Ukuzivelela Kwezinto—Ubuxoki Nenyaniso

UNjingalwazi uRichard Dawkins, isazinzulu esikholelwa ekuziveleleni kwezinto¹⁶ sathi: “Ingcamango yokuba izinto zazivelela ayinakuphikiswa kanye njengaleyo yokuba ilanga likho yaye likhupha ubushushu.” Kakade ke, uhlolisiso nezinto esizibonayo zingqina ukuba ilanga lishushu. Ngaba ngokwenene ayinakuphikiswa nayo imfundiso yokuba izinto zazivelela?

Ngaphambi kokuba siphendule loo mbuzo, kukho nto ithile emele isicacele. Izazinzulu ezininzi ziye zaphawula ukuba, emva kwexesha elide kuye kwenzeke utshintsho oluncinane kwinzala yezinto eziphilayo. Ngokomzekelo, abantu banokukhetha uhlobo oluthile lwezinja luzalise izinja zolunye uhlobo ngenjongo yokuba ekugqibeleni inzala yazo ibe nemilenze emifutshane okanye uboya obude kunezo zinja izalwa zizo.a Ezinye izazinzulu zibhekisela kolu tshintsho luncinane ngokuthi ‘kukuzivelela kwezinto kancinane’ [microevolution].

Noko ke, abo bakholelwa ekubeni izinto zazivelela bafundisa ukuba emva kweebhiliyoni zeminyaka, olu tshintsho luncinane luye lubangele iinguqu ezinkulu ezenza intlanzi ijike ibe sisilwanyana esiza kuphila emanzini nasemhlabeni, zize iimfene zibe ngabantu. Iinguqu ezinkulu ngolo hlobo kubhekiselwa kuzo ngokuthi “kukuzivelela kwezinto okuphawulekayo (macroevolution).”

UCharles Darwin wafundisa into yokuba utshintsho oluncinane esilubonayo lubonisa ukuba utshintsho olukhulu lunako ukwenzeka ngoxa kungekho bani wakha walubona.¹⁷ Wayevakalelwa kukuba izinto zokuqala eziphilayo, ekuthiwa zazingaphucukanga kangako, zathi ngcembe “zitshintsha kancinane” ngokuqengqeleka kweminyaka kwatsho kwavela izigidi zezinto ezahlukahlukeneyo eziphila emhlabeni ngoku.¹⁸

Le ngcamango ibonakala isengqiqweni kwabaninzi. Bazibuza oku, ‘ukuba utshintsho oluncinane lunokwenzeka kwizinto eziphilayo zohlobo olunye, yintoni enokubangela ukuba ukuzivelela kwezinto kungabangeli utshintsho oluphawulekayo emva kwexesha elide?’b Kodwa ke, enyanisweni imfundiso yokuba izinto zazivelela isekelwe kwiintsomi ezintathu. Qwalasela nje oku kulandelayo.

Ubuxoki 1. Ukuguquka kwemizila yemfuza kubangele kwakho izinto eziyimfuneko ukuze kuvele izidalwa ezitsha. Imfundiso yokuzivelela kwezinto ngokuphawulekayo isekelwe kwibango lokuba ngokusuka nje kuguquke imizila yemfuza kwizilwanyana nakwizityalo kunokuvela uhlobo olutsha olungenanto yakwenza kwaphela nolo luphuma kulo.¹⁹

Inyaniso. Iimpawu ezininzi zesityalo okanye isilwanyana zilawulwa yimiyalelo equlethwe yimizila yemfuza yaso efumaneka kanye ngaphakathi kwinucleus yeseli nganye.c Abaphandi baye bafumanisa ukuba ukuguqulwa kwale mizila yemfuza kunokuvelisa iimpawu ezithile kwinzala yezilwanyana neyezityalo. Kodwa ke, ngaba ukuguqulwa kwemizila yemfuza kuvelisa inzala yolunye uhlobo olwahluke ngokupheleleyo? Yintoni etyhilwa luhlolisiso lwemizila yemfuza oluye lwenziwa kangangenkulungwane?

Ngasekupheleni kweye-1930, izazinzulu zazithe phithi yingcamango entsha. Zazicinga ukuba ekubeni izinto eziphilayo zixhomekeke ekulungelweni yiloo ndawo zikuyo ukuze ziqhubeke zikho, ukutshintsha kwemizila yemfuza yazo kwakunokuvelisa iintlobo ezahluke ngokupheleleyo kwezo ziphuma kuzo. Ngenxa yoko, ngoku zicinga ukuba xa abantu benokukhetha iintlobo ezithile baze batshintshe imizila yazo yemfuza, banokuphumelela kweli linge. UWolf-Ekkehard Lönnig, isazinzulu kwiMax Planck Institute for Plant Breeding Research eJamani wathi: “Iingcali ngezinto eziphilayo kuquka iingcali zemizila yemfuza nabafuyi abakwazi kuyivala imilomo.”d Yintoni le yayibonwabise kangaka? ULönnig, owachitha iminyaka emalunga nama-30 ephanda ngokutshintshwa kwemizila yemfuza yezityalo, wathi: “Aba baphandi babecinga ukuba lide lafika ixesha lokwenza iinguqu kwiindlela eziqhelekileyo zokuvelisa iintlobo ezithile zezilwanyana nezezityalo. Babecinga ukuba xa benokukhetha iintlobo ezithile baze baguqule imizila yemfuza yazo, oko kwakunokubanceda bavelise izilwanyana nezityalo zodidi oluphambili.”²⁰ Enyanisweni, abanye babenethemba lokuvelisa iintlobo ezahluke ngokupheleleyo kwezo ziphuma kuzo.

Izazinzulu zaseUnited States, eAsia naseYurophu zaseka uphando olubiza imali eninzi kwiinzame ezazibonakala ziza kuza neziqhamo ngokukhawuleza kule ngcamango yokuzivelela kwezinto eziphilayo. Yaba yintoni imiphumo yolo phando emva kweminyaka engaphezu kwengama-40? Umphengululi uPeter von Sengbusch uthi: “Phezu kwayo nje intywenka yemali eyachithwa apho, yawa phantsi yonke loo mizamo nakuba kwakusetyenziswa imitha.”²¹ ULönnig wathi: “Ngeminyaka ye-1980, ehlabathini lonke atshabalala amathemba nelo hlombe zazinalo izazinzulu. Amazwe aseNtshona ayeka ukuxhasa olu phando lokuvelisa izinto ngokuguqula imizila yemfuza. Zonke izinto ezaveliswa ngale ndlela . . . zafa, ezinye zabuthathaka kunezo zemvelo.”e

Phezu kwawo onke la matiletile, kolu phando luthabathe malunga neminyaka eli-100, nalapho izazinzulu ziye zachitha iminyaka engama-70 zizama ukuvelisa izinto ngokuguqula imizila yemfuza, zitsho zafikelela kwisigqibo ngokuphathelele ukuveliswa kohlobo olutsha nolwahlukileyo lwezinto eziphilayo. Emva kokuhlolisisa bonke obo bungqina, uLönnig wathi: “Ukuguqula imizila yemfuza akunakuze kuvelise uhlobo olutsha nolwahluke ngokupheleleyo lwesityalo okanye isilwanyana. Izazinzulu zifikelele kwesi sigqibo ngenxa yalo lonke uvavanyo nemiphumo eziyifumeneyo kuphando ezalwenza kwinkulungwane yama-20 nasemva kokuhlolisisa izinto ezinokwenzeka.”

Ngaba ukuguqulwa kwemizila yemfuza yezinto eziphilayo kunokuvelisa olunye uhlobo olutsha nolwahluke ngokupheleleyo? Kubonakala kungenakwenzeka oko. Uphando lukaLönnig lwamenza wafikelela kwisigqibo sokuba “enoba umntu angazama kangakanani na ukuguqula uhlobo oluthile lwezinto eziphilayo, kukho imida angasokuze ayitsibe.”²²

Khawucinge nje ngezinto ezinokwenzeka ukuba oku kungasentla kunokwenziwa. Ukuba izazinzulu ezifunde zayityekeza azikwazi ukuvelisa iintlobo ezintsha nezahluke ngokupheleleyo kwiinzame zazo zokuguqula imizila yemfuza, ibinokwenzeka njani ke into yokuba oku kwenzeke ngamabonandenzile? Ekubeni uphando lubonisa ukuba ukuguqula imizila yemfuza akunakuvelisa uhlobo olutsha nolwahluke ngokupheleleyo, yayinokwenzeka njani ke into yokuba kuvele izinto ezahluke ngokuphawulekayo?

Ubuxoki 2. Ukuphila kwezinto ngenxa yendawo ezihlala kuyo kuye kwavelisa iintlobo ezintsha. UDarwin wayekholelwa ukuba izinto ezithile zaziza kuqhubeka ziphila ngenxa yendawo ezihlala kuyo zize ezo zingalungelwayo yiloo ndawo zife. Izazinzulu zanamhlanje ezikholelwa ukuba izinto zazivelela zifundisa ukuba njengoko izinto eziphilayo zazisasazeka, ezinye zazo zaya zitshintsha ngenxa yendawo ezihlala kuyo. Zithi yiloo nto eyabangela ukuba kubekho iintlobo ezintsha nezahluke ngokupheleleyo.

Inyaniso. Njengokuba kuye kwaphawulwa, ubungqina bophando bubonisa phandle ukuba ukuguqulwa kwemizila yemfuza akunako ukuvelisa izityalo okanye izilwanyana ezitsha nezahluke ngokupheleleyo. Sekunjalo, bubuphi ubungqina eziza nabo izazinzulu ezikholelwa ukuba izinto zazivelela ukuxhasa ibango lazo lokuba izinto zixhomekeka kwindawo ezikuyo ukuze ziphile nokuze zivelise uhlobo olutsha? Incwadana enemifanekiso eyapapashwa ngowe-1999 yiNational Academy of Sciences (NAS) yaseUnited States ibhekisela “kwiintlobo ezili-13 zeentaka ezincinane uDarwin awayesenza uphando kuzo kwiZiqithi zeGalápagos, ngoku ezaziwa njengeentaka ezincinane zikaDarwin.”²³

Kwiminyaka ye-1970, iqela elalisenza uphando nelalikhokelwa nguPeter R. noB. Rosemary Grant beYunivesithi yasePrinceton lathi lakuphanda ngezi ntaka lafumanisa ukuba emva konyaka wembalela eyayikwezo ziqithi, iintaka ezazinemilomo emikhulu zazisinda kunezo zinemilomo emincinane. Ekubeni ubukhulu nokumila kwemilomo kuyenye yeendlela eziphambili zokwahlula ezi ntlobo zili-13, iziphumo zolu hlolisiso zabonakala zibalulekile. Le ncwadana inemifanekiso yeNAS iqhubeka isithi, “aba bakwaGrant baye baqikelela ukuba xa imbalela ifika rhoqo emva kweminyaka eli-10 kwezi ziqithi, kunokuvela uhlobo olutsha lwezi ntaka kwiminyaka engama-200.”²⁴

Noko ke, into engazange iyikhankanye le ncwadana kukuba kwiminyaka eyalandela loo mbalela, ezi ntakana zinemilomo emincinane zaphinda zaninzi kunezinye. Aba baphandi bafumanisa ukuba njengoko imozulu yayitshintsha kweso siqithi, kwisithuba esingangonyaka ezona ntaka zaba ninzi zezinemilomo emikhulu, kodwa emva koko yazezo zinemilomo emincinane. Baphawula nokuba ezinye kwezo ntaka zazizalisa ezohlobo olwahlukileyo kuze kuvele amantshontsho aphila ixesha elide kunoonina nooyise. Bagqiba kwelokuba xa oko kwakunokuqhubeka kusenzeka, ezo ntlobo zimbini zokuqala zazinokuphela, kuze kuqhubeke kukho olo lutsha kuphela.²⁵

Ngoko ke, ngaba ukuqhubeka kwezinto ziphila ngenxa yendawo ezikuyo kubangela ukuvela kweentlobo ezintsha nezahluke ngokupheleleyo? Kumashumi eminyaka eyadlulayo, uGeorge Christopher Williams, ingcali ekholelwa ekubeni izinto zazivelela, waqalisa ukuthandabuza ukuba oku kunokwenzeka.²⁶ Ngowe-1999, enye ingcali yale mfundiso, uJeffrey H. Schwartz, yathi indawo eziphila kuyo izinto zohlobo oluthile inokuzinceda zikwazi ukumelana neemeko, kodwa ayinakuze ikwazi ukuvelisa naluphi na uhlobo olutsha.²⁷

Ngoko ke, iintaka ezincinane zikaDarwin “azilohlobo lutsha.” Ziselolo hlobo lweentaka ezincinane. Isibakala sokuba zikwazi ukuzalisana senza zithandabuzeke iindlela ezisetyenziswa zezinye iingcali zale mfundiso ukuchaza indlela ezahlukana ngayo iintlobo zezi ntaka. Ngaphezu koko, inkcazelo engezi ntaka ibonisa ukuba kwanawona maziko aphambili enzululwazi anokuzenza iimpazamo kwingxelo yawo.

Ubuxoki 3. Ingxelo yefosili ingqina ukuba kwenzeka utshintsho oluphawulekayo kwizinto eziphilayo. Incwadana enemifanekiso yeNAS ekhankanywe ngaphambili ishiya umfundi ecinga ukuba iifosili ezifunyaniswe zizazinzulu zibubungqina obucacileyo bokuba kwenzeka utshintsho oluphawulekayo kwizinto eziphilayo. Ithi: “Kufunyaniswe iindidi ezininzi zezinto eziphilayo ezidibana ngazo iintlanzi nezinto eziphila emanzini nasemhlabeni, izinto eziphila emhlabeni nasemanzini nezinto ezirhubuluzayo, phakathi kwezinto ezirhubuluzayo nezincancisayo, izilwanyana ezinkulu nezo zincinane, kangangokuba kunzima ukuqonda ixesha ezenzeka ngalo ezi nguqulelo.”

Inyaniso. La mazwi okuzithemba kule ncwadana yeNAS ayothusa. Ngoba? UNiles Eldredge, okholelwa ekubeni izinto zazivelela uyavuma ukuba le ngxelo yefosili ibonisa ukuba kangangexesha elide “zincinane iinguqu ezenzeka kwizinto eziphilayo zohlobo oluthile okanye azibikho kwaukubakho.”f²⁹

Ukuza kuthi ga namhlanje, ehlabathini lonke izazinzulu ziye zavumbulula zaza zagcina inqwaba yeefosili ezinkulu ezimalunga nama-200 ezigidi kunye nezincinane ezifikelela kwiibhiliyoni. Abaphengululi abaninzi bayavuma ukuba le ngxelo ingaka neneenkcukacha ezininzi ibonisa ukuba zonke iintlobo eziphambili zezilwanyana zabakho ngesiquphe zaza zahlala zilolo hlobo zazilulo kwasekuqaleni, ngoxa iintlobo zazo ezininzi zazikhawuleza zife.

Yintoni ebangela ukuba izazinzulu ezininzi ezaziwayo ezikholelwa ekubeni izinto zazivelela zithi yinyaniso into yokuba izinto zazivelela ngokuphawulekayo? Esinye sazo, uRichard Lewontin sabhala ngokunyaniseka sisithi izazinzulu ezininzi zikulungele ukwamkela izinto ezingenasihlahla zenzululwazi ngenxa nje “yenkolelo esele zinayo nezibambeleleyo kuyo.”g Izazinzulu ezininzi azifuni nokuva ngobukho boMyili okrelekrele kangangokuba uLewontin ude athi, “akukho nto idibanisa uThixo nenzululwazi.”³⁰

Ngokuphathelele oku, ingcali ngezentlalo, uRodney Stark, ocatshulwe kwiScientific American esithi: “Sekudlule iminyaka engama-200 kukhuthazwa into yokuba ukuze umntu ahambisane kakuhle nenzululwazi umele alubekele bucala unqulo.” Walek’ umsundulu athi kwiiyunivesithi ezenza uphando, “abantu bonqulo abamele bakhuphe nelimdaka ngoThixo.”³¹

Ukuze uyamkele imfundiso yokuba izinto zazivelela ngokuphawulekayo, umele ukholelwe ukuba izazinzulu ezithi uThixo akanakwaziwa nezithi uThixo akakho azivumeli iinkolelo zazo ziphembelele uphando lwazo lwenzululwazi. Umele ukholelwe ukuba zonke izinto ezintsonkothileyo eziphilayo zibekho ngokuguqulwa kwemizila yemfuza nangenxa yeendawo eziphila kuzo, phezu kwako nje ukusilela kwezazinzulu kwimizamo yokuvelisa uhlobo nokuba lunye lwento ephilayo entsha ngokupheleleyo. Umele ukholelwe nokuba zonke izidalwa zaguquka ngokuthe ngcembe zisusela kuhlobo olunye lokuqala, nakuba ifosili ibonisa ngokucacileyo ukuba izityalo nezilwanyana zemvelo azizange zichithe izigidi ngezigidi zeminyaka zitshintsha zisiba zezinye iintlobo, kodwa zaba zizo kwasekuqaleni. Ngaba inkolelo enjalo isekelwe kwinyaniso okanye kubuxoki? Inyaniso kukuba, inkolelo yokuzivelela kwezinto ifuna “ukholo.”