It's a split that began with the great theorist of evolution, Charles Darwin. Some of Darwin's first readers, though awed by the observations in his 1859 masterwork On the Origin of Species and agreeing with his sweeping conclusions, couldn't help but notice a gap. While he artfully laid out the evidence for how life changes over time, Darwin didn't address the essential question: How did life start? One of his biggest fans, the eminent German natural philosopher Ernst Haeckel, commented on this issue in 1862: “The chief defect of the Darwinian theory is that it throws no light on the origins of the primitive organism—probably a simple cell—from which all the others have descended.”
Darwin's gap wasn't an oversight; it was a choice. Darwin knew he was in for a formidable scientific battle with the theory of evolution by natural selection, a topic on which there was voluminous living and fossil evidence from around the globe. The origin of life, however, was a completely different story. Darwin was fascinated by the question but believed at the time that the pursuit of the evolutionary origins of life in the distant past was beyond the scope of scientific testing. As such, any comment on the topic was sheer speculation, which would only invite equally insubstantial rebuttals, muddying the waters of his evolutionary argument. In a letter to his close friend Joseph Dalton Hooker in 1871, he put it more bluntly: “It is mere rubbish thinking, at present, of (the) origin of life; one might as well think of the origin of matter.”
A century and a half after Darwin, many of the members of the Committee on the Origins and Evolution of Life still feel the same way. A number of evolutionary biologists strongly believe that it's impossible to unravel the series of events that led to life on Earth. In essence, they believe, the evidence is lost in the mists of time. Unlike dinosaur fossils, the four-billion-year-old organic evidence from the dawn of life has been destroyed, degraded, or changed so much that its earlier form is unrecognizable. Life has erased its own trail. Alternatively, some believe the emergence of terrestrial life was a unique, one-off, random event that's much too complex to experimentally reproduce. There was, however, one scientist in the meeting room whose view of the origins of life on Earth was shaped by a lesser-known great book of science, one that argues that tracing our family tree back to origins requires looking to the stars.
Antonio Lazcano is an outlier on the Committee on the Origins and Evolution of Life in more ways than one. A Mexican and a biology professor at the Universidad Nacional Autónoma de México, he's one of the few non-Americans ever to sit on the committee. Of medium build and with salt-and-pepper hair, Lazcano has a languid intensity, seeming to be perennially engaged in whatever the topic of conversation is. As a lunch mate, he's as happy discussing—and at times making lengthy pronouncements on—the arts, books (he's encyclopedic about Mexican culture), politics, or the history of science as he is his tablemate's latest research.
After several days of listening to presentations, Lazcano is still eager to talk. He sleeps only five hours a night and, when not sleeping, is a peripatetic thinker and autodidact on his favorite topic—how life on Earth began. He's the former president of the foremost group on the topic, the International Society for the Study of the Origin of Life. For Lazcano, our origins matter deeply when it comes to understanding ourselves. Evolution is, at its core, about the historical contingency of life, and to Lazcano, history means genealogy. Who, or what, begat whom? In this context, Darwinian evolutionary theory ties us to the Earth. It's the origin of life that ties us to the cosmos.
In his quest to understand our extreme genealogy, Lazcano is a great connector, someone whose life as well as his research brings the past closer. When I sit down with him for a drink in the aptly named Fuzion Restaurant, I realize that Charles Darwin is not that far away. Through Lazcano, I’m only four degrees of separation from the giant of evolution himself. And it all began with a book. “As a child, I’d always wanted to be either an astronomer or a chemist,” says Lazcano, between sips of mint tea. “Then, when I was about eleven my father gave me a copy of Oparin's Origin of Life.” It was a book that changed both Lazcano's life and the course of the Stardust Revolution.
ON THE ORIGIN OF LIFE
A century before and an ocean away, Alexander Ivanovich Oparin sat inside a Moscow apartment's sitting room, listening with rapt attention to the impassioned interjections of young university students like himself crammed into the too-small space. He listened most closely when the older man, Kliment A. Timiryazev, spoke. It was 1916, and there had been violent demonstrations on the cobbled streets outside, and the whispers that the czar's days were numbered had grown into shouts of defiance. But those gathered in Timiryazev's salon weren't plotting political revolution; they were galvanized by another great revolutionary way of thinking—evolution.
Timiryazev was Darwin's Russian bulldog. Since the publication of On the Origin of Species, Timiryazev, a leading plant physiologist at the University of Moscow, had grown to become the leading Russian proponent of a revolutionary new way of thinking about life's unfolding. As a young scientist, he had made an impromptu pilgrimage to the elderly Darwin's home, surprising his intellectual hero but nonetheless being invited to tea. Timiryazev was also an early Marxist. As such, his salon sessions married the ideas of inevitable biological change with those of irrepressible social change. Both evolution and dialectical materialism—a material rather than divine process of change based on competition and contradictions within a particular social environment—looked to history and competition as the basis for understanding biology and society. They viewed both as moving toward a better world.
When Oparin heard Timiryazev for the first time at a public lecture in Moscow, he was galvanized by the evolutionary firebrand. Already interested in botany and agronomy—his father worked in textiles and dyes—Oparin enrolled at the University of Moscow. Timiryazev had resigned his post at the university in 1911 in protest over the Ministry of Education's violent suppression of a student protest. In the great tradition of the day, Timiryazev continued to teach in the salon of his Moscow home, where Oparin and others gathered to listen to the great man.
At the university, Oparin studied the burgeoning field of biochemistry at a time when biologists and chemists were crossing one another's boundaries in pursuit of an understanding of life as a molecular, Chemical phenomenon. They debated the molecular nature of the genetic material and whether bacteria even contained genetic material—most believed they did not (they do). As a student in the laboratory of renowned biochemist Alexei N. Bakh at the university's Karpov Physicochemical Institute, Oparin was at the heart of one of the world's foremost research labs, where researchers were teasing apart and identifying as best they could the molecular components whose interaction we call life.
In 1917, as the Russian Revolution reached its bloody climax, a twenty-three-year-old Oparin, steeped in the latest biochemistry and evolutionary theory, stepped out into an amazing and turbulent post-czarist society that was pulsating with competing visions for a new society. While Hubble was at work on Mount Wilson observing distant galaxies—work that would provide the underpinnings of the big bang—Oparin was contemplating biological beginnings. The young Russian biochemist was drawn to the big question of life's essential nature at a time when age-old answers—just as age-old forms of social rule in the form of czars and counts—no longer fit the times. A young man full of revolutionary zeal and new scientific insights, Oparin was ready to go where Darwin had feared to tread. Following the revolution, the streets and salons of Moscow were filled with pamphlets and booklets extolling new social and political visions. In November 1923, one of those revolutionary tracts, by A. I. Oparin, was ambitiously titled The Origin of Life.
THE SPONTANEOUS-GENERATION DEBATE
At first, Oparin's manifesto was lost in a tumultuous sea of competition. By 1936, however, his treatise had matured into a Russian masterwork, The Origin of Life, creating a buzz among biologists who could read Russian. Meanwhile, Oparin, dressed daily in a bow tie and with a
crisply trimmed, Leninesque beard, had become the associate director of the Biochemical Institute of the USSR. Two years later, a fellow Russian working at a US university translated Oparin's treatise into English as Origin of Life. It was immediately recognized in the United States as a definitive tome, one that a New York Times book reviewer concluded was a “landmark for discussion for a long time to come.” The reviewer was right. Oparin's book has defined the modern discussion of the origin of life because it wasn't merely filling a gap left by Darwin. It was also addressing one of the greatest, and largely forgotten, scientific debates of all time: the spontaneous generation of life.
The fact is, as Oparin notes in the first pages of his treatise, if you'd talked to leading natural philosophers throughout most of history, from Aristotle to Newton and on to Lamarck, the origin of life wasn't a troubling problem of the distant past; it was a present-day no-brainer. Life happened spontaneously all the time. You only had to look at the abundant daily anecdotal evidence—life sprouting unbidden at every turn from places where none existed before, whether it was mold on days-old bread or mushrooms on the forest floor. “Even in our own time of crowning achievement in the natural sciences,” Oparin wrote, “the layman of civilized European countries not infrequently believes that worms are generated from manure, that the enemies abounding in the garden or field, the various parasites operative in our daily existence, arise spontaneously from refuse and every sort of filth.” It's remarkable to think that ours is the first century (if not, then only the second) in human history in which the majority of people do not believe in the spontaneous generation of life.
However, not all protobiologists adhered to a belief in life's daily re-creation. For more than four hundred years, an intermittent back-and-forth debate simmered. In an age that had no awareness of microbes, the experimental evidence alternately appeared to support one side and then the other, with spontaneous generation usually carrying the day. Savants, theologians, and alchemists attributed various causes to the spontaneous generation of life, at times divine; at others, simply part of the eternal, natural order of the cosmos. But in all these cases, life was always a distinct, mysterious, secret force apart from the rest of matter. It was the force vital. It was a centuries-long debate that Darwin wanted to avoid.
The vision of an essential, unbridgeable gulf between nonlife and life was formalized into modern chemistry in the first half of the nineteenth century by the Swedish chemist Jöns Jacob Berzelius. Berzelius, who developed the system of element symbols used in the periodic table, saw a firm line between the chemistry of life and nonlife, and as a result he saw clear limits of what chemists could concoct in the laboratory. “Art cannot combine the elements of inorganic matter in the manner of living nature,” he asserted in 1827. According to Berzelius, it was impossible for chemists to create “living” substances such as sugars, fats, and proteins. He coined the term “organic chemistry,” meaning life chemistry, as distinct from inorganic chemistry, thus forging a dualist language that still haunts the teaching of chemistry and biology today.
Even as Berzelius was writing about the unbridgeable gap between the molecules of life and all others, a friend was proving him wrong. The first bridge between the molecules of life and nonlife came from synthesizing the main ingredient of urine in a test tube. Urea is the main waste product in urine. In fact, it is the reason we pee. Urea is our body's way of getting rid of otherwise toxic nitrogen leftovers from metabolism. It was clear to nineteenth-century chemists that urea was a product, albeit a waste product, of life. So, when in 1828 the German chemist Friedrich Wöhler created urea in laboratory glassware, other scientists were impressed. Wöhler heated ammonium cyanate to produce copious amounts of synthetic urea, chemically identical to the stuff in urine yet without the need for beer, coffee, or kidneys. This event prompted a profound realization that chemists are still absorbing: there's no chemical difference between, for example, the biologically produced methane in a cow's fart and the abiotically formed methane in the atmosphere of Jupiter. Both methanes are a single atom of carbon combined with four atoms of hydrogen.
Within a year of Berzelius's drawing a line in the sand between the realms of the inorganic molecules and life molecules, Wöhler showed—and other chemists after him also soon demonstrated, with a chemist's cupboard of molecules from sugars and amino acids—that biological molecules could be created from nonliving material. This directly challenged the then-predominant understanding of spontaneous generation that life arose from the self-organizing of previously living matter that alone carried vital force. Wöhler's results showed that life molecules could be created from what was thought of as matter that lacked the force vital. His achievement, however, was hardly a clean flush to the notion of the spontaneous generation of life. Instead, it helped set the stage for a showdown between the warring scientific camps.
In Paris in 1859, the same year that On the Origin of Species was published, one of France's most prominent natural philosophers tried to end the debate with a decisive blow. Félix Archimède Pouchet, director of the Natural History Museum in Rouen, published a massive, seven-hundred-page treatise purporting to experimentally prove spontaneous generation. Pouchet described his experiments, like those done by earlier scientists, which demonstrated that heated broths of organic matter, left to sit for several days, spontaneously became cloudy with microscopic life. Evidently, Pouchet argued, under divine direction, a vital force was at work, and organic particles carrying this life force were self-organizing into microbes.
Pouchet had thrown down the gauntlet to any opponents, and the next year, the French Academy of Sciences officially refereed the intellectual duel. It offered a 2,500-franc prize to whoever could shed new light on the question of spontaneous generation. The winner, announced in 1862, was none other than Louis Pasteur. Today, we think of the legendary French chemist and bacteriologist every time we drink a glass of pasteurized milk—milk that's been heated and then rapidly cooled to kill any harmful bacteria. But each glass of milk could equally give us pause to think about the origins of life, for Pasteur's sterilization work was ultimately driven by the debate over the spontaneous generation of life. From his ample experience with microorganisms through work in the French beer and wine industry, Pasteur had a hunch that what Pouchet described as divine intervention is what we today call dirty lab ware and exposure to airborne contamination. At the time, there was no general understanding of the amazing ubiquity of microorganisms—bugs, in the vernacular; bacteria and viruses, to be more specific. While telescopes were revealing a new view of the heavens, microscopes were about to open our eyes to the invisible realm of the microbes, in the air and on surfaces, that cause disease.
Pasteur needed to prove that Pouchet had somehow inadvertently seeded his samples with invisible life and that an organic broth—such as an infusion of hay, when properly sterilized with heat—would remain lifeless. Pasteur had flasks made with various S-shaped necks that would allow the flow of air into the flasks, but not the entry of microbe-carrying dust, which would settle out and be trapped in the lower curve of the S-neck. In earlier work, he'd filtered and captured airborne dust particles, demonstrating that the dust carried the seeds of life. Now he showed that a broth added to one of these flasks and subsequently sterilized by heat remained clear and lifeless for months. However, in flasks in which the S-neck was broken, microbes quickly populated the broth, indicating that the microbes had entered from outside the broth.
In 1861, Pasteur published his results in an essay, “Mémoire sur les corpuscules organisés qui existent dans l’atmosphère” (loosely translated as “A Memoir on Organized Corpuscles in the Air”), which not only gave a fatal blow to the theory of spontaneous generation of life but laid the cornerstone for the modern germ theory: that diseases don't emerge spontaneously but are spread via the transfer of microorganisms. In his triumphal lecture at the Sorbonne in 1864, Pasteur proclaimed that spontaneous generation was dead: “Never will the doctrine of
spontaneous generation recover from the mortal blow of this simple experiment.” The next year, well on his way to hero status in France, Pasteur pocketed the 2,500-franc prize—though legend has it that, given his developing understanding of germ exposure, Pasteur refused to shake hands when he received the prize.
AN ELEMENTAL VIEW OF LIFE
For seventy years after Pasteur's definitive discovery, the question of the origin of life on Earth struggled to find a solid grounding. Some scientists, such as the famous Lord Kelvin—a lifelong opponent of evolutionary theory—found comfort in the idea that life was simply eternal. Others, such as the Swedish chemist Svante Arrhenius, proposed that the seeds of life on Earth arrived by cosmic delivery from elsewhere in the universe—the concept of panspermia, or “life everywhere,” which avoided the question of this universal life's origins.
Into this gap came Alexander Oparin and his gem of a book Origin of Life. For Oparin, panspermia and eternal life were back-steps into a nineteenth-century “pit of vitalist conceptions,” both lacking a physical, scientific framework. Oparin sought to understand life not as something that occurs in spite of the laws of physics and chemistry but as something that occurs as a result of them. “The problem of the origin of life cannot be solved in isolation from a study of the whole course of the development of matter which preceded this origin,” Oparin wrote. “Life is not separated from the inorganic world by an impassable gulf—it arose as a new quality during the process of the development of that world.”
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