A Brief History of Creation

by Bill Mesler

  It became one of the most recognizable and beautiful images in science: the twisting double helix of DNA, two long strands of nucleotides wrapped around each other like a tiny caduceus. It was a structure that might have been envisioned by Salvador Dali. Most critically, it had all the attributes that scientists expected to find in the carrier of genes. As early as 1927, the Soviet scientist Nikolai Koltsov had proposed that genes were passed along by a hereditary molecule consisting of “two mirror strands that would replicate.”¶ In 1934, Haldane had guessed that genes copied themselves by means of complementary templates. By the time Crick and Watson set out to find proof that DNA was indeed the carrier of genetic information, they knew they were looking for complementary strands that could serve as a template. The structure of the DNA double helix fit like a glove.

  In May of 1953, three complementary papers announcing the discovery of the double-helix structure of DNA appeared in Nature—one authored by Crick and Watson, one by Maurice Wilkins, and a final paper by Franklin. The structure, Watson and Crick wrote, “suggests a possible copying mechanism for DNA.” The articles appeared just a few weeks before Miller published the results of his own experiment in Science. Yet in contrast to the barrage of stories that trumpeted the discovery of the generation of amino acids from inorganic elements, the discovery of DNA’s structure received almost no notice in the popular press. A short article entitled “Form of ‘Life Unit’ in Cell Is Scanned” had been slated to run in the New York Times, but it was pulled at the last minute, presumably because the editors thought it insignificant.#

  Despite having just made one of the most important discoveries of the century, Crick was put back to work on the structure of hemoglobin. The idea that proteins still played a significant role in inheritance did not die quickly. Many scientists persisted in the belief that DNA and proteins had a kind of symbiotic relationship in controlling the flow of genetic information, that while DNA shared information with proteins, proteins also shared information with DNA, making them cocarriers of genetic inheritance. Crick gradually won support for what he had at first controversially called the “central dogma” of biology: that genetic information can be passed from nucleic acid to protein, but not vice versa. Acceptance of DNA as the sole carrier of genetic information would come only after Crick spent the next thirteen years deciphering the intricate language that organisms have used to speak to each other for billions of years, the genetic code.

  An iconic 1953 image of Watson and Crick with a DNA double helix model.

  THE GENETIC CODE IS the oldest language we know of. It is as old, or at least nearly as old, as biology itself. For billions of years, it has been “spoken” by every cell of every living thing. It has only four letters, each recorded by the presence of a specific chemical. It is typically translated as A, C, G, and T, the letters corresponding, respectively, to the chemicals adenine, cytosine, guanine, and thymine, which are the bases of nucleotides, all arranged in long strings composed of three-letter words.

  It should have come as no surprise that the code’s eventual unraveling began in Great Britain, the nation where Alan Turing and his Bletchley Park colleagues had turned their skills to breaking German ciphers during the war and constructed one of the world’s first computers. With the help of several scientists, including the Russian-émigré physicist George Gamow, most noted for his advancement of the Big Bang theory, Crick and colleagues managed to crack the basic underlying structure of biology’s genetic language. By 1966, three years after Crick received a Nobel Prize for his role in establishing the structure of DNA, the code had been deciphered in its entirety, showing how each three-letter sequence, known as a codon, translated into corresponding positions in proteins. With this discovery, human beings could read the cellular language of living things.

  As Crick worked on breaking the code, he also confronted the question of how exactly DNA communicates with proteins. A language that could not be understood was useless on its own. DNA had to be able to direct proteins to facilitate the sequential arrangement of amino acids. There had to be some kind of messenger between the two. Since the 1940s, some scientists had suspected that large molecules of a nucleic acid called ribonucleic acid, or RNA, played a role in the creation of proteins within cells. By 1958, Crick and others had largely worked out RNA’s role in passing genetic information from DNA to proteins. Crick also noticed that RNA played a versatile role in the cell, that it resembled in some ways both DNA and proteins, the agents of replication and metabolism. Though it carried genetic information, he wrote, some RNA must have once been capable of doing “the job of a protein.” He even speculated that the first living organism might have “consisted entirely of RNA.” His remark would eventually come to be seen as prophetic by many in the field of origin-of-life research.

  AS THE CENTRALITY of nucleic acids in genetics began to be established in biology, it started to transform the way scientists looked at the origin of life. If, as it seemed, a particular subcomponent of a cell preceded the others, then either metabolism or genetics had to have developed first. One school of thought, which would come to be called “metabolism first,” saw the protein or something like it as the earliest key component of life. In contrast, other scientists, including Stanley Miller, thought that work on proteins was barking up the wrong tree, and that the development of DNA and of genetic machinery was the likely first step. Once replicating, mutable molecules existed, all else would follow through evolution. A protein bereft of a gene, they thought, could lead nowhere.

  Sidney Fox always remained firmly in the metabolism-first camp. As most scientists in the field began to tilt heavily to replication or some combination of the two, he started to complain bitterly about what he called the “nucleic acid monopoly.” But the biggest problem Fox faced wasn’t so much his insistence on the protein-first model for the earliest life. Rather, it was his dogged insistence that he had largely solved the problem of abiogenesis through his experiments on proteinoid microspheres. During the 1970s, Fox became fixated on the existence of differential electric charge that he found on the membranes of the microspheres, which to his mind was not unlike that which exists in living cells. As late as 1988, in his book The Emergence of Life, Fox went so far as to claim that these microspheres showed signs of a “rudimentary consciousness.”

  The claim was met with incredulity and, in some cases, even ridicule in the origin-of-life circles in which Fox had once been so prominent. But he never lost the high esteem of administrators at NASA, and he continued to receive generous funding into the twilight of his career. And although he was an atheist, Fox even managed to secure an official position as an occasional adviser to Pope John Paul II on the subject of the origin of life. By the time of his death in 1998, Fox was mostly ignored by his origin-of-life colleagues, and his unique ability to promote his own work among the organs of power stirred up more than a little jealous resentment.

  The true legacy of Sidney Fox’s work is more mixed. Fox’s skills as an institution builder were instrumental in turning the study of the origin of life into a mainstream academic discipline. When many scientists were leaning toward the idea that the origin of life was a random, unique event, Fox stayed true to Oparin’s vision of life’s beginnings being part of an inevitable evolutionary progression. And though few scientists still view proteinoid microspheres as significant, the idea of the importance of some type of preprotein, a polymer of amino acids, has never been fully dismissed and would form the basis of many later theories as to how the first organism may have come into being.

  LIKE SIDNEY FOX, Francis Crick would, in his later years, face many strains on his reputation. Some stemmed from his outspoken stance on controversial subjects; others, to his penchant for broad, daring hypothesizing. When correct, these ideas reinforced his reputation for genius. When wrong, they could make him appear a bit of a crackpot. He embraced the spirit of the late 1960s, wearing sideburns and colorful shirts and experimenting with LSD. He lent his name to a campaig
n to legalize marijuana in Britain. He also made several ill-advised comments in support of euthanasia and eugenics, which he came to regret.

  Religion was another controversial topic that Crick did not shy away from. After his work on elaborating the nature of genetics, he had been named a founding fellow of Churchill College. It was a prestigious appointment. Named in honor of Winston Churchill, the college was meant to become a kind of British counterpart to American scientific universities like Caltech and MIT. But Crick soon resigned in protest of the building of an exclusively Christian chapel rather than, as Crick preferred, a nondenominational meditation room that could be used by people of all faiths. Crick was not fond of religion in general or Christianity in particular, which, he once joked, “may be OK between consenting adults in private but should not be taught to young children.”

  Crick moved on to the Salk Institute in California, named for the discoverer of the polio vaccine. There Crick turned his focus more thoroughly to the question of the origin of life. Joined by an old friend from Cambridge, Leslie Orgel, a leading authority in the origin-of-life field, Crick began to contemplate an early stage in the history of life in which amino acids were ordered into primitive proteins using a simple code that might have then evolved into the genetic code used in all modern organisms. He became fixated on the reasons why alternative codes had not arisen, spawning competing lines of descent.

  Frustrated with his inability to make headway into the problem of the origin of life, Crick began exploring the idea that life might have originated elsewhere in the universe. In a 1973 article entitled “Directed Panspermia” in the planetary science journal Icarus, he and Orgel presented a theory that the Earth had been deliberately seeded with bacterium-like life-forms by an intelligent species from another solar system. Orgel treated the subject almost as a joke. Crick was not entirely unserious, though he knew it was wild speculation. They had based much of their argument on the puzzling abundance of molybdenum in cells. Since molybdenum is extremely rare in the Earth’s crust, maybe, they argued, our ancestors emerged on a molybdenum-rich planet. Most scientists were quick to point out that pushing the problem of the origin of life off Earth did little to solve the problem, and quite a bit to complicate it.

  But the idea that life might have arisen elsewhere in the universe was not quite dead, and Crick’s hypothesis would seem, for a brief spell at least, almost prescient. Two decades after Crick’s musing, a rock was found in the Antarctic that would reignite the idea that life might indeed not have originated on this planet, or at least that it was not exclusive to the Earth.

  * An estimated one out of every five people on Earth followed the broadcast.

  † Bragg’s record as youngest Nobel laureate was finally broken in 2014 by Malala Yousafzai, who won the Nobel Peace Prize at the age of seventeen.

  ‡ The term “nucleic acid” is something of a misnomer. It is now known that both DNA and RNA are present as well in prokaryotic cells, which have no nucleus.

  § The use of Franklin’s crystallography has become one of the more enduring controversies over ethics in science. Watson and Crick certainly drew upon Franklin’s data without her consent, though it is doubtful that she would have objected. Franklin and Crick grew to be good friends in the years following the discovery. When Franklin died of ovarian cancer in 1958, possibly caused by radiation exposure from her X-ray work, she passed her final weeks at Crick’s home. In 1962, Crick, Watson, and Wilkins shared the Nobel Prize in Physiology or Medicine for their discovery of the structure of DNA. Franklin was not under consideration, since the Nobel cannot be issued posthumously, and for many years, her vital contributions to the understanding of DNA were overlooked. The perception of her as victim of an overwhelmingly patriarchal scientific establishment was reinforced by Watson’s overtly sexist portrayal of her in The Double Helix. Watson called Franklin “the product of an unsatisfied mother who unduly stressed the desirability of professional careers that could save bright girls from marriages to dull men. . . . The thought could not be avoided that the best home for a feminist was in another person’s lab.” The line is typical of the way Watson described her throughout the book, and a good example of the obstacles women have faced in the laboratory.

  ¶ Koltsov’s theories on genetics led to his denunciation by Trofim Lysenko. In 1940, Koltsov was fatally poisoned by the Soviet secret police. His wife committed suicide on the same day.

  # History is littered with cases of groundbreaking discoveries being initially overlooked by the lay press and general public. Albert Einstein proposed the theory of relativity in 1905, yet his name did not appear in a newspaper until 1917.

  LIFE EVERYWHERE

  We are made of star-stuff. We are a way for the cosmos to know itself.

  —CARL SAGAN, Cosmos: A Personal Voyage, 1980

  SHORTLY AFTER MOST of the planets in the Milky Way had formed some four and a half billion years ago, a volcano erupted on Mars, spewing molten lava onto the surface of the planet. As the lava cooled, it hardened into solid rock. For the next half-billion years, the rock lay relatively undisturbed until, one day, an asteroid came crashing onto the planet’s surface. The impact was so powerful that the heat from the blast violently compacted the rock, melting away portions of it and creating a series of tiny cracks. The impact also tore the rock away from its resting place below the surface of the planet, and bounced it above the Martian surface.

  Four billion years later, another asteroid slammed into Mars. This one struck with such fury that the rock was hurled skyward, through the planet’s atmosphere and deep into space. Finally, slowed by the gravitational pull of the sun, and nudged by that of Jupiter, the rock settled into an orbit not unlike that of the planet that had once been its home. It circled the sun for sixteen million years, until one day, just as humans were starting to form permanent settlements along the Euphrates River, its orbit brought it into Earth’s gravitational field. The tiny rock, by then no larger than a softball, hurtled down through our atmosphere and embedded itself deep in an ice field in Antarctica.

  Another thirteen thousand years passed. Slowly the rock was pushed to the surface by the force of the ice field butting up against a nearby mountain range, like a splinter being forced from a finger. It came to rest in the Allan Hills region of Antarctica, at the base of the Transantarctic Mountains, one of the largest and least explored mountain ranges in the world.

  On a relatively mild December day in 1984, a team of meteorite hunters from NASA’s Johnson Space Center in Houston began combing the area around Allan Hills known as the Far Western Icefield. Since the early 1970s, NASA had sent dozens of such missions to the Antarctic, which had long been recognized as an ideal place to find meteorites. The extreme environment meant that it was relatively sterile compared to almost anywhere else on the Earth’s surface, minimizing the dangers of contamination. And the vast flat sheets of pristine white ice that blanketed most of the Antarctic meant that meteorites were easy to spot.

  The person who spotted the Mars rock was a novice meteorite hunter named Roberta Score, on her first such expedition for NASA. It was the middle of summer in the Southern Hemisphere, clear and warm for the coldest point on Earth, almost above freezing. She spotted it in the distance, blue in the sunlight and barely bigger than a softball, likely unnoticeable in any other place on Earth. Score retrieved it and gave it a name: Allan Hills 84001, or ALH84001 for short. Score also took a few notes. She noticed that the rock was “covered with dull fusion crust. . . . Areas not covered by the fusion crust have a greenish-gray color and a blocky texture.” Years later, when the rock attracted serious scientific scrutiny, the blocks that Score had observed would become the center of what, for a time at least, seemed like one of the most important discoveries in the history of science.

  When the expedition returned, ALH84001 was shipped back to Johnson Space Center. It was placed in the containment facility originally built to contain the lunar samples brought back by Apollo 11, where it sat
along with the agency’s rapidly growing collection of meteorites. Initially, nobody at Johnson suspected that ALH84001 was anything more than a typical meteorite composed of leftover debris from the formation of the solar system, something that had come loose from an asteroid. A chip of it was parceled out for display to the Smithsonian National Museum of Natural History, where it sat, rather unremarkably, for the next five years.

  In 1990, a young Smithsonian curator charged with doing some more detailed tests on the composition of the little meteor fragment found that it abounded with carbonate minerals. Although they can be produced through nonbiological means, carbonates on Earth are almost always found in areas that have been exposed to water. This was the first real clue that ALH84001 might be anything but a run-of-the-mill meteorite.

  By 1993, mineralogy, isotopic composition, and analyses of trace gases trapped inside the rock had established that ALH84001 was indeed a Martian meteorite. It was certainly not the only Martian rock to have fallen onto the Earth. But the technology used to identify extraterrestrial rocks was relatively new, and out of the thousands of meteorites that had been studied by that time, only nine had been conclusively identified as Martian.

  ALH84001 began to draw serious attention from labs and research institutions around the world. Pieces were parceled out for study in the United States and abroad. Scientists in Germany were the first to estimate the age of the rock using radiometric dating. They judged it to have formed four and a half billion years ago. This assessment did not quite establish it as the oldest known rock in the universe; another Martian meteor was found to be a tad older. But because of a margin of error that ran in the tens of millions of years, it very well might have been. In any event, over the next several years, ALH84001 became, in the words of one observer, “the most studied 2 kilograms of rock in history.”