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the total is still a very minimum of 100 million protein molecules in eachcell。 such a staggering figure gives some idea of the swarming immensity of biochemicalactivity within us。鈥�
it is all an immensely demanding process。 your heart must pump 75 gallons of blood anhour； 1；800 gallons every day； 657；000 gallons in a year鈥攖hat鈥檚 enough to fill four olympic…sized swimming pools鈥攖o keep all those cells freshly oxygenated。 （and that鈥檚 at rest。 duringexercise the rate can increase as much as sixfold。） the oxygen is taken up by themitochondria。 these are the cells鈥櫋ower stations； and there are about a thousand of them in atypical cell； though the number varies considerably depending on what a cell does and howmuch energy it requires。
you may recall from an earlier chapter that the mitochondria are thought to have originatedas captive bacteria and that they now live essentially as lodgers in our cells； preserving theirown genetic instructions； dividing to their own timetable； speaking their own language。 youmay also recall that we are at the mercy of their goodwill。 here鈥檚 why。 virtually all the foodand oxygen you take into your body are delivered； after processing； to the mitochondria；where they are converted into a molecule called adenosine triphosphate； or atp。
you may not have heard of atp； but it is what keeps you going。 atp molecules areessentially little battery packs that move through the cell providing energy for all the cell鈥檚processes； and you get through a lot of it。 at any given moment； a typical cell in your bodywill have about one billion atp molecules in it； and in two minutes every one of them willhave been drained dry and another billion will have taken their place。 every day you produceand use up a volume of atp equivalent to about half your body weight。 feel the warmth ofyour skin。 that鈥檚 your atp at work。
when cells are no longer needed； they die with what can only be called great dignity。 theytake down all the struts and buttresses that hold them together and quietly devour theirponent parts。 the process is known as apoptosis or programmed cell death。 every daybillions of your cells die for your benefit and billions of others clean up the mess。 cells canalso die violently鈥攆or instance； when infected鈥攂ut mostly they die because they are told to。
indeed； if not told to live鈥攊f not given some kind of active instruction from another cell鈥攃ells automatically kill themselves。 cells need a lot of reassurance。
when； as occasionally happens； a cell fails to expire in the prescribed manner； but ratherbegins to divide and proliferate wildly； we call the result cancer。 cancer cells are really justconfused cells。 cells make this mistake fairly regularly； but the body has elaboratemechanisms for dealing with it。 it is only very rarely that the process spirals out of control。 onaverage； humans suffer one fatal malignancy for each 100 million billion cell divisions。
cancer is bad luck in every possible sense of the term。
the wonder of cells is not that things occasionally go wrong； but that they manageeverything so smoothly for decades at a stretch。 they do so by constantly sending andmonitoring streams of messages鈥攁 cacophony of messages鈥攆rom all around the body：
instructions； queries； corrections； requests for assistance； updates； notices to divide or expire。
most of these signals arrive by means of couriers called hormones； chemical entities such asinsulin； adrenaline； estrogen； and testosterone that convey information from remote outpostslike the thyroid and endocrine glands。 still other messages arrive by telegraph from the brainor from regional centers in a process called paracrine signaling。 finally； cells municatedirectly with their neighbors to make sure their actions are coordinated。
what is perhaps most remarkable is that it is all just random frantic action； a sequence ofendless encounters directed by nothing more than elemental rules of attraction and repulsion。
there is clearly no thinking presence behind any of the actions of the cells。 it all just happens；smoothly and repeatedly and so reliably that seldom are we even conscious of it； yet somehowall this produces not just order within the cell but a perfect harmony right across the organism。
in ways that we have barely begun to understand； trillions upon trillions of reflexive chemicalreactions add up to a mobile； thinking； decision…making you鈥攐r； e to that； a rather lessreflective but still incredibly organized dung beetle。 every living thing； never forget； is awonder of atomic engineering。
indeed； some organisms that we think of as primitive enjoy a level of cellular organizationthat makes our own look carelessly pedestrian。 disassemble the cells of a sponge （by passingthem through a sieve； for instance）； then dump them into a solution； and they will find theirway back together and build themselves into a sponge again。 you can do this to them overand over； and they will doggedly reassemble because； like you and me and every other livingthing； they have one overwhelming impulse： to continue to be。
and that鈥檚 because of a curious； determined； barely understood molecule that is itself notalive and for the most part doesn鈥檛 do anything at all。 we call it dna； and to begin tounderstand its supreme importance to science and to us we need to go back 160 years or so tovictorian england and to the moment when the naturalist charles darwin had what has beencalled 鈥渢he single best idea that anyone has ever had鈥濃�攁nd then； for reasons that take a littleexplaining； locked it away in a drawer for the next fifteen years。
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25 DARWIN鈥橲 SINGULAR NOTION
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in the late summer or early autumn of 1859； whitwell elwin； editor of the respectedbritish journal the quarterly review； was sent an advance copy of a new book by thenaturalist charles darwin。 elwin read the book with interest and agreed that it had merit； butfeared that the subject matter was too narrow to attract a wide audience。 he urged darwin towrite a book about pigeons instead。 鈥渆veryone is interested in pigeons；鈥潯e observedhelpfully。
elwin鈥檚 sage advice was ignored； and on the origin of species by means of naturalselection； or the preservation of favoured races in the struggle for life was published in latenovember 1859； priced at fifteen shillings。 the first edition of 1；250 copies sold out on thefirst day。 it has never been out of print； and scarcely out of controversy； in all the time since鈥攏ot bad going for a man whose principal other interest was earthworms and who； but for asingle impetuous decision to sail around the world； would very probably have passed his lifeas an anonymous country parson known for； well； for an interest in earthworms。
charles robert darwin was born on february 12； 1809；1in shrewsbury； a sedate markettown in the west midlands of england。 his father was a prosperous and well…regardedphysician。 his mother； who died when charles was only eight； was the daughter of josiahwedgwood； of pottery fame。
darwin enjoyed every advantage of upbringing； but continually pained his widowed fatherwith his lackluster academic performance。 鈥測ou care for nothing but shooting； dogs； and rat…catching； and you will be a disgrace to yourself and all your family；鈥潯is father wrote in a linethat nearly always appears just about here in any review of darwin鈥檚 early life。 although hisinclination was to natural history； for his father鈥檚 sake he tried to study medicine at edinburghuniversity but couldn鈥檛 bear the blood and suffering。 the experience of witnessing anoperation on an understandably distressed child鈥攖his was in the days before anesthetics； ofcourse鈥攍eft him permanently traumatized。 he tried law instead； but found that insupportablydull and finally managed； more or less by default； to acquire a degree in divinity fromcambridge。
a life in a rural vicarage seemed to await him when from out of the blue there came a moretempting offer。 darwin was invited to sail on the naval survey ship hms beagle； essentiallyas dinner pany for the captain； robert fitzroy； whose rank precluded his socializing withanyone other than a gentleman。 fitzroy； who was very odd； chose darwin in part because heliked the shape of darwin鈥檚 nose。 （it betokened depth of character； he believed。） darwin wasnot fitzroy鈥檚 first choice； but got the nod when fitzroy鈥檚 preferred panion dropped out。
from a twenty…first…century perspective the two men鈥檚 most striking joint feature was their1an auspicious date in history： on the same day in kentucky； abraham lincoln was born。
extreme youthfulness。 at the time of sailing； fitzroy was only twenty…three； darwin justtwenty…two。
fitzroy鈥檚 formal assignment was to chart coastal waters； but his hobby鈥攑assion really鈥攚as to seek out evidence for a literal； biblical interpretation of creation。 that darwin wastrained for the ministry was central to fitzroy鈥檚 decision to have him aboard。 that darwinsubsequently proved to be not only liberal of view but less than wholeheartedly devoted tochristian fundamentals became a source of lasting friction between them。
darwin鈥檚 time aboard hms beagle； from 1831 to 1836； was obviou