Tag: biosphere

Looking for the Logos of Life IX: Entangled Life

Entangled Life: How Fungi Make Our Worlds, Change Our Minds, and Shape Our Futures, by Merlin Sheldrake, Random House, 2020, 368 pp. Kindle Edition.

Image: Agaricus bisporus mycelium. Rob Hille. 9 December 2011 from Wikimedia Commons
I would describe this as a tantalizing book. Merlin Sheldrake writes in the mode so common to current popular science books, breathlessly exclaiming that these discoveries change how we think about everything. Boiled down, his message is that fungi created the world we know and continue to underpin its foundations. The case he makes is no better and no worse than most such claims, which I suspect every editor for publishers of nonfiction books tries to attach to every work that crosses his or her desk. Much of what Sheldrake describes is new looks at well known phenomena: the section on psilocybin mushrooms and LSD, for instance. It offers glimpses of a deeper understanding of what the chemicals fungi do to animal nervous systems, but reaches no firm conclusions.

It offers a lot of new information and speculation on the myriad roles that fungi have come to play in the biosphere, and a bunch of interesting potential applications to human problems (you can make, among many other things besides antibiotics, beer, wine and bread, fungal dog biscuits (Mutt-rooms)  and packing foam) He also discusses mycoplasma-remediation as a solution to contaminated sites from oil spills to herbicides. They will even break down discarded cigarette filters.

Interesting as these things are, they are not, in my view going to fundamentally alter our view of life.

Nevertheless, this is an enjoyable book. Sheldrake knows his fungi from intimate experience, and he writes well, except for the occasional hyperbolic outburst or awkward analogy. He explains a lot of exciting new research using DNA sequencing, tracer analysis and ingenious lab experiments to understand the role that fungi play in terrestrial ecosystems as decomposes, parasites and symbiotic partners with plants and each other. He spent many hours himself, doing down and dirty work in the forests of Panama, following the roots of a tiny mycoheterotrophic plant and the mycelial network of its fungal associate. He also talked to a wide range of fungus researchers in fields like anthropology as well as biology and shares their insights into the roles fungi play in nature and culture. Some of the most interesting characters are the fungal enthusiasts – mushroom freaks, one might say, truffle hunters and entrepreneurs working to create products from fungus ranging from ersatz leather to bricks. I like this better than 3D printing, with its inputs of resins, metals etc. Also I doubt you can make a fungal firearm at home.

I wish he had been even more comprehensive: for instance he says little about fungi and human illness. His discussions of fungi and food omit such important staples as tempeh. He talks a little about his own work on mycotrophy, but doesn’t mention the possibility that plants may be able to survive mycotrophically when competitions squeeze them out of the struggle for light. How else is it possible for plants in the New Jersey Pine Barrens, like turkey beard (Xerophyllum asphodeloides) pine barrens reed grass (Calamovilfa brevipilis) pine barrens gentian (Gentiana autumnal) and maybe even scrub oak (Quercus ilicifolis) to appear so quickly after fire, after a long interval since the last fire and no individuals could be seen in the unburned forest? Do their mycorrhizal root systems simply live off their fungal partners until a burn clears the space for them to send up shoots, leaves, flowers and fruits?

What do fungi tell us about life in general, if anything? His theme is interconnectedness. The title echoes Darwin’s image of the “entangled bank.” He frequently repeats the view that life is less about individuals than about networks of interaction and exchange, some mutually beneficial, some exploitative, some switching back and forth depending on circumstances. Like like Lynn Margulis, discoverer of the symbiotic origins of cellular organelles and the authors I discussed in my previous post Looking for the Logos of Life VIII: Organism and Superorganism, Sheldrake questions the reality of individuals.

Why the determination to shatter us into fragments? Whatever I mean by “I” doesn’t include the microbes indigenous to my body. I am not them, and it’s arguable whether I am even the parts of my body that are the result of the form encoded in the DNA I got from my parents. When I think of the Pythagorean theorem, it isn’t a soggy collection of bacteria doing that, or sharing in the contemplation. [??] The scientists want to abolish me entirely or reduce me to an aggregation of trillions of cells, of diverse descent. Meanwhile the social theorists would reduce me to nothing but culturally determined categories: white, male, middle class, straight, cis gendered, etc. But what I think about I’m free to select from a vast web of tradition both ancient and up to the minute, delivered to me in multiple modes. That’s the most relevant entanglement: the mycelium of ideas. It’s in the tangled network that is my brain, but it is there because I chose to attend to those ideas as they came to me and because I made the effort, sometimes racked my brain, to connect them to what was already there. 

Anyway, fungi are amazing enough in their own right: in their chief domain, the soil, they are virtually sovereign, with allies like bacteria and the numerous arthropods, earthworms, nematodes, etc, that shred and stir the vast amounts of dead plant material that enter their realm every year. Constantly grazed by animals, they regenerate at phenomenal rates in every cubic centimeter of dirt. Without them, dead plant material would pile up, as it does in bogs, where lack of oxygen excludes them. Carbon would be locked away and CO2 levels would fall to the point of global cooling, as they did in the  Permian ice ages, which followed the Carboniferous age of coal formation.

In his ecological classic, The Biosphere, V. I. Vernadsky talked about the speed of life – the rate of expansion of a disk of cells, imagined as multiplying to cover the earth. Sheldrake makes an even more startling calculation: according to his reckoning, if all the fungal hyphae that have been produced were laid end to end, they would extend further than the limit of the visible universe, i.e. they would have expanded faster than the speed of light. Even though this is a bit like saying that if one airplane can fly from New York to Los Angeles in five hours, two can make it in two and a half hours, it’s still a remarkable image. It gives some hint just how ubiquitous and prolific fungi are in our world.

 

Looking for the logos of life VI: Gaian analysis

Williams, G. R. 1996. The Molecular Biology of Gaia. Columbia University Press. 210 pp.

This is a book I wish I had read when it was first published. Williams lays out so many interesting scientific problems so clearly that I would have expected that it would have considerable influence on subsequent research, somewhat as Schrodinger’s What is Life? the subject of the first post in this series. I was somewhat surprised that Google Scholar only finds a few citations of this book. Perhaps William’s scholarly papers have been more extensively cited.

William’s goal is to see why the famous Gaia hypothesis has attracted so much popular interest, while receiving little positive notice from practicing biologists. He wants to determine whether the hypothesis is actually useful, either as a metaphor or a verifiable model of the function of the biosphere. The central question is whether it can explain why the Earth has remained habitable throughout the several billion-year history of the biosphere. That it has is not in question: all evidence points to the occupation of Earth continuously by the descendants of the first living things, which originated 3.5 billion years ago. This strongly implies that the earth has not frozen or boiled and that life has not otherwise been poisoned or starved during that time. Some factor or factors has kept the conditions on at least some of the Earth within the ranges essential to living organisms of some kind. In fact the conditions have not become intolerable to land plants and metazoans at least for hundreds of millions of years. The concept of the continuity of descent, expressed beautifully by Loren Eisley’s image of each of us trailing a long chain of ghostly ancestors, stretching back to those first living things, is to me one of the most useful ways to imagine what evolution is all about. If there had ever been a break in that chain, you and I would simply not exist.

The Gaia hypothesis states that this stability is the result of homeostasis: the regulation by negative feedback (like a thermostat) of a living super organism, Gaia. In its strongest form, the hypothesis is that life on the planet, the biosphere, regulates itself just as a single organism, whether a single cell or a multicellular individual, does. This idea has an obvious appeal: just as networks of interacting macromolecules make up a cell, which is capable of regulating its internal environment, so do networks of interacting cells make up tissues, organs and whole organisms that are able to regulate their internal environment. At least some organisms, like ants and bees, live in self-regulating colonies. Why shouldn’t all the organisms on earth form a self-regulating system?

Williams answers that for biologists the problem is how such a self-regulated super organism could be put together in the first place. Natural selection can explain how self-replicating systems can evolve, because natural laws can discriminate among multiple variant copies that compete for limited resources. The Earth is not self-replicating. There are no variants among which nature can select. There is only one. This problem led Lynn Margulis to argue that Darwinian evolution was not really that important, and that symbiogenesis was the true explanation. Margulis’s great contribution was the discovery that certain cellular organelles, chloroplasts and mitochondria, were once free-living organisms. More broadly, she showed that evolutionary advances by the incorporation and integration of separate living parts were behind the origin of the eukaryotes and that similar processes continue to operate in the form of horizontal gene transfer. The trouble with claiming that symbiogenesis is a replacement for Darwinian natural selection is that it appears obvious that all such new combinations remain subject to survival of the fittest.

Would it be possible for a Gaia-like system to arise in part of the biosphere and then spread, supplanting the less effective parts? Only if it’s self-regulating effects were confined to where it first existed, as might work for something like the terrestrial nitrogen cycle. It seems less likely where the atmosphere and oceans are involved, since they carry the products all over the planet.

Williams also points out that there is more than one possible explanation for the continuous suitability of the Earth for living things. He lists four: luck, inertia, equilibrium, and homeostasis. He analyzes each possibility in turn, and shows how each may contribute to the persistence of habitable conditions. In the case of homeostasis, he distinguishes between negative feedbacks from purely physical and chemical forces involving the lithosphere, atmosphere and hydrosphere and ones that require the biosphere. It is possible that even if there were no life on Earth, the temperature would stay within habitable limits (basically the range where liquid water can exist) just because of feedback among the temperature and the release and sequestration of carbon from air, ocean and rocks.

According to Williams, if you try to assess this possibility, the difficulty is that today the rates of almost all steps in this process, except volcanism, are under catalysis by organisms. We don’t know what an abiotic planet would be like. As of the time he wrote this book, not enough was known about the global chemical cycles at the molecular level to settle the question how much life matters. He gives an example of what was known about the molecular biology of nitrogen to show how complex the regulation of these cycles is likely to be. Nutrients move among four pools: inorganic forms in the lithosphere, hydrosphere and atmosphere; nutrients in forms available for uptake by organisms in the same three spheres and the biosphere itself as accumulated by organisms; nutrients incorporated into living cells and tissues; and bio products, from the cellulose of wood in trees to dead plants and animals to dissolved organic compounds to fossil fuels. All these are connected by flows and many of those flows (mobilization, assimilation, regeneration, sequestration and excretion) are controlled by living organisms, via enzyme-catalyzed, energy-requiring reactions.

I like this book because Williams thinks about Earth and ecology very much as I do. I learned from my professors at Cornell in the early 1970s about five processes of ecology: population dynamics, natural selection, energy flow, nutrient cycling and cultural evolution. These are closely interrelated ways of looking at the overall phenomenon of life on earth, or as I like to define ecology, the structure and function of the biosphere. Is the function of the biosphere to regulate the habitability of the planet, or does the planet have the property of remaining a stable habitat for life without life being involved? You can’t really answer that question with only one habitable planet and one biosphere to study.

I will add that I tried to read another account of the same problem of why the Gaia hypothesis had been largely criticized by biologists while being so well received by non-biologists: The Gaia Hypothesis: Science on a Pagan Planet by Michael Ruse (University of Chicago Press, 2013) I did not find it helpful, being mostly a historical narrative, with a focus on a wide variety of –isms, such as Platonism, Mechanism, Organicism, Hylozoism (the belief that all matter possesses life) and Paganism. I have never been much interested in –isms or cultural explanations for why people accept of don’t accept given ideas. Williams gives us a scientific way of thinking about the problem.