{"id":25260,"date":"2015-02-02T16:59:35","date_gmt":"2015-02-02T14:59:35","guid":{"rendered":"https:\/\/bilimvegelecek.com.tr\/?p=25260"},"modified":"2018-05-14T12:56:08","modified_gmt":"2018-05-14T09:56:08","slug":"lamarck-ve-evrim-kurami-2","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2015\/02\/02\/lamarck-ve-evrim-kurami-2","title":{"rendered":"Lamarck ve evrim kuram\u0131 – 2"},"content":{"rendered":"

T\u00fcm canl\u0131lar\u0131n ortak bir k\u00f6kene sahip oldu\u011fu d\u00fc\u015f\u00fcncesini sav d\u00fczeyinde, tutarl\u0131 bir d\u00fc\u015f\u00fcnce sistemiyle ifade eden pek \u00e7ok d\u00fc\u015f\u00fcn\u00fcr olmu\u015ftur. Ancak evrim olay\u0131n\u0131 bilimsel bir zemine oturtmaya \u00e7al\u0131\u015fan ilk ki\u015fi Lamarck\u2019t\u0131r. O, ya\u015fam denen olgunun salt fizik kanunlar\u0131 taraf\u0131ndan belirlendi\u011fini ve insano\u011flunun, canl\u0131lar\u0131n olu\u015fumu muammas\u0131n\u0131, herhangi bir ilahi m\u00fcdaheleye ihtiya\u00e7 duymaks\u0131z\u0131n ak\u0131l erdirerek \u00e7\u00f6zebilece\u011fini d\u00fc\u015f\u00fcn\u00fcyordu. <\/em><\/p>\n

Bir \u00f6nceki yaz\u0131m\u0131zda, Lamarck\u2019\u0131n hayat hik\u00e2yesini kaleme ald\u0131k.(1) <\/sup>\u015eimdi, bu ilgin\u00e7 do\u011fa bilgininin ismiyle \u00f6zde\u015fle\u015fmi\u015f evrim kuram\u0131na daha yak\u0131ndan bakal\u0131m. (2), (3)<\/sup><\/p>\n

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Mikhail Dmitrievich Ezuchevsky taraf\u0131ndan yap\u0131lan bu resimde Lamarck, Napoleon Bonaparte\u2019a Zoological Philosopy (Zoolojik Felsefe) kitab\u0131n\u0131 sunarken…<\/figcaption><\/figure>\n

Lamarck, t\u00fcrlerin evrildiklerini ileri s\u00fcren ilk d\u00fc\u015f\u00fcn\u00fcr de\u011fildi elbette. Evrimsel de\u011fi\u015fim fikrinin izini, insanl\u0131k tarihinin \u00e7ok gerilerinde s\u00fcrmek m\u00fcmk\u00fcn: T\u00fcm canl\u0131lar\u0131n ortak bir k\u00f6kene sahip oldu\u011fu d\u00fc\u015f\u00fcncesi, do\u011fay\u0131 g\u00f6zlemlemeye ve mant\u0131k y\u00fcr\u00fctmeye merakl\u0131 pek \u00e7ok insan\u0131n akl\u0131na \u201cdo\u011fal\u201d olarak gelip yerle\u015fen bir d\u00fc\u015f\u00fcnce olsa gerek. Ancak, 18. y\u00fczy\u0131l\u0131n sonlar\u0131na dek, evrim olay\u0131n\u0131 sadece bir fikir olmaktan \u00e7\u0131kar\u0131p onu sav d\u00fczeyine \u00e7eken ve bu sav\u0131, tutarl\u0131 bir d\u00fc\u015f\u00fcnce sistemi kurup do\u011frulamaya \u00e7al\u0131\u015fan insan say\u0131s\u0131 \u00e7ok azd\u0131r. \u00d6rne\u011fin \u0130htilal d\u00f6nemi \u00f6ncesi, Frans\u0131z Ayd\u0131nlanmas\u0131 s\u00fcrecinde pek \u00e7ok d\u00fc\u015f\u00fcn\u00fcr t\u00fcrlerin k\u00f6keni problemati\u011fine de\u011findi: Diderot, D\u2019Alembert, Maupertuis, Buffon ve di\u011ferleri. Ancak evrim olay\u0131n\u0131 bilimsel bir zemine oturtmaya \u00e7al\u0131\u015fan ilk ki\u015fi, Lamarck oldu. Lamarck, evrime ili\u015fkin d\u00fc\u015f\u00fcncelerini (organik de\u011fi\u015fimden bahsederken hi\u00e7bir zaman evrim ya da transformizm s\u00f6zc\u00fcklerini kullanmad\u0131) birka\u00e7 eserde toplad\u0131; bunlar\u0131n en \u00f6nemlileri \u015funlard\u0131r: Omurgas\u0131z Hayvanlar Sistemi<\/em> (1801), Canl\u0131 Varl\u0131klar\u0131n Te\u015fekk\u00fcl\u00fc \u00dczerine Ara\u015ft\u0131rmalar<\/em> (1802), Zoolojik Felsefe<\/em> (1809) ve Omurgas\u0131z Hayvanlar\u0131n Do\u011fa Tarihi<\/em> (1815-1822).<\/p>\n

Hen\u00fcz bir kuram kurmaya te\u015febb\u00fcs etmeden \u00f6nce, t\u00fcrlerin sabit olmad\u0131\u011f\u0131, onlar\u0131n bir d\u00f6n\u00fc\u015f\u00fcm s\u00fcrecine tabi olup, zamanla nas\u0131l de\u011fi\u015ftikleri fikrine nas\u0131l varm\u0131\u015ft\u0131 Lamarck? Birka\u00e7 etken rol oynam\u0131\u015ft\u0131 bu ba\u011flamda.<\/p>\n

Evrim fikrinin do\u011fu\u015fu<\/strong><\/p>\n

Evrimsel d\u00fc\u015f\u00fcncenin ilk tohumlar\u0131, canl\u0131lar\u0131n tasnifini yapt\u0131\u011f\u0131 y\u0131llarda, t\u00fcrler aras\u0131 s\u0131n\u0131rlar\u0131n ne kadar ele gelmez, bir t\u00fcr\u00fc bir di\u011ferinden ay\u0131rt eden \u00f6zelliklerin zaman zaman ne kadar flu oldu\u011fu ger\u00e7e\u011fini g\u00f6zlemlemesiyle ekildi Lamarck\u2019\u0131n ruhuna. O kadar ki, \u00e7al\u0131\u015fmalar\u0131nda kar\u015f\u0131 kar\u015f\u0131ya kald\u0131\u011f\u0131 pek \u00e7ok durumda, net bir s\u0131n\u0131fland\u0131rma yapman\u0131n imk\u00e2ns\u0131za yak\u0131n oldu\u011funu g\u00f6rd\u00fc: Bir t\u00fcrden di\u011ferine ge\u00e7erken, ger\u00e7ek bir s\u00fcreklilik, derin akrabal\u0131k ba\u011flar\u0131 s\u00f6z konusu olmal\u0131yd\u0131.<\/p>\n

Daha sonra, jeoloji alan\u0131nda y\u00fcr\u00fctt\u00fc\u011f\u00fc \u00e7al\u0131\u015fmalar \u0131\u015f\u0131\u011f\u0131nda, yery\u00fcz\u00fcn\u00fcn, ak\u0131l almayacak kadar uzun s\u00fcreler boyunca, ad\u0131m ad\u0131m, \u00e7ok k\u00fc\u00e7\u00fck hamleler sonucu \u015fekillendi\u011fini anlad\u0131. B\u00f6ylece, yerk\u00fcrenin sadece birka\u00e7 biny\u0131ll\u0131k bir tarihe sahip oldu\u011fu; yery\u00fcz\u00fcn\u00fc de, ge\u00e7mi\u015fte meydana gelmi\u015f ama art\u0131k ger\u00e7ekle\u015fmeyen bir dizi do\u011fal afetlerin \u015fekillendirdi\u011fi iddias\u0131n\u0131 savunanlara -yani o zamanlar ra\u011fbet g\u00f6ren \u201cafet\u00e7ilik\u201d kuram\u0131na- kar\u015f\u0131 \u00e7\u0131km\u0131\u015f oldu. \u201cDo\u011fan\u0131n, t\u00fcm eserlerinde, hi\u00e7bir \u015feyi aniden yapmad\u0131\u011f\u0131n\u0131, aksine her yerde yava\u015f\u00e7a ve kademe kademe hareket etti\u011fini d\u00fc\u015f\u00fcnmeliyiz\u201d diye yazacakt\u0131. Y\u0131llar sonra Darwin de ayn\u0131 g\u00f6zlemden yola \u00e7\u0131karak ak\u0131l y\u00fcr\u00fctecekti…<\/p>\n

Madem ki do\u011fada her canl\u0131 organizmay\u0131 kendi do\u011fal ortam\u0131na m\u00fckemmelce uyarlanm\u0131\u015f buluruz, o vakit her organizma da zamanla a\u011f\u0131r a\u011f\u0131r de\u011fi\u015fmi\u015f olmal\u0131yd\u0131. Jeoloji ve biyoloji d\u00fcnyalar\u0131 birbirine et ve t\u0131rnak gibi ba\u011fl\u0131yd\u0131.<\/p>\n

\u00d6te yandan Lamarck, hayvan soylar\u0131n\u0131n t\u00fckenmedi\u011fi kan\u0131s\u0131ndayd\u0131 (hatal\u0131 olarak) ve bu da, kendi g\u00f6z\u00fcnde, evrimsel d\u00f6n\u00fc\u015f\u00fcm\u00fcn ger\u00e7ek oldu\u011fu sav\u0131n\u0131 destekleyen bir di\u011fer unsurdu: Fosille\u015fmi\u015f hayvanlar\u0131 g\u00fcn\u00fcm\u00fczde canl\u0131 olarak g\u00f6remememizin nedeni, onlar\u0131n zamanla d\u00f6n\u00fc\u015fm\u00fc\u015f olmalar\u0131ndan kaynaklan\u0131yordu. Hatta bu hayvanlar d\u00fcnyan\u0131n me\u00e7hul b\u00f6lgelerinde h\u00e2l\u00e2 ya\u015f\u0131yor olabilirdi!<\/p>\n

\u0130\u015fte Lamarck\u2019\u0131, evrimi bir olgu olarak kabul etmeye iten ba\u015fl\u0131ca nedenler bunlard\u0131. Ancak do\u011fadaki organik de\u011fi\u015fimin mekanizmas\u0131 ne olabilirdi? Bu soruya yan\u0131t arayan Lamarck, ya\u015fam denen olgunun salt fizik kanunlar\u0131 taraf\u0131ndan belirlendi\u011fini ve insano\u011flunun, canl\u0131lar\u0131n olu\u015fumu muammas\u0131n\u0131, herhangi bir ilahi m\u00fcdaheleye ihtiya\u00e7 duymaks\u0131z\u0131n ak\u0131l erdirerek \u00e7\u00f6zebilece\u011fini d\u00fc\u015f\u00fcn\u00fcyordu. B\u00f6ylece, t\u00fcrlerin ortaya \u00e7\u0131k\u0131\u015f\u0131n\u0131 a\u00e7\u0131klamaya y\u00f6nelik mant\u0131kl\u0131 ve \u00f6zg\u00fcn, ayn\u0131 zamanda kapsaml\u0131 bir \u201csistem\u201d geli\u015ftirmeye ba\u015flad\u0131.<\/p>\n

Lamarck\u2019\u0131n kuram\u0131<\/strong><\/p>\n

Lamarck\u2019\u0131n mant\u0131\u011f\u0131n\u0131 anlayabilmemiz i\u00e7in, ilk\u00f6nce onun canl\u0131lar d\u00fcnyas\u0131na nas\u0131l bakt\u0131\u011f\u0131n\u0131 anlamam\u0131z gerekir. Bitkiler ve hayvanlar\u0131, \u00f6zellikle de omurgas\u0131zlar\u0131 inceleyen Lamarck, do\u011fada basitten karma\u015f\u0131\u011fa do\u011fru bir derecelenmenin var oldu\u011funa kanaat getirdi. Bir di\u011fer ifadeyle, en basit yarat\u0131k gruplar\u0131ndan (ha\u015flaml\u0131lar, \u201cinfusoria\u201d) en karma\u015f\u0131klar\u0131na (karma\u015f\u0131k omurgal\u0131lar ve memeliler) do\u011fru uzanan bir hiyerar\u015fi, bir s\u0131rad\u00fczeni vard\u0131. Kimi yorumcular, bir \u201cy\u00fcr\u00fcyen merdiven\u201d benzetmesini kullan\u0131r Lamarck\u2019\u0131n bu g\u00f6r\u00fc\u015f\u00fcne a\u00e7\u0131kl\u0131k getirmeye \u00e7al\u0131\u015f\u0131rken. Lamarck\u2019\u0131n sisteminde, her hayat \u015fekli, mikroskobik d\u00fcnyada, yani merdivenin en alt basama\u011f\u0131nda, bir \u201ckendili\u011finden \u00fcreyi\u015f\u201d (g\u00e9n\u00e9ration spontan\u00e9e) sonucu ortaya \u00e7\u0131kar. Do\u011fada mevcut olan bir \u201chayatiyet g\u00fcc\u00fc\u201d (le pouvoir de la vie), canl\u0131 organizmalar\u0131, daha fazla karma\u015f\u0131kl\u0131k ve organizasyon elde etmelerini sa\u011flayacak \u015fekilde, bu merdivenin en alt basama\u011f\u0131ndan \u00fcst basamaklar\u0131na do\u011fru iter. \u00d6rne\u011fin g\u00fcn\u00fcm\u00fczde g\u00f6rd\u00fc\u011f\u00fcm\u00fcz ku\u015flar, kadim zamanlarda ya\u015fam\u0131\u015f s\u00fcr\u00fcngenlerin torunlar\u0131d\u0131r; ayn\u0131 mant\u0131k ile, g\u00fcn\u00fcm\u00fczde ya\u015fayan s\u00fcr\u00fcngenlerin torunlar\u0131n\u0131n torunlar\u0131 \u00e7ok ileri bir zamanda ku\u015fa d\u00f6n\u00fc\u015fecektir. \u00dcst basamaklardaki canl\u0131lar \u00f6ld\u00fc\u011f\u00fcnde, topra\u011fa kar\u0131\u015f\u0131rlar ve \u00e7\u00f6z\u00fcnen bedenlerinden sal\u0131nan kimyasal maddelerden, kendili\u011finden \u00fcreyi\u015f sonucu, yeni canl\u0131lar do\u011far ve b\u00f6ylece ya\u015fam d\u00f6ng\u00fcs\u00fc tamamlanm\u0131\u015f olur.<\/p>\n

Y\u00fcr\u00fcyen merdiven diye adland\u0131rd\u0131\u011f\u0131m\u0131z model ile Lamarck, do\u011fada g\u00f6zlemledi\u011fi ve karma\u015f\u0131kl\u0131\u011fa dayal\u0131 bir s\u0131rad\u00fczene a\u00e7\u0131kl\u0131k getirmeyi ama\u00e7l\u0131yordu. Bu model, Antik Yunan \u00c7a\u011f\u0131\u2019ndan beri kullan\u0131lagelmi\u015f Do\u011fa Merdiveni (Scala Naturae<\/em>) ya da B\u00fcy\u00fck Varl\u0131k Zincirini and\u0131r\u0131yordu asl\u0131nda.<\/p>\n

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\u201cDe\u011fi\u015fen ortam kar\u015f\u0131s\u0131nda canl\u0131lar, huylar\u0131n\u0131 de\u011fi\u015ftirmek zorunda kal\u0131r. \u00d6rne\u011fin a\u011fa\u00e7lar\u0131n alt yapraklar\u0131 yok olmu\u015f ise, z\u00fcrafa art\u0131k a\u011fa\u00e7lar\u0131n \u00fcst yapraklar\u0131na do\u011fru uzan\u0131r. De\u011fi\u015fen huylar, baz\u0131 organlar\u0131n daha fazla, baz\u0131lar\u0131n\u0131nsa daha az kullan\u0131l\u0131\u015f\u0131na ya da hi\u00e7 kullan\u0131lmay\u0131\u015f\u0131na yol a\u00e7ar ki, bunun sonucu olarak canl\u0131larda yap\u0131sal ve fizyolojik de\u011fi\u015fimler ba\u015f g\u00f6sterir: A\u011fac\u0131n \u00fcst k\u0131s\u0131mlar\u0131na do\u011fru uzanan z\u00fcrafan\u0131n boynu uzar. \u201d<\/figcaption><\/figure>\n

En basit formlardan ba\u015flayarak gitgide daha fazla karma\u015f\u0131kl\u0131k kazan\u0131\u015f, Lamarck\u2019a g\u00f6re d\u00f6n\u00fc\u015f\u00fcm\u00fcn birincil nedeni ya da ilkesidir. Ancak bu d\u00f6n\u00fc\u015f\u00fcm s\u00fcreci dosdo\u011fru ilerlemez, \u00e7\u00fcnk\u00fc do\u011fal ortam\u0131n etkisiyle, yoldan sapmalar ger\u00e7ekle\u015fir. Lamarck\u2019\u0131n \u201colaylar\u0131n etkisi\u201d (l\u2018influence des circonstances) dedi\u011fi bu ikinci ilke, sonu\u00e7 olarak t\u00fcm canl\u0131lar\u0131n do\u011fal ortamlar\u0131na uyarlanmalar\u0131n\u0131n temelinde yatan unsurdur. \u015eekil-i\u015flev etkile\u015fimi \u00fczerine kurulu bir d\u00f6n\u00fc\u015f\u00fcm s\u00fcrecidir bu. \u015e\u00f6yle ki:<\/p>\n

S\u00fcre\u00e7, do\u011fal ortam\u0131n (\u00e7ok yava\u015f) de\u011fi\u015fmesiyle ba\u015flar. De\u011fi\u015fen ortam kar\u015f\u0131s\u0131nda canl\u0131lar, huylar\u0131n\u0131 de\u011fi\u015ftirmek zorunda kal\u0131r. \u00d6rne\u011fin a\u011fa\u00e7lar\u0131n alt yapraklar\u0131 yok olmu\u015f ise, z\u00fcrafa art\u0131k a\u011fa\u00e7lar\u0131n \u00fcst yapraklar\u0131na do\u011fru uzan\u0131r; ya da g\u00f6l suyunun s\u0131cakl\u0131\u011f\u0131 artm\u0131\u015f ise bal\u0131klar daha derin sulara y\u00f6nelir. De\u011fi\u015fen huylar, baz\u0131 organlar\u0131n daha fazla, baz\u0131lar\u0131n\u0131nsa daha az kullan\u0131l\u0131\u015f\u0131na, ya da hi\u00e7 kullan\u0131lmay\u0131\u015f\u0131na yol a\u00e7ar ki, bunun sonucu olarak canl\u0131larda yap\u0131sal ve fizyolojik de\u011fi\u015fimler ba\u015f g\u00f6sterir: A\u011fac\u0131n \u00fcst k\u0131s\u0131mlar\u0131na do\u011fru uzanan z\u00fcrafan\u0131n boynu uzar ya da daha derin ve serin, dolay\u0131s\u0131yla daha karanl\u0131k sulara g\u00f6\u00e7 eden bal\u0131\u011f\u0131n g\u00f6zleri daha fazla \u0131\u015f\u0131k almak i\u00e7in irile\u015fir. B\u00f6ylece tetiklenen fizyolojik de\u011fi\u015fiklikler \u201cyumu\u015fak kal\u0131t\u0131m\u201d denilen soya\u00e7ekim mekanizmas\u0131 sonucu, ebeveynden yavrulara ge\u00e7er. Bu senaryo nesilden nesile yinelenince, de\u011fi\u015fimler zamanla kal\u0131c\u0131l\u0131k kazan\u0131r, adaptasyonlar do\u011far. \u0130\u015fte bu y\u00fczden g\u00fcn\u00fcm\u00fczde z\u00fcrafalar\u0131n boynu uzun ya da derin sularda ya\u015fayan baz\u0131 bal\u0131klar\u0131n g\u00f6zleri iridir.<\/p>\n

\u00d6zetleyecek olursak, Lamarck, evrimle\u015fme olay\u0131n\u0131 a\u00e7\u0131klarken hiyerar\u015fik bir sistem kurmu\u015ftu: Bu hiyerar\u015fi, yukar\u0131da belirtti\u011fimiz \u00fczere, d\u00f6n\u00fc\u015f\u00fcm\u00fcn birincil ve ikincil ilkelerini i\u00e7eriyordu. \u0130kincil ilke de, iki ayr\u0131 yasadan olu\u015fuyordu: \u201cKullan\u0131l\u0131\u015f ve kullan\u0131lmay\u0131\u015f\u201d ile \u201ckazan\u0131lan \u00f6zelliklerin bir sonraki soya aktar\u0131m\u0131\u201d (yumu\u015fak kal\u0131t\u0131m). \u201cDo\u011fada rastlad\u0131\u011f\u0131m\u0131z her hayvan halinin, bir yandan, d\u00fczenli bir derecelenme yaratmaya e\u011filimli ve giderek artan bir organizasyon karma\u015f\u0131kl\u0131\u011f\u0131n\u0131n sonucu; \u00f6te yandan da, giderek artan organizasyon karma\u015f\u0131kl\u0131\u011f\u0131ndaki muntazaml\u0131\u011f\u0131 hep imha etmeye e\u011filimli, \u00e7ok say\u0131da ve \u00e7ok farkl\u0131 ko\u015fullar\u0131n etkisinin bir sonucu oldu\u011fu a\u00e7\u0131k\u00e7a ortaya \u00e7\u0131kacakt\u0131r. \u201d<\/p>\n

Sorunlu bir kuram<\/strong><\/p>\n

Lamarck\u2019a yap\u0131lan ele\u015ftirilerin belki de en ciddisi, \u00f6nermelerini herhangi bir deneyle desteklemiyor olmas\u0131yd\u0131. Oysa 19. y\u00fczy\u0131l\u0131n ba\u015flar\u0131nda, bilim d\u00fcnyas\u0131 h\u0131zla de\u011fi\u015fmekte, bilim de gitgide daha deney temelli, somut g\u00f6zlemleri esas alan bir disipline d\u00f6n\u00fc\u015fmekteydi. Lamarck ise bu d\u00f6n\u00fc\u015f\u00fcme ayak uyduramam\u0131\u015ft\u0131. \u00d6rne\u011fin yap\u0131lan ele\u015ftirilere g\u00f6re Lamarck\u2019\u0131n t\u00fcrlerin yava\u015f\u00e7a de\u011fi\u015ftiklerine dair sav\u0131n\u0131 fosil kay\u0131tlar\u0131yla desteklemek m\u00fcmk\u00fcn de\u011fildi; aksine g\u00f6zlemler, her yeni jeolojik zaman diliminin ba\u015flamas\u0131yla aniden yeni t\u00fcrlerin ortaya \u00e7\u0131kt\u0131\u011f\u0131n\u0131 g\u00f6stermiyor muydu? Veya, Lavoisier\u2019nin modern kimyan\u0131n temellerini atmas\u0131ndan y\u0131llar sonra, Lamarck\u2019\u0131n h\u00e2l\u00e2 bir simya yanl\u0131s\u0131 olmay\u0131 s\u00fcrd\u00fcrmesi anla\u015f\u0131l\u0131r \u015fey de\u011fildi.<\/p>\n

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Lamarck’\u0131n do\u011fa tarihi kitab\u0131ndan \u00e7izimler<\/figcaption><\/figure>\n

Lamarck, kendine bi\u00e7ti\u011fi rol ile bilim camias\u0131n\u0131n ele\u015ftirilerine maruz kal\u0131yordu: Kendini, kurdu\u011fu sistemler sayesinde do\u011fan\u0131n i\u015fleyi\u015fine \u0131\u015f\u0131k tutmay\u0131 ba\u015farm\u0131\u015f bir bilgin olarak g\u00f6rd\u00fc\u011f\u00fc yerde, zamane biliminsanlar\u0131, aya\u011f\u0131 yere basmayan bir spek\u00fclasyon merakl\u0131s\u0131n\u0131 g\u00f6rebiliyordu ancak. \u00d6rne\u011fin kullan\u0131l\u0131\u015f ve kullan\u0131lmay\u0131\u015f yasas\u0131nda hayvanlar d\u00fcnyas\u0131ndaki \u00e7e\u015fitlili\u011fe nas\u0131l \u0131\u015f\u0131k tutabildi\u011fiyle gurur duyuyordu Lamarck. Oysa pek \u00e7ok do\u011fa bilgininin g\u00f6z\u00fcnde bu \u201cyasa\u201d bir spek\u00fclasyondan \u00f6teye gitmiyordu.<\/p>\n

Lamarck\u2019\u0131n kuram\u0131n\u0131n baz\u0131 y\u00f6nlerini sadece bizler de\u011fil, o zaman\u0131n biliminsanlar\u0131n\u0131n da anlamakta zorland\u0131\u011f\u0131n\u0131 biliyoruz. Daha yak\u0131ndan bakal\u0131m.<\/p>\n

Yumu\u015fak kal\u0131t\u0131m<\/strong><\/p>\n

Bir canl\u0131 varl\u0131\u011f\u0131n ya\u015fam\u0131 boyunca elde etti\u011fi \u00f6zellikleri kal\u0131t\u0131m yoluyla bir sonraki soya aktarmas\u0131 ilkesi olan yumu\u015fak kal\u0131t\u0131m, Lamarck\u2019\u0131n icad\u0131 de\u011fildi: Yumu\u015fak kal\u0131t\u0131m fikrinin izini en az\u0131ndan Antik Yunan \u00c7a\u011f\u0131na kadar s\u00fcrmek m\u00fcmk\u00fcn. Lamarck, yeni bir kal\u0131t\u0131m kuram\u0131 \u00f6nermiyordu. Onun zaman\u0131nda yumu\u015fak kal\u0131t\u0131m o kadar a\u015fik\u00e2r bir fikirdi ki, herhangi bir delil ortaya koyma gereksinimi bile duyulmuyordu. Hatta y\u0131llar sonra Darwin de yumu\u015fak kal\u0131t\u0131m ilkesini benimseyecekti. Dolay\u0131s\u0131yla, Lamarck\u2019\u0131n kuram\u0131n\u0131 yumu\u015fak kal\u0131t\u0131ma indirgemek hem teknik olarak do\u011fru olmaz, hem de evrim kuram\u0131n\u0131n sadece bir par\u00e7as\u0131 oldu\u011fu i\u00e7in Lamarck\u2019a haks\u0131zl\u0131k etmek olur.<\/p>\n

\"\"
Lamarck’\u0131n do\u011fa tarihi kitab\u0131ndan \u00e7izimler 2<\/figcaption><\/figure>\n

B\u00fct\u00fcn bunlara ilave olarak, yumu\u015fak kal\u0131t\u0131m\u0131n modern biyolojide bir yeri olmad\u0131\u011f\u0131n\u0131 ekleyelim. 1880\u2019li y\u0131llarda August Weismann\u2019\u0131n ve 20. y\u00fczy\u0131lda ba\u015fka biliminsanlar\u0131n\u0131n da g\u00f6sterdi\u011fi gibi, bir canl\u0131n\u0131n ya\u015fam boyunca kazand\u0131\u011f\u0131 \u00f6zellikleri bir sonraki soya aktarabilmesi m\u00fcmk\u00fcn de\u011fil. Bir di\u011fer ifadeyle, molek\u00fcler biyolojinin \u201cmerkez\u00ee dogma\u201ds\u0131 olarak bilinen sonuca g\u00f6re, bilginin proteinden n\u00fckleik asite geri ge\u00e7mesi olanaks\u0131zd\u0131r.<\/p>\n

Hayatiyet g\u00fcc\u00fc ve esas neden<\/strong><\/p>\n

Yukar\u0131da bahsedildi\u011fi gibi, Lamarck\u2019a g\u00f6re, do\u011fada var olan bir \u201chayatiyet g\u00fcc\u00fc\u201d, nesilden nesile, t\u00fcm canl\u0131 varl\u0131klar\u0131n daha fazla karma\u015f\u0131kl\u0131k kazanmas\u0131na neden olur. B\u00f6ylece d\u00fcnyaya gelen her canl\u0131, ebeveynine g\u00f6re bir nebze daha karma\u015f\u0131kla\u015f\u0131r. Bu karma\u015f\u0131kl\u0131k art\u0131\u015f\u0131 tek bir nesilde g\u00f6zle g\u00f6r\u00fclmeyecek kadar azd\u0131r, ancak s\u00fcre\u00e7 on binlerce, y\u00fcz binlerce y\u0131l boyunca tekrarlan\u0131nca, karma\u015f\u0131kl\u0131k gitgide belirginlik kazan\u0131r. Peki bu olay\u0131n temelinde yatan mekanizma nedir? \u015eu a\u00e7\u0131klamay\u0131 getirir Lamarck: Embriyo anne karn\u0131nda geli\u015fmeye ba\u015flarken ilk \u00f6nce kalp olu\u015fur. Organlar da kalbin pompalad\u0131\u011f\u0131 kan\u0131n p\u0131ht\u0131la\u015fmas\u0131 sonucu ortaya \u00e7\u0131kar. Hayatiyet g\u00fcc\u00fc, her nesilden bir sonrakine, kan\u0131n hep biraz daha g\u00fc\u00e7l\u00fc pompalanmas\u0131n\u0131 sa\u011flar ve bu da biraz daha karma\u015f\u0131k organlar\u0131n yarat\u0131lmas\u0131na neden olur.<\/p>\n

Hayatiyet ilkesi, Lamarck i\u00e7in mistik bir dirimselcilik (vitalizm) inanc\u0131ndan kaynaklanm\u0131yordu. Canl\u0131 olmak, onun i\u00e7in, maddenin bir \u00f6zelli\u011fi de\u011fildi, maddenin belli bir organizasyonundan ibaretti. Ayr\u0131ca, hep daha fazla karma\u015f\u0131kl\u0131\u011f\u0131n yarat\u0131lmas\u0131na neden olan hayatiyet g\u00fcc\u00fc -Lamarck\u2019\u0131n bir ba\u015fka de\u011fimiyle \u201cesas neden\u201d- do\u011fan\u0131n bir ama\u00e7 g\u00fctt\u00fc\u011f\u00fc anlam\u0131n\u0131 da ta\u015f\u0131m\u0131yordu kendisi i\u00e7in. Aksine o, \u201cdo\u011faya, i\u015fleyi\u015finde herhangi bir niyet ya da ama\u00e7 atfetmenin ger\u00e7ek bir hata\u201d olaca\u011f\u0131n\u0131 net bir \u015fekilde ileri s\u00fcrm\u00fc\u015ft\u00fc.<\/p>\n

Kullan\u0131l\u0131\u015f ve kullan\u0131lmay\u0131\u015f<\/strong><\/p>\n

Lamarck\u2019a g\u00f6re canl\u0131lar\u0131n \u00e7evrelerine uyarlan\u0131\u015f\u0131, kullan\u0131l\u0131\u015f ve kullan\u0131lmay\u0131\u015f (usage et non-usage) ilkesinden, yani nesiller boyunca hep ayn\u0131 hareketleri tekrarlamalar\u0131ndan kaynaklan\u0131yordu. Lamarck\u2019tan evvel, bir organ\u0131n i\u015flevini belirleyen unsurun, o organ\u0131n yap\u0131s\u0131 oldu\u011fu kabul ediliyordu. Lamarck, bu d\u00fc\u015f\u00fcnceyi tersine \u00e7evirerek, asl\u0131nda i\u015flevin yap\u0131y\u0131 belirledi\u011fini ileri s\u00fcrm\u00fc\u015ft\u00fc. Bu d\u00fc\u015f\u00fcnce, yumu\u015fak kal\u0131t\u0131m fikriyle harmanlan\u0131nca, canl\u0131lar\u0131n \u00e7evrelerine uyarlanmalar\u0131n\u0131 ve zamanla d\u00f6n\u00fc\u015fmelerini a\u00e7\u0131klayabiliyordu.<\/p>\n

Kullan\u0131l\u0131\u015f ve kullan\u0131lmay\u0131\u015f ilkesi, Lamarck\u2019\u0131n en \u00e7ok gurur duydu\u011fu bulu\u015flar\u0131ndan biriydi, \u00e7\u00fcnk\u00fc bu ilke ile, hayvanlar d\u00fcnyas\u0131ndaki biyo\u00e7e\u015fitlili\u011fe geni\u015f anlamda \u0131\u015f\u0131k tutabildi\u011fine inan\u0131yordu. Ancak bu ilke Lamarck\u2019\u0131n zaman\u0131nda bile pek \u00e7ok ele\u015ftiriye maruz kalm\u0131\u015f, do\u011fa bilginleri aras\u0131nda s\u0131k\u00e7a alay konusu olmu\u015ftu. \u00c7\u00fcnk\u00fc e\u011fer bu d\u00fc\u015f\u00fcnce do\u011fru ise, hayvanlar, istekleri do\u011frultusunda evrimle\u015febilir olmuyor muydu? Darwin de \u201cLamarck\u2019\u0131n, hayvanlar\u0131n istemleri sonucu zaman i\u00e7inde uyarland\u0131klar\u0131 … sa\u00e7mal\u0131\u011f\u0131\u201dndan bahsederek, ac\u0131mas\u0131zca ele\u015ftirecekti Frans\u0131z do\u011fa bilginini. Asl\u0131nda Lamarck, uyarlanmalar\u0131n bir istem sonucu de\u011fil, elde edilen huylar sonucu ortaya \u00e7\u0131kt\u0131\u011f\u0131n\u0131 iddia ediyordu, ama ne yaz\u0131k ki s\u0131k\u00e7a yapt\u0131\u011f\u0131 gibi, kendini yanl\u0131\u015f ifade ediyordu.<\/p>\n

Ama tabii ki Lamarck\u2019\u0131n iddias\u0131n\u0131n bilimsel bir kar\u015f\u0131l\u0131\u011f\u0131 yoktu. Ayr\u0131ca kullan\u0131l\u0131\u015f ve kullan\u0131lmay\u0131\u015f ilkesini bitkilere nas\u0131l uyguluyordu? Veya, \u00f6rne\u011fin bir canl\u0131n\u0131n renginin \u00e7evresine uygun olu\u015fu, hangi huydan kaynaklanabilirdi? \u0130lke pek \u00e7ok durumda ge\u00e7ersiz ve yetersiz g\u00f6r\u00fcnd\u00fc\u011f\u00fc gibi, Lamarck taraf\u0131ndan herhangi bir delille de desteklenmemi\u015fti.<\/p>\n

Kendili\u011finden \u00fcreyi\u015f, ince s\u0131v\u0131lar<\/strong><\/p>\n

Kendili\u011finden \u00fcreyi\u015f, yani canl\u0131n\u0131n, canl\u0131dan de\u011fil de cans\u0131z maddeden ortaya \u00e7\u0131kt\u0131\u011f\u0131n\u0131 ileri s\u00fcren ve \u00e7ok eskilere, \u00f6rne\u011fin Antik Yunan \u00c7a\u011f\u0131 ve Aristoteles\u2019e dayanan bu ilke, iki bin k\u00fcsur y\u0131l kabul g\u00f6rm\u00fc\u015f ve ancak 19. y\u00fczy\u0131lda Pasteur\u2019\u00fcn deneyleriyle yanl\u0131\u015f oldu\u011fu kesin bir \u015fekilde kan\u0131tlanm\u0131\u015ft\u0131. Ya\u015fam d\u00f6ng\u00fcs\u00fcn\u00fc tan\u0131mlama pe\u015finde olan Lamarck i\u00e7in, uygun bir ba\u015flang\u0131\u00e7 noktas\u0131yd\u0131 kendili\u011finden \u00fcreyi\u015f. Do\u011fada her an, aral\u0131ks\u0131z yer alan bir s\u00fcre\u00e7ti bu, fakat \u00fcreyen canl\u0131lar ilk ba\u015fta mikroskobik yarat\u0131klar olduklar\u0131 i\u00e7in bizlerin onlar\u0131 \u00e7\u0131plak g\u00f6zle g\u00f6rmemiz olas\u0131 de\u011fildi. Bu yarat\u0131klar, buharla\u015fm\u0131\u015f maddenin, molek\u00fcllerin i\u00e7ine s\u0131zmas\u0131 ve \u0131s\u0131, \u0131\u015f\u0131k ve Lamarck\u2019\u0131n \u201cince s\u0131v\u0131lar\u201d (fluides subtils) diye adland\u0131rd\u0131\u011f\u0131 bir unsurun etkimesiyle ortaya \u00e7\u0131k\u0131yordu.<\/p>\n

\"\"
Lamarck\u2019\u0131n L\u00e9on Fagel taraf\u0131ndan yap\u0131lm\u0131\u015f, Paris\u2019de Jardin des Plantes\u2019de yer alan heykeli.<\/figcaption><\/figure>\n

Sonu\u00e7 olarak, yukar\u0131da g\u00f6stermeye \u00e7al\u0131\u015ft\u0131\u011f\u0131m\u0131z gibi, Lamarck\u2019\u0131n evrim kuram\u0131 pek \u00e7ok hata i\u00e7ermekteydi. Peki nas\u0131l oluyor da Lamarck, aradan 200 y\u0131l ge\u00e7mi\u015f olmas\u0131na ra\u011fmen, h\u00e2l\u00e2 g\u00fcncel kalmay\u0131 ba\u015farm\u0131\u015f olman\u0131n \u00f6tesinde, g\u00fcn\u00fcm\u00fczde baz\u0131lar\u0131 taraf\u0131ndan evrim kuram\u0131n\u0131n kurucusu say\u0131l\u0131yor? Bu sorunun birka\u00e7 yan\u0131t\u0131 olsa gerek, ama bizce Lamarck\u2019\u0131n, t\u00fcrlerin sabit olarak yarat\u0131lmad\u0131klar\u0131, bir evrimle\u015fme s\u00fcreci sonucu d\u00f6n\u00fc\u015f\u00fcp ortaya \u00e7\u0131kt\u0131klar\u0131 fikrini \u0131srarla ileri s\u00fcrmesi; ayr\u0131ca bu sav\u0131 desteklemek i\u00e7in, pek \u00e7ok hatalar i\u00e7erse de, herhangi bir ilahi g\u00fcce ba\u015fvurma ihtiyac\u0131 duymaks\u0131z\u0131n, ortaya tutarl\u0131 bir kuram koyabilmesi, onun evrim tarihinin \u00f6n saflar\u0131nda yer almas\u0131n\u0131n ba\u015fl\u0131ca nedenleridir.<\/p>\n

Kaynaklar<\/strong><\/p>\n

1) \u00d6l\u00e7er, \u201cLamarck ve Evrim Kuram\u0131,\u201d Bilim ve Gelecek, Say\u0131: 130, Aral\u0131k 2014, ss.72-75.<\/p>\n

2) J. Gould, The Structure of Evolutionary Theory<\/em>, Harvard University Press, 2002.<\/p>\n

3) Sapp, Genesis: The Evolution of Biology<\/em>, Oxford University Press, 2003.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

T\u00fcm canl\u0131lar\u0131n ortak bir k\u00f6kene sahip oldu\u011fu d\u00fc\u015f\u00fcncesini sav d\u00fczeyinde, tutarl\u0131 bir d\u00fc\u015f\u00fcnce sistemiyle ifade eden pek \u00e7ok d\u00fc\u015f\u00fcn\u00fcr olmu\u015ftur. Ancak evrim olay\u0131n\u0131 bilimsel bir zemine oturtmaya \u00e7al\u0131\u015fan ilk ki\u015fi Lamarck\u2019t\u0131r. O, ya\u015fam denen olgunun salt fizik kanunlar\u0131 taraf\u0131ndan belirlendi\u011fini ve insano\u011flunun, canl\u0131lar\u0131n olu\u015fumu muammas\u0131n\u0131, herhangi bir ilahi m\u00fcdaheleye ihtiya\u00e7 duymaks\u0131z\u0131n ak\u0131l erdirerek \u00e7\u00f6zebilece\u011fini d\u00fc\u015f\u00fcn\u00fcyordu. […]<\/p>\n","protected":false},"author":508,"featured_media":25266,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[169,38,32,1473,510],"tags":[482,200,2932],"class_list":["post-25260","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-132-sayi","category-dergi-sayilari","category-evrim","category-genis-aci","category-surekli-bolumler","tag-bilim","tag-evrim","tag-lamarck"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts\/25260","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/users\/508"}],"replies":[{"embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/comments?post=25260"}],"version-history":[{"count":0,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts\/25260\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/media\/25266"}],"wp:attachment":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/media?parent=25260"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/categories?post=25260"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/tags?post=25260"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}