CO2 levels were anywhere from one hundred to one thousand times higher in Hadean times making the oceans more acidic. The combination of high carbon dioxide levels, mildly acidic oceans (PH 5-7), and warm alkaline fluids flowing through thin electrically conductive Iron sulfide vent walls would have made them ideally suited to react carbon dioxide with hydrogen gas to form methane (C4) as long as oxygen is not present. Under these conditions with temperatures between 25 and 125 degrees centigrade, the formation of all four of the macromolecules essential for life: amino acids, fatty acids, carbohydrates and nucleotides should form spontaneously from the reaction between hydrogen gas and carbon dioxide releasing energy in the process. Lane had found his geologic “mitochondria” in the form of alkaline vents on the ocean bottom. His hypothesis of a seamless transition between inorganic processes and organic processes was realized. Nick lane’s book The Vital Question is dense but accessible for the lay person who has patience. I think this is one of those landmark books that offer very plausible hypotheses for the vital questions concerning evolution, and the origins of life.

The book covers three inter-related topics: the origin of life, the origin of complex organisms (eukaryotes), and the consequences of having a dual system of inheritance (nuclear and mitochondrial genes) in complex organisms.Lane proposes that the system by which most organisms convert energy to usable biochemicals (especially ATP) provides an important clue about how life originated. Organisms pump hydrogen ions outside of a membrane in a fashion analogous to a pump that pushes water into a water tower. Much as the flow of water out of a tower can be used to power an electric generator, organisms use this hydrogen ion gradient to produce ATP which serves as universal source of energy for cells.Lane argues that deep-sea alkaline hydrothermal vents provided all the conditions necessary for the origin of life. These vents continuously provide hydrogen and carbon dioxide which can be combined to yield energy and organic compounds. These vents also contain metallic compounds, especially iron and sulfur containing compounds, that could serve as catalysts for the chemical reactions needed by the precursors of living organisms. Furthermore, the structures created in these vents contain pores that could serve as nurseries for the precursors of living organisms. Most importantly, boundaries in these pores permit the creation of an electrochemical gradient similar to hydrogen ion gradient that exists in living things.Complex organisms, called eukaryotes, are much larger than bacteria and have multiple structures inside the cell, especially mitochondria and nucleus. This branch of the tree of life includes all multi-cellular organisms such as fungi, plants, and animals. The other two branches of the tree of life, bacteria and archaea, have never produced multi-cellular organisms despite their great versatility with regard to the substances they can consume and environments they can grow in. Lane describes the evidence that eukaryotes arose from a merger (symbiosis) between bacterial and archaeal organisms. He also proposes that this happened just once in Earth's history. This isn't a new theory but Lane extends it by developing hypotheses about the detailed events in this process, such as the origin of the cell nucleus.Complex organisms have DNA in two different places, the cell nucleus and the mitochondria. The final section of Lane's book explains the consequences of this, arguing that certain attributes shared by all eukaryotes, such as senescence, and sex are logical consequences of this arrangement. This is because the actions of ordinary, nuclear, genes must be tightly matched to those of mitochondrial genes for the electrochemical gradients in the mitochondria work optimally. This has substantial consequences for human health. Lane argues, for example, that the high frequency of spontaneous miscarriages in people could be the result of occasional mismatches between nuclear and mitochondrial DNA. Another, equally provocative, example is the role of free radicals in health. He proposes that free radicals produced when mitochondria are not functioning optimally may impair health but that anti-oxidant substances such as vitamin C only make things worse by interfering with normal feedback controls.It is difficult to say who the intended audience is because it isn't either a typical popular science book or an academic treatise. Its style is informal, all terms are carefully explained, and it has many helpful the illustrations. But a sizable fraction of the material is much more challenging than typical popular science books. Many times, I had to slow down and reread sections to make sure I understood the topic at hand. But it isn't an academic work or even a textbook; the kinds of details academic readers want, such as detailed citations, simply aren't there. It would help if you have a general familiarity with college level biology and some chemistry. Having some knowledge of biochemistry might help but it isn't necessary since Lane mostly avoids describing biochemical details.If you can manage to give this book the careful reading it deserves, you will be amply rewarded with a fresh and intriguing view of the topics at hand.Some of this material is covered in an entirely different way in Franklin Harold's "In Search of Cell History." If you like one of these books you will enjoy the other as well. Furthermore, comparing their different viewpoints will allow you to see the issues more clearly.

A fascinating book that explores the origins of life and the origins of complex cells. Lane provides interesting insights into these topics and makes a convincing case. The book is a bit of a challenge and requires a careful read. For the most part, his explanations were clear and the writing was good, but from time to time, he would explain many possible ways something could have happened but then would go on to say why he thought they did not happen this way. I found that this added to the challenge of an already difficult book.

This book is an excellent review of the origins, based on molecular and cellular biology of the main groups of life (Bacteria, Archaea, and Eukaryotes...us, eventually!) It is written at a level where recent high school biology and perhaps undergrad university study wold be a help, and while I have all of that, and more, it would still be intelligible. Nick Lane is a good, pleasant style writer. While there are parts I don't quite understand because I am not as familiar with this discipline, it is very neat to see the pathways by which we evolved from 'water, rocks and carbon dioxide'. The wonder of abiogenesis is not out of reach.I heard about this book through Sean M. Carroll, the theoretical physicist of Mindscape podcast and blog, a source I trust, and I was pleased.

good nick,good book.

One of the best and influential book I have read in my lifespan

It is a very well written book, very entertaining, lots of knowledge. However, be aware that this book present only a single possibility (i.e., a theory) for the origin of life, which has also presented problems in recent years. Although very appealing, alkaline hydrothermal vents are not without their troubles.

Un livre essentiel pour suivre l'évolution de la connaissance, ici sur l'origine de la vie et les mécanismes qui en son le fondement,