Imagine a planet in rage, with active volcanoes spewing lava and gases, constantly impacting meteorites, and strong electrical storms. Then, tiny beings that were capable of living in such a hostile environment began to take hydrogen from the water and expel oxygen as a residue , an enormously toxic gas that caused a true holocaust on a worldwide scale.
Successively, some of the inhabitants of this place developed mechanisms to decontaminate themselves and later take advantage of the dangerous element. This adventure-filled story took place on our planet about 3.9 billion years ago, and its protagonists, bacteria, offer us many clues about the mystery of the origin of current life forms. We invite you to know some details of this epic from the hand of one of its great scholars.
In 1967 an American magazine published “The origin of mitosis in cells” , an article that had previously been rejected fifteen times in prestigious scientific journals. Its author, who signed at that time as Lynn Sagan due to her first marriage, was a short and restless woman, who thanks to her amazing tenacity was able to question the prevailing neo-Darwinian theories at the time and turn the understanding of the evolution of the species.
Those who knew her highlighted her friendly nature and always ready to exchange ideas: “she was fascinated by any story one told her”, recalls Juli Peretó, a researcher at the University of Valencia and a friend of the scientist. “Whenever he came to Spain he asked me to explain what we were working on, he took advantage of any occasion to share ideas and news. His curiosity was not only scientific : in restaurants he tried all the foods, he was interested in the ways of cooking them, in their Travel was trying to get in touch with people, to know how people lived in that place. “
Indeed, the boundless curiosity of the American biologist led her to defend the “Theory of serial endosymbiosis” to explain the origin of the eukaryotic cell . Although these ideas had already been formulated before by Konstantin Merezhkovsky and Ivan Wallin, both ignored in their time, Margulis was their most active promoter. Let’s see what this theory consists of.
Bacteria-eating bacteria or the great leaps of evolution
Darwin himself in his famous book The Origin of Species pointed out some of the apparent inconsistencies that his theory was unable to explain. If, according to him, evolution worked by an accumulation of small gradual changes that are fixed as characters by natural selection, how was it possible that neither in the fossil record nor in current organisms these intermediate forms were found? One of the most evident abrupt transitions is observed in the differentiation between prokaryotic and eukaryotic cells . While eukaryotes have a nucleus, a cellular structure that encloses the genome in an envelope of membranes, in prokaryotes the genetic material floats freely in the cell. And there are no intermediate ways: either you are eukaryotic or you are prokaryotic.
While the neo-Darwinists tried tooth and nail to defend their position, Margulis began to dive into the literature and rescued, adding new evidence, the theory of symbiogenesis that Merezhkovsky had proposed forty years earlier. According to this hypothesis, eukaryotic cells would have originated from different prokaryotic cells through a symbiotic relationship that became stable.
In other words, one bacterium would have literally engulfed another, and with the passage of time these consortia between species became permanent. The evolutionary force that generated this new type of cell was not the accumulation of small mutations, but a sum of complex structures that already existed previously. Despite the initial reluctance with which the scientific community embraced these ideas, over time experimental evidence has accumulated that has confirmed them.
Margulis wanted to apply symbiogenesis to the origin of all species. For her, life on Earth was the result of a symbiosis of organisms, everything was symbiotic, and in her publications she presented abundant examples to demonstrate her theories. This is the case of the cow, which can digest cellulose thanks to the microbial symbionts housed in its stomach, or the fish that live on the seabed and host bacteria that glow in the dark. ” We usually associate the word bacteria or microbe with disease, when they are just life! You are a walking bag of bacteria,” he once told an interviewer.
Indeed, Margulis became the most ardent defender of microorganisms, dedicating hundreds of pages and lectures to vindicate their fundamental role in the evolution of life and in the world we inhabit today. ” Bacteria were the inventors, on a reduced scale, of all the chemical systems essential for life,” he says in the book Microcosmos , written with his son Dorian Sagan. “This ancient and high biotechnology led to the development of fermentation, photosynthesis, the use of oxygen in respiration and the fixation of atmospheric nitrogen.”
He criticized the conceited postures that place thehuman being in the center of the worldor who interpret evolution as a path from lower beings (thebacteria) to higher beings (man). Her obsession with the microbial universe led her to the extreme of “keeping in her portfolio, along with the photographs of her children, images of her favorite protists,” said Antonio Lazcano Araújo, professor at the National Autonomous University of Mexico and collaborator of the scientist . Reason was not lacking:bacteria today inhabit all environments that can be imagined,from the acid tanks of chemical companies to the extremely salty waters of the Dead Sea. For 2 billion yearsbacteria populated the Earth exclusively, and in the event of some kind of nuclear catastrophe, they would probably be the only survivors as well.
The great scientist was clear: “There is no particular species that is the center of life, we can cause our own extinction, but not that of life on the planet.Life existed without us … and will continue without us, self-regulating“This concept of self-regulation on a planetary scale is closely linked to the theory of his colleague Lovelock, known as‘Gaia hypothesis’, whatMarguliscontributed to develop. Despite the spiritual connotations that the word ‘Gaia’ may have, an ancient Greek term that means ‘Mother Earth’,Margulis always insisted that it was a way of synthesizing a larger concept.To refer to the planet as “a feedback system with homeostatic tendencies detected from chemical anomalies in Earth’s atmosphere” was simply long and tedious. Our Earth, Gaia, is a network of ecosystems, a biological construction whose atmosphere has been produced, maintained and transformed by the metabolic processes of the biosphere. And toLynn Margulis, in this universe of connections thebacteriathey played, of course, a crucial role.
In this world of self-regulating biological interactions and ecosystems, new man-made technologies may seem out of place. The scientist did not think so, who recognized that technology is already part of the human strategy for survival. “We are already superorganisms,” he commented on one occasion, “because we need external factors to survive (electricity, oil, gas …). Everything comes to us through networks, and we are the nodes of those networks.”
The scientist compared the human being with the pioneer species, which are defined in ecology as those that expand and colonize new habitats rapidly, grow without measure and transform their environment at great speed. However, he warned, “on many occasions this rapid expansion of the pioneers leads them to their own disappearance. We do not know if we will become a climax community or a simple transitory pioneer species. But, whatever it is, our destiny will be inseparable from the of our technology “.
However, in this technology so essential for the human being Margulis did not include the television in any way. “He was totally against television, he said it was one of the worst enemies for culture,” explains Juli Peretó. “Once she came to Valencia to present one of her books and made a little trouble with the cameras, she didn’t let them film her, just record her voice. Imagine the scene, all the cameras were pointed at the ceiling and she was talking into the microphones. a woman of good character, on that occasion she got quite angry, she made a whole case against television. “
Iron fist with silk glove
An ardent defender of her ideas, Lynn Margulis starred in a multitude of scientific controversies. “He did not mind facing everyone if he had something clear,” explains Antonio Camacho, a researcher at the Cavanilles Institute for Biodiversity and Evolutionary Biology (Valencia) who coincided with Margulis on many occasions. “Of course, he did it with absolute elegance. He overwhelmed you with many examples and case studies, it was obvious that he documented a lot to defend his ideas. It was the perfect example of the use of the ‘iron fist with a silk glove’. The fist was his devastating arguments and the glove, his way of debating. He never personalized his rivalries, I think it was very difficult for someone to feel offended when Margulis criticized him. “
The truth is that Margulis came to defend very controversial positions. For example, the biologist stated that it was not clear that HIV causes AIDS, and that this disease could be a form of syphilis. She was famous for her questioning about the origin of the 9/11 attacks , and believed that the collapse of the buildings was due to “a carefully controlled explosion with powerful explosives that would have been disposed of many weeks, or months, earlier.”
He also stated that the only microorganisms that can harm us are those that share an evolutionary history with us, that is, those that would have participated in the process of symbiogenesis to give rise to our species. Despite the fact that his theory about the origin of the eukaryotic cell through endosymbiosis is already fully accepted in the scientific community, Margulis believed that absolutely all speciation processes originated by this mechanism. He maintained that natural selection was only the way to eliminate genetic errors, but that it could not generate novelty and, therefore, was not a key force for the appearance of new species. “I do not consider my ideas controversial, I consider them correct”, this woman stated flatly, who had, without a doubt, things quite clear.
Being a woman in a man’s world
Margulis began her scientific activity in the 1960s, when research, like many other disciplines, was predominantly a matter of men. “Despite being 22 years old and already the mother of two very active children, my enthusiasm for cell genetics and evolution outweighed any thought of becoming a full-time homemaker,” she recounted when speaking of the time when he entered the department of genetics at the University of Berkeley.
Although hers is one of the first female names to appear in biology textbooks, Margulis acknowledged that she never had problems due to being a woman. “One night, during a period I was at Caltech (California Institute of Technology),” he explained in an interview, “I heard women tell horrible stories about their situation, but I can’t say the same thing happened to me. I believe that the problem is not between the sexes, but between people who do not know anything beyond their field “.
Indeed, Margulis harshly criticized this deeply segmented way of doing science , so that specialists in one area know nothing about what is being advanced in others. “She was very interested in the connection between disciplines and the various manifestations of nature. It was, in a way, holistic,” explains Ignacio Bayo, a scientific popularizer who dealt with her on numerous occasions. “All of our conversations revolved around work but always from a very broad perspective.” He spoke of “scientific tribalism” and warned that this fragmentation greatly hindered the advancement of knowledge.
She led by example: with a doctorate in genetics, she was interested in the ecology, evolution and taxonomy of microorganisms. His studies led him to propose the classification of living beings in the five kingdoms that today is studied in almost all institutes. Over the age of seventy, this woman of inexhaustible energy worked until the end of her days in the Department of Geosciences and the Division of Life Sciences of NASA financed her research. He was a member of the National Academy of Sciences in the United States and a Foreign Member of the Russian Academy of Natural Sciences, also having seven honorary doctorates.
Despite her prolific scientific activity, Margulis perfectly reconciled her family and work life, mixing it on many occasions. “She treated her children as if they were students and her students as if they were her children,” recounted Dorion Sagan, the result of the scientist’s first marriage to the astronomer Carl Sagan. Dorion Sagan is also a co-author of many of the books in which Margulis presented her scientific ideas. Interested in bringing science within everyone’s reach, she edited abundant educational material, as well as several popular books and videos.
She made her theories known throughout the world through conferences and seminars and was pleased to be considered, above all, a teacher. He called things by their name, and therefore always questioned the language used when talking about biological or evolutionary phenomena: cooperation, competition, struggle … “These are words that may be appropriate for basketball, the computer industry or financial companies, but when it comes to evolution, they paint with too fat a brush, “wrote Margulis and Sagan in their book Capturing Genomes.
Passion for life
One may wonder if great thinkers and scientists like Lynn Margulis , passionate about their work and with a never-quenching thirst for knowledge, spend any of their hours of the day ‘disconnecting’ from science and their usual concerns. In the case of Margulis, the answer is yes, because she was undoubtedly a great passionate about life and someone who, according to those who knew her, enjoyed everything. “She was very fond of swimming,” recalls Juli Peretó. “If there was a swimming pool in or near the hotel where he was staying, he would always ask if he could take a bath.”
In addition, he liked to cook for many people and listened to classical music. Ricard Guerrero, emeritus professor at the University of Barcelona and a great friend of Margulis, explains: “He loved to read. One of his favorite writers was Emilie Dickinson, he knew many of her poems by heart. Sometimes he asked me to recite something in between from a seminar. It was impressive to do this for an audience that was listening to science talk. ” Margulis and Guerrero worked together on a translation of Lorca’s poem La casada infiel . ” When she was young she began to read Lorca and did not understand anything , in fact I keep a book of hers where you can see the annotations written in pencil of the words that I was looking for in the dictionary. With The Unfaithful Married We look for the translations that there were and none He convinced us, so we got down to work, “explains Guerrero.
From all these anecdotes we can sense the close relationship that Lynn Margulis maintained with our country, which she visited frequently and where she was very successful thanks to her impeccable Spanish, yes, with a curious mixture of Latin and Spanish expressions since she learned the language during a stay in Mexico.
“Lynn was without a doubt the most interesting person I have ever met, and in my opinion, the most important microbiologist of the 21st century, ” says Ricard Guerrero. “With our team he learned about the great advances in bacteriology, together we observed many new microorganisms and especially the relationships between them.” Precisely in the Ebro Delta, Margulis and his collaborators isolated a giant spirochete ( Spirosymplokos deltaiberi ) that is viviparous and lives in environments without oxygen, a species with which they tried to better document their ideas about the endosymbiotic origin of cilia and flagella, a theory that However, he died without being able to demonstrate clearly.
On the other hand, although the hypothesis of symbiogenesis seems much more reasonable than that of gradual evolution to explain the jump to the eukaryotic cell, there are still many unknowns to solve. Javier Sampedro, in his book Deconstructing Darwin , explains some of them. For example, 347 genes have been found that are shared by all eukaryotic cells and that have not been observed, so far, in any prokaryote. And furthermore, these genes are related to three unique cellular mechanisms of nucleated cells: endocytosis, the signal transduction system by which cells communicate with the outside world, and the entire complex of nuclear mechanisms that deal with processes. related to the activation of genetic material.
A mystery that some scientists have tried to explain, in the purest Margulian style, with a new bacterial fusion: the chronocyte would be a protist that joined the feast of endosymbiosis by contributing the 347 missing genes. The problem is that, until now, no one has found the famous chronocyte.
The mysteries of evolution do not end at the origin of the eukaryotes. There are many enigmas that keep those men and women who dedicate all their efforts to answering the classic question “Where do we come from?” Lynn Margulis , who came to his laboratory until the end of his days, was one of these people. The standard-bearer of that fascinating microbial world that she showed us in her books and lectures shed a lot of light on that mysterious tunnel of questions that is the origin of our existence and of life itself.
As she herself wrote in the foreword to Capturing Genomes : “The entire evolutionary saga of how species originated and died out may be the greatest narrative ever told. After all, it is the story of each and every one of us.”
