IN 1953, StANLEY Miller, a graduate student at ty of Cook taining a little er to represent a primeval o, ture of meto represemosped tubes, and introduced some electrical sparks as astand-in fer a feer in turned green ay acids, sugars, and ot do it ted supervisor, te .”

        Press reports of time made it sound as if about all t o give t. As time    nearly so simple. Despite ury of furtudy, osyntoday thinking we .

        Stists are noty certain t tmosp as Miller and Urey’s gaseous ste rative blend ofnitrogen and carbon dioxide. Repeating Miller’s experiments s ive amino acid. At all events, creating aminoacids is not really teins.

        Proteins are    oget of them.

        No one really kno types of protein in ttle miracle. By all ty proteins s exist.

        to make a protein you o assemble amino acids (ion torefer to icular order, in mucyou assemble letters in a particular order to spell a     are often exceedingly long. to spell collagen, type of protein, you e eigters in t order. But to make collagen, youe 1,055 amino acids in precisely t sequence. But—and    crucial point—you don’t make it. It makes itself, spontaneously, dire, and the unlikelihoods e in.

        taneously self-assembling are,frankly, nil. It just isn’t going to o grasp s existence is, visualize astandard Las Vegas slot mac broadened greatly—to about y feet, to be precise—to aodate 1,055 spinning ysymbols on each wheel (one for eaon amino acid).

        1opull t order? Effectively forever. Evenif you reduced to typiumber of amino acids for a protein, t all ty-turally    amino acids kno discovery,but only ty of to produce us and most oty-sed, calledpyrrolysine, e Uy and is found only in a siype ofarc tle furtory) called Methanosara barkeri.

        prescribed sequence are 1 in 10260(t is a 1 follo in itself is a largeroms in the universe.

        Proteins, in s, are plex entities.    byprotein standards, yet even it offers 10190possible amino acid binations, y c Max Perutz ty-to u. For random events to produce even a single protein unning improbability—like a ronomer Fred hoyle.

        Yet alking about several ypes of protein, peral to tenance of a sound and    goes on from tein to be of use must not only assemble amino acids in tsequence, but t engage in a kind of cself into a veryspecific sructural plexity, a protein is no good to you ifit ’t reproduce itself, and proteins ’t. For treplig—it    make a copy of itself in seds—but    do virtually notuation. Proteins ’t exist    DNA, and DNA    proteins. Are o assume t taneously ing eacher? If so: wow.

        And till. DNA, proteins, and ts of life couldn’t prosper some sort of membrao tain tom or molecule ly. Pluy atom from your body, and it is no more alive than is a grain of sand.

        It is only uring refuge of a cell t terials    take part in t    teresting c    the cell has no purpose.

        As t Paul Davies puts it, “If everyty of molecules ever arise in t place?” It is rats inyour kitc togeto a cake—but a cake t oreover divide    is little     t is also little    and it.

        So s for all ty? ell, one possibility is t perisn’t quite—not quite—so    first it seems. take teins. t t ein c assemble all at once?    if, in t slot ma, some of t    if, in oteins didn’t suddenly burst intobeing, but evolved .

        Imagine if you took all ts t make up a    tainer er, gave it a vigorous stir, andout stepped a pleted person. t ’s essentially ionists) argue    proteinsspontaneously formed all at o—t c ive sele processt alloo assemble in cer a time bumped into some oterand in so doing “discovered” some additional improvement.

        s    of    t    associated ually somet may be beyond us to cook tanley Miller and    t readily enougs of molecules in nature get togeto formlong tly assemble to form starcals    do anumber of lifelike te, respond to enviroal stimuli, take on a patternedplexity. tself, of course, but trate repeatedly tplexity is a natural, spontaneous, entirely onplace event. t be agreat deal of life in t large, but tage of ordered self-assembly, iransfixing symmetry of snoo turn.

        So poural impulse to assemble t many stists no lifemay be more iable t it is, in t andNobel laureate    de Duve, “an obligatory maion of matter, bound to arisee.” De Duve t it likely t sus ered perimes in every galaxy.

        Certainly terribly exoti t animate us. If you e anot, s of a fe togetions to form some sugars, acids, and ot lives. As Daes: “t tances from hing else.”

        ttom line is t life is amazing and gratifying, per edly attest    existeo be sure, many of tails of life’s beginnings remaiy imponderable. Every sario you ions necessary for life involves er—from ttle pond”

        s t are no populardidates for life’s beginnings—but all t t to turn monomers intopolymers (o begin to create proteins) involves o biology as“deion linkages.” As one leading biology text puts it,    a tiny    ofdisfort, “Researc sus    icallyfavorable in tive sea, or indeed in any aqueous medium, because of tionla is a little like putting sugar in a glass of er and    bee a cube. Its    someure it does. tual cry of all ttleare for our purposes    it is enougo kno if you make monomers    t turn into polymers—except     ot unansions.

        One of t surprises in t decades    ory life arose. ell into t    t life urous souls felt t maybe it back 2.5 billion years. But t date of 3.85 billion years is stunningly early. Eart bee solid until about 3.9 billion years ago.

        “e    only infer from ty t it is not ‘difficult’ for life of bacterial grade toevolve on plas e ditions,” Stepimes in 1996. Or as    it else “life, arising assoon as it could, o be.”

        Life emerged so sly, in fact, t some auties t must    eart inguisory. t Lord Kelvin y as long ago as 1871 at a meeting of tision for t ofSce    “t    to teorite.” But it remained little more tion until one Sunday iember 1969 ralians artled by a series of sonis and t of a fireball streaking from east to    across trange crag sound as it passed a be some likeo metedspirits and ot awful.

        tounately, no oe ype knooiming could ter. Less tronauts uro Eart traterrestrial in.

        teorite o be 4.5 billion years old, and it udded y-four types in all, eigion of earteins. In late 2001, more ty years after it craseam at ter in California annou tained plex strings ofsugars called polyols, h before.

        A fees rayed i landedagiss of Nort tually ric, it is no, is about 25 pert anic molecules. Getenougo a suitable place—Eartand you s you need for life.

        tions of panspermia, as extraterrestrial theories are known.

        t is t it doesn’t ansions about    merely movesresponsibility for it elseimes excites even trespectable ads to levels of speculation t    be safely called imprudent. FrancisCrick, codiscoverer of tructure of DNA, a Eartely seeded elligent aliens,” a Gribbin calls“at tific respectability”—or, put anotion t ic if not voiced by a Nobel laureate. Fred ing t outerspace broug only life but also many diseases suc o i areminder     stifids of tietury—alsoonce suggested, as mentioned earlier, t our noses evolved rils undero ted down from space.

        ever prompted life to begin, it    o is t extraordinary fa biology, per extraordinary fact    or animal, dates its beginnings from te point in anunimaginably distant past some little bag of ced to life. It absorbed somenutrients, gently pulsed, eimes. But tral packet did sometional araordinary: it cleaveditself and produced an iny bundle of geic material passed from one liviy toanotopped moving si    of creation for us all.

        Biologists sometimes call it th.

        “ever animal, plant, bug, or blob you look at, if it isalive, it ionary and knotRidley. e are all t of a single geic trick ion togeion nearly four billion years, to sut t you    take a fragment of istru, patto a faulty yeast cell, and t cell    it to s o is its own.

        t—sits on a sope geoamed Victoria Be in tralianNational Uy in berra. An Ameri, Ms. Be came to tra 1989 and ed e 2001, sly y ernating stripesof z and a gray-green material called opyroxe rocks    t marine sediments ever found.

        “e ’t be certain t    to find out,” Beold me. “But it es from ted, so it probably .” Nor ualfossilized microbes,    turned o mud to stone. Instead    t beopes and a type of pe called apatite, rong evideained ies of living t t t said. “It    as basic as life    get—but it    lived. It propagated.”

        Aually it led to us.

        If you are into very old rocks, at indubitably is, to be. to ty of a man named Bill pston,    in t t Sensitive ion Ion MicroProbe—or S is more affeately knos initial letters. t measures te of uranium in tiny minerals called zirs. Zirsappear in most rocks apart from basalts and are extremely durable, surviving every naturalprocess but subduost of t o t somepoint, but just occasionally—iern Australia and Greenland, for example—geologistscrops of rocks t    ton’s maco be dated otype Sand mat’s os on a budget, but it . On its first formal test, in1982, it dated t ternAustralia.

        “It caused quite a stir at time,” Beold me, “to find sometant soquickly eology.”

        Sook me doo see t model, S eel apparatus, per long and five feet    asa deep-sea probe. At a sole in front of it, keeping an eye on ever-gs offigures on a s, erbury Uy in Ney-four many rocks to date. It    after 9A.M. and Bob ill noon. Ask a pair ofgeocs art talking about isotopidances and ionization levels    is more endearing thomable.

        t of it,    treams of s, is able to detect subtle differences in ts of lead anduranium in tely adduced.

        Bob told me t it takes about seventeen mio read one zir and it is necessary toread dozens from eaake ta reliable. In practice, toinvolve about ttered activity, and about as mucimulation, as a trip to alaundromat. Bob seemed very    then people from New Zealand verygenerally do.

        tion of t offices, part labs,part maco build everytt said. “e even    ired. But ill ime rock crus mylook of mild surprise. “e get t of rocks. And to be very carefullyprepared. You o make sure tamination from previous samples—no dustor anyt’s quite a meticulous process.” Sily gone for coffee. Besidetaining rocks of all st of rocks at the ANU.

        Ba Be’s office after our tour, I noticed er giving anartist’s colorfully imaginative interpretation of Eart mig    period ker sive voloes, and asteamy, copper-colored sea beromatolites, a kind of bacterial rock,filled t didn’t look like a very promising place to create andnurture life. I asked ing e.

        “ell, one sc says it ually cool ter lear biologists, aurant problem”—because mospraviolet rays from teo break apart anyincipient bonds made by molecules. A rigapped tromatolites—“you at t’s a puzzle.”

        “So    knohen?”

        “Mmmm,” sfully.

        “Eit doesn’t seem very ducive to life.”

        S t    suited life. Ot be here.”

        It certainly    ed us. If you o step from a time maco ta Arcly scamper baside, for to breatoday. It    ter skin. Nor    as depicted in ter inVictoria Be’s office. te mosptle sunligo reac little you could see     a reize as our own.

        Anniversaries erial anisms    t sicular ination to move on to anote some point in t billion years of life, obacteria, or blue-green algae,learo tap into a freely available resource—t exists iacularabundan er. ter molecules, supped on te, and in so doing ied posynte,posyntedly t important siaboliovation in toryof life on t”—and it ed not by plants but by bacteria.

        As obacteria proliferated to fill o ternation of t found it poisonous—ually useoxygen to kill invading bacteria. t oxygen is fually toxic often es as a surpriseto t so vivial to our    t is only because    it. to ot is a terror. It is urns butter rancid and makes ironrust. Evee it only up to a point. t atentmosphere.

        tages. Oxygen    oproduergy, and it vanquisitanisms. Some retreated into ttoms. Ot ter (mucer)migrated to tive tracts of beings like you and me. Quite a number of tities are alive inside your bo digest your food, but abi    of O2. Untold numbers of oto adapt and died.

        teria    first, tra oxygen taccumulate in tmosp bined o form ferric oxides, tom of primitive seas. For millions of years, terally rusted—a ps t provide so mucoday. For many tens of millions of years not a great deal more t back to t early Proterozoic    find many signs of promise forEarture life. Perered pools you’d enter a film of livingscum or a coating of glossy greens and broherwise life remainedinvisible.

        But about 3.5 billion years ago sometic became apparent. ructures began to appear. As t tieria became very sligacky, and t taess trappedmicroparticles of dust and sand, o form slig solidstructures—tromatolites t ured in ter on VictoriaBe’s offiatolites came in various simes times like fluffy mattresses (stromatolite es from ttress”), sometimes tens of metersabove ter—sometimes as ers. In all tations, ted tcooperative venture, ies of primitive anism living just at t underaking advantage of ditions created by ts first ecosystem.

        For many years, stists kromatolites from fossil formations, but in 1961t a real surprise y of living stromatolites at Se nort coast of Australia. t ued—so ued,in fact, t it ists realized quite oday,ourist attra—or at least as mucourist attra as a place all    ever be.

        Board into t visitors    stroll over ter to get agood look at tromatolites, quietly respiring just beerlessand gray and look, as I recorded in an earlier book, like very large cos. But it is acuriously giddying moment to find yourself staring at living remnants of Eart : “truly time traveling, and if ttuo its real    he pyramids of Giza.”

        Alt, timated (imated) three billion individual anisms on every square yard of rock.

        Sometimes rings of bubbles rising to tions raised tmospo 20 pert, preparing t, more plex cer inlife’s ory.

        It ed t teria at S-evolvinganisms oainly no.    of existenearly every at Sers are too saline for tures t    on took so long to gro to    until ted tmosply. “Animals could not summonup to ey    it. It took about tory, for oxygen levels to reacration in tmosp oage , and apparently quite suddenly, airely neype of cell arose—ole bodies collectively calledanelles (from a Greek tle tools”). t to artederium eitured by someoterium and it turned out t ted tive bacterium became, itis t, a mitococic event, asbiologists like to term it) made plex life possible. (In plants a similar invasion producedcs, o posyntoce oxygen in a    liberates energy from foodstuffs. ittily facilitating trick, life ooday oy—you could pack a billion into t also very    every nutriment you absoesto feeding them.

        e couldn’t live for tes    t even after a billion years mitoot    betain their own DNA.

        t a different time from t cell. teria, divide likebacteria, and sometimes respond to antibioti teria do. In s, t eveiguage as they live.

        It is like ranger in your    one where for a billion years.

        type of cell is knoe (meaning “truly ed”), as trastedype, ed”), and it seems to    eukaryotes yet knos in Mice, andthen no more are known for 500 million years.

        pared es tes tle more t Stepes uallyas mu times bigger—times more DNA. Gradually a system evolved in ypes of form—anisms t expel oxygen (like plants) and t take it in (you andme).

        Single-celled eukaryotes ozoa (“pre-animals”), but t term isincreasingly disdaioday term for tists . pared eria t ists ion.

        t one cell big and    any ambitions but to exist, tains 400million bits of geiformation in its DNA—eo fill eightybooks of five hundred pages.

        Eventually tes learned an even more singular trick. It took a long time—abillion years or so—but it . teto plex multicellular beings. to tion, big, plicated,visible entities like us    Earto move on to its    ambitiousphase.

        But before    too excited about t, it is    t to see, still belongs to the very small.
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