HETERODOX: A Review/Essay of Symbiotic Planet by Lynn Margulis (1998)

HETERODOX: A Review/Essay of “SYMBIOTIC PLANET: A New Look at Evolution” by Lynn Margulis (1998) © H. J. Spencer [31December2019] <4,600words; 7 pages> ABSTRACT This book summarizes the scientific evidence for three of the most radical theories that are changing our basic ideas about Life and Biology: Symbiotic Evolution, the Gaia Hypothesis and the radical Five- Kingdom classification of all life forms. Lynn Margulis is best qualified to discuss these topics as she was either the originator or a major developer of these ideas. It is hoped that this positive review will help expand the well-deserved reputation of this tough-minded, female scientist to a much wider audience of the general public, while refreshing fresh interest in these important ideas. INTRODUCTION This short book (130 pages) documents the evidence that much of the public's views on Evolution and Biology are obsolete and need a major upgrade to conclude the 150 year-long war between biological science and religion that has been exploited by the so-called New-Atheists. Unfortunately, this book is difficult for any reader unfamiliar with much biology, so I have 'linearized' its presentation here. 0.1 AUTHOR'S BIOGRAPHY Lynn Margulis (1938 - 2011) is one of the most important biologists in the last one hundred years. She has extended Darwin's revolutionary ideas on Evolution with her own radical theory of Symbiosis to explain the origin of species - a chasm that Darwin failed to cross in spite of the title of his masterpiece. Margulis proposed the theory that nucleated cells resulted from the symbiotic mergers of bacteria. Along with James Lovelock, she was the co-developer of the Gaia hypothesis that views the Earth functioning as a single, self-regulating system. Finally, she has been the principal promoter of Robert Whittaker's Five-Kingdom Life Classification. Most of these suggestions were viewed as unorthodox at the time (and often initially rejected) and are still resisted by several mainstream academic biologists. Slowly her theories are being validated to the point where she was elected a member of the US National Academy of Sciences in 1983 and was awarded the National Medal of Science in 1999 by Bill Clinton. In 2002, the science magazine Discover recognized Margulis as one of the 50 most important women in science. Margulis should be much better known by the general public but she has been long-opposed by leading neo-Darwinian biologists, such as Richard Dawkins and John Maynard Smith. Furthermore, her theories are more complicated than Darwinism and more people are interested in the biology of humans and animals, rather than microscopic cells and bacteria that are often viewed as just 'germs'. Lynn was born in Chicago to a Zionist family; her parents were Morris Alexander (an attorney who ran a company making road paints) and Leona Wise Alexander, who operated a travel agency. Lynn was the eldest of four daughters. Lynn Alexander was a gifted child, entering the University of Chicago Laboratory Schools at fifteen. Four years later she earned a BA in Liberal Arts, then a master's degree in genetics and zoology in another three years. Next she transferred to the University of Wisconsin to gain another master's degree in biology. Lynn married future astronomer Carl Sagan, when she was 19 (he was 24); they divorced 7 years later after having two sons, Dorion and Jeremy. Three years later she married Thomas Margulis (a crystallographer); they had a son Zachary and daughter Jennifer before they divorced in 1980.  2 1. SYMBIOSIS 1.1 DEFINITION Margolis did not invent the concept of symbiosis for Webster's Dictionary defines this concept as: the intimate living together of two kinds of organisms, especially when mutually beneficent. Once alerted to this idea, we can find numerous examples everywhere. Margolis has spent much of her professional life thinking about this rich concept. She points out that many trees and plants need hundreds of fungal symbionts (called mycorrhizae) to fix nitrogen from the air to form the amino acids needed in proteins. This symbiosis is believed to have triggered the first appearance of plants 450 million years ago. Now we know that we need vast colonies of bacteria in our gut and on our skin (named as our microbiome). 1.2 CELLULAR BIOLOGY Biology has known for many years now that all life forms are constructed from two types of cells: those without a nucleus (prokaryotes) and those with all their genetic material enclosed in a distinct nucleus (eukaryotes) forming the biological domain of eukarya (everything except bacteria) that not only contains the well-known plants and animals but also fungi and protists (algae and protozoa) that occur alone (unicellular) or in multi-cellular colonies. [see my essay SENSES, for many more details]. Until a suggestion in 1905 by the Russian botanist Konstantin Merezhovsky (1855-1921), these two types of life were assumed to have evolved (and lived) separately. He hypothesized that some organs and organisms appeared through symbiotic mergers - a process he called symbiogenesis. This idea was largely ignored (in fact, the 2008 edition of the Oxford Dictionary of Biology even fails to include it). It does merit an entry in Wikipedia, that describes it as the origin of eukaryotic cells from prokaryotes. 2. UNORTHODOX Margulis has exhibited a willful independence in both her personal life and her professional career as a biologist, as she describes in her second chapter, entitled "Against Orthodoxy". She admits to being both a religious agnostic and a staunch Darwinian Evolutionist while rejecting its modern synthesis (or “neo-Darwinism” that tries to explain genetic variation by random mutations of genetic DNA). She agrees (as I do) that Natural-Selection eliminates and perhaps maintains but it does not create new life forms (especially species: contrary to Darwin's subtitle). I actually view Darwin's theory as one that explains the production of many diverse varieties within a species, like humans do in dog-breeding. Margulis relates how she once challenged the well-known paleontologist Niles Eldredge to identify any case in which the formation of a new species had been documented. His only answer was Dobzhansky's fruit fly experiments that were later shown to be varieties of the same species. It seems there are about 30 million species of animals but only one type of bacteria that freely exchange DNA. 2.1 SYMBIOGENESIS In the course of her research, Margulis discovered that an American anatomist, I. E. Wallin proposed in the 1920s that several vital cell components, like mitochondria and chloroplasts, originated as symbiotic bacteria. When he was not being ignored, he was strongly condemned for daring to suggest that 'germs' could contribute anything positive to life forms that were rigidly believed to exist as only animals or plants. Additionally, in reading old biology books, Margulis did find links to the symbiogenesis ideas of Merezhovsky. This stimulated her focus on the role of bacteria and her laboratory evidence that symbiotic associations between prokaryotic bacteria were absorbed into eukaryotic cells in the form of forerunners of distinct, independent organelles in a process that Margulis called Endosymbiosis (some symbionts living within a larger organism). Since Margulis proposed that this process had occurred several times over extended timeframes, she added the word 'serial' to emphasize its recurrence; so this is why she has described her theory as Serial Endosymbiosis Theory (or SET). 2  3 Among the many lines of evidence supporting SET are the fact that new mitochondria and plastids (chloroplasts) are formed only by binary fission, plus special transport proteins (porins) are found in all the outer membranes of mitochondria, chloroplasts and bacterial cells; also some mitochondria and chloroplasts contain single, circular DNA molecules, similar to those found in bacteria. When Margulis tried to get her SET research published, it was rejected fifteen times until accepted by the Journal of Theoretical Biology in 1967. It now seems that as an endosymbiont evolves into an organelle, most of its genes are eventually transferred to the genome of the larger, host cell. 3. GREAT MERGERS Even though Margulis writes that the central idea of SET is that new species arise from symbiotic mergers among members of old ones she is correct in stating that this aspect is not even discussed in polite scientific society: a fact confirmed in the Oxford Dictionary of Biology entry on 'Endosymbiont Theory' that totally ignores this radical feature. Margulis describes the four stage mergers, each involving symbiogenesis, in the evolution of plants, with their large cells and observable organelles to finally produce green algae. She begins with the mobile spirochetes (corkscrew body) absorbing the heat-loving archaebacterium (oldest forms of bacteria) to form the nucleocytoplasm - the principal substance of the ancestors of animal, plants and fungal cells. The next merger was a swimming protist (nucleated micro-organisms) that is an anaerobe (poisoned by oxygen), merging with an oxygen-breathing bacterium; this then was absorbed by the modified spirochete from the first step, now thought to have occurred about 2,000 million years ago. The final merger occurred when the 'triple combo' incorporated with swimming green algae that have become blue/green cyanobacteria (both forms contain chlorophyll, capable of photosynthesis). This final contribution eventually became the chloroplast organelles in plants. A similar evolution occurred in the ancestors of animals: the 'trapped' bacteria became animal organelles. 4. TAXONOMY Taxonomy is the science of identifying, naming and classifying organisms. In modern times, it was driven by botanists like John Ray, Carl Linnaeus and George Cuvier, who all believed that all species were eternally separate forms created once by their omnipotent God. Margulis alerts us to the dangers of poor taxonomies and the problems of assuming simple tree structures, preferring blending and recursive models. This is used to introduce the new Five-Kingdom model consisting of 1) all bacteria; 2) Protoctists [nucleated micro-organisms: covering algae, slime molds, ciliates]; 3) all fungi; 4) plants; 5) animals. This scheme is based on DNA analysis and reflects the fact that animals and plants are far more similar to each other than to all other kinds of life on Earth. This replaces Aristotle's ancient classification of assigning any life form exclusively to plant or animal, so when swimming microbes were discovered they had to be defined as animals because plants were not motile whereas when non- motile green microbes were discovered they were first classified as plants; these confusions often reflected academic differences between botanists and zoologists. The largest embarrassment is found with protozoa (Latin for 'first animals') because they swim but some are ancestral to both animals and plants and even fungi. Since all plants and all animals are multicellular, this adjective is usually redundant. Margulis firmly believes that non-nucleated bacteria appeared first while all nucleated creatures arose from bacterial symbiosis, as described above and admits to the deep frustration of trying to construct a single evolutionary scheme covering both botany and zoology reflecting metabolism, cell morphology, genetics and developmental biology. Margulis does not include viruses in her scheme as they cannot remain alive outside living cells that remain viable through ceaseless metabolism but they can spread genes among bacteria and other cells. All of us are a massive colony of micro-organisms. 3  4 5. SCUM (Life's Origin) Chapter 5 addresses The Great Mystery: the Origin of Life on Earth. From the SET perspective, this is equivalent to understanding: How did the very first bacterial cell originate? Provocatively, Margulis restates this as: "We need to understand life from scum." She does summarize the famous experiments of Stanley Miller and Harold Urey in 1953 who exposed certain primitive gases to electric sparks and then found several organic compounds, including two amino acids that are present in all living cells. Microfossils indicate that bacteria existed over 3.5 million years ago, on our planet believed to be about 4.5 million years old. All genes are made of sections of DNA, while its related molecule RNA is needed by all cells to make (inside ribosomes) long-chain proteins, whose 3D shapes are critical to the chemical capabilities. Cells typically contain three to ten thousand proteins. All the DNA of one of the simplest cells (the mycoplasma geniticulum bacteria) has been sequenced and it shows that its 5,000 genes imply significant complexity made worse by the discovery that some microbes can change the RNA molecule expressed by a given gene during its life history. Margulis admits that so far nothing close to a laboratory re-creation of a bacterial cell has been achieved. She has been most impressed with the bacterial suggestions of Harold Morowitz (as documented in his book: Beginning of Cellular Life - 1992) that may have started with 'oily bubbles' that spontaneously form self-sustainable membranes, like liposomes (microscopic membrane vesicles). Morowitz critically adds biological memory to the contributions of physics and chemistry; some metabolic pathways may be almost as old as the Earth itself. Chemists have discovered autocatalytic reactions that cycle around making more of the starting product; RNA has this unusual capability. Ilya Prigogine has called these dissipative structures: life is a series of selves - organisms or cells. However, DNA requires both RNA and enzyme proteins to complete its replication. This suggests that RNA preceded DNA. Furthermore, there are some forms of RNA (called ribozymes) can auto-splice themselves, re-arranging their own molecular forms that can even accelerate their own replication. The challenge is that any viable cell needs more than fifteen kinds of DNA and RNA, at least 500 different types of protein (usually about 5,000). There are some bacteria that are autotrophs (make their own food from inorganic sources, such as sunlight or hydrogen-rich chemicals); in contrast, most animals are heterotrophs needing pre-formed organic matter (plant or animal tissue) made by autotrophs. All these clues suggest that the first cells in our lineage were membrane-bounded, based on RNA and DNA to form self-maintaining protein systems. In details of cell structure and metabolic activity, they very much resemble us today. Margulis claims that the insides of our bodies today are chemically more akin to the external environment of the early Earth, in which life originated, than they are like our present oxygen-rich world. Life, always made of cells that grow and divide, has preserved its past as chemistry, illustrating that life is intrinsically a memory-storing system. I agree with her statement that the Book of Life is written in neither mathematics [physics] nor English [philosophy]: it is written in the language of carbon chemistry. Aristotle and Galileo were far too simplistic, as we still are when comparing our 25,000 human genes with the 5,000 bacterial genes. 6. SEX Margulis brings her own idiosyncratic mind to the concept of sex that she sees as universal across all animals and plants, called meiotic-sex. She is highly motivated from a temporal genetic perspective to distinguish symbiosis from sex. She defines biological sex as a gender attraction strong enough to lead to recombination of genes inside mated cells. In sexual creatures, new living organisms result from the two gendered cells (gametes) that meet and recombine, such that the new being's genetic constitution is unique. We now know that half the genes come from the egg and half from the sperm cell, in animal- style sex, forming a zygote. In contrast, bacteria pass their genes with abandon as one bacterium receives a few genes at a time from another bacterium, whether dead or alive; it is always one-sided. 4  5 This process is deeply cellular: meiosis is the special form of cell division where the parent cell's nucleus goes through two consecutive double separations of the gene-carrying chromosomes. In the first, two structurally similar (homologous) chromosomes become paired and may exchange genes before moving apart into distinct daughter nuclei that each further divide producing four identical gametes, each with only half the number of chromosomes (haploid) of the parent cell. Compared with temporary symbiosis, sex differs in that the cyclical fusion / separation are for more predictable and the offspring greatly resemble their parents, so this is a weak biological technique to generate variety as its aim is to maintain structure and processes. In mammalian sex, the zygote cell continues to divide but the cellular products stay close together: a sphere of cells grows and differentiates to form tissues and organs in a fishy-looking body. As organs develop under local control, the embryo loses its fishy look, re-absorbs its gill slits and tail and begins to take human shape. The infant, if female, is born with her lifetime allotment of unfertilized eggs already in place in her tiny ovaries. Males do not produce sperm until adolescence when the process begins and continues until death, or for 90 years. Animal fossils are found all around the world (dating back between 540 and 650 million years ago). Yet hundreds of millions of years earlier, Margulis claims that sexual protists already had cloned and were sticking together. Water-based animals evolved in the oceans over 500 MYA (million years ago) appearing long before the kingdoms of land-dwelling organisms (like plants and fungi) appeared. Geologists only begin their dating from the start of the Cambrian era (540 MYA). All animals are aerobes as their mitochondria must have oxygen that had to have been accumulating long before their first appearance. Calcium ions, abundant in the oceans, are poisonous inside cells unless their concentration is less than one thousand times lower than in the sea. Programmed death is viewed by Margulis as a non-negotiable consequence of the sexual mode of life; mortality is the price animals pay for complex tissues and life histories; she sees death as the grim price exacted by meiotic sexuality, almost as a sexually transmitted disease appearing about a billion years ago. 7. FUNGI Chapter seven illustrates the convoluted style of Lynn Margulis: she entitled it 'Ashore' but it takes three pages before the meaning of this clue emerges; the transition from marine-based life-forms onto the land, millions of years ago. The actual heroes of this chapter are the little known group of organisms called fungi that in some taxonomies have a whole kingdom of their own before they were recognized to be more closely related to animals than plants, based on molecular studies. The challenge here is that fungi can either exist as single cells or make up extended multicellular bodies (mycelium). Most fungal cells possess multiple nuclei with walls of chitin, chemically distinct but similar to cellulose. The interest in fungi for Margulis is that they are the quintessential symbiont most usually found with plant roots called mycorrhizae (over 5,000 types); the necessary presence of the fungus enhances the absorption of elements (nitrogen and phosphorus) by the plant; in exchange, the fungus gains soluble organic nutrients from the root cells. The oldest plant fossils illustrate plant- fungal complexes 450 MYA. The move to land occurred as plants evolved from water-dwelling algae. Since algae contain photosynthesizing chlorophyll, they can live in shallow water and in moist situations on land (i.e. the shore). Water is always vital to life; so much so that cytoplasm (the cell's principal fluid) is more than 80% water. Indeed, Margulis even describes life as 'animated water'. Lichens are classified as fungi and although slow-growing they can live in regions that are too cold or exposed for plants. Algae and lichens can break solid rock down into soil. Today, the number and diversity of land species vastly exceeds marine life, where life began. The biomass of life on land is thousands of times greater than that still in the seas that is comparable to that of fungus-lichen rock dwellers. Astonishingly, most of the land-based biomass (85%) is contributed by trees that are adept at sealing in water as vascular plants. Fungi are vital in ecosystems that recycle biologically important elements like carbon, nitrogen. 5  6 8. GAIA This final chapter may be the one with the widest appeal to the general reader, so I will expend quite some effort in summarizing its main points. Margulis was one of the first scientists to correspond with the originator of the GAIA theory, James Lovelock - a scientist as unusual (and independent) as her. She relates the little known origin of this revolutionary theory [that I accept]. Lovelock was consulting with NASA in the mid-1960s, helping to devise ways to detect life on Mars. He realized that life on any planet would have to use its fluids to recycle the elements required by life; on Earth this would be the atmosphere, oceans, lakes and rivers. Nutrients had to be supplied and wastes removed, making the chemistry of a living planet markedly different from that of a lifeless one. Lovelock was concerned about the amount of free methane in the Earth's atmosphere because oxygen reacts very strongly with this gas to produce CO2. He also knew that hydrogen and nitrogen react explosively in the presence of oxygen yet all co-exist on Earth; so these high levels must be being actively maintained. Lovelock asked Margulis about this mystery. She knew that most methane gas is produced by methanogenic bacteria that live in water-logged soil and cattle rumen, where it is released from the mouth (not by flatulence, as many believe). There is a further mystery about the Earth that it has become cooler in the past three billion years, while cosmologists theorize that the Sun, as a typical star, should have become hotter and warmed us up. So, Lovelock theorized that temperature and atmospheric regulation must occur on a global scale. These ideas led him to view our planetary environment had to be organically homeostatic: kept within a viable range for all the life forms here. This suggestion of 'optimization' generated the usual result from many intellectuals, like they resisted Maupertuis' Action-Optimization in 1744 (that predicted Newtonian physics) as this could only be achieved by intelligent humans, like themselves [for details see my Least-Action essay]. The word Gaia was suggested by novelist, William Golding (Lord of the Flies) who was a neighbor in the UK; this was related to the Greek word for 'Mother Earth' and forms the root of linked words, such as geology, geometry and Pangaea. Margulis thinks this was too good as it appealed to some religious people and feminists with its hint of a living goddess; however, it does also appeal to environmentalists. Margulis supports GAIA as a scientific theory but vacillates about whether this implies all life on Earth is a Super-Organism, evolving from the present ten million species. She denies this is a living organism because they all need energy (from the Sun?) and produce waste (plenty of that in the seas?). Although Margulis claims that GAIA is only an emergent property of Earth's life forms, she does admit that "GAIA is a tough bitch, not at all threatened by humans" as we are real Johnny-come-lately organisms that she dismisses as "upright, mammalian weeds". She regrets that the Goddess idea has encouraged anti-science movements and excoriates the Puritan-Feminists for the "rape" and destruction of the sunlit Earth. She diminishes its appeal by seeing it as only a convenient name for the regulation of temperature, acidity/alkalinity (pH) and gas mixtures - a purely scientific perspective. Margulis is betting on her favorite life-form: bacteria. These 'primitive' creatures first removed the huge quantities of hydrogen (H2) from Earth's atmosphere and then from the hydrogen sulfide (H2S) emitted by volcanoes. Later, they released oxygen from water (H2O). She even claims that bacteria survived the numerous extra-terrestrial impacts over their three billion year history whose energy vastly exceeds all our stock-piled nuclear weapons. I am not so sanguine as Lynn, nor do I think most people who first survived a nuclear war would be satisfied to know that bacteria are ready to repeat the Great Game of Life. Amusingly, Margulis reminds us of one our deeper senses, proprioception [see my essay SENSES, for details]. Animals use this sense for awareness of movement and spatial orientation. Lynn believes that the Earth (GAIA?) has enjoyed a proprioception system for millennia, long before humans appeared. She claims that this Sense-of-Self is as old as life itself - a nice thought. 6  7 9. CONCLUSIONS 9.1 SUMMARY As the author writes (in the prologue): "This book is about planetary life, planetary evolution and the ways our views of them are changing." She also writes about the difficulties of changing cultural views; people are overwhelmingly resistive to change: even scientists are deeply effected by these deep trends. Margulis illustrates this with the ancient idea of 'The Great Chain of Being' that for many centuries placed humans at the exact center of the universe. The Judeo-Christian version positioned people above animals but a little lower than the angels; everything superseded by the Almighty. As an atheist, Margulis dismisses these ideas stating that all living beings today are equally evolved, all have survived over three thousand million years of evolution from common bacterial ancestors. It is so difficult for many people to imagine they are simply a massive colony of micro-organisms - with no soul. This book illustrates the difficulties Life Scientists (zoologists and botanists) have in placing many life forms into a fixed, global classification (taxonomy), contrary to widespread public misperceptions. Even Darwin's mistitled masterpiece fails to challenge the Linnaen Taxonomy of his time, based on the traditional simplifications of linearity and timelessness. Of course, Darwin did not know anything of DNA (or even Mendel's gene idea) because he was still trapped in the oldest of human false assumptions: "if we cannot see it, then it cannot exist". An ongoing error that is blocking many people from accepting the New Health Paradigm based on our unique personal microbiome. She also rejects the hierarchical view: there are no higher beings; even 'primates' being named because the category includes us. We are not special, just latecomers on the evolutionary stage. Margulis is more impressed with the similarities, not the differences. She cannot repeat enough that most life has evolved from a long line of progenitors, ultimately the earliest bacteria that have to merge to generate complexity; her major intellectual contribution: Endosymbiosis including her laboratory proof of the theory of the origin of key cellular organelles, like animal mitochondria and plant plastids. It is a great pity that Margulis has been so "educated" as a scientist that she cannot see the value of GAIA as a planetary unifying 'religion' for a divided humanity. A major problem is the huge number of new terms (many italicized here), invented to describe the new science of biology that are a mystery to most people (including other scientists) who are not biologists. Here, I feel like a translator. 9.2 RECOMMENDATIONS I cannot recommend this book for the general reader, because it is somewhat repetitious and rambling but mainly it does not present its central idea of symbiogenesis in a logically coherent or historical manner, but more in an autobiographical memory sequence of the author. As a non-biologist, it took me a huge effort to create a linear story of Endosymbiosis. This book does make a very positive contribution (in only 150 pages) in demonstrating that big ideas do not need a big book to be discussed. I guess that Lynn Margulis is more an artist, with a creative imagination, than a systematic author; perhaps her son Dorion has helped her a lot in their many jointly-authored books to present a more systematic view of their ideas. Readers who are unfamiliar with human (and cellular) biology may get some further value from reading my companion SENSES essay. I must confess that trying to understand the important ideas referred to in this book was a real challenge for an ex-physicist but the effort was well worth it and a pleasure to re-present them in a linear way that hopefully helps many more to understand this deep picture of living matter; not the super-simplicities of physics and its mathematical models of isolated, inert matter. Life is important; not stones. 7