IN 1953, StANLEY Miller, a graduate student at ty of Cook taining a little er to represent a primeval ocean, ture of meto represent Eartmosped tubes, and introduced some electrical sparks as astand-in for liger a feer in turned green and yelloty 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 can.

    Scientists 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 need to 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 need to arrange eigters in t order. But to make collagen, youneed to arrange 1,055 amino acids in precisely t sequence. But—and  crucial point—you don’t make it. It makes itself, spontaneously, direction, and the unlikelihoods come 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 ninety feet, to be precise—to accommodate 1,055 spinning ysymbols on each wheel (one for each common amino acid).

    1opull t order? Effectively forever. Evenif you reduced to typical number of amino acids for a protein, t all ty-turally occurring amino acids kno discovery,but only ty of to produce us and most oty-second, calledpyrrolysine, e University and is found only in a single type ofarc tle furtory) called Methanosarcina barkeri.

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

    Proteins, in s, are complex entities.  byprotein standards, yet even it offers 10190possible amino acid combinations, y c Max Perutz ty-to unravel it. 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 complexity, a protein is no good to you ifit can’t reproduce itself, and proteins can’t. For treplicating—it can make a copy of itself in seconds—but can do virtually notuation. Proteins can’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 membrane to contain tom or molecule ly. Pluck any 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 can 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 couldmoreover 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 macion, 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 completed person. t ’s essentially ionists) argue  proteinsspontaneously formed all at once. t—t c ive selection processt alloo assemble in cer a time bumped into some oterand in so doing “discovered” some additional improvement.

    Cions  of  t  associated ually somet may be beyond us to cook tanley Miller and  t readily enougs of molecules in nature get togeto formlong cantly assemble to form starcals can do anumber of lifelike te, respond to environmental stimuli, take on a patternedcomplexity. tself, of course, but trate repeatedly tcomplexity is a natural, spontaneous, entirely commonplace event. t be agreat deal of life in t large, but tage of ordered self-assembly, ineverytransfixing symmetry of snoo turn.

    So poural impulse to assemble t many scientists no lifemay be more inevitable t it is, in t andNobel laureate Cian de Duve, “an obligatory manifestation of matter, bound to arisee.” De Duve t it likely t sucions ered perimes in every galaxy.

    Certainly terribly exotic in 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  existences. to be sure, many of tails of life’s beginnings remain pretty imponderable. Every scenario you ions necessary for life involves er—from ttle pond”

    s t are no popularcandidates 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  ofdiscomfort, “Researc sucions  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  become a cube. Its  someure it does. tual cry of all ttlearcane 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 become solid until about 3.9 billion years ago.

    “e can only infer from ty t it is not ‘difficult’ for life of bacterial grade toevolve on planets e conditions,” 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 ofScience  “t  to teorite.” But it remained little more tion until one Sunday inSeptember 1969 ralians artled by a series of sonicbooms and t of a fireball streaking from east to  across trange crackling sound as it passed and left be some likened to metedspirits and ot awful.

    tounately, no one eorite ype knooiming could ter. Less tronauts urned to Eart traterrestrial origin.

    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 announced t tained complex strings ofsugars called polyols, h before.

    A fees rayed into Eart landednear tagiss of Nort tually ric, it is no, is about 25 percent organic molecules. Getenougo a suitable place—Eartance—and 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 can be safely called imprudent. FrancisCrick, codiscoverer of tructure of DNA, and edt Eartely seeded elligent aliens,” an idea t 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 insert areminder   scientific minds of tietury—alsoonce suggested, as mentioned earlier, t our noses evolved rils underneato ted down from space.

    ever prompted life to begin, it  once. t is t extraordinary factin biology, per extraordinary fact  or animal, dates its beginnings from tc some point in anunimaginably distant past some little bag of ced to life. It absorbed somenutrients, gently pulsed, ence. times. But tral packet did sometional and extraordinary: it cleaveditself and produced an iny bundle of genetic material passed from one living entity toanotopped moving since. It  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 genetic trick ion togeneration nearly four billion years, to sucent t you can take a fragment of ic instruction, patc into a faulty yeast cell, and t cell  it to s o is its own.

    t—sits on a sope geoc named Victoria Bennett in tralianNational University in Canberra. An American, Ms. Bennett came to tract in 1989 and ed e 2001, sly y ernating stripesof z and a gray-green material called clinopyroxene. t rocks  t marine sediments ever found.

    “e can’t be certain t  to find out,” Bennett told me. “But it comes from ted, so it probably .” Nor ualfossilized microbes,  turned ocean mud to stone. Instead  t beopes and a type of pe called apatite, rong evidence t tained colonies of living t t t said. “It  as basic as life can get—but it  lived. It propagated.”

    And eventually it led to us.

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

    “It caused quite a stir at time,” Bennett told me, “to find sometant soquickly echnology.”

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

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

    Bob told me t it takes about seventeen minutes to read one zircon and it is necessary toread dozens from eaco make 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.” Sine, tly gone for coffee. Besidetaining rocks of all st of rocks at the ANU.

    Back in Bennett’s office after our tour, I noticed er giving anartist’s colorfully imaginative interpretation of Eart mig  period knoo earter sive volcanoes, and asteamy, copper-colored sea beneatromatolites, 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 learned t biologists, aurant problem”—because mospraviolet rays from tended to break apart anyincipient bonds made by molecules. And yet rigapped tromatolites—“you at t’s a puzzle.”

    “So  knohen?”

    “Mmmm,” sfully.

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

    S t  suited life. Ot be here.”

    It certainly  ed us. If you o step from a time maco tancient Arcly scamper back inside, for to breatoday. It  ter skin. Nor  as depicted in ter inVictoria Bennett’s office. te mosptle sunligo reac little you could see   anEart recognize as our own.

    Anniversaries erial organisms  t sicular inclination to move on to anotence. At some point in t billion years of life, cyanobacteria, or blue-green algae,learned to tap into a freely available resource—t exists in spectacularabundance in er. ter molecules, supped on te, and in so doing invented posynte,posyntedly t important single metabolic innovation in toryof life on t”—and it ed not by plants but by bacteria.

    As cyanobacteria proliferated to fill o ternation of t found it poisonous—ually useoxygen to kill invading bacteria. t oxygen is fundamentally toxic often comes as a surpriseto t so convivial to our  t is only because  it. to ot is a terror. It is urns butter rancid and makes ironrust. Even olerate it only up to a point. t atentmosphere.

    tages. Oxygen  oproduce energy, and it vanquisitor organisms. 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 body rigo digest your food, but abiniest  of O2. Untold numbers of oto adapt and died.

    teria  first, tra oxygen taccumulate in tmosp combined 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 encounter 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 tines, teria became very sligacky, and t tackiness trappedmicroparticles of dust and sand, o form slig solidstructures—tromatolites t ured in ter on VictoriaBennett’s office romatolites came in various simes times like fluffy mattresses (stromatolite comes from ttress”), sometimes tens of metersabove ter—sometimes as ers. In all tations, ted tcooperative venture, ies of primitive organism living just at t underneataking advantage of conditions created by ts first ecosystem.

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

    Board into t visitors can stroll over ter to get agood look at tromatolites, quietly respiring just beneaterlessand 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 ttuned to its real  he pyramids of Giza.”

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

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

    It ed t teria at S-evolvingorganisms on Eartainly no.  of existence nearly 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 once tage , and apparently quite suddenly, anentirely neype of cell arose—one tle bodies collectively calledorganelles (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 complex life possible. (In plants a similar invasion producedcs, o posyntoce oxygen in a  liberates energy from foodstuffs. ittily facilitating trick, life on Eartoday ociny—you could pack a billion into t also very  every nutriment you absorb goesto feeding them.

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

    t a different time from t cell. teria, divide likebacteria, and sometimes respond to antibiotics in teria do. In s, t even speak tic language as they live.

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

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

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

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

    t one cell big and  any ambitions but to exist, contains 400million bits of genetic information in its DNA—enouged, to 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 . to formtogeto complex multicellular beings. to tion, big, complicated,visible entities like us  Earto move on to its next ambitiousphase.

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