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in a lab； à la stanley miller and haroldurey； but the universe does it readily enough。 lots of molecules in nature get together to formlong chains called polymers。 sugars constantly assemble to form starches。 crystals can do anumber of lifelike things—replicate； respond to environmental stimuli； take on a patternedplexity。 they’ve never achieved life itself； of course； but they demonstrate repeatedly thatplexity is a natural； spontaneous； entirely monplace event。 there may or may not be agreat deal of life in the universe at large； but there is no shortage of ordered self…assembly； ineverything from the transfixing symmetry of snowflakes to the ely rings of saturn。
so powerful is this natural impulse to assemble that many scientists now believe that lifemay be more inevitable than we think—that it is； in the words of the belgian biochemist andnobel laureate christian de duve； “an obligatory manifestation of matter； bound to arisewherever conditions are appropriate。” de duve thought it likely that such conditions would beencountered perhaps a million times in every galaxy。
certainly there is nothing terribly exotic in the chemicals that animate us。 if you wished tocreate another living object； whether a goldfish or a head of lettuce or a human being； youwould need really only four principal elements； carbon； hydrogen； oxygen； and nitrogen； plussmall amounts of a few others； principally sulfur； phosphorus； calcium； and iron。 put thesetogether in three dozen or so binations to form some sugars； acids； and other basicpounds and you can build anything that lives。 as dawkins notes： “there is nothingspecial about the substances from which living things are made。 living things are collectionsof molecules； like everything else。”
the bottom line is that life is amazing and gratifying； perhaps even miraculous； but hardlyimpossible—as we repeatedly attest with our own modest existences。 to be sure； many of thedetails of life’s beginnings remain pretty imponderable。 every scenario you have ever readconcerning the conditions necessary for life involves water—from the “warm little pond”
where darwin supposed life began to the bubbling sea vents that are now the most popularcandidates for life’s beginnings—but all this overlooks the fact that to turn monomers intopolymers （which is to say； to begin to create proteins） involves what is known to biology as“dehydration linkages。” as one leading biology text puts it； with perhaps just a tiny hint ofdisfort； “researchers agree that such reactions would not have been energeticallyfavorable in the primitive sea； or indeed in any aqueous medium； because of the mass actionlaw。” it is a little like putting sugar in a glass of water and having it bee a cube。 itshouldn’t happen； but somehow in nature it does。 the actual chemistry of all this is a littlearcane for our purposes here； but it is enough to know that if you make monomers wet theydon’t turn into polymers—except when creating life on earth。 how and why it happens thenand not otherwise is one of biology’s great unanswered questions。
one of the biggest surprises in the earth sciences in recent decades was the discovery ofjust how early in earth’s history life arose。 well into the 1950s； it was thought that life wasless than 600 million years old。 by the 1970s； a few adventurous souls felt that maybe it wentback 2。5 billion years。 but the present date of 3。85 billion years is stunningly early。 earth’ssurface didn’t bee solid until about 3。9 billion years ago。
“we can only infer from this rapidity that it is not ‘difficult’ for life of bacterial grade toevolve on planets with appropriate conditions；” stephen jay gould observed in the new yorktimes in 1996。 or as he put it elsewhere； it is hard to avoid the conclusion that “life； arising assoon as it could； was chemically destined to be。”
life emerged so swiftly； in fact； that some authorities think it must have had help—perhapsa good deal of help。 the idea that earthly life might have arrived from space has a surprisinglylong and even occasionally distinguished history。 the great lord kelvin himself raised thepossibility as long ago as 1871 at a meeting of the british association for the advancement ofscience when he suggested that “the germs of life might have been brought to the earth bysome meteorite。” but it remained little more than a fringe notion until one sunday inseptember 1969 when tens of thousands of australians were startled by a series of sonicbooms and the sight of a fireball streaking from east to west across the sky。 the fireball madea strange crackling sound as it passed and left behind a smell that some likened to methylatedspirits and others described as just awful。
the fireball exploded above murchison； a town of six hundred people in the goulburnvalley north of melbourne； and came raining down in chunks； some weighing up to twelvepounds。 fortunately； no one was hurt。 the meteorite was of a rare type known as acarbonaceous chondrite； and the townspeople helpfully collected and brought in some twohundred pounds of it。 the timing could hardly have been better。 less than two months earlier；the apollo 11 astronauts had returned to earth with a bag full of lunar rocks； so labsthroughout the world were geared up—indeed clamoring—for rocks of extraterrestrial origin。
the murchison meteorite was found to be 4。5 billion years old； and it was studded withamino acids—seventy…four types in all； eight of which are involved in the formation of earthlyproteins。 in late 2001； more than thirty years after it crashed； a team at the ames researchcenter in california announced that the murchison rock also contained pletrings ofsugars called polyols； which had not been found off the earth before。
a few other carbonaceous chondrites have strayed into earth’s path since—one that landednear tagish lake in canada’s yukon in january 2000 was seen over large parts of northamerica—and they have likewise confirmed that the universe is actually rich in organicpounds。 halley’s et； it is now thought； is about 25 percent organic molecules。 getenough of those crashing into a suitable place—earth； for instance—and you have the basicelement