Dobzhansky - Nothing in Biology MakeSLSe’nse , f, ?_...

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Unformatted text preview: Nothing in Biology MakeSLSe’nse , f, ?_ Except in, the Light of _- It THEODOSIUS DOBZHANSKY - ,_ estimation that the earth rotates around the-Sun, - ' and-not vice versa, have not been by direct therVations even to the extent the sphericity of the earth Yet scientists accept the model as an accurate’representation bf reality. Why? Because it makes sense of a multitude of'faCts which are other- = meaningless or extravagant. To-nonspecialists y most’pf these facts are unfamiliar. Why then do we * ” ' * acce tthe “mere theo ” that” earth-is a ere AS RECENTLY AS 1966: Sheik Abd 91,, B“ " ' revolving ‘a Sprgerical 311:? Are fivéVEply asked the king of Saudi Arabia to suppress aheresy ' submitting to authority? NM quite: we know that that was spreading in hisland. Wrote the shelk: . r ‘, t, those whp took time {Q study‘file evidehcefound it, “The Holy Koran, the Prophet’s teachmgs,_the m— H; convinéiné; ‘_ g ‘* * fig ‘ r a - jority of Islamic scientists, and? the actual factsau. . ' sheik"isjgpfobably'ignomnti-‘ofy.ther>’evi—'~‘i prove that the sun is running in its orbit . . L and that ‘ _, ,. " 'v'en’ fidfe so ’ ‘ the earth is fixed and stable, spread outby’ for ‘ ' » '7 ' I ” .Wduld‘ Any; -- his-mankind. . . . Anyouewho professed Otherwise p , " ’ ‘ Would utter a charge of falsehood toward God, the L Koran, and the Prophet.” * ' ' ' - The good sheik evidently bolas 'the‘ them;.‘It“.is ludicrots, t0. theory to be a “mere theory,” not a',"‘fac't:**,?1n' this : Korean: primers of methadone. They , , he is technically correct. A theory can beYe‘rified’by' matters evgfilmomlhpofimg filleai‘r'n'i‘nk- 9:553:31“: a mass of facts, but it becomes a proven' theory? not , and hjsrelatidns‘tb 66¢ -m;wfittéh in: a fact. The sheik was perhapsrunaware the fiéreshndmltua s big-b "palm; of Space Age had begun before. he asked the king to : a‘ge whentheywere writtenfas wen as"_¢o‘peap1es’_o£ suppress the Copernican hereSY-‘The ;,sphericity of r _ ell‘?other,agesg. T " king of‘Ai'raBiaadidinarcotian the earth had been seen by'astronauts, and even by with the sheik’s demand. He knee that mépeopxe many earth-bound people ont'he'lr television screens. fear. enlightennien't, “because enhghtennoent threatens Perhaps the sheik could retort that those who ven- mail-vested inferestg._.Edficafion is my“ be mg ‘ tureg beyond the confines of God’s ‘earth’ suffer hal— : ‘ bfdfhaé 6135a ~ _' {Li “ , ~' L lucinations, and thatthe‘earth‘is reallyyflat. ' __ j I ‘- " ' r”- ’* ’ ‘ " " Parts of the Copernican world model-such as the]; ' One of the'world’s’leading geneticists; _ 7, _ , dosius 130me is professor. crummy 1 I j y’ Rockefeller University, and adjunctjpmfeee I. ' sot of genetics, University Californ'm,. _ Davis 95616. Born in Russia, in 1900, he isja , V graduate of the University of Kiev‘and _: ' ‘ taught (with J'.'Phi1ipchenko) at the Uni- - versity of Leningrad before coming to the _ _ --.r 11.8., in 1927; thereafter he taught atColuml- , bia‘U ersity and the California Institute of Technology be- fore joining the Rockefeller faculty, in He president of the Genetics Society of the V 1 Society of Naturalists, the Society for the Study. of Evolution; ' the American Society of Zoologism-andthe hard de Chardin Association. 'are, National Medal of Science “(1964) and'the Gold for Distinguished Achievement in"? 119393 18 honorary doctorates from"universlties unv convention. ' a [Sheik binBaz and hisilike refuse to accept the ; radiometric eVidenCe, because it is‘a “mere theory.” is theralternative? 'One'can jsuppo'sethat I j-ngreator saw fit-to play deceitful tricks on geologists ' I biologists, Hecarefullyarranged to have various previded. with isotope ratios, just right to mis- a" 33.1“; ‘ years old, others-2 million;z'while'-inlfact they are only 7' yearsold.‘ of pseudo-explanation nOt very new; OneV'ofthe early antievolutionists, PJIH.‘ rGoSSe‘ppublish'edfia'i book entitled Omphalos ..“.'(‘“the" Navel")The"giSt‘O£ this amazing book is that Adam, though'ghe had no mother, was created with a - naVel, and that fossils were placed by the Creator . 'we find them-now4éa deliberate act on His to give the appearance ; of great antiquity and geologic upheavals; It is easy to see thefatal flaw in " , all such notions. They (are, blasphemies, acclising ' God of absurd deceitfulness. This is Vasrevolting as it'isuncalled’for. g ' ‘_ . .f, ‘1 ,y en'desc "ya; is probably 'aboutas great; The A’ diversity of, sizes, structures, andways of'life’gis stag- , parasites cells of other organismsredUCed-to bar-‘- Test_"essentialS-:-irihiute amounts of DNA '1 or . ' which subvert the biochemical machinery of the host ’ ., 1019115 to replicate their genetic information, rather ‘then'that'ofthehost.fi _ . _ ~ -' * , :,_:v’:;lt is smatteer 'bpinion, or of definition-whether was are considered living organisms or peculiar V absences; Thefaét that such climates :95.me93 axis: is in itself highly significant It means the. borderline between “m3 and h v > matteriis obliterated. At 'the'opposite end of the ,V 7 ' sixnplicity—complexity spectrum you have vertebrate animals, including The human brain has some 12 billion neuro s,‘ the synapses between. the neurons are perhaps a thousand times as numerous. - V Some organisms live in a great variety of environ— ments. Man is at the top of the scale in this respect. He is not only a truly cosmopolitan species but, ow- ing to his te _ ologic' achievements, can survive for atleast ailimited time on the surface of the moon and ’spaces._By contrast, some are I v Emeline)! Perhaps'the narrows-it eco- ' ogic niche’of. all is that of a species of the fungus , 1 portion ofthe elytra of the beetle Aphenopa Whichfigfeund only. in some limestone caves in canoe.» Larvaeof the fly Psilopo' petrolei _.»_seé_pages of} crude oil in California oil- 5- us into that, certain rocks are 2; billion ' many other possible ways 0 ’ ploited by any existing spe (1 studied; the number _, r _ I , i and cf smaller and smaller minorities thefarther Laboulbeniam'ae, which grows exclusively on r » light of evolution theory; but what a senseless oper- - fields; as far as is known they occur nowhere else. This is the only insect able to live and feed in oil, and its adult can walk on the surface of the oil only as long as no body part other than the tarsi are in, “ contact with the oil. Larvae of the fly Drosophila car- ‘ ‘ cinophila develop only in the nephric grooves be - neath the flaps of the third maxilliped of the land crab Geocarcinua ruricola, which is restricted to 'cer— " tain islands in the Caribbean. Is there an explanation, to make intelligible to rea; son this colossal diversity of living beings? came these extraordinary, Seemingly whimsical superfluous creatures, like the fungus Laboulbem‘a, the beetle Aphenops cronei, the flies Psilopa petrolei and Drosophila carcinophila, and many, many more apparent biologic curiosities? The only explanation that makes senseis that the organic diversity has evolved in response to the diversity of environment on the planet earth. No single species, however per- fect and however versatile, could exploit all L a opportunities for living. Every one of the millionsof, _' cies; ' but to envisage the situation is as follows: the en _' I . merit» presents’challenges to living species, to Which 3’, r ’the‘la‘tter may respond’by adaptive genetic changes: ’ An runoccupied’ecologic niche, an unexploited l - portunity for living, is a challenge; So is. , - mentalvchange,rsuch as the Ice Ageclima‘te "giying “place/to: a Wanner. climate..sNatural'5sélection'majy cause a living. species to respond to the" ' ‘ adaptive genetic changes. These changes: may ‘theispecies’to occupy the formerly empty 'e’cdlqgfiqi, , r V » niche as a new. opportunity fer living, or to the environmental change if it is unfaVOrablerBut the response may or may not be "successful. This depends On many factors, the chief ot'which is the ‘ genetic composition of the responding species at the A tinie the response is' called for. Lack of successful response may cause the spec1es to become extinct. look. Nevertheless, thenumber of species has not dwindled; indeed, it has probably grown with» time. All. this is understandable in the ation it would have been, on God’s part, to fabricate 'e‘., a multitude of species ex nihilo and then let most I ofthem die out! ' 3 is, 'of course, nothing conscious or intention- al in the action of natural selection._ A biologic - does-not say to itself, “Let me try temorrow ’ (or-Ea million years from now) to grow in a different iisoili, or use a different food, 0r subsist on a different » of a different crab.” Only a human being could make such conscious decisions. This ‘ispwhy the species Homo sapiens' is the apex of evolution. Natural selection is at one and the same time a blind ' ‘ and a' creative process. Only a creative but blind process could produce, on-the one hand, the tre- Hmendous biologic success that is the human species fand, on the other, forms of adaptedness as narrow as constraining as those of the overspecialized fungus, beetle, and flies mentioned above. I v Antievo1utionists fail to understand how natin-al selection operates. They fancy that all existing spe- cieswere generated by supernatural fiat a few years ago, pretty much as we find them. . * todaygfiBut'what is the sense of having as many as : ,, 3 plan, and species are produced not because needed for some purpose but simply be- ‘f-Z-causeuthere is an environmental opportunity and genetic wherewithal to make them possible. Was the ‘ JCreator' in a iocular mood when he made Psilopa ' petrolei for California oil—fields and species of Dras- ‘ land crabs on only certain islands, in the Ca— nbb'e'an? The organic diversity becomes, however, reasonable, and understandable if the Creator jhas " living world not by capricebutby 'evo-V' :lution',;pr0pelled by natural selection. It is, wrong to ‘7; hold ation‘ and evolution as mutually exclusive 'éltéma,. es; I a creationist and _an_=e‘?01_uti9niSt. ': Evolu " fis ’Godls,..or Nature’s, method of Creation; isnot an event that happened in 4004 .B.c.;, ' V 'stillunderway. N f ~ of life is no less remarkable, than its I' f Most forms of life are Similar in many re— 1 'spects; ,The'universal biologic siinilarities are pars , V ticularly'. striking the j biochemical dimension. ' From viruses to'man, heredity is'coded in just two, 'mexnically related substances: DNA and RNA. The V genetic code is as simple as it is universal. There are four genetic “letters” in DNA: adenine, gua- ' l '7 ‘e,}thymi_ne, and cytOSine‘. Uracil replacesthymine RNA. The entire evolutionary development of the . 'living'world'has taken place not (by invention of new in the genetic “alphabet”, but elabora- ‘ ,‘tion'offever-new,combinations of letters. r ' ' 77Not'pnly is'the DNA—RNA genetic cede universal, g., “{oa;3.~;mim0n,species living on earth? If natural _ selection, is the main factor that brings evolution any number of species is understandableir . naturalselectiOn does not work according to a fore- ophila‘rto live exclusively on some body-parts of ' it;~.-,i$~a"p:" 'ess that began some ,10 billion ago _ -. 7 canea'npha' iof hemoglobin have identical"_'~ ' .zé‘e’f.ibdt they differ in arr's'inglééfilfiéofhciaf(9u 7, L 141) in the £°w~ 5191‘“ if? him“ 31.9??? but so is the method of translation of the sequences of thejg‘fletters” in DNA—RNA into sequences 'of amino acids proteins.” The same 20’ amino acids compose "Locunflessdifierent proteins alL-or' at least inmost,“ organisms Difiemnt amino acids are codedr"byione_to six nucleotide. triplets in DNA and RNA- .the.bi<>‘chemic‘a1':univ,ersalsextend beyond the , genetic- code; and its {translation into proteins: strikingimifpmiitiesgprevafl in, the sauna: mam, lism of 'the'imostigidiverse hiring-beings. Adenosine tfip‘hosphate, biotin;_.‘, riboflavin, homes, pyridoxin, K and B15: andgfolic acid implement meta— bolic proceSSes everywhere, ' .g 9L ‘y ' What do these biochemical or biologic universals mean? They suggest that life- arose from inanimate matter only I once, and- thatfall- organisms, no matter how diverse in other respects; conserve the basic featuresof” the printordial'life.’ "(It is also possible that there-Were several,- Or even many; ‘originsof ’ life; :ifslso,_'the progeny of only one of them has sur- . x the earth.):__But sit-there {.‘wasnofevolution; every one ofpthe‘ millions 1of ' , Species ,iwas” ICreated; by’ separate " fiat} however 201-; L E ‘Lfensiiiéithsinofien meals ’toielisious-feelies‘eedits , , ’ ,thféianfievolufienists‘must‘azfin a . of»cheatirig.:They v ' ' satay" arranged exactly ' arenas: 9f; ~ _ ' ’Cre‘étion I was evolution; intentionallyite fi ' f . : 'Theifireinarkable T advances of molecular}, biology ~-in*r‘ecent* ‘ what made it possibluo u’r‘idermg' 1d. how‘itis‘that‘diverseorganisms are ' such monotonously" similar materials: proteins"'corn- posedC-ofonly' 20 kinds of mm acids and coded 'only'vby DNA and RNA. each with only four kinds .’of5nucle0tides. The method is astonishingly simple. All: English. words, sentences, andbooks ' ,arepmade'up of sequences _of,26 letters of the alphav (The? can be represented Thy only'three "the Morse 'idots'dash. and can) The meaning * of a -‘ word or a Sentence, isgdefined not so much by what lettersit contains byj'the sequence ’ of; Ii'ettsrs- It is *iiiith' media: sit is ‘ , coded by the sequencesof the genetic 5‘letters”--the nucleoti” itHe'LDNA. They translated into the sequences of amino acids in the proteins. . : Molecular studies havejmade possible an approach to exact measurements of degrees of biochemical Similarities and differences among organisms. Some ‘of enzymes and other» proteins are quasiuni— versal, oratany rate widespread, in the living world. They are .functionallysimilar'inydifierent living be. ingsrrin that they catalyze chemical reactions. But‘whén such proteins are isolated and their struc— taxes deemed chemically. they are. often found to containniore or less different sequences of acids, in "different organisms. For example, “the, p ' sequences of l o acids in man and ‘ . j’li‘in: difier-frornf‘eattle hemoglobin l7» ammo acid ’substitutions,'18’fmm-horse;.2o from'donke‘y, 25 from *‘ "land 71:froxnfish (carp); = ' o Cr ’e‘Cis an e‘v‘yme thatplays an im- r-rQle in the metahdisin "of (aerobic r cells. It undiin'the most diverse ~* organisms, from man .0. .jMargoliaSh,:ngngFitCh, and others ‘fthe‘ amino '.’acid -- seguence's in cyto- ” 'ejC different branches of the living world. VISimilaritiesT as Ivzell ‘ as i differences ave broughtito 'ylightLV‘lThe cytochrome C of V. , edifierent‘T'ordersiof’mammals and birds differ in 2 to r 5:17farnino'acids,‘ classes of vertebrates in 7 to 38, and ~ p'vertebrates and insects in 23 to 41; and animals dif- -_.{fer;.from yeasts andy-molds-inHSB to 72 amino acids. Fitch'and‘Margoliash prefer to express their find- ‘ 5" ‘ ings inIL'Wh'at' are“ called ' “minimal mutational dis- tances? It has‘been mentionedabov‘e thatldifierent‘ »» - amino : acids f are coded by; difierenti triplets of L nuc- ‘ f DNAof the genes; ‘this'jcode is nowknown; I x "of single finutations‘ to «h octane. organism-into that mutational distances between beings isre’as,.f°110W55 f : a and group differences 1 are only quantitatiVelyfinOt qualitatively, different. “fit/idem? supporting the above propositions is’ampl'e‘ andisfgmwi'ng rapidly. .MuehZWOrrl-n been done in {meant on individual variations in iamino 7 acid sequences of hemoglobins of blood. More 100 variants have been Vdetected.,Most of them » involve substitstians of single wide-substitu- v -i :tiohs that have arisen by? serials: metathesis the} . Personalin Whom theyslr‘é their 811- ! of eVolution. Comparative anatomy and i l r be multiplied indefinitely. ’ mutations invol‘telwbétitufions‘df 'sii‘z'g'le’huce exhibit striking similarities. A century; a ' SOmQWhere in'vthje DNA-chain for, ~- retain.v‘i*'lherefore,’-" one 'calculatefthe ‘ ,,20010gist Ernst Haeckel) to be carried-_by',}tliexr _ H .1 , p _ ‘ p V p _ 1 development the evolutionary history of'its human cytochrome C and the cytochrome C of other . Hcant; > _ : 1_ ,‘ Pmbably everybody knows the sedentary , fnacles which seem to have no similarityntog. 1 .r . crustaceans, such as the scopepodsé-EHOW I: Z ‘ lax-Val stage, the naupliusg: “ "damp 5“” bamacle and .3 Cyclops'ilookf " ‘ silt-is evidentthatthe ‘ ,_ , . , . ' 'takably "similar. .They are evidently _relatixres. They: {tildes 6111193121 pfqtem stithé "*lévels Pf, 'sbeciés, , genus,;3fehilyrotder,» classed phylum "are com- 7 ’ 5?: of elements that? vary al'soamon'g individu- '_ have functioning gills. But why should sit haveune '- ‘ '--’I'!iere arfe about 'aooojspecies «if ansopmdlfliés" archipelago is only about that of the smegofenefi - ‘ ' throughout the’arcmpelégc: they able findings make Sense in the light of evolu'fiéfié _ . they are nonsense otherwise. ' ' ~ ,_ , Comparative Anatomy and EmbryOlogy The biochemical universals are the most I: sive and the most recently discovered, but they are not the only vestiges of creation by proclaim the evolutionary origins of the ' inhabitants of the world. In 1555 Pierre Belon 'esta. lished the presence of homologous bones in thefilsuf " , perficially very different skeletons of man and _ Later anatomists traced the homologies in the shell etons, as well as in other organs, of all vertebrates; ' Homologies are also traceable in the external etons of arthropods as seemingly unlike as a lobster; a .fiy,'and a butterfly. Examples of homologies‘can : c Embryos of apparently quite diverse similarities led some biologists (notablyfth’e‘fGerrhan ’ ' thuszasm so far as to mterpret the embryoni larities as meaning that the embryo repeats it was said to pass through stages in"whieh5'it ' sembles its remote ancestors. In other wordsfiearl day biologists supposed that by studying embfy development one can, as it were, read 03 through which the evolutionary developmenfliéd passed. This so-called biogenetic law. is no longer credited in its original form. And yet‘embryonie similarities are undeniably impressive and ‘ presence oi'gill slits in human embryosfa'nd'in; bryospofsother terrestrial vertebrates ‘i’sra‘noth if ‘ rn'ous example. Of course, at no stage 6fvit’ls ment isa-human embryo a fish, ndriddes 'itil‘eVer'i‘ respire with the aid of gills? Is the 'Creator playing practical jokes? > - 7 ' " Adoptive Radiationi Hawaii’s Flies ‘ mistakable gill slits unlessits remote““ancestorsfdid' i World as a whole. About a ’quarter"'of I ' occur iniHawaii, although the‘total’? area the, ' JerseyQAll but 17 of the species’in endei ' = mic- (found nowhere else). Furthermorejz'a - majority of the. Hawaiian endemics dornotjoccur: Single islands or even to a part of an island. What is *the'explanation of this extraordinary proliferation of drosophilid species in so small a territory? Re- } “and others makes the situation understandable. ' The Hawaiian islands are of volcanic origin; they L. I were never parts of any continent. Their ages are ’ between 5.6 and 0.7 million years. Before man came j their inhabitants were descendants of immigrants that had been transported across the ocean by air Currents and other accidental means. A single dro- ' species, which arrived in Hawaii first, before ' ere Were numerous competitors, faced the chal- ' ' lenge of an abundance of many unoccupied ecologic niches. Its descendants responded to this challenge * bylevolutionary adaptive radiation, the products of which are the remarkable Hawaiian drosophilids of today. To. forestalla possible misunderstanding, let ' it made clear that the Hawaiian endemics are by, '- no means so similar to each other that they could , endemic species of drosophilids. The most prob-— I ,‘able‘jexplanation of this fact is that these other ' '. Were colonized by drosophilids after mast V ' ' ecologicniches had already been filled'by earlier, * * I This surely is a hypoth ' v the Greater went on manufacturingg9’9 ” fl -. 51}an ‘and‘niorejdrosophilid species for . extravagant surfeit :of .themil‘inj :' ‘ ‘ archiiielagogI leave-it to you to decide which 'hy-i ; ‘ f: files Se . _ . i' _' encei,,With0ut that light it becomes a pile of sundry , ' facts-sesomecf'rthem'interesting or curiOus but mak~_ ’ . , _, _> , , . I, _ _ _ w , f 'ing no meaningful picture as a whole. , r ' ' V ' L I ' * ‘ ‘ ‘ thee. '. 3 not to iinply that 'we know everything that _ 'Teilhard’sstéach.‘ . ‘ ‘ ' t r -v “@6214 View show _ doubtat all that 3:11th : J rifefarnongjbiologists, as they should, a} , » and growing science. Antievolutignists - ...
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This note was uploaded on 09/06/2008 for the course BIOMEDE 418 taught by Professor Hunt during the Winter '08 term at University of Michigan.

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Dobzhansky - Nothing in Biology MakeSLSe’nse , f, ?_...

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