busy being born: on the molecular origins of life · ask evolutionary biologist christopher wills...

Busy Being Born: On the Molecular Origins of Life

(San Diego Reader September 12, 2002)

Ask evolutionary biologist Christopher Wills and organic chemist Jeffrey Bada, who are studyingthe origin of life on earth at the University of California, San Diego, to define life and both willanswer, "an autonomous self-replicating system that replicates imperfectly via naturalselection." Key for this pair is understanding how the abiotic or non-living world developed intothe biotic one. Co-authors of The Spark of Life: Darwin and the Primeval Soup (2001), Wills andBada believe life could arise only in optimal conditions and over a significant period of time.

Bada echoes Wills. "When I talk to the lay public about the origin of life, I’m talking aboutsomething that can’t be seen even with the best microscope."

The mid-western Bada, who is in his 60s and has taught at Scripps Institution of Oceanographysince 1970, concentrates on the chemistry of amino acids in marine environments and onexobiology, the search for extraterrestrial life—not Klingons but unseeable organic compoundsthat have evolved "in the solar system and beyond." For the past 10 years, Bada has directedNASA’s Specialized Center of Research and Training in Exobiology, a program whose goal is tofind "the importance of extraterrestrial input on the primitive Earth."

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And yet as impressive as their bios are, both men still face a monumental problem. If biologicalevidence that developed during the Earth’s first billion years has been ground to dust in themaws of the planet’s tectonic plates, how can we be reasonably sure that life originated in oneparticular way? The answer is, we cannot be sure—not scientifically. We can only hypothesize.

Part of the trouble in Origin City comes from how we think about origins as a culture. Thepopular (and paltry) imagination sees origins in facile mechanistic terms, like a car equippedwith an ignition switch. In her 1818 novel Frankenstein Mary Shelley never shows us VictorFrankenstein creating the eponymous monster. Her Promethean doctor assembles his Creaturefrom pieces of corpses but is never seen to flip any switch. Instead, he merely states, "Afterdays and nights of incredible labour and fatigue, I succeeded in discovering the cause ofgeneration and life; nay, more, I became myself capable of bestowing animation upon lifelessmatter." About the only science the occult-driven Frankenstein engages in is galvanism—the 19th

century conceit that beings could be helped, even brought to life, via electric current.

The origin of life has also been "explained" as either inexplicable or divine, limbs of the samebody. The Bible and other tracts—philosophic, spiritual, religious—argue that there’s noargument as to how life got started: God did it (quickly not slowly), and that’s that. Lack ofevidence seems to make a purposive creation more probable.

Until the past two decades, simplistic explanations of life’s origin have guided scientists. Anagnostic Darwin ends his Origin of Species by writing that "the Creator" breathed life "originallyinto a few forms or into one." That hardly sounds like an evolutionist. Up to and during Darwin’stime, scientists and theologians believed life sprunginto being via spontaneous generation, which is similar to galvanism. Frogs born of the mudthey wallow in, for example. I recall hearing the news conference, two days before the July 20,1969 moon landing, during which Wernher von Braun, the German rocket engineer, said thatthe feat was "equal in importance to that momentin evolution when aquatic life came crawling up on the land" (italics added). In the 2000s, asmattering of researchers, among them Michael Behe, have bivouacked a new anti-evolutionarycamp called "intelligent design." The group contends that evolution could not have built asystem as sophisticated as a first cell. It is, in Behe’s words, "irreducibly complex." Any structurethat exceptional had to have sprung fully formed. In short, a miracle.

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There’s nothing miraculous about the United States income tax code. The code is aself-enabling system that no one understands except a certain caliber of tax attorney, who aloneis capable (to our benefit and peril) of managing its recondite regulations. Even (former)Secretary of the Treasury Paul O’Neill hires a tax accountant. The tax code can be said to have"a life" because it is so highly complex and evolved. In fact, its complexity is the result of itsdevelopment, a 90-plus-year accretion of more (never fewer) regulations. The tax code didn’thappen over night and it certainly wasn’t intelligently designed.

As the tax code did in one century, life seeped into being during its 10 to 200 million-year prime.Wills has called this variable interval no more than "a moment." But it is a moment that, in histhinking and research, he has tried "to blur," propounding a series of stages and a number oflocales—in the molecular world and on the earth’s surface—for creation to begin. To shape themultiple endeavors of life—breeding, mutation, survival—only a process is possible. Not a birth,but a very slow arrival.

***

Around 14 billions years ago, the universe originated with the Big Bang. Seven billion yearslater our solar system began to form. The materials which would become the earthaccumulated: from space dust, gases, meteorites, and comets comprising frozen gases and ice.Eventually, the planet orbed into a sphere and its circling around the sun became fixed bygravity.

As the planet formed, the continual volley of meteorites and the decay of the planet’sradioactive elements created intense heat. In such heat, heavier elements sank. The core thatdrew down iron and nickel was, itself, soon bounded by a lower-density mantle. The silicatesrose or stayed on the surface and, eventually, the surface cooked up a crust. The heat andpressure on the crust, however, was so great that it cracked into plates. The mantle’s circulatingheat, called convection currents, pushed the plates—inches over centuries. This snail-paced butinexorable drift would form and separate continents.

Toward the end of the Hadean period, meteorites slowly stopped bombarding the earth. Freefrom assault, the crust solidified. The earth’s atmosphere developed, coalescing at first into asmoggy concentration of hydrogen, methane, ammonia, and water vapor, which nearly blottedout the sun. Hydrogen, the lightest element, escaped into space, and methane and ammonia,supplied from outgassing volcanoes, became unstable and converted to carbon dioxide and

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nitrogen. Regulating the build-up and retention of the atmosphere was the relative size of theearth and its gravity. Had the earth been smaller, even the heaviest gasses would have leakedinto space.

Without meteor showers, the earth began to cool. In the atmosphere, water vapor condensedand fell as rain. During a deluge that lasted more than 100,000 years, the planet’s surfacedepressions flooded, and global oceans were formed. The crust, much of it now underwater,hardened as it inched along, while in the downpour the heavier elements gravitated to theocean basins. The creation of the oceans was fundamental to the onset of life.

Wills and Bada describe the early earth as a "water world," punctuated by emerging land areason which "mighty tides" washed in and out. "On islands that happened to stand athwart thesemassive movements of water," they write, "the tides could easily have swept across far widerregions than would be accessible to the tides of today." They believe these "enormous tidalfloods" may have moved "in predictable patterns." And here, in the tidal washing of the land’ssurface, the "synthesis and sorting of organic compounds" began.

Organic compounds, common to all living organisms, are substances that contain carbon.Atoms of carbon most often bond with atoms of hydrogen, nitrogen, or oxygen, and create analmost endless variety of compounds. Amino acids are organic compounds, which, when linked,form proteins. Twenty amino acids are found in living organisms. Just as amino acids buildproteins, nucleobases—another kind of organic compound—build the large molecules DNA andRNA.

Scientists speculate that organic compounds may have originated in the oceans, from outerspace, or in an oil slick that once covered the earth. Organic compounds may have arisen fromhydrothermal vents, or undersea openings, where the crust is thin and superheated waterproduces chemical reactions. They may have ridden in on particles of cosmic dust, which havebeen showering the planet throughout its existence. We know today that organic compoundspiggyback to earth on meteorites. A meteorite that fell near Murchison, Australia, in 1969,contained several of the building blocks of life, including amino acids and some of thenucleobases in DNA and RNA. It is these meteor-moored compounds that Bada has exploredon this planet and plans to investigate in 2011 when soil and rock samples are returned fromMars. Bada, who has helped design the module that will retrieve those samples, hopes touncover evidence of simple molecules on Mars that may have contributed to the building blocksof life on earth.

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The third source of organic compounds may have been a planet-wide oil slick several metersthick. "The most abundant component," Wills and Bada write, "must have been tarry material,"which, "tended to coagulate into gooey lumps or films." They describe the surface of the earthas "one giant Exxon Valdez disaster." The slick "could have been like a giant time-releasecapsule, continuously supplying adenine and amino acids to the oceans of the early Earth."Eventually, the oil would have "congealed into tar and then been broken down slowly bysunlight." But the ocean would have retained the organic compounds created in the tar.

Whether synthesized here or flown in from elsewhere, this grand stew of organic material wascooked during what’s called the prebiotic period, a post-Hadean time some 200 million yearslong.

Could it be that finding the right balance among the oceans, the island chains, the atmosphere,and the size and gravity of the earth was necessary for life to begin? Wills and Bada say thismay be part of the equation. They cite the Gaia hypothesis, formulated in 1975 by Britishchemist James Lovelock and American biologist Lynn Margulis, and named for the Greekgoddess of the earth. Gaia suggests that earth is a biosphere where carbon-rich sediments anda carbon-cycling system regulate the temperature. "Variations on the Gaia theme," write Willsand Bada, "may account for the Earth’s apparent ability to keep to a narrow range oftemperatures as the Sun has gradually warmed over the last four billion years." But thishypothesis only works with "living organisms": Protoorganisms had to evolve before the earthbecame self-regulating. Indeed, for millions of years, the first life-creating system, in order toreach some level of organization, had to battle a severely inhospitable terrestrial environment.

***

As collaborators, Christopher Wills and Jeffrey Bada are working in what may be a golden ageof life sciences at UCSD. The campus has nurtured a host of chemists and biologists whocontinue to hothouse new ideas about life and its origins. The most celebrated pair of UCSDbiochemists are Stanley Miller and Harold Urey (Miller died in 2007; Urey in 1981). UnderUrey’s tutelage, Miller, while a graduate student at the University of Chicago in 1953,synthesized amino acids by replicating the supposed prebiotic conditions of the earth—severalgasses (hydrogen, ammonia, methane), a little water, an electrical charge, and no oxygen—in abi-level rigging of glass flasks. Having taught at UCSD since 1958, Miller has, among otherthings, worked on dating the origin of life within a 10-million-year time-frame. (The Spark of Lifeis dedicated to Miller.) Nobel laureate and double helix codiscoverer Francis Crick researchedgenes at the Salk Institute until his death in 2004. Also at Salk is Sydney Brenner, whodiscovered, with Crick and others, messenger RNA, a genetic strand that orders the amino

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acids in proteins. Still another Salk veteran was Leslie Orgel (died in 2007), who made nucleicacid polymers and is researching a "first gene" that copied itself before complex proteincatalysts evolved. And Gustaf Arrhenius of Scripps Institution of Oceanography, havingcollected carbon isotope evidence from rocks in Greenland, claims that life has existed for 3.8billion years.

Each of these scientists has struggled with Wills’s "infuriating" question about the origin of life:How did organic molecules "come together" to make a protoorganism?

Some scientists, like Leslie Orgel, argue that one day there appeared a "naked gene on thebeach," which had already fully formed in the oceans or on "the surface of some mineralparticles." It’s been proposed that this gene, Wills and Bada write, "was capable of makingcopies of itself from the building blocks supplied by the primordial soup. . . . The geneticmaterial grew in size and complexity, coding for more and more compounds, with which itsurrounded itself." Wills and Bada, however, discount this theory. They believe "a limitedamount of organization" had to have "appeared in the molecular world" before genesdeveloped.

Another idea is that life sprung into action in what Bada portrays as a "self-sustained littlechemical factory." The enclosed factory would have been composed of only metabolizingmolecules. But Bada disagrees that such an isolated structure could have advanced and labelsthe idea, "life as we don’t know it."

Wills and Bada contend that the molecular precursors of a first self-replicating entity rootedthemselves on the shores of a vast percolating ocean-soup. For millions of years, organiccompounds had gathered in the soup. The compounds were then splashed for millions of moreyears onto the intertidal zones of the emerging land masses. There, in the tidal zones, formedwhat Wills calls an "ill-smelling residue," a mineral-rich "organic scum." This scum would havesettled in nooks and crannies on the rocky shore.

As more and more molecules aggregated in the scum, organic compounds would have begunto produce more complex groups. For example, write Wills and Bada, "in those early tidal flats,wherever amino acids and sugars were concentrated," a "brownish polymer," or repeating chainof a simple molecular group, would have formed. The "accumulating sugars could haveprovided some sort of protective function—perhaps by producing a slimy impervious layer thatwould have repelled water as tides and waves periodically swept by." Such a layer might have

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separated groups of molecules.

One kind of protective layer that Wills and Bada believe developed early on was atwo-dimensional-like membrane. This membrane wasn’t like the lipid or water-insoluble surfacethat houses a cell today. It was a barrier between one group of molecules and another. Badadescribes the membrane as "sticky yet discrete," allowing for simple separation, and Willselaborates. These membranes were probably "made of a silky material that floated about in theprimitive soup. They would have had [the equivalent of] an inside and an outside, across whichcharged differences could be generated. [This would have led] to the charging up of thesemolecules." Perhaps the membrane’s surface was composed of one-half an amino acid that isnegatively charged, which then attracts—to interact or bond with—a surface of positivelycharged aminos. Charged molecules may have combined and grown into energy-richcompounds that became sources of food for other compounds.

With the mix of ocean surf and the deposit of more and more organic molecules in the tidepools, "billions of tiny experiments" in life-making got going. Wills and Bada hold that tidalaction, an agent itself of constant change, is essential to these experiments because on andwithin the scum favorable and unfavorable aggregates of molecules began to be sorted. Usuallywe associate a sorting-out process of favorable and unfavorable—the fit and the less fit—withevolution. But Wills and Bada suggest that "the sorting-out capability could somehow [havebeen] decoupled from the reproductive capability" before life began, in what they describe as"the molecular equivalent of birth and death." They believe the stronger molecules stuck to therocks and "lived" while the weaker molecules got washed into the ocean and "died." Initially,there was a simple piling-on of molecules. In the piles, however, "different collections ofmolecules would have clung to different types of particles" on the rocky surfaces, eventually"becoming stratified according to their sizes and chemical properties."

These different collections, still being sorted out, resided in what Wills and Bada call a"molecular ecosystem." Supported by this ecosystem, a given robust collection of moleculesmay have been able to accomplish several things at once: attract, with its stickiness and itscharged surfaces, other molecules coming in with the tides; absorb energy from sunlight thatwould aid its development; and protect its expanding aggregate from the ultraviolet light thatwould normally fry anything exposed.

***

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We are now almost ready for the arrival. But, due to further complex development of the firstliving organism, it may be easier to describe the newborn before analyzing its composition. Willsand Bada adopted the term protobiont, used by the Russian biochemist Aleksandr Oparin in his1926 The Origin of Life, to describe the firstself-replicating entity in the molecular ecosystem. The protobiont has several characteristics: itis an organized collection of molecules; it can multiply "inside the complex, slimy layers ofmolecules" that cling to the rocks; and it carries rudimentary genetic information. The genesboth house the protobiont’s hereditary characteristics and transmit instructions forself-duplication.

Wills and Bada believe that the protobionts made a "skeleton," or platform, out of a group ofmolecules. The platform secured itself by selecting (and affixing) the architecturally strongestorganic compounds from the primitive soup. To illustrate this link between protobiont andenvironment, Wills offers—from much further up the evolutionary ladder—the sea snail. With thecalcium carbonate molecules of seawater a snail builds a shell, a structure or platform withinwhich it can survive. "The ability to build the shell is coded in the snail’s genes," he says, "butthe shell itself isn’t." The shell’s materials must come from "outside the organism to enable theorganism to complete itself." In this way, the protobiont needed the village of its environment inorder to be raised.

The protobiont may have also contained what Wills and Bada describe as a "fragment ofgenetic material [which was] made up of a short piece of nucleic acid or a similar molecule."Whatever that genetic material was, it was like DNA, the nucleic acid common to almost all lifetoday. We recall that DNA’s structure, the familiar spiraling double helix, is also like a zipper.The sides of the zipper interlock, linking nucleobases into base pairs: adenine with thymine,guanine with cytosine. The human genome is built of 3.2 billion base pairs; the tiny bacterium,mycoplasma, has 500,000 base pairs. Bada believes the first entity’s structure contained just 30to 50 base pairs. That was "the minimal size needed to store information in this molecule. And,remember, it’s the sequence of the bases that stores the information." As more bases linked,the entity would have had more data to copy and more opportunity to mutate.

What information might have been stored first in the entity’s code? Wills and Bada write that the"most primitive distinction that the early genetic code must have made was betweenwater-loving and water-hating amino acids." If a molecule was coded to "love water," then itwould have readily received organic compounds from the soup. If a molecule was coded to"hate water," then it would have built up a structure to repel water, helping the entity survivesome of the ocean’s pummeling action on the shores. As we have seen before, the two kinds ofmolecules may have allowed the entity to do two life-enhancing things simultaneously—growand protect its growth.

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One final sorting-out process remains—what Wills and Bada call, imperfect replication. It’sessential to remember that our knowledge of prebiotic chemistry is, as Wills laments, "full of somany missing steps [that] it’s difficult to see how these steps might have happened." It musthave taken billions of chances for each step to occur—for cosmic dust, hydrothermal vents, anda planet-wide oil slick to seed the primeval soup with organic compounds; for ocean tides tobegin pummeling the shores; for organic compounds to stick and polymerize in the scum; forthe protobiont to develop fledgling nucleic bases that would remember bits and pieces ofthemselves across a generation. The final step necessary for self-replication would have beenfor the protobiont to evolve from copying a small part of itself to copying enough of itself that itpassed on a living and autonomous organism.

"Life can’t get anywhere," Wills says, "if organisms make exact copies of themselves." In orderto get somewhere—that is, to survive the severity of its environment—the protobiont was forcedto adapt. The primary source of adaptation for the protobiont came through mistakes madewhile its genetic information was passed on. We may grasp the theory of the protobiont, Willssays, by looking at "the process of DNA replication itself. DNA is comprised of two strands thatspiral, or grow, with each other in the double helix. Suppose you have a sequence of pairs thatis A T. If the self-replicating DNA makes a mistake and puts a G in place of the T, you have AG, or a mutation. In this way, organisms acquire mutations and natural selection sorts thesemutations out. Humans," he continues, "are very good at repairing our mistakes. We have allkinds of machines in the cell that repair mistakes. As a consequence, we don’t have anywherenear the number of mutations per unit time as the bacteria does."

Early on, the protobionts were, like bacteria, mutating at a very high rate. In fact, before theprotobiont became a living organism, different sections of its genetic code, Wills says, musthave "replicated extremely imperfectly." At first the protobiont retained a very small percentageof its precursor’s genes, which would not have specified "all the information needed for a livingorganism." To retain more genes, the protobiont may have evolved a better self-replicatingsystem in which it reduced the number of its mistakes. But once the protobiont had stabilized itsrate of mistakes, and enough genetic information was being copied to "secure" its autonomy,then, as Wills and Bada write, this "would have represented the first stirrings of life."

***

How long did it take for the protobiont to arrive? If protobionts were bacteria-like in theirmutative proliferation, wouldn’t that have meant an extremely long time to evolve? Wills says

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no. In fact, he believes life got going in less than 10 million years. He cites three reasons.

One is an idea developed by Stanley Miller. Miller has written that "life must have arisen in 10million years or less based on the known rate of decomposition of organic compounds." In thisinferno, organic molecules "died" when, returned to the ocean, they were sucked through thehydrothermal vents in the deep-sea trenches every 10 million years.

Second is that, at the molecular level, chemical reactions take place very quickly. Combine thisrapidity with the third reason: the growing shoreline space of the young planet. While theprotobiont was using its 10 million years to form and replicate, it also formed and replicated inseveral billion places—those tiny terrestrial niches where organic scum collected. If incipient lifehad only one chance in a million billion chances in one locale, the likelihood of its developing isvery slim. But if that one chance had a million billion molecular eco-systems within which toexperiment, the odds are much better. Quite good, in fact. Enough to cause Bada to say thatthere were probably "multiple origins of life."

Let’s say that life originated around 3.8 billion years ago and then took tens of millions of yearsto reach full autonomy or, as Wills says, "be on its way." As it did, there would have beenmassive amounts of decomposed organic compounds—those with "imperfect"characteristics—available to "feed" it. On one hand that’s a lot of feed; on the other hand, that’sa lot of dying, an area which scientists, like doctors, seldom discuss. Why is unclear. Perhapsit’s because decomposition is seldom studied under the biologist’s microscope. Living matterattracts the majority of their scrutiny. But the importance (not to mention the amount) ofdecomposition to the evolution of life is prodigious.

Consider this oblique angle. Estimates suggest that the structure of DNA was fixed more than 3billion years ago. This includes the DNA of our common ancestor in the bacterial realm. So whatwere the chances that deoxyribonucleic acid developed its very particular sequence? In TheFifth Miracle: The Search for the Origin and Meaning of Life(2000), Paul Davies collects several metaphors to try to explain the unlikelihood of lifedeveloping on earth as it did. Among them is a quotation from the British astronomer Fred Hoylewho "likened the odds against the spontaneous assembly of life to those for a whirlwindsweeping through a junkyard and producing a fully functioning Boeing 747." The possiblecombinations of billions and billions of interacting molecules to make DNA are, as Britishzoologist Richard Dawkins is fond of intoning about evolutionary possibilities in general,unimaginable but not incalculable.

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DNA "against all odds" sounds fantasy-headed, like a George Lucas movie. But, despite therelentlessness of earth’s geology, DNA beat the odds. We know from the paleobiochemicalrecord that virtually all organisms—the estimate is greater than 99 percent—have died out. Weknow that all protobionts have been annihilated by plate tectonics. Hence, the self-maintainingbiomolecule that came after the protobiont was, up to that date, the most improbable entity tohave gotten that far. And still, no matter which organism got through, there is an abyss betweenthe one that made it and all those others that didn’t, all those molecules that were recycled, allthose mutations that dropped off the turnip truck. Such loss is evolution’s stamp. Tooverproduce the very many so the very few survive.

***

Christopher Wills says that perhaps the fiercest of the ongoing arguments among origin-of-liferesearchers is whether an origin theory can be tested in the lab. This fascinates him because,he says, "Every other science is approachable in the lab, why not the origin." The success ofStanley Miller’s 1953 experiment is precisely what attracted an array of scientists to study life’sonset. By the middle of this century, Wills believes, biochemists will in a series ofheadline-grabbing experiments create life, and, thereafter, such experiments by high schoolkids will be common. Wills imagine the biology teacher’s challenger to her students, "‘Let’s seewho can be the first in the class to make life.’ I have a hunch it’s going to be far easier than wethink." And yet, he stresses, it has to be "ineluctably" proven, so that people will accept themolecular ab ovo view. To create life in the lab will be a momentous occurrence for tworeasons: first, because it may permanently alter the creationist view that God is the only author;and second, because replication may be less complicated than we thought since even highschool kids will be able to do it.

Wills, of course, is not claiming that the mystery of creation will be solved with suchexperiments; the exact conditions that gave rise to life on the early earth are neither knowablenor reproducible. So what will the lab-based synthesis of self-replicating organic compoundsprove?

According to Loren Eiseley, a naturalist and author of The Immense Journey (1957), not much.A demonstrable origin, for Eiseley, "suffers from the defect of explaining nothing, even if itshould prove true. It does not elucidate the nature of life." Eiseley is pushed not so much by thecomplexity of origin science as he is by "the loneliness of a man who knows he will not live tosee the mystery solved, and who, furthermore, has come to believe that it will not be solvedwhen the first humanly synthesized particle begins . . . to multiply itself in some unknownsolution." For Eiseley the origin’s incredibly lucky conditions "will never come again." And it’s

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this never comingagain thatbroods the egg. We—all creatures—are doomed to sit on what he calls "the egg of night."

To illustrate the quandary, Eiseley writes, "My memory holds the past, and yet paradoxicallyknows, at the same time, that the past is gone and will never come again." Humans may beable to recognize that the irreversibility of their own pasts resonates with the irreversibility oflife’s beginning. But, if DNA’s existence coincides almost with that beginning, does DNA hold itspast in the same way that an individual’s memory holds its past? Is part of the genetic code ofany biomolecule a key for deciphering that biomolecule’s past? Or does the code only giveinstructions for replication, that is, what will be?

It is possible that DNA has "remembered" its past, that a genetic sequence may contain theorigin’s right splash of atmospheric and terrestrial conditions. But that sequence may havemutated through the aeons as well as been buried and re-buried, ad infinitum. The origin of lifethat may be locked in DNA appears to us like a million Rosetta stones, concealed under a fewbillion years of planetary evolution.

No doubt a "knowable" origin has been entombed by what Paul Davies calls "the carnage ofnatural selection." What seems truly irreducible about the first biomolecule is that carnage is notonly programmed into its DNA—the overproduction and death of "too many" organisms so thatthe very few survive—but that carnage has been in motion so long that it has made the origin ofthat biomolecule more inscrutable than it may be. Carnage also suggests the immense amountof failure that is necessary to create and sustain life. The rate of mutation’s failure to replicatelife is many times that of the rate of mutation’s success in continuing life. While the number ofspecies alive today is a few million, the number of extinct species, according to calculationsdone in 1952 by paleontologist George Gaylord Simpson, is 500,000,000. With such odds, nowonder every species and every bacteria tries every trick in the book to ward off the hangman.

Merrily we mutate. Mercifully we die. Is that it? Mutation and death, carnage and renewal,annihilation and rebirth—ultimately achieving a kind of platitudinal purposelessness? All entities,whether they do or don’t replicate, have to die with or without ascribing themselves a purpose.Life may have no purpose because the "autonomous self-replicating system" that drives theliving bestows little more to do, in the grand scheme, than accomplish the next round ofautonomous and imperfect self-replication. Is that purposeless? I don’t know. I do know thatbecause I’m drawn to summer’s resplendence out my window, to the feathery top of aEucalyptus bending in a coastal breeze, I think (and it may only be my code) that theirredeemable fact of our origin means very little.

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busy being born: on the molecular origins of life · ask evolutionary biologist christopher wills...

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