{"id":17074,"date":"2025-03-26T14:08:17","date_gmt":"2025-03-26T13:08:17","guid":{"rendered":"https:\/\/letrat.eu\/?p=17074"},"modified":"2025-03-26T14:09:18","modified_gmt":"2025-03-26T13:09:18","slug":"will-ratcliff-origjina-e-jetes-evolucioni-i-jetes-shumeqelizore","status":"publish","type":"post","link":"https:\/\/letrat.eu\/?p=17074","title":{"rendered":"Will Ratcliff – (Origjina e Jet\u00ebs) Evolucioni i Jet\u00ebs Shum\u00ebqelizore"},"content":{"rendered":"

William Ratcliff – (Origjina e Jet\u00ebs) Evolucioni i Jet\u00ebs Shum\u00ebqelizore (di\u00e7 si pasqyr\u00eb diskursive, fjala e fundit e shkenc\u00ebs sa i p\u00ebrket origjin\u00ebs s\u00eb jet\u00ebs)<\/strong>
\nsenad guraziu, ars poetica, mars 2025 – pak fjale, sqarim…<\/em><\/p>\n

…nuk mohohet fakti se jeta, ashtu n\u00eb natyr\u00ebn e vet, gjithmon\u00eb ‘enigmatike’, ishte dhe ende \u00ebsht\u00eb, t\u00eb jetosh \u00ebsht\u00eb unikalitet, di\u00e7 si “dimension” n\u00eb vete, di\u00e7 skajshm\u00ebrisht unike dhe universale, dhe vet\u00ebm t\u00eb ‘gjallosh” \u00ebsht\u00eb unike, pa le pastaj t’jesh i vet\u00ebdijsh\u00ebm se gjallon (meq\u00eb jo gjith\u00e7ka e gjall\u00eb e ka iden\u00eb e gjallimit – dhe kjo grupnaj\u00eb gjallesash pa “iden\u00eb e jet\u00ebs” \u00ebsht\u00eb jasht\u00ebzakonisht e madhe, ishte dhe di\u00e7 si pararendje e jet\u00ebs son\u00eb), dmth. jeta ishte dhe ngeli misterioze po aq sa dhe interesante, jo vet\u00ebm filozofikisht por dhe shkenc\u00ebrisht, interes dhe enigm\u00eb me plotkuptimin e fjal\u00ebs…<\/p>\n

…shikuar me prizmin evolutiv (dmth. t\u00eb darvinizmit), b\u00ebn t\u00eb thuhet se m\u00ebnyra si do ket\u00eb ndodhur ‘evolucioni’ i jet\u00ebs shum\u00ebqelizore akoma \u00ebsht\u00eb nj\u00ebra nga enigmat m\u00eb t\u00eb m\u00ebdha t\u00eb shkenc\u00ebs moderne, p\u00ebr t\u00eb ndodhur hapi evolucionar nga nj\u00ebqelizorja n\u00eb shum\u00ebqelizoren e gjallimit (dhe vet\u00ebm ky hap i vetem) mbase do ken\u00eb kaluar me qindra miliona vite, ndoshta dhe tejkaluar miliard-vje\u00e7ari i zanafilles tokesore si planet… patjet\u00ebr se ishte hap i madh i \u00e7udis\u00eb s\u00eb ashtuquajtur “jet\u00eb”…<\/p>\n

…si\u00e7 e dim\u00eb, as pas 3-4 shekuj t\u00eb shkencave, shkenc\u00ebtar\u00ebt dhe mendimtar\u00ebt e bot\u00ebs, m\u00eb t\u00eb diturit e m\u00eb t\u00eb ndriturit e mendjes njer\u00ebzore nuk pajtohen rreth “zanafill\u00ebs s\u00eb jet\u00ebs”, sipas linjes shkencore darvinistike (dmth. evolucionare), organizmat m\u00eb t\u00eb hersh\u00ebm pat\u00ebn lindur spontanisht nga sinteza e materialeve abiotike (dmth. ishte spontanitet, faza bazike si “procese kimike” pakashum\u00eb) – mir\u00ebpo ata q\u00eb teorin\u00eb e evolucionit e konsiderojn\u00eb “p\u00ebrrall\u00eb ateistike”, dmth. e qart\u00eb se nuk pajtohen me hipotezat abiotike, me lindjen e jet\u00ebs nga “asgj\u00ebja”…<\/p>\n

…sidoqoft\u00eb, shembulli me nism\u00ebn e jet\u00ebs nga “asgj\u00ebja” s’\u00ebsht\u00eb “asgj\u00eb” si mospajtim, n\u00ebse t\u00eb krahasohej me faktin q\u00eb fizikan\u00ebt e kozmolog\u00ebt modern\u00eb madje insistojn\u00eb se dhe universi komplet qe nisur nga hi\u00e7asgj\u00ebja (nga ai “Bangu” i Maaaadh – si\u00e7 e quajn\u00eb ata), pa ku na qenka nisja e nj\u00eb planeti fillikat, pastaj nisja e jet\u00ebs n\u00eb at\u00eb planet, ehuuu ku \u00ebsht\u00eb universi e ku 1 planet i vet\u00ebm, absurd dhe t\u00eb “krahasohet”, n\u00ebse mund t’niset i gjith\u00eb universi, me pluhnajash e me miliarda galaktikash nga “asgj\u00ebja” (nga ndonj\u00eb ngjeshje e ‘singularizuar’, ngjeshje deri n\u00eb paskaj\u00ebsi e materies, e padukshme por ekzistente, tekefundit ekzistenc\u00eb teorike) at\u00ebher\u00eb pse t’mos niset dhe jeta e Tok\u00ebs me veset abiotike, pik\u00ebrisht nga hi\u00e7asgj\u00ebja…<\/p>\n

…nd\u00ebr “dyshimtar\u00ebt” m\u00eb t\u00eb m\u00ebdhenj kuptohet nuk jan\u00eb vet\u00ebm teolog-filozof\u00ebt, jan\u00eb dhe vet\u00eb shkenc\u00ebtar\u00ebt teist\u00eb (besimtar\u00eb) q\u00eb ngulin k\u00ebmb\u00eb se “dizajni inteligjent” \u00ebsht\u00eb shuplaka dhe grushti teistik p\u00ebr evolucionin darvinian, ky evolucion sipas tyre \u00ebsht\u00eb pra nj\u00eb lloj p\u00ebrralle ateist\u00ebsh rreth “krijimit”, le q\u00eb s’p\u00ebrputhet as me Biblen… dmth. me Zotin, por s’p\u00ebrputhet me asgj\u00eb – shkurt, k\u00ebta t\u00eb fundit pohojn\u00eb se hipoteza materialiste q\u00eb organizmat m\u00eb t\u00eb hersh\u00ebm kan\u00eb lindur spontanisht (pa ndihm\u00ebn e Per\u00ebndis\u00eb) nga sinteza e materialeve abiotike, \u00ebsht\u00eb p\u00ebrrall\u00eb dhe nonsens…<\/p>\n

…nga ana tjet\u00ebr e marramendjes, n\u00eb t\u00eb tashmen, n\u00eb modernizmin ton\u00eb t\u00eb ngulfatur nga tekno-avancimet dhe me shkencat e ‘panum\u00ebrta’, sado p\u00ebrparime t’jen\u00eb b\u00ebr\u00eb, pa p\u00ebrjashtime dhe pa harruar asgje, n\u00eb t\u00eb gjitha fushat e shkenc\u00ebs, pa i shmangur as teknologjikat… q\u00ebkur avancimet teknologjike jan\u00eb nj\u00ebkoh\u00ebsisht dhe instrumentet e shkenc\u00ebs, misterioziteti i “jet\u00ebs” ende nuk \u00ebsht\u00eb kap\u00ebrthyer me mjetet e biologjis\u00eb moderne, mendjet m\u00eb t\u00eb m\u00ebdha t\u00eb njer\u00ebzimit, pavar\u00ebsisht n\u00eb cilin “drejtim” operojn\u00eb apo kan\u00eb operuar, me qasjet e tyre t\u00eb interesit intelektual, her\u00eb t\u00ebrthorazi e her\u00eb drejtp\u00ebrdrejt, sikur prore merren dhe me “enigm\u00ebn interesante”, q\u00eb ne shkurt e quajm\u00eb “jet\u00eb”…<\/p>\n

…gjat\u00eb historis\u00eb intelektuale t\u00eb njer\u00ebzimit, rreth-e-rrotull “jet\u00ebs” kan\u00eb ardhur n\u00eb jet\u00eb panum\u00ebr teori, jan\u00eb kryer panum\u00ebr studime, kemi sa t\u00eb duash teori e teoremash, mendime, paragjykime, sugjerime, hamend\u00ebsime, propozime (her\u00eb shkencore, her\u00eb pseudo-shkencore, her kuazi-shkencore, her\u00eb fot t\u00eb q\u00eblluara, her\u00eb mistike-religjioze, e her\u00eb dhe sharlatanizma, as kjo s’duhet mohuar : ) kemi sa t\u00eb duash fantazi, \u00ebndrra, iluzione, fanta-shkenc\u00eb, ide fantastike… e \u00e7far\u00eb tjet\u00ebr jo, intelekti s’pushon kurr\u00eb, nuk mohohet fakti se 3-4 shekujt e fundit shkencat e mir\u00ebfillta kan\u00eb p\u00ebrparuar shum\u00eb, si linearitet zhvillimor… por dhe si aspekt shum\u00ebdimensional (ose dmth. si aspekt i gjithansh\u00ebm i p\u00ebrparimit), nd\u00ebr avancimet kuptohet hyn dhe biologjia, si deg\u00eb m\u00eb e madhe nga ku deg\u00ebzohen plot deg\u00ebzash e n\u00ebn-shkencash tjera, mir\u00ebpo prap\u00ebseprap\u00eb m\u00ebnyra si do ket\u00eb evoluar jeta shum\u00ebqelizore akoma \u00ebsht\u00eb nj\u00ebra nga enigmat m\u00eb t\u00eb m\u00ebdha t\u00eb biologjis\u00eb…<\/p>\n

…m\u00eb posht\u00eb nj\u00eb material i koh\u00ebve m\u00eb t\u00eb fundit, intervist\u00eb me Profesorin William Ratcliff (GIT – Georgia Institute of Technology) – di\u00e7 si pasqyr\u00eb diskursive, fjala e fundit e shkenc\u00ebs sa i p\u00ebrket origjin\u00ebs s\u00eb jet\u00ebs – ngjitur k\u00ebtu sa m\u00eb shkurt q\u00eb munda, duke i filteruar vet\u00ebm p\u00ebrgjigjet e Prof. Ratcliff (William Croft Ratcliff – Associate Professor and Co-Director of the Interdisciplinary Ph.D. in Quantitative Biosciences – https:\/\/biosciences.gatech.edu\/people\/will-ratcliff ) mir\u00ebpo ia shtova (di\u00e7 si parashtes\u00eb) shkrimin nga autorja e revist\u00ebs Quanta, Yasemin Saplakoglu (di\u00e7 si intro e postuar nga ajo me ndihm\u00ebn e ‘newsletter’, 24 Mars 2025, q\u00ebkur shtojca do sh\u00ebrbente si thuktim abstrakt i gjith\u00eb materies s\u00eb podcast) – dhe dmth. tutje pjes\u00ebt m\u00eb t\u00eb r\u00ebnd\u00ebsishme nga biseda me Prof. Ratcliff, gj\u00ebra sqaruar nga ai gjat\u00eb intervist\u00ebs p\u00ebr revist\u00ebn “Quanta”, podcast i hedhur n\u00eb eter m\u00eb 20 Mars 2025<\/p>\n

***
\nSi ia filloi jeta?<\/strong>
\n(Yasemin Saplakoglu – Newsletter, Quanta M, 24 Mars 2025)<\/em><\/p>\n

Nj\u00eb nga ngjarjet m\u00eb t\u00eb r\u00ebnd\u00ebsishme n\u00eb historin\u00eb e jet\u00ebs tok\u00ebsore ishte shfaqja e qelizave shum\u00ebqelizore. P\u00ebr pjes\u00ebn m\u00eb t\u00eb madhe t\u00eb historis\u00eb s\u00eb jet\u00ebs, e cila filloi af\u00ebrsisht 3.9 miliard\u00eb vjet m\u00eb par\u00eb, kishte vet\u00ebm nj\u00eb m\u00ebnyr\u00eb e t\u00eb gjalluarit: si nj\u00eb qeliz\u00eb e vetme. Format e para t\u00eb jet\u00ebs ishin, n\u00eb t\u00ebr\u00ebsin\u00eb e tyre, nj\u00ebsi mikroskopike t\u00eb vetme, t\u00eb p\u00ebrcaktuara qart\u00eb, q\u00eb riprodhoheshin duke u ndar\u00eb n\u00eb dy qeliza t\u00eb reja, secila prej t\u00eb cilave e vazhdonte rrug\u00ebn e saj. Jeta q\u00ebndroi e till\u00eb (nj\u00ebqelizore) p\u00ebr miliarda vjet.<\/p>\n

Por m\u00eb pas disa nga k\u00ebto qeliza filluan t\u00eb bashk\u00ebpunojn\u00eb mes vete. Ato kaluan nga ekzistenca ‘vetmitare’ n\u00eb jet\u00ebn grupore. Kur nj\u00eb qeliz\u00eb u b\u00eb ‘dy’ (2 qeliza bashk\u00eb) dhe m\u00eb pas m\u00eb shum\u00eb, ato mbet\u00ebn s\u00eb bashku dhe p\u00ebrfundimisht filluan t\u00eb funksionojn\u00eb si nj\u00eb lloj i ve\u00e7ant\u00eb grumbulli i gjall\u00eb: si nj\u00eb organiz\u00ebm shum\u00ebqelizor.<\/p>\n

Pavar\u00ebsisht suksesit t\u00eb vazhduesh\u00ebm t\u00eb jet\u00ebs nj\u00ebqelizore, shfaqja e jet\u00ebs shum\u00ebqelizore ka rezultuar t’jet\u00eb nj\u00eb p\u00ebrshtatje ose adaptim jasht\u00ebzakonisht i suksessh\u00ebm. Jeta p\u00ebr vete e shpiku ‘p\u00ebrshtatjen’ jo nj\u00eb her\u00eb, por t\u00eb pakt\u00ebn nja 20 her\u00eb. Ngjarjet e pavarura evolucionare rezultuan n\u00eb bim\u00ebt shum\u00ebqelizore t\u00eb sotme, n\u00eb k\u00ebrpudhat dhe n\u00eb kafsh\u00ebt. Karakteristika ky\u00e7 e adaptimit shum\u00ebqelizor \u00ebsht\u00eb se mund\u00ebson ndarjen e pun\u00ebs (funksioneve): brenda nj\u00eb organizmi t\u00eb vet\u00ebm, qelizat i plot\u00ebsojn\u00eb rolet specifike, duke i p\u00ebrjashtuar t\u00eb tjerat.<\/p>\n

Trupat tan\u00eb, psh., p\u00ebrb\u00ebhen nga triliona qeliza me identitete dhe detyra t\u00eb ndryshme. Qelizat e imunitetit i luftojn\u00eb trupthat e jasht\u00ebm, ‘pushtuesit’ e organizmit. Qelizat nervore na ndihmojn\u00eb t\u00eb l\u00ebvizim, t\u00eb ndjejm\u00eb, t\u00eb mendojm\u00eb. Qelizat e zemr\u00ebs e pompojn\u00eb gjakun gjithandej trupit ton\u00eb.<\/p>\n

Duke i ndar\u00eb pun\u00ebt mes qelizave, organizmat shum\u00ebqelizor\u00eb mund t\u00eb rriten n\u00eb dy drejtime, si m\u00eb t\u00eb m\u00ebdhenj por dhe m\u00eb kompleks\u00eb, e po ashtu dhe t\u00eb zhvillojn\u00eb m\u00ebnyra t\u00eb reja jetese. Mir\u00ebpo jeta shum\u00ebqelizore e ka koston e vet: mbijetesa varet nga funksionimi i nj\u00eb sistemi t\u00eb nd\u00ebrlidhur me k\u00ebrkesa t\u00eb larta energjitike, n\u00eb t\u00eb cilin sistem vdekja e disa qelizave mund ta shkaktoj\u00eb dhe vdekjen e pjes\u00ebs tjet\u00ebr.<\/p>\n

M\u00ebnyra se si evoluoi jeta shum\u00ebqelizore \u00ebsht\u00eb nj\u00ebri nga misteret m\u00eb t\u00eb m\u00ebdha t\u00eb biologjis\u00eb. Afatet, linjat kohore jan\u00eb t\u00eb turbullta, t\u00eb paqarta. Nj\u00ebsoj t\u00eb paqarta jan\u00eb dhe arsyet. Provat si ‘dokumente’ fosilike p\u00ebr pjes\u00ebn m\u00eb t\u00eb madhe t\u00eb historis\u00eb s\u00eb jet\u00ebs thjesht nuk jan\u00eb ekzistente. T\u00eb dh\u00ebnat fosilike q\u00eb i kemi n\u00eb dispozicion sugjerojn\u00eb se jeta shum\u00ebqelizore filloi t’jet\u00eb m\u00eb e ‘zakonshme’ rreth 600 milion\u00eb vjet m\u00eb par\u00eb. Por prova t\u00eb tjera evidente sugjerojn\u00eb se organizmat shum\u00ebqelizor\u00eb t\u00eb thjesht\u00eb mund t’ken\u00eb ekzistuar dhe rreth nj\u00eb miliard vjet m\u00eb par\u00eb.<\/p>\n

Kjo pasiguri nuk i ka penguar shkenc\u00ebtar\u00ebt t\u00eb cil\u00ebt duan ta gjurmojn\u00eb origjin\u00ebn dhe historin\u00eb e jet\u00ebs komplekse. Disa prej tyre k\u00ebrkojn\u00eb t\u00eb gjejn\u00eb fosile organizmash t\u00eb vegj\u00ebl apo dhe molekula, nd\u00ebrsa t\u00eb tjer\u00eb p\u00ebrpiqen t\u00eb kultivojn\u00eb strategji laboratorike shum\u00ebqelizore nga organizmat nj\u00ebqelizor. Teorit\u00eb jan\u00eb t\u00eb shumta dhe shumica e teorive nuk p\u00ebrshtaten s\u00eb bashku. Mir\u00ebpo duke patur parasysh q\u00eb jeta shum\u00ebqelizore ka evoluar aq shum\u00eb her\u00eb, at\u00ebher\u00eb s’\u00ebsht\u00eb nevoja q\u00eb shkenc\u00ebtar\u00ebt t\u00eb kufizohen n\u00eb nj\u00eb shpjegim t\u00eb vet\u00ebm. \u00c7do studim i ri dhe eksperiment ideatik na afron m\u00eb shum\u00eb drejt\u00eb t\u00eb kuptuarit t\u00eb momentit kritik evolucionar q\u00eb e mund\u00ebsoi ekzistenc\u00ebn ton\u00eb.<\/p>\n

N\u00eb “Eksperimentin e Evolucionit Afatgjat\u00eb Shum\u00ebqelizor”, Will Ratcliff (Multicellularity Long-Term Evolution Experiment – Georgia Institute of Technology) merret me kultivimin e ‘kolonive’ nj\u00ebqelizore n\u00eb shkall\u00ebt kohore t\u00eb 10.000 brezave, me q\u00ebllim p\u00ebr t\u00eb evoluar forma t\u00eb reja t\u00eb shum\u00ebqelizore. N\u00eb v. 2021 ai publikoi nj\u00eb zbulim t\u00eb madh, duke treguar se n\u00eb vet\u00ebm dy vjet, “tharmi” (nj\u00ebqelizor) u rrit n\u00eb nj\u00ebsi shum\u00ebqelizore aq t\u00eb madhe sa t\u00eb shihej me sy t\u00eb lir\u00eb.<\/p>\n

Ratcliff merret gjithashtu me qasje teorike. Koh\u00ebt e fundit ai p\u00ebrdori nj\u00eb model kompjuterik p\u00ebr t’kuptuar pse qelizat prokariote, si\u00e7 jan\u00eb bakteret – t\u00eb cilat, ndryshe nga qelizat tona eukariote, s’kan\u00eb b\u00ebrtham\u00eb dhe organele – nuk e evoluan kurr\u00eb versionin e tyre shum\u00ebqelizor.<\/p>\n

Fizika e ujit t\u00eb ftoht\u00eb t\u00eb detit, qindra miliona vjet m\u00eb par\u00eb, mund t’ket\u00eb qen\u00eb nj\u00eb tjet\u00ebr faktor p\u00ebr evolucionin e jet\u00ebs shum\u00ebqelizore t\u00eb kafsh\u00ebve, raportoi Veronique Greenwood p\u00ebr Quanta, Korrikun e kaluar. Uji i ftoht\u00eb, si\u00e7 psh. uji n\u00eb Tok\u00eb kur planeti ishte i mbuluar me akull rreth 700 milion\u00eb vjet m\u00eb par\u00eb, \u00ebsht\u00eb m\u00eb i dendur dhe p\u00ebr k\u00ebt\u00eb arsye m\u00eb i v\u00ebshtir\u00eb p\u00ebr t’notuar n\u00eb t\u00eb nga organizmat nj\u00ebqelizor.<\/p>\n

N\u00eb nj\u00eb eksperiment, paleobiologu Carl Simpson (Uni. of Colorado Boulder), pa se algat nj\u00ebqelizore filluan t\u00eb sillen kolektivisht teksa notonin p\u00ebrgjat\u00eb shum\u00eb brezave, duke e p\u00ebrshkuar mas\u00ebn xhelatinore gjithnj\u00eb e m\u00eb t\u00eb dendur n\u00eb pjatat laboratorike, duke i simuluar kushtet e ngjashme me ato q\u00eb, eventualisht mund ta ken\u00eb shkaktuar t\u00eb pakt\u00ebn nj\u00eb form\u00eb shum\u00ebqelizore.<\/p>\n

Shum\u00eb shkenc\u00ebtar\u00eb supozojn\u00eb se organizmat e par\u00eb shum\u00ebqelizor filluan si kolektivitet i qelizave identike, p\u00ebrpara se qelizat t’ia fillonin me ‘specializimet’. Mir\u00ebpo provat e fundit sugjerojn\u00eb se krijesat e lashta nj\u00ebqelizore ishin tashm\u00eb \u00e7udit\u00ebrisht komplekse. Ato qeliza e bartnin potencialin e ‘specializimit’ gjat\u00eb gjith\u00eb koh\u00ebs, duke u ve\u00e7uar si forma t\u00eb reja p\u00ebr t’kryer detyra t\u00eb caktuara, p\u00ebrpara se t’riktheheshin n\u00eb form\u00ebn standarde – t\u00eb ngjashme me qelizat tona staminale – si\u00e7 raportoi Jordana Cepelewicz p\u00ebr Quanta, n\u00eb v. 2019. K\u00ebto gjetje sugjerojn\u00eb se specializimi qelizor mund t’kishte ekzistuar shum\u00eb m\u00eb p\u00ebrpara se jeta shqumqelizore ta b\u00ebnte at\u00eb si ve\u00e7ori m\u00eb t\u00eb p\u00ebrhershme.<\/p>\n

***
\nOrigjina e Jet\u00ebs – Diskutim rreth Evolucionit t\u00eb Jet\u00ebs Shqum\u00ebqelizore, me Will Ratcliff<\/strong> (Georgia Institute of Technology) – pak dhe p\u00ebr arsye t\u00eb gjat\u00ebsis\u00eb s\u00eb tekstit… ngeli n\u00eb Anglisht sepse duhej koh\u00eb, m\u00eb vjen keq, m\u00eb s\u00eb miri do t’ishte n\u00eb Shqip, por s’pata koh\u00eb m\u00eb shum\u00eb, artikullin si ‘intro’ m\u00eb lart po jua nis t\u00eb p\u00ebrkthyer, nd\u00ebrsa p\u00ebr materien nga Podcast-interview po e ngjes edhe linkun edhe tekstin e shkurtuar<\/em>…<\/p>\n

[ https:\/\/www.quantamagazine.org\/how-did-multicellular-life-evolve-20250320\/<\/a> – Podcast hosts: Janna Levin, Steven Strogatz, March 20, 2025 ]<\/p>\n

We contain approximately 40 trillion cells. We want to understand how initially dumb clumps of cells\u2026 can evolve into increasingly complex multicellular organisms, with new morphologies, cell-level integration, division of labor, and differentiation.
\nCells have a nucleus, which contains the DNA that encodes the genetic information that the cells use to perform their basic functions that, you know, then makes proteins that are the action parts of a cell. And so, cells are these fantastic biological machines, right, in which you have this concentrated soup of highly functional macromolecules.<\/p>\n

Life wasn\u2019t always cellular. Cells are like one of these great innovations of life. And once sort-of cells evolved, they really took off, and it has been the sort-of basic building block of life for the last three-and-a-half billion years. Multicellular organisms are a kind of organism that is built upon the basis of cells, but where many cells live within one group and function essentially collectively. So, we are a multicellular organism, we contain approximately 40 trillion cells, which divide labor and perform all these various functions to allow us to do things in the multicellular, you know, environment – run around, have eyes, see things, talk on podcasts – that wouldn\u2019t be possible for single-celled organisms, right? So, the evolution of multicellularity is a way of increasing biological complexity by taking what were formerly free-living individuals and turning them into parts of a new kind of individual: a multicellular organism. And it\u2019s evolved, not once or twice, but many times. We don\u2019t really have a great number, because we keep discovering more, actually. But there\u2019s at least 50 independent transitions to multicellularity that we know of.<\/p>\n

As people, we tend to be very animal-centric, but then there\u2019s a whole slew of things that are a little bit more esoteric. There\u2019s cellular slime molds that live on land that, you know, move around like a slug, and then will grow as single cells and come together, like a transformer, to then do something as a group, you know. So, there\u2019s different flavors of multicellularity that have evolved in different lineages. And I think partly we\u2019ve known about this for a while, but especially as we develop the tools to understand bacteria and archaea – the big domains of single-cell life that have been around for a very long time – we\u2019re finding more and more types of multicellular bacteria and archaea that we just didn\u2019t know existed, because, unless you\u2019re looking at them with a high-powered microscope or using other advanced techniques, you can\u2019t just see it.<\/p>\n

We have reasons to think that cellular life exists around three-and-a-half billion years ago, and Earth is only four-and-a-half billion years old total. So, it\u2019s fairly early in Earth\u2019s, you know, history as a planet. But it probably happened earlier, and by that time they\u2019ve already done the things that are required to evolve cells, and have all these basic building blocks of life, like DNA, which contains the, sort-of, code of the organism.<\/p>\n

The evolution of multicellularity is broader than just animals. It\u2019s a process, through which lineages that are single-celled can form groups, which then become units of adaptation. Evolutionary units that can get more complex through, you know, natural selection. And the Cambrian explosion is an incredible period where animals, which had already been around for probably 100 million years or more, just start to figure out all of these innovations which are hallmarks of extant animals. Before the Cambrian explosion, things were soft and gelatinous and didn\u2019t have eyes or skeletons. It\u2019s questionable if they had brains. They don\u2019t have any of these things. And then in a relatively short period of time, just a few tens of millions of years, all of these things show up. And we think it\u2019s probably due to these, like, ecological arms races, where you have predators attacking prey. The prey start evolving defensive mechanisms. You have just this explosion of animal complexity in what appears to be a very short period of time in geological terms.<\/p>\n

The interesting thing about multicellularity, it\u2019s evolved in very different time periods and different lineages. So, cyanobacteria were evolving multicellularity with honest-to-goodness development and cell differentiation around 3 billion years ago. It doesn\u2019t take that long after you get cells that you start to get multicellular organisms evolving.<\/p>\n

The red algae, which are a seaweed, they begin evolving multicellularity around a billion years ago. The green algae start doing it around then too. Fungi, probably anywhere between a billion and half a billion years ago. Plants, we know that pretty well, that\u2019s about 450 million years ago. Animals, they really start to take off around 600 million years ago. Again, it\u2019s really hard to put an accurate date on that, so we have to be, sort of you know, hedgy. And then the brown algae – the most complex kelp – they actually only began evolving in multicellularity around 400 million years ago.<\/p>\n

I think we should not think of it as one process, but something where there are ecological niches available for multicellular forms, and there has to be a benefit to forming groups and evolving large size. That benefit has to be fairly prolonged. And most of the time, there isn\u2019t, but occasionally there will be an opportunity for a lineage to begin exploring that ecology and not be inhibited by something else that\u2019s already in that space. That might be why something like animals has only evolved once, because once you already have an animal, then it suppresses any other innovation to that space, like a first-mover advantage.<\/p>\n

John Tyler Bonner is an evolutionary biologist, who worked on multicellularity decades ago, and he has this quote, that there\u2019s always room one step up on the size scale. The ecology of single-celled organisms, that\u2019s a niche that\u2019s been battled over for billions of years. And there\u2019s lots of ways to make a living in that space and that\u2019s why we are in a world of microbes. But, once you start forming multicellular groups, you can participate in a whole new ecology of larger size. You might be immune to the predators that were eating you previously, or maybe you\u2019re able to overgrow competitors for a resource like light. If you imagine that you\u2019re an algae growing on a rock in a stream, single-celled algae will get the light but, hey, if something can form groups, now they\u2019re intercepting that resource before it gets to you. They win. Groups also have advantages when it comes to motility and even division of labor and trading resources between cells.<\/p>\n

There\u2019s many different reasons to become multicellular. And there isn\u2019t just one reason why a lineage would evolve multicellularity. But what you need for this transition to occur is those reasons have to be there, and that benefit has to persist long enough that the lineage sort of stabilizes in a multicellular state and doesn\u2019t just go back to being single-celled or die out. You can imagine there\u2019s lots of ephemeral reasons to become multicellular, and then they go away, and then the single-celled competitors just win again.<\/p>\n

Big picture, we want to understand how initially dumb clumps of cells, cells that are one or two mutations away from being single-celled, don\u2019t really know that they\u2019re organisms – they don\u2019t have any adaptations to being multicellular, they\u2019re just a dumb clump – how those dumb clumps of cells can evolve into increasingly complex multicellular organisms, with new morphologies, with cell-level integration, division of labor, and differentiation amongst the cells. Just like, we want to watch that process of how do these simple groups become complex.<\/p>\n

And this is, like, one of the biggest knowledge gaps in evolutionary biology. I mean, in my opinion. But it\u2019s something where we can use the comparative record. We know multicellularities evolved dozens of times, and the only truly long-term evolution experiments we\u2019ll have access to are these ones that happened on Earth over the last hundreds of millions or billions of years. But because they\u2019re so old, and because those early progenitors, those early transitional steps, aren\u2019t really preserved, we don\u2019t really know the process through which simple groups evolve into increasingly complex organisms.<\/p>\n

What we\u2019re doing in the lab is: we are evolving new multicellular life using in-laboratory directed evolution over multi-10,000 generation timescales, to watch how our initially simple groups of cells – dumb clumps of cells – figure out some of these fundamental challenges. How do you build a tough body? How do you overcome diffusion limitation when you, after you\u2019ve built a tough body and made a big group? How do you start to divide labor amongst yourselves when you only have one genome? How can you make that one genome be used for different purposes in different cells to underpin new behaviors at the multicellular level? Does this thing become entrenched in a multicellular state which prevents it from ever going back, or at least going back easily, to being single-celled?<\/p>\n

We\u2019re watching this stuff occur with a long-term evolution experiment, which, we\u2019re now on generation 9,000 of what we call the Multicellularity Long-Term Evolution Experiment\u2026 M.U.L.T.E.E\u2026 MuL-TEE\u2026 absolutely a pun. It\u2019s also named in homage of the long-term evolution experiment, which is a 70,000 and counting generation experiment with single-celled E. coli, started by Rich Lenski and now run by Jeff Barrick. So, we\u2019re basically trying to do something similar, but in the context of understanding how multicellular organisms evolve from scratch. How they can, sort of, co-opt basic physics and bootstrap their way to becoming organisms.<\/p>\n

It is a wild idea to try to make multicellularity happen in the lab – it’s kinda directed evolution. How to encourage this transition? We start out with a single-celled yeast. We did some preliminary experiments where we evolved them in an environment – it\u2019s just a test tube that\u2019s being shaken in incubator – where it\u2019s good to grow fast, because they have access to sugar water, and the faster you eat the sugar water, the more babies you can make. And it\u2019s, you know, scramble competition, everyone has access to the same food. And then at the end of the day, we put them through a race to the bottom of the test tube, where we just put them on the bench for initially five minutes, but as they get better and better at sinking quickly, we make that time shorter and shorter to keep the pressure on them. And here, there\u2019s an advantage to being big, because big groups sink faster through liquid media than small groups. This is just due to, you know, surface area-to-volume scaling relationships. Bigger groups will have more, you know, gravity pulling them down relative to the friction from their surface. You take the winners of that race to the bottom, the best ones. They go to fresh media and you just, kind of, keep repeating this very simple process.<\/p>\n

Yeast have a budding mechanism, where a mother cell will pop off a baby, from one of their poles, and then they can keep dividing and adding new cells to the same cell. In our early experiments that were just open-ended, we got these simple groups forming that have this beautiful fractal geometry. We had this easy mutation – it turns out it\u2019s just one mutation in a regulatory element of the cell – that prevents daughter cells from separating. Super simple. Every time the cells divide, they pop off a baby but remain attached. And so, you get this sort of growing fractal branching pattern. Imagine something like a coral, or maybe like a branching plant. They kind of look like that, and they end up becoming more spherical with these you know nice branches. We call our yeast snowflake yeast. And you have this life cycle where they grow until they start to have packing-induced strain, they run out of space. And now if they add more cells, they just break a branch. And so, you have this emergent life cycle where they\u2019re growing, they\u2019re jamming, they\u2019re breaking branches. Those little baby snowflakes pop off. And they even have a genetic bottleneck in this life cycle, in that the base of the branch that came off is one cell. So, as mutations arise, they get segregated between groups, and every group is basically clonal. Every cell in the group has the same genome.<\/p>\n

The big mutation is the one that doesn\u2019t let the daughter detach from the mother. That\u2019s the key thing for forming simple groups. We figured out what this mutation was, and when we started our long-term evolution experiment, we started them with basically one genotype, so one clone, that already had this mutation engineered into it, but with replicate populations. Because what we want to understand is, how do these simple groups of cells evolve to become more complex? And I don\u2019t want that to be confounded by the mechanism through which they form groups in the first place. We have actually 15 parallel evolving populations, that started out the same in the beginning, but we actually have different metabolic treatments for them. One of them, is taking all their sugar, and they are burning it up with aerobic respiration, using air from the environment to respire their sugar. One of them, we broke their mitochondria in the very beginning, so they don\u2019t get to use respiration, they can only ferment, and they get a much lower energetic payoff from that. But they don\u2019t have to worry about oxygen diffusion anymore. So, sort of a trade-off there. And then one of them can do both; it first ferments and then it respires.<\/p>\n

We thought initially, that the ones that could use oxygen would be the ones that evolved the most interesting multicellular traits. But it turns out that they\u2019ve actually stayed very simple for almost 10,000 generations. They haven\u2019t done that much in the last 8,950 generations. They peaked early, and they\u2019re only about six times bigger than the ancestor, and we don\u2019t see any beginnings of cell differentiation. They\u2019re just simple kind of bigger snowflakes. The anaerobic ones, they have evolved to be more than 20,000 times bigger than their ancestor.<\/p>\n

It turns out that this is because there\u2019s a trade-off that\u2019s introduced by oxygen. If you form a body, and oxygen is this valuable resource that if you get it you can grow a lot more, but it can\u2019t diffuse very far into the organism, then all of a sudden, the bigger you are, the smaller a proportion of your cells are able to access this really valuable resource, and your growth rate just falls off a cliff.<\/p>\n

Your interior is so small compared to your surface. The bigger you are, the larger your radius is, the smaller a proportion of your biomass has access to oxygen. And so, in our case, the anaerobic line, they\u2019ve done the interesting things because they\u2019re not being constrained by oxygen. They\u2019ve evolved large size. They\u2019ve evolved all these interesting behaviors. And they\u2019re solving all these fundamental multicellular problems.<\/p>\n

The anaerobic ones, because they don\u2019t get this a sugar high from the availability of oxygen early on, they have to be resourceful. They have to come up with all kinds of other innovations, and they do. The ones that have access to oxygen, as they get bigger and bigger, their slower and slower growth rates really push back against them, and kind of act in the opposite direction of any benefits that come from size. But if you remove oxygen, now bigger is better. The smaller ones go extinct and the bigger ones win. And then they figure out a way to get bigger. And they can really push the envelope on size and explore large size in a way that the ones with oxygen can\u2019t, because they\u2019re getting pushed back on by growth rate. But then as they get bigger and tougher, they actually start to have real trade-offs that are created by forming big bodies. They\u2019re so big that now they\u2019re struggling to bring sugar into these groups, because they\u2019re actually becoming macroscopic. You know, they\u2019re bigger than fruit flies now. They\u2019re large.<\/p>\n

They also face another constraint. I mentioned that they grow and would normally break due to physical strain arising from packing problems. But they solve that, by figuring out how to make tough bodies, by making their cells long enough that they actually wrap around one another and entangle. This is now a vining procedure where, if you break one branch of a vine, you know, the ivy is still not coming off your shed. Because entanglement percolates those forces throughout the entire, entangled structure. And so now, you don\u2019t just break one bond to break apart the snowflake yeast, you have to break apart hundreds of thousands. And it becomes much, much tougher as a material. And we even understand the genetic basis of this, all the way up to the physics, it\u2019s really cool to be able to watch mutations arising that change the properties of cells that underpin emergent multicellular changes, which natural selection can see and can act upon, and can, sort-of, drive innovation in that multicellular space.<\/p>\n

– – –
\n[ Janna Levin<\/strong> – Comment: ]
\nHe\u2019s got this hypothesis going on on the basis of what we believe about the importance of oxygen, and we even talk about it when we\u2019re looking for other planets and life on other planets. Will there be oxygen, and is there water? And all this stuff that we\u2019re really so certain is what\u2019s needed to really accelerate life and life radiating. But now, he\u2019s amazingly saying, well maybe, maybe that\u2019s just not the case here. You have these oxygen hogs that got stuck. Evolution is not just mutation. It\u2019s mutation and environmental pressure. So, it\u2019s the hostility of the environment in some sense that drives the mutation<\/em>.
\n– – –
\nClusters versus organisms. What would make an organism different than a colony? And how do you know which kind of thing you\u2019re getting through these selection experiments? This question really cuts to the core of what do we mean by multicellularity. And I think a lot of confusion in my field, for the last half a century, has come down to poorly resolved questions of philosophy about what do we mean by these words, and people inadvertently speaking at cross purposes.<\/p>\n

Part of this is that the word multicellular really means three different things, and we\u2019re not very clear with our language. It\u2019s treated as a noun in English to say, you know, multicellularity, but it\u2019s really an adjective which modifies different nouns. So, you could have a multicellular group. That\u2019s just, you know, a group that contains more than one cell. You could have a multicellular Darwinian individual, and that is a multicellular group which participates in the process of evolution as an entity at the group level. So, something which reproduces, where mutations can arise which generate novelty in a multicellular trait, and which natural selection can act on and cause evolutionary change in a population of groups. That\u2019s adaptation at the group level so that would be a multicellular Darwinian individual.<\/p>\n

And then you have multicellular organisms. And the sort of philosophical distinctions of what\u2019s an individual and what\u2019s an organism, there\u2019s been a lot of work done in the last 20 years, and I\u2019m pretty happy with the results of where that field is right now, which is that organisms are functional units. Organisms have integration of parts and work well at the organismal level with, you know, high-function minimal-conflict.<\/p>\n

We are all three. We\u2019re a group. We\u2019re a Darwinian individual. And we\u2019re organisms. And so, the distinction is that are, sort of, progressively higher bars for how you get to these additional steps, and they tend to occur sequentially. The first step would be forming a group. The second step would be making that group capable of Darwinian evolution. And then, as a consequence of group adaptations, you can get organisms, which would be functional integration of cells, which are now parts of the new group organism.<\/p>\n

And so, a trait that would be diagnostic of that would be cellular specialization or differentiation, especially if it comes down to reproductive specialization. People love that in evolutionary biology because if cells give up their direct reproduction, they\u2019re no longer making offspring, that\u2019s something which is a behavior that you really can\u2019t ascribe to the direct fitness interests of that cell.<\/p>\n

Your skin cells will never make a new You. Never. They are entrenched in the, not on the line of descent. But it\u2019s okay, because they are helping you make you know your reproductive cells reproduce. And so, the vast majority of our cells are not directly on the line of descent, but that is a derived state.<\/p>\n

Originally, every cell made copies of itself. They were on the line of descent. Originally, simple groups don\u2019t have this kind of reproductive specialization. But over millions of generations of multicellular adaptation, you get organisms that have, now, cellular parts, where those parts work together to allow the organism to do things that it couldn\u2019t have done before, and an important part of that is specialization.<\/p>\n

What does it mean to be in the line of descent, in relation to skin cells versus what, like gonadal cells? Sperm and eggs, for example, and this isn\u2019t a strict requirement. You could have something like plants that don\u2019t have this type of line of descent segregation. But nonetheless, you know, if you look at a tree, it makes flowers, it makes seeds. You have this differentiation into cells that will be the reproductive structures, and those that don\u2019t. If you\u2019re a wood cell, you just give up your life to make wood. Wood is basically a series of tubes. You differentiate into a tube, then you die. They\u2019re doing it for the good of the multicellular group, and it\u2019s also for the good of their own genome. Because usually those that are on the line of descent are related to them. And that\u2019s how you, kind of, square it. So, there\u2019s apparent altruism at the level of the cell, but there isn\u2019t really altruism at the level of the genome.<\/p>\n

When talking about Darwinian adaptation at the level of the group, Richard Dawkins said that there\u2019s no selection except at the level of the gene. And Stephen Jay Gould would say there\u2019s no selection except at the level of the individual. I think there should be some sociological studies on this, in evolutionary biology, because it has been much more, do you believe the consensus rather than, like, actually rigorously thinking through it. And in the last 15, 20 years, I\u2019d say the anti-group selection sentiment, that was very powerful all the way up through the 2000s, has mostly melted away, as people have embraced more pluralistic philosophies that, like, there is sort of one evolutionary process, you can view it through different perspectives, sometimes it makes more sense to use a group selection model. And, I think if we\u2019re thinking about individuals, in this, in the Gould sense, selection acting on the traits of individuals, for multicellular organisms those individuals are groups.<\/p>\n

It\u2019s always a little bit of a confusing distinction, I mean, the individual is made of other things. People are happy to sort-of round them up to just one, but there was a point where it wasn\u2019t just one. It was a simple group, and it wasn\u2019t so clear that that group was an individual. Like a snowflake yeast, you can break off any cell, put it into its own flask of media, and it\u2019ll turn back into another snowflake yeast. That wouldn\u2019t happen with one of my arm cells. If you go for a really long time in my experiment, that stops happening. But in the beginning, cells are just in groups as vehicles. And then over time, they gain enough adaptations, as a consequence of selection acting on the traits of groups, and really caring about the fitness of groups, that cell-level fitness, outside of the context of groups, starts to really take it on the nose. They don\u2019t do so well as being outside of groups anymore. And you know, they\u2019re evolving, the beginnings of division of labor, different cell states from one genome. This is unpublished work, so I want to be appropriately hedged here. But we\u2019ve done like single-cell RNA sequencing, and we can see new cell states evolving over the five thousand-generation timescale. We go from one, sort of, putative cell type to three. And we think we know what they\u2019re doing, like we think it is actually adaptive differentiation, as opposed to just sort of noisy chaos. The cells have differentiated in their gene expression, into different sort of behaviors.<\/p>\n

By seeing these interesting transitions in the lab, by inducing them through the selection the researcher is putting on – to what extent these multicellular transitions that are being provoked shed any light on what happened historically in the wild? This question is an important scientific question. In order for our experiments to have meaning, they need to be somewhat generalizable. Now, I think the caveat here is that there is no one answer to how multicellularity evolved. It likely evolved in very different ways, and for very different reasons, in plants and animals and mushroom-forming fungi. It\u2019s not a single thing.<\/p>\n

But nonetheless, the thing that does unite it all is this evolutionary process. You have to have group formation, those groups become units of selection, and they turn into organisms as a consequence of group adaptation. And that evolutionary process, while it might play out in different ways in different lineages, some of these things are fundamental. So that transition to individuals that become organisms, that\u2019s universal. And size is universal, and the physical side-effects that come with size, scaling laws, challenges with diffusion, and the opportunities that come to break those trade-offs through innovations, those things are all generalizable, even if they take different paths in different lineages, because they\u2019re all proximate creatures of their environment and their gene pool. And we\u2019ve never seen those processes play out in nature. And I don\u2019t know that we ever will, because they\u2019re historical things that we don\u2019t have the actual samples to see it.<\/p>\n

And one of the things that we can do is, while we\u2019re not saying this is how multicellularity evolved in any one lineage, what we\u2019re saying is this is how multicellularity can evolve, and this is how some of these things that, maybe looking in hindsight, you think you need really complex developmental control\u2026 oh, actually it turns out you don\u2019t, because physics gives you all these things for free, that are kind of noisy, but they work, and you can bootstrap those into your evolutionary life cycle and build upon them, without necessarily having to evolve those traits for a reason. A lot of things in our experiment have turned out to be easier than we expected, and while the details may differ, I suspect that some version of these things that we\u2019re seeing in our experiment play out in the different transitions in nature.
\n 
\n <\/p>\n","protected":false},"excerpt":{"rendered":"

William Ratcliff – (Origjina e Jet\u00ebs) Evolucioni i Jet\u00ebs Shum\u00ebqelizore (di\u00e7 si pasqyr\u00eb diskursive, fjala e fundit e shkenc\u00ebs sa i p\u00ebrket origjin\u00ebs s\u00eb jet\u00ebs) senad guraziu, ars poetica, mars 2025 – pak fjale, sqarim… …nuk mohohet fakti se jeta,… Lexo →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[80],"tags":[],"class_list":["post-17074","post","type-post","status-publish","format-standard","hentry","category-zhvillimi-tekno-shkencor"],"_links":{"self":[{"href":"https:\/\/letrat.eu\/index.php?rest_route=\/wp\/v2\/posts\/17074","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/letrat.eu\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/letrat.eu\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/letrat.eu\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/letrat.eu\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=17074"}],"version-history":[{"count":0,"href":"https:\/\/letrat.eu\/index.php?rest_route=\/wp\/v2\/posts\/17074\/revisions"}],"wp:attachment":[{"href":"https:\/\/letrat.eu\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=17074"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/letrat.eu\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=17074"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/letrat.eu\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=17074"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}