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d—but mostly they die because they are told to。
indeed； if not told to live—if not given some kind of active instruction from another cell—cells 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—a cacophony of messages—from 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—or； 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’s because of a curious； determined； barely understood molecule that is itself notalive and for the most part doesn’t 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 “the single best idea that anyone has ever had”—and then； for reasons that take a littleexplaining； locked it away in a drawer for the next fifteen years。
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25DARWIN’S SINGULAR NOTION
小x说s网
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。 “everyone is interested in pigeons；” he observedhelpfully。
elwin’s 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—not 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。 “you care for nothing but shooting； dogs； and rat…catching； and you will be a disgrace to yourself and all your family；” his father wrote in a linethat nearly always appears just about here in any review of darwin’s early life。 although hisinclination was to natural history； for his father’s sake he tried to study medicine at edinburghuniversity but couldn’t bear the blood and suffering。 the experience of witnessing anoperation on an understandably distressed child—this was in the days before anesthetics； ofcourse—left 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’s nose。 （it betokened depth of character； he believed。） darwin wasnot fitzroy’s first choice； but got the nod when fitzroy’s preferred panion dropped out。
from a twenty…first…century perspective the two men’s most striking