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had turned green and yellow ina hearty broth of amino acids； fatty acids； sugars； and other organic pounds。 鈥渋f goddidn鈥檛 do it this way；鈥潯bserved miller鈥檚 delighted supervisor； the nobel laureate haroldurey； 鈥渉e missed a good bet。鈥�
press reports of the time made it sound as if about all that was needed now was forsomebody to give the whole a good shake and life would crawl out。 as time has shown； itwasn鈥檛 nearly so simple。 despite half a century of further study； we are no nearer tosynthesizing life today than we were in 1953 and much further away from thinking we can。
scientists are now pretty certain that the early atmosphere was nothing like as primed fordevelopment as miller and urey鈥檚 gaseous stew； but rather was a much less reactive blend ofnitrogen and carbon dioxide。 repeating miller鈥檚 experiments with these more challenginginputs has so far produced only one fairly primitive amino acid。 at all events； creating aminoacids is not really the problem。 the problem is proteins。
proteins are what you get when you string amino acids together； and we need a lot of them。
no one really knows； but there may be as many as a million types of protein in the humanbody； and each one is a little miracle。 by all the laws of probability proteins shouldn鈥檛 exist。
to make a protein you need to assemble amino acids （which i am obliged by long tradition torefer to here as 鈥渢he building blocks of life鈥潱n a particular order； in much the same way thatyou assemble letters in a particular order to spell a word。 the problem is that words in theamino acid alphabet are often exceedingly long。 to spell collagen； the name of a montype of protein； you need to arrange eight letters in the right order。 but to make collagen； youneed to arrange 1；055 amino acids in precisely the right sequence。 but鈥攁nd here鈥檚 anobvious but crucial point鈥攜ou don鈥檛 make it。 it makes itself； spontaneously； withoutdirection； and this is where the unlikelihoods e in。
the chances of a 1；055…sequence molecule like collagen spontaneously self…assembling are；frankly； nil。 it just isn鈥檛 going to happen。 to grasp what a long shot its existence is； visualize astandard las vegas slot machine but broadened greatly鈥攖o about ninety feet； to be precise鈥攖o acmodate 1；055 spinning wheels instead of the usual three or four； and with twentysymbols on each wheel （one for each mon amino acid）。
1how long would you have topull the handle before all 1；055 symbols came up in the right order？ effectively forever。 evenif you reduced the number of spinning wheels to two hundred； which is actually a moretypical number of amino acids for a protein； the odds against all two hundred ing up in a1there are actually twenty…two naturally occurring amino acids known on earth； and more may await discovery；but only twenty of them are necessary to produce us and most other living things。 the twenty…second； calledpyrrolysine； was discovered in 2002 by researchers at ohio state university and is found only in a single type ofarchaean （a basic form of life that we will discuss a little further on in the story） called methanosarcina barkeri。
prescribed sequence are 1 in 10260（that is a 1 followed by 260 zeroes）。 that in itself is a largernumber than all the atoms in the universe。
proteins； in short； are plex entities。 hemoglobin is only 146 amino acids long； a runt byprotein standards； yet even it offers 10190possible amino acid binations； which is why ittook the cambridge university chemist max perutz twenty…three years鈥攁 career； more orless鈥攖o unravel it。 for random events to produce even a single protein would seem astunning improbability鈥攍ike a whirlwind spinning through a junkyard and leaving behind afully assembled jumbo jet； in the colorful simile of the astronomer fred hoyle。
yet we are talking about several hundred thousand types of protein； perhaps a million； eachunique and each； as far as we know； vital to the maintenance of a sound and happy you。 andit goes on from there。 a protein to be of use must not only assemble amino acids in the rightsequence； but then must engage in a kind of chemical origami and fold itself into a veryspecific shape。 even having achieved this structural plexity； a protein is no good to you ifit can鈥檛 reproduce itself； and proteins can鈥檛。 for this you need dna。 dna is a whiz atreplicating鈥攊t can make a copy of itself in seconds鈥攂ut can do virtually nothing else。 so wehave a paradoxical situation。 proteins can鈥檛 exist without dna； and dna has no purposewithout proteins。 are we to assume then that they arose simultaneously with the purpose ofsupporting each other？ if so： wow。
and there is more still。 dna； proteins； and the other ponents of life couldn鈥檛 prosperwithout some sort of membrane to contain them。 no atom or molecule has ever achieved lifeindependently。 pluck any atom from your body； and it is no more alive than is a grain of sand。
it is only when they e together within the nurturing refuge of a cell that these diversematerials can take part in the amazing dance that we call life。 without the cell； they arenothing more than interesting chemicals。 but without the chemicals； the cell has no purpose。
as the physicist paul davies puts it； 鈥渋f everything needs everything else； how did themunity of molecules ever arise in the first place？鈥潯t is rather as if all the ingredients inyour kitchen somehow got together and baked themselves into a cake鈥攂ut a cake that couldmoreover divide when necessary to produce more cakes。 it is little wonder that we call it themiracle of life。 it is also little wonder that we have barely begun to understand it。
so what accounts for all this wondrous plexity？ well； one possibility is that perhaps itisn鈥檛 quite鈥攏ot quite鈥攕o wondrous as at first it seems。 take those amazingly improbableproteins。 the wonder we see in their assembly es in assuming that they arrived on thescene fully formed。 but what if the protein chains didn鈥檛 assemble all at once？ what if； in thegreat slot machine of creation； some of the wheels could be held； as a gambler might hold anumber of promising cherries？ what if； in other words； proteins didn鈥檛 suddenly burst intobeing； but evolved 。
imagine if you took all the ponents that make up a human being鈥攃arbon； hydrogen；oxygen； and so on鈥攁nd put them in a container with some water； gave it a vigorous stir； andout stepped a pleted person。 that would be amazing。 well； that鈥檚 essentially what hoyleand others （including many ardent creationists） argue when they suggest that proteinsspontaneously formed all at once。 they didn鈥檛鈥攖hey can鈥檛 have。 as richard dawkins arguesin the blind watchmaker； there must have been some kind of cumulative selection processthat allowed amino acids to assemble in chunks。 perhaps two or three amino acids linked up for some simple purpose and then after a time bumped into some other similar small clusterand in so doing 鈥渄iscovered鈥潯ome additional improvement。
chemical reactions of the sort associated with life are actually something of amonplace。 it may be beyond us to cook them up in a lab； 脿 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鈥攔eplicate； respond to environmental stimuli； take on a patternedplexity。 they鈥檝e 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鈥攖hat it is； in the words of the belgian biochemist andnobel laureate christian de duve； 鈥渁n obligatory manifestation of matter； bound to arisewherever conditions are appropriate。鈥潯e 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： 鈥渢here is nothingspecial about the substances from which living things are made。 living things are collectionsof molecules； like everything else。鈥�
the bottom line is that life is amazing and gratifying； perhaps even miraculous； but hardlyimpossible鈥攁s we repeatedly attest with our own modest existences。 to be sure； many of thedetails of life鈥檚 beginnings remain pretty imponderable。 every scenario you have ever readconcerning the conditions necessary for life involves water鈥攆rom the 鈥渨arm little pond