at they have arrived at a foodopportunity and fall onto it。
so why； if the seas are so vast； do we so easily overtax them？ well； to begin with； theworld’s seas are not uniformly bounteous。 altogether less than a tenth of the ocean isconsidered naturally productive。 most aquatic species like to be in shallow waters where thereis warmth and light and an abundance of organic matter to prime the food chain。 coral reefs；for instance； constitute well under 1 percent of the ocean’s space but are home to about 25percent of its fish。
elsewhere； the oceans aren’t nearly so rich。 take australia。 with over 20；000 miles ofcoastline and almost nine million square miles of territorial waters； it has more sea lapping itsshores than any other country； yet； as tim flannery notes； it doesn’t even make it into the topfifty among fishing nations。 indeed； australia is a large net importer of seafood。 this isbecause much of australia’s waters are； like much of australia itself； essentially desert。 （anotable exception is the great barrier reef off queensland； which is sumptuously fecund。）because the soil is poor； it produces little in the way of nutrient…rich runoff。
even where life thrives； it is often extremely sensitive to disturbance。 in the 1970s； fishermenfrom australia and； to a lesser extent； new zealand discovered shoals of a little…known fishliving at a depth of about half a mile on their continental shelves。 they were known as orange1the indigestible parts of giant squid； in particular their beaks； accumulate in sperm whales stomachs into thesubstance known as ambergris； which is used as a fixative in perfumes。 the next time you spray on chanel no。 5（assuming you do）； you may wish to reflect that you are dousing yourself in distillate of unseen sea monster。
roughy； they were delicious； and they existed in huge numbers。 in no time at all； fishing fleetswere hauling in forty thousand metric tons of roughy a year。 then marine biologists madesome alarming discoveries。 roughy are extremely long lived and slow maturing。 some maybe 150 years old； any roughy you have eaten may well have been born when victoria wasqueen。 roughy have adopted this exceedingly unhurried lifestyle because the waters they livein are so resource…poor。 in such waters； some fish spawn just once in a lifetime。 clearly theseare populations that cannot stand a great deal of disturbance。 unfortunately； by the time thiswas realized the stocks had been severely depleted。 even with careful management it will bedecades before the populations recover； if they ever do。
elsewhere； however； the misuse of the oceans has been more wanton than inadvertent。
many fishermen “fin” sharks—that is； slice their fins off； then dump them back into the waterto die。 in 1998； shark fins sold in the far east for over 250 a pound。 a bowl of shark finsoup retailed in tokyo for 100。 the world wildlife fund estimated in 1994 that the numberof sharks killed each year was between 40 million and 70 million。
as of 1995； some 37；000 industrial…sized fishing ships； plus about a million smaller boats；were between them taking twice as many fish from the sea as they had just twenty…five yearsearlier。 trawlers are sometimes now as big as cruise ships and haul behind them nets bigenough to hold a dozen jumbo jets。 some even use spotter planes to locate shoals of fish fromthe air。
it is estimated that about a quarter of every fishing net hauled up contains “by…catch”—fishthat can’t be landed because they are too small or of the wrong type or caught in the wrongseason。 as one observer told the economist： “we’re still in the dark ages。 we just drop a netdown and see what es up。” perhaps as much as twenty…two million metric tons of suchunwanted fish are dumped back in the sea each year； mostly in the form of corpses。 for everypound of shrimp harvested； about four pounds of fish and other marine creatures aredestroyed。
large areas of the north sea floor are dragged clean by beam trawlers as many as seventimes a year； a degree of disturbance that no ecosystem can withstand。 at least two…thirds ofspecies in the north sea； by many estimates； are being overfished。 across the atlantic thingsare no better。 halibut once abounded in such numbers off new england that individual boatscould land twenty thousand pounds of it in a day。 now halibut is all but extinct off thenortheast coast of north america。
nothing； however； pares with the fate of cod。 in the late fifteenth century； the explorerjohn cabot found cod in incredible numbers on the eastern banks of north america—shallowareas of water popular with bottom…feeding fish like cod。 some of these banks were vast。
georges banks off massachusetts is bigger than the state it abuts。 the grand banks offnewfoundland is bigger still and for centuries was always dense with cod。 they were thoughtto be inexhaustible。 of course they were anything but。
by 1960； the number of spawning cod in the north atlantic had fallen to an estimated 1。6million metric tons。 by 1990 this had sunk to 22；000 metric tons。 in mercial terms； thecod were extinct。 “fishermen；” wrote mark kurlansky in his fascinating history； cod； “hadcaught them all。” the cod may have lost the western atlantic forever。 in 1992； cod fishingwas stopped altogether on the grand banks； but as of last autumn； according to a report innature； stocks had not staged a eback。 kurlansky notes that the fish of fish fillets and fish sticks was originally cod； but then was replaced by haddock； then by redfish； and lately bypacific pollock。 these days； he notes drily； “fish” is “whatever is left。”
much the same can be said of many other seafoods。 in the new england fisheries offrhode island； it was once routine to haul in lobsters weighing twenty pounds。 sometimes theyreached thirty pounds。 left unmolested； lobsters can live for decades—as much as seventyyears； it is thought—and they never stop growing。 nowadays few lobsters weigh more thantwo pounds on capture。 “biologists；” according to the new york times； “estimate that 90percent of lobsters are caught within a year after they reach the legal minimum size at aboutage six。” despite declining catches； new england fishermen continue to receive state andfederal tax incentives that encourage them—in some cases all but pel them—to acquirebigger boats and to harvest the seas more intensively。 today fishermen of massachusetts arereduced to fishing the hideous hagfish； for which there is a slight market in the far east； buteven their numbers are now falling。
we are remarkably ignorant of the dynamics that rule life in the sea。 while marine life ispoorer than it ought to be in areas that have been overfished； in some naturally impoverishedwaters there is far more life than there ought to be。 the southern oceans around antarcticaproduce only about 3 percent of the world’s phytoplankton—far too little； it would seem； tosupport a plex ecosystem； and yet it does。 crab…eater seals are not a species of animal thatmost of us have heard of； but they may actually be the second most numerous large species ofanimal on earth； after humans。 as many as fifteen million of them may live on the pack icearound antarctica。 there are also perhaps two million weddel seals； at least half a millionemperor penguins； and maybe as many as four million adélie penguins。 the food chain isthus hopelessly top heavy； but somehow it works。 remarkably no one knows how。
all this is a very roundabout way of making the point that we know very little about earth’sbiggest system。 but then； as we shall see in the pages remaining to us； once you start talkingabout life； there is a great deal we don’t know； not least how it got going in the first place。
。。！
19THE RISE OF LIFE
，小，说，网
in 1953； stanley miller； a graduate student at the university of chicago； took twoflasks—one containing a little water to represent a primeval ocean； the other holding amixture of methane； ammonia； and hydrogen sulphide gases to represent earth’s earlyatmosphere—connected them with rubber tubes； and introduced some electrical sparks as astand…in for lightning。 after a few days； the water in the flasks had turned green and yellow ina hearty broth of amino acids； fatty acids； sugars； and other organic pounds。 “if goddidn’t do it this way；” observed miller’s delighted supervisor； the nobel laureate haroldurey； “he missed a good bet。”
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’t 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’s gaseous stew； but rather was a much less reactive blend ofnitrogen and carbon dioxide。 repeating miller’s 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 ne