An Introduction to Lynn Margulis
by Alfred Tauber, M.D., Professor of Philosophy Emeritus, Zoltan Kohn Professor Emeritus of Medicine, and Director, Center for Philosophy and History of Science at Boston University email: ait at bu.edu
Lynn Margulis (1938-2011) was a “visionary biologist,” who “with courage, intellect, a twinkle in her eyes and considerable fortitude changed our view of cellular evolution.”1 Indeed, she is best known as an evolutionary biologist, who championed symbiosis as a major source of evolutionary change and tirelessly supported this thesis through experimental and theoretical writings to become the foremost proponent of modern Serial Endosymbiotic Theory (SET). As one commentator affirmed, her theoretical contributions to our general orientation to post-neo-Darwinian thinking will be marked by “a pre-Margulis phase, a Margulis phase, and a post-Margulis phase.”2
According to SET, the evolution of eukaryotic cells arose from classical Darwinian natural selection and by symbiotic mergers of prokaryotic organisms. In 1967, Lynn presented the hypothesis that symbiosis of eubacteria and archaebacteria (Archaea) into early cells gave rise to intracellular organelles: mitochondria were descended from parasitoid bacteria and chloroplasts arose from once free-living photosynthetic bacteria. Robert Schwartz and Margaret Dayhoff proved the symbiogenesis hypothesis in 1978 by showing that mitochondria and chloroplasts possess their own genes and their own translation machinery. However, the general application of horizontal genome transfer as a major motor of evolutionary change remained an oddity among those committed to neo-Darwinian orthodoxy.
When descent expands from a genetics confined to mutated loci to mechanisms by which genomes are shared, the neo-Darwinian paradigm suffers grievous assault. Given the lineal heterogeneity of all organisms, Lynn not only challenged the gradualism of Darwinian evolution, but she further envisioned a dynamic biology that broke the bounds of previous thinking about the classification of life. Because she deeply appreciated how genealogies are in essence classification systems, she regarded taxonomy as “the most important enterprise in biology, truly both ‘Queen’ and ‘King’ of the biological sciences.”3 She upset the entrenched dogma, which divided the organic world into plants and animals with a few (unexplained) oddities thrown into the dominant schema, by proposing a modification of Robert H. Whittaker’s Five Kingdoms taxonomy. The oddities of unicellular organisms were Lynn’s foci, the key, as it were, to a New Biology.
Lynn’s perspective, namely a view framed by efforts to explain the evolution of microbiota, contrasted with the prevalent orientation of neo-Darwinist evolutionary biologists trained in the tradition of zoology. When focused upon animal evolution over the past 500 million years, Lynn asserted that nearly 90% of the evolution of life on Earth, including most fundamental evolutionary innovation, was ignored. More to the point, she insisted that the data of unicellular organisms be accounted for in the evolutionary record. We now appreciate that eukaryotic cells arose from several symbioses. Suggestions that their nuclei, mitochondria, and chloroplasts originated from ancient symbioses had been repeatedly postulated throughout the 20th century but they were dismissed and ridiculed insomuch as they conflicted with the main tenets of classical biology. Nevertheless, today animals can no longer be considered individuals in any sense of classical biology: anatomical, developmental, physiological, immunological, genetic, or evolutionary. ”Individuals” are now formulated as ”holobionts,“ whose, anatomical, physiological, immunological, and developmental functions evolved in shared relationships of different species. Thus the holobiont, with its integrated community of species, becomes a unit of natural selection, whose evolutionary dynamics suggest complexity hitherto largely unexplored. Lynn holds a legitimate claim as “the master architect for re-thinking biology in terms of interacting consortia.”4
For animals, as well as plants, there have never been individuals. This new paradigm for biology poses new questions and seeks new relationships among the different living entities on earth. Drawing upon genetics, cell biology, protoctistology, Earth systems science, taxonomy, and astrobiology, Lynn reconceived notions of atomistic organisms that characterized a biology she sought radically to revise. Indeed, when species, understood in terms of lineal descent, is replaced with the dynamics of co-operative symbiotic interactions, evolutionary biology melds into ecology. Driven by her vision of biology’s unity and earth’s biota as a planetary phenomenon, she promoted the Gaia Hypothesis as a self-regulated ecosystem and helped bring such communal thinking into its fullest expression, which has had a lasting cultural impact on environmental consciousness.
Lynn combined the attributes of an original thinker with the strengths of firm intellectual commitments and fearless defense of her ideas. Although she confidently remarked in an interview, “I don’t consider my ideas controversial. I consider them right,”5,6 in private conversation she acknowledged that her combative style too often polarized discussion and detracted from argument based on facts. However, the standing of facts remained her lodestone, which she tirelessly emphasized. For instance, in a celebrated 2009 debate commemorating Darwin’s birth, Lynn answered Richard Dawkins’ neo-Darwinist challenge with a memorable quip: When he rhetorically asked why symbiosis should be embraced considering how SET was “unparsimonious and uneconomical” compared with neo-Darwinism, she replied, “Because it's there.”7 Indeed, the “there-ness” of her general view has ascended into the scientific mainstream.
Lynn Margulis prophetically saw the emergence of a New Biology that would demand new dynamic models. She correctly “predicted that we would come to recognize the impact of the microbial world on the form and function of the entire biosphere, from its molecular structure to its ecosystems. The weight of evidence supporting this view has finally reached a tipping point. The examples come from animal–bacterial interactions… and also from relationships between and among viruses, Archaea, protists, plants, and fungi. These new data are demanding a reexamination of the very concepts of what constitutes a genome, a population, an environment, and an organism.”8
After two decades at Boston University, Lynn moved to the University of Massachusetts in 1988, where, as Distinguished University Professor, she continued to teach and conduct productive research. She was honored with election to the United States (1983) and Russian Academies of Sciences (1997) and awarded the National Medal of Science by President William Clinton (1999), the Alexander von Humboldt Prize (2002-2005), the Darwin-Wallace Medal, Linnean Society of London (2009), 19 honorary doctorates, and numerous visiting professorships and honorific lectures. A prolific writer, she wrote or co-authored over 50 books, more than 170 original scientific papers, 40 films, and numerous book chapters, scientific reviews, and non-technical papers. Her advocacy for scientific literacy extended her research activities to innovative production of educational materials, which include interactive lecture DVDs, booklets and teaching units. A tireless lecturer and writer for the general public, she popularized science and envisioned a library of teaching materials designed for the virtual educational opportunities of the 21st century. In this too, she became a visionary and designed a curriculum that would preserve understanding life’s past through the science that first discovered it. Welcome to the Lynn Margulis archive at ScholarWorks.
References
1 James A. Lake, “Lynn Margulis (1938-2011). Biologist who revolutionized our view of early evolution,” Nature 480 (2011): 458
2 Mark A.S. McMenamin, “Lynn Margulis (1938-2011). Pioneering American biologist and geoscientist,” 21st Century Science and Technology Winter 2011-2012: 26-29.
3 Lynn Margulis and Michael J. Chapman, Kingdoms and Domains. An Illustrated Guide to the Phyla of Life on Earth, New York: W. H. Freeman, 2009, p. 6.
4 Scott F. Gilbert, Jan Sapp, and Alfred I. Tauber, “A symbiotic view of
life: We have never been individuals,” Quarterly Review of Biology 87(2012): 325-41. http://www.jstor.org/stable/10.1086/668166?origin=JSTOR-pdf&
5 Dick Teresi “Lynn Margulis,” Discover, 32(2011), 66-71.
6 Andrew H. Knoll, “Lynn Margulis, 1938-2011,” Proceedings of the National Academy of Sciences (USA) 109(2012): 1022.
7 Richard Dawkins and Lynn Margulis, "Homage to Darwin" debate at Oxford University, May 8, 2009. http://www.voicesfromoxford.com/homagedarwin_part3.html
8 Margaret McFall-Ngai, Michael G. Hadfield, Thomas C. G. Bosch, Hannah V. Carey, Tomislav Domazet-Loso, Angela E. Douglas, Nicole Dubilier, Gerard Eberl, Tadashi Fukami, Scott F. Gilbert, Ute Hentschel, Nicole King, Staffan Kjelleberg, Andrew H. Knoll, Natacha Kremer, Sarkis K. Mazmanian, Jessica L. Metcalf, Kenneth Nealson, Naomi E. Pierce, John F. Rawls, Ann Reid, Edward G. Ruby, Mary Rumpho, Jon G. Sanders, Diethard Tautz, and Jennifer J. Wernegreen, “Animals in a bacterial world, a new imperative for the life sciences,” Proceedings of the National Academy of Science (USA), 110 ( 2013) 3229-3236.