IN MEMORIAM LYNN MARGULIS (1938-2011) Pioneering American Biologist and Geoscientist by Mark A.S. McMenamin est known for what is now called en- to propose what would become her Bdosymbiosis or endosymbiotic theo- trademark theory, but from now on, the ry, American geoscientist and biologist history of endosymbiosis theory will be Lynn Margulis played a critical role in divided into a pre-Margulis phase, a convincing Western science that the Margulis phase, and a post-Margulis University of Massachusetts chloroplasts of eukaryotic cells were de- phase. scended from once free-living photosyn- Margulis served as midwife to a much convinced us that endosymbiosis was re- thetic bacteria, and that mitochondria broader concept, a concept that the Rus- quired to understand the constitution of were descended from free-roaming para- sian biologist Konstantin S. Merezh- the eukaryotic cell. Margulis strived to sitoid bacteria. Margulis was not the first kovsky (1855-1921) called symbiogene- uncover the full implications of symbio- sis. Symbiogenesis is defined as the genesis theory, doing so with an icono- origination of new organisms through the clastic fervor. Mark McMenamin is a professor of ge- symbiotic association and unification of Shortly after she arrived at the Univer- ology at Mount Holyoke College in the two or more species. sity of Massachusetts, Amherst in 1988, Department of Geology and Geography. The Western reception of symbiogen- she and I began to work closely on sub- His research is primarily focussed on pale- esis had a long gestation and a difficult jects of shared interest, such as the Edia- ontology, particularly the Ediacaran biota. birth. It was Lynn Margulis who finally caran fossil record and early Russian re- EXAMPLE OF A PROTOCTIST, WHICH MITOCHONDRIA IN YEAST CELL EVOLVED FROM BACTERIAL SYMBIOSIS Margulis viewed mitochondria, which generate the energy for cell The protoctist Mixotricha paradoxa. Protoc- metabolism, as descended from free-roaming parasitoid bacteria. tists evolved from bacterial symbiosis, and Here, an electron micrograph of a yeast cell, showing mitochondria are neither plant nor animal, Margulis said. (small black bodies). The arrow points to a mitochondrion that is ap- This is an example of an individual com- parently dividing. posed of at least five kinds of organisms. Source: A.W. Linnane, Monash University, Australia, in Lynn Margulis Early Life Source: Lynn Margulis, Symbiotic Planet: A New View (Boston: Jones and Bartlett Publishers, Inc., 1984), p. 76 of Evolution (New York: Basic Books, 1998), p. 63. 26 Winter 2011-2012 21st Century Science & Technology IN MEMORIAM turned to me and announced The great Russian symbiogeneticist that Neo-Darwinism was dead Andrey S. Famintsyn (1835-1918) had and that, as a result, we needed arrived at a similar conclusion a century an entirely new evolutionary before, noting that the major steps in paradigm. At the time, I was un- evolution are not in the least elucidated aware of any credible challenge by Darwin, and remain, as before, an to the prevailing evolutionary unresolved question. Margulis framed model. Lynn proceeded to ex- this as an astonishing scientific insight, plain how the stepwise natural and I have since come to realize that selection required by the Neo- once again she was on the trail of some- Darwinian Modern Synthesis thing important, a major advance in sci- had never actually been dem- ence that would be fully revealed only onstrated in the vast majority of after much argument and debate, finally cases. leading to acceptance by the scientific The concept that most major community. evolutionary changes occurred By 1989, Margulis was in full swing by slow accumulation of muta- with this aspect of her research, spear- tions, lacked decisive scientific heading conferences and sponsoring support. Rather, all known cas- book projects with the aim of showing es of what might be called spe- that virtually all evolutionary innovation ciation in the laboratory in- was the result of symbiogenesis. We volved sudden reproductive might even say that it was Lynn Margulis, isolation via genital infections, not Charles Darwin, who actually ex- University of Massachusetts rendering the infected individu- plained the mechanics of the origin of Margulis looking at Spirochaeta perfilievia, a sul- als able to interbreed only with species. fide-requiring round body-forming spirochete conspecifics that had already A Contagious Enthusiasm bacteria, provided by her Russian colleague, Ga- contracted the same venereal Margulis’s enthusiasm for moving sci- lina Dubinina, who studied the organism for 40 disease. ence forward was contagious, and in- years. For Margulis, this was com- spired by endosymbiosis theory, ground- pelling evidence that symbio- breaking Russian research, and the search. In one of our first discussion genesis was not only responsible for the Lovelock-Margulis articulation of the sessions at the university, we discovered makeup of the eukaryotic cell, but that it Gaia hypothesis, my wife, Dianna, and I a mutual interest in the work of the great was also responsible for virtually all spe- proceeded to consider the biosphere as Russian biogeochemist Vladimir I. Ver- ciation events in animals, plants, fungi, a whole from a symbiogenesis perspec- nadsky (1863-1945). and protists. In other words, symbiosis tive. Our primary goal was to enhance Vernadsky was virtually unknown equates to evolutionary transformation at Mount Holyoke College’s introductory among our Western colleagues at the both the macroevolutionary (new major geology course, History of Life (Geology time. We developed this interest together cell types) and microevolutionary (new 102). for over 20 years, collaborating on the species) levels. I wanted, at long last, to provide first full English translation of Vernadsky’s my students with an great work The Biosphere.1 The work adequate explanation continues to this day, and in my final proj- for how and why vascu- ect with Lynn, only a few months before lar land plants trans- her death, I uncovered in the Vernadsky formed dry land surface archives at Columbia University, an ex- into undulating forest. change of letters between Vernadsky’s son Our solution, the idea George Vernadsky and George Evelyn that cooperation among Hutchinson (1903-1991), discussing the fungi, vascular plants, preparation of Vladimir Vernadsky’s re- and other organisms in a search for a wider audience. Margulis ex- vast symbiotic net- pressed delight with this find in one of my work—a geophysiologi- last communications with her. cal entity we called Hy- Neo-Darwinism Is Dead persea, with the ability One day while walking together across to induce upward nutri- the Amherst College campus, Margulis ent flow (hypermarine University of Massachusetts upwelling)—was pub- Margulis answers questions from students on a field trip lished by Columbia Uni- 1. The Biosphere, Vladimir Vernadsky (New York: Copernicus, 1998) English translation ed. Mark to Harvard Forest, in Petersham, Mass., during a course versity Press in 1994 as A.S. McMenamin. on Environmental Evolution. Hypersea: Life on Land. IN MEMORIAM 21st Century Science & Technology Winter 2011-2012 27 In her foreword to the book (she also ized fossil remains of coccoid symbi- took the splendid cover photomicro- otic microbes. graph), Margulis announced that Hyper- The importance of symbiosis in the sea blended Vernadskian biospheric acquisition of early animal shells re- thinking and Lovelockian Gaian spatial mains an unsettled question, but here “connectedness” to allow us to “look again, Lynn Margulis may be on the right wide-eyed upon a land surface whose track. history we thought we understood. Re- The Oxygen Revolution turning to where we stood before, en- Preston Cloud is also known for his lightened by a century of biological and discovery of the Oxygen Revolution, an- paleontological insight, we now see this nouncing the discovery at the same time place for the first time.” that Margulis was about to publish her Her foreword encapsulates the classic endosymbiosis research. The Oxygen Lynn Margulis approach to appreciating Revolution occurred approximately 2 the full symbiogenetic glory of the natu- billion years ago, when diatomic oxy- ral world. gen gas released by photosynthesis (Pho- Due at least in part to her difficulties tosystem II) overwhelmed Earth’s reser- with the Neo-Darwinian synthesis, Mar- voirs of native and ferrous iron, thereby gulis astonished many of her colleagues allowing oxygen to accumulate in the by changing her departmental affiliation oceans and atmosphere and thus com- from biology to geosciences. This made pletely altering the geochemistry of the good sense, for Margulis had come to ad- planet. mire how the geosciences superintend a BU Photography Russian scientists are chagrined at the rich temporal data set that biologists tend Margulis at Boston University in 1982. fact that Cloud, apparently unfamiliar to neglect. with Vernadsky’s work, was able to link For example, the great American geol- ture of an Early Cambrian stem group the Proterozoic banded iron formations ogist Preston Cloud determined that the (mickwitziid brachiopods) proved to to the concept of an anoxic early Earth Cambrian Explosion must represent a be packed with spherules of hydroxy- atmosphere. truly massive case of punctuated evolu- apatite. These tiny spherules might Discovery of the Oxygen Revolution tion. Cloud argued that the filter feeding best be interpreted as the permineral- by