Monday, April 24, 2017

Book Review: Andrew H Knoll, Life on a Young Planet

Andrew H Knoll: Life on a Young Planet, Princeton University Press (2003, 2015), 246 pages, index, numerous photos and diagrams, very extensive "further reading" list for those who want to pursue the origin of life and early evolutionary development.

We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time      T S Eliot

Despite an almost bewildering diversity of form and function, all cells share a common core of molecular features.. The reciprocal observation is equally striking. In spite of their fundamental unity of molecular structure, organisms display extraordinary variation in size, shape, physiology, and behavior. Life's unity and diversity are both remarkable in their own ways; together they comprise the two great themes of comparative biology. (page 17, emphasis added)

Animals may be evolution's icing, but bacteria are the cake (page 19)

abbreviations used in this article:

CO2: carbon dioxide, involved in the photosynthesis / respiration cycle. It is also a greenhouse gas, trapping heat (infrared radiation) and warming the earth.

Mya: million years ago 

geological periods discussed:

Cambrian: 543 Mya to 485 Mya. During the "Cambrian Explosion", "large" - multicellular - plants and animals appeared. "Modern" - oxygen breathing- forms of life proliferated in the seas and soon spread to land in the following order: plants, arthropods (insects and their kin) and, finally, our own ancestors, the vertebrates (marine tetrapods)

Proterozoic (also called the pre-Cambrian): about 2.5 billion to 543 million years ago. Aside from colonial microbial stromatolites which formed coral-like structures in water, life was microbial. See two stromatolite photos below.


            Most definitely a nerd book. The intended readership are both science literate general readers and workers in the earth and life sciences. To appreciate this text fully you need a decent background - self-acquired or school learned - in the earth sciences, paleontology and evolutionary theory in particular. A basic grounding or working knowledge in biology (ecology) and (bio)chemistry helps. On the plus side, the author's style is remarkably readable. Essentials are generally well explained, allowing the novice to tread into deeper waters than they otherwise would be capable of handling.

            The subject of Life on a Young Planet is the appearance and evolution of early life on earth before the Great Cambrian Explosion, about 600 million years ago (Mya), when "large" (visible to the naked eye) plants and animals wildly proliferated and "the world as we know it" was born. On young earth, life was microscopic: bacteria, one celled animals and plants.

 How old is life? The first microfossil traces of life are hotly contested. Mineralogical processes can produce microfossil like structures. Finding "biomarkers", chemical signatures of life (or of its decomposition products), in association with putative microfossils can, in some circumstances, provide a strong case that one is dealing with real microfossils. Today, claims of microfossils 3.7 years old are being made. If confirmed, they would indicate an extraordinary early emergence of life. The solar system was born 4.5 billion years ago and the earth itself is only about 4 billion years old!

The modern tree of life, based on genetic similarity. Modern multicellular animals and plants are found in the upper right hand corner among the "more evolved" Eukaryota. Click on image to enlarge.

Everything you wanted to know about Archaea - the extremophiles - but were afraid to ask: 

 A modern testate amoeba, which lives in a mineral shell which is secreted by this one celled "animal" (technically, a protist, neither animal or plant). Testate amoebas are Eukaryota, "more evolved" lifeforms, and lie on the rightmost branch of the Tree of Life along with animals and plants. See above diagram. They are one of earliest animal-like life forms dating back at least 750 Mya, well before the Cambrian Explosion when modern multicelled animals and plants proliferated, diversified and flourished. Testate amoeba are still important members of contemporary aquatic and soil ecosystems!

 A fossil testate amoeba shell unearthed by author Knoll. The white bar on the lower left of the photo is 25 microns (millionths of a meter). The shell is thus about 100 microns in length, the width of the average human hair. It was secreted about 720 to 635 Mya in the pre-Cambrian.

          Video of living testate amoeba. The shell is composed of sand grains cemented together with silicic acid secreted by the amoeba.

           Over time early microbes developed communal "biofilms". Later, biofilms would evolve into the tissues of higher multicellular organisms like plants and animals). Stromatolites are pseudo-corals consisting of layers of mineral matter (sand grains or fine sediments) alternating with photosynthesizing microbial mats. Stromatolites may achieve impressive dimensions and some stomatolite fossils have been dated at a credible 3.5 billion years. Interestingly, living stromatolites are found in some seas today.

 living stromatolites, Shark Bay, Australia

 pre-Cambrian stromatolite fossil from Bolivia

        Life on a Young Planet argues that life is a co-dependent, co-evolving network of energy flows, chemical cycles and living organisms, a living tissue or fabric which includes the body of the earth itself, its seas and atmosphere. The health of individual organisms and species ultimately depends upon the integrity of the whole fabric, a lesson humanity is painfully learning today because of our disruption of vital ecological systems and the chemical equilibria of the planet.

         An interesting example of co-dependence and co-evolution are the Eukaryota, the domain which includes dominant modern life-forms like plants and animals. It is now believed that the Eukaryota arose from the symbiotic co-dependence of single celled organisms. It is believed that the mitochondria - the sub-cellular "organelles" which our bodies' cells use to burn sugars with oxygen to liberate vital energy - were once free living organisms. Several lines of evidence support this conclusion, including the fact that mitochondria contain their own DNA (genetic code) and replicate independently when our bodily cells replicate.

         From the micro-level to the macro-level, the co-dependence and co-evolution of life is evident. Plants absorb carbon dioxide (CO2) from the air and water from the soil. Using the energy of visible light rays from the sun, sugars, starches and other energy rich molecules are synthesized from CO2 and water during photosynthesis. Oxygen is released as a by-product. Photosynthesized energy rich hydrocarbons  (sugar, starch, oil, fat) form the basis of the food web. Herbivores eat plants to incorporate energy rich hydrocarbons to power their metabolisms. Carnivores eat herbivores to incorporate energy rich molecules incorporated in the herbivores bodies. Through co-dependent co-evolution, efficient carbon cycling was established over time: the photosynthesis / respiration cycle. Plants absorb CO2, synthesize energy rich hydrocarbons and release oxygen during photosynthesis. Animals respire the oxygen released by plants to burn energy rich hydrocarbons, releasing CO2 in the process. A rough equilibrium between photosynthesis and respiration has been established over time allowing all organisms to flourish. Too much oxygen, and our forests would burn up in planetary conflagrations while too little would prevent the emergence of animal life.

          But  co-dependent co-evolution runs even deeper. Both plants and animals are Eukaryota. When these organisms die most of their organic matter is quickly recycled by decomposers: insects, worms, fungi, bacteria.. But not all organic matter is recycled. In water, organic matter may precipitate to the bottom as sediment before it decomposes. Such environments are often anoxic, contain little or no oxygen. Now, Eukaryota like plants and animals require oxygen and are therefore incapable of extracting energy from buried sediments (and, in the process, recycling vital bio-elements back into the environment, in this case, sea or lake water). Only anaerobic prokaryota - micro-organisms not requiring oxygen for metabolism - are capable of processing buried organic matter to liberate essential bio-elements like nitrogen and sulfur. In effect, without the recycling activity of the "lowly" prokaryota, we "more evolved" Eukaryota would disappear as vital bio-elements were buried and removed from biospheric circulation! The "web of life" is much more than a fuzzy New Age or mystical meme. It is a literal, physical reality upon which our very lives depend..

         As prof Knoll puts it so eloquently,

"Life on a Young Planet records that moment in time when biologists and Earth scientists began working together to build an integrative picture of our planet's history. We now know that we can only understand life's evolutionary trajectory by embedding it in the chronicle of Earth's dynamic environmental history. That is the lesson of deep Earth history, and it is also a lesson for today, when human technology has emerged as an environmental force of geological prominence. Whether we look outward, searching for a second example of life, or forward, hoping to navigate wisely through an era of mounting global change, the record of Earth and life through time provides a fundamentally  important catalog of experience that can help guide our actions." (page XV, emphasis added)

          As is so often the case with the best science writing, much of the charm of this book comes from it's evolutionary approach to science itself. The clash of competing theories, the fruitful alliances between disciplines, the slow unearthing of critical clues.. all these are grain for Prof Knoll's mill. For those interested in life's early history and deep ecology and who possess the requisite science background, this book is a must read. Even novice earth science readers should find it a challenging and stimulating read (and don't forget the extensive suggested reading list for aid..) Definitely recommended.

"For scientists, unanswered questions are like Everests unclimbed, an irresistible lure for restless minds" (page 224)  

Tuesday, April 18, 2017

(More) hidden costs of fossil fuel use

 Fort McMurray, Alberta, summer 2016, a monster forest fire - nicknamed The Beast - consumed some 500,000 hectares of boreal forest, an area larger than the province of Prince Edward.

"The fire destroyed 2,400 structures, nearly 10 per cent of the city, when it ripped through in May and forced more than 80,000 residents to flee." 

Links to our articles on the Big Fire:

         A year, nearly, has passed since The Beast passed through Alberta, enough time to begin to register some of its long term effects. Since calamitous fires like the Beast will become more common in a greenhouse gas warmed world, we can begin, if not to measure, at least to appreciate what some of the costs of continued fossil fuel use will be.
externalized cost: Fundamentally, cost externalization occurs when a company transfers some of its moral responsibilities as costs to the community directly or as degradation to the environment. For example, railroads and airlines transfer the cost of fuel, noise, and terminal infrastructure to the community. Airlines and auto manufacturers transfer the cost of degraded air quality to the community and the environment. By externalizing to the community or the environment, many true costs become lost in analysis because the true cost is non-quantifiable and neither the community nor the environment have effective advocates to recoup the damages. A major modern theme in the relationship of business to society is the society's ability (or inability) to resist this kind of externalization. In its extreme, society collapses as business realizes its profits. (Wikipedia: cost externalizing) 
       In effect, the long term human and environmental costs of present and future Fort McMurray-type fires are the externalized costs of employing fossil fuels to power our industrial lifestyles. The continually rising costs of these "negative externalities" pose vital questions to industrial society:

1- are the benefits of our modern lifestyles worth the cost?

2- are their other ways - renewable energy, for example - to obtain the benefits of modernity while avoiding the rising externalized costs whose impacts we are finally beginning to appreciate? 

      What then will some of the future costs of continued fossil fuel use be? What can we expect?

       For openers, the brave, self-sacrificing men who physically and emotionally over-extended themselves fighting The Beast are (probably) damaged for life:

"The University of Alberta study found one in five of the 355 firefighters surveyed reported persistent respiratory issues including coughing, breathlessness, wheezing and chest tightness. And they're battling more than just physical ailments — mental-health issues affect 1 in 6." 

       While it is still too early to tell what the long term impacts of the Fort McMurray fire will be, the earlier Slave Lake fire of 2011 may offer some insights:

"Coutts said the Slave Lake fire hit his department hard — half the firefighters quit within the subsequent two years, and many reported ongoing respiratory issues."

       Imagine! Fifty percent felt obliged to quit their profession because of psychological and / or physical aftereffects. These are the kind of human - and social - costs we should expect on our greenhouse gas warmed future earth. Think of all the money invested in training those fire fighters and all their experience lost. Then there are long term public health costs, to be borne primarily by the taxpayer (not the fossil fuel corporations or their "officers"). Consider also the human costs of post-traumatic stress disorder and broken health: self-medication, drug and alcohol abuse, broken families.. A vast out-rippling of hidden costs and suffering resulting from our collective addiction to fossil fuels. Are the benefits really worth the costs? (Especially as these costs will escalate dramatically in the coming decades..) 

  'At the end of the day, you're basically trading a piece of your life away to help people.' 

         At least researchers on post-traumatic stress disorder are making some money from the fire (but the taxpayers still foot the bill..)

        "I'm not a professor, I'm just someone learning to deal with mental illness" - climate changed induced mental illness.. (see video link in above article)