Ukusombuluka kwemvelo iintolwana namaqiniso

“Ukusombuluka kwemvelo kuliqiniso engekhe laphikwa njengombana nelanga litjhisa,” kutjho uProfesa Richard Dawkins, osisazi esidumileko sokusombuluka kwemvelo.¹⁶ Kuliqiniso, irhubhululo nokuhlola okunqophileko kufakazela bona ilanga liyatjhisa. Kodwana ihlolomlingo nokubona ngokunqophileko kufakazela indlela efanako engekhe yaphikiswa yifundiso yokusombuluka kwemvelo?

Ngaphambi kobana siphendule umbuzo loyo, kufuze sikhanyise okuthileko. Abososayensi abanengi batjheje bona ngokukhamba kwesikhathi, inzalo yezinto eziphilako kungenzeka itjhuguluke kancani. Isibonelo, abantu bangakghona ukuzalanisa izinja bekube kulapho iinzukulwana zazo ziba neenyawo ezifitjhani namtjhana zibe neenhluthu ezide kunabokhokho bazo.a Abanye abososayensi banamathelisa ibizo elithi “ukusombuluka kwemvelo” ematjhugulukweni amancani layo.

Namtjhana kunjalo, izazi zokusombuluka kwemvelo zifundisa bona amatjhuguluko amancani layo abuthelelene iimnyaka engaphezu kwamabhiliyoni begodu enza amatjhuguluko amakhulu afunekako bonyana enze ifesi, ifesi yatjhuguluka yaba silwana esiphila ngemanzini nangaphandle njengesirhwarhwa, sona saba sidalwa esifana nefene, ifene yatjhuguluka yaba mumuntu. Amatjhuguluko amakhulu abazicabangela wona la ahlathululwa “njengokusombuluka kwemvelo.”

Isibonelo, uCharles Darwin wafundisa bona amatjhuguluko amancani esingakghona ukuwabona atjengisa bona kunamatjhuguluko amakhulu—okungekho noyedwa okhe wawabona—angenzeka.¹⁷ Wathi ngemva kwesikhathi eside, ezinye, iimbunjwa zeemhlobo yokuphila elula eziyihloko zahlangana kabuthaka bona zikhule—“ngehlelo lokutjhugulula izinto elenzeka kabuthaka khulu”—eengidini ezihlukahlukeneko zeemhlobo yokuphila ephasini.¹⁸

Ebantwini abanengi, lokhu kuzwakala kunengqondo. Kodwana bayazibuza, ‘Nengabe amatjhuguluko amancani angenzeka hlangana nezinto eziphilako, kubayini ukusombuluka kwemvelo kubhalelwa ukwenza amatjhuguluko amakhulu ngemva kwesikhathi eside kangaka?’b Kodwana eqinisweni, ifundiso yokusombuluka kwemvelo iyame eentolwaneni eentathu. Cabangela okulandelako.

Iintolwana 1. Ukutjhuguluka kwezakhi zefuzo kuveza izinto ezitlhogekako bona kubunjwe iimhlobo emitjha. Ifundiso yokusombuluka kwemvelo yakhelwe ekutjhugulukeni kwezakhi zefuzo—ukutjhuguluka ngokuzenzakalelako kubangela izakhi zeentjalo neenlwana—kungakhiqiza ingasi iimhlobo yezinto ezitja kwaphela kodwana iveza iimndeni emitjha yeentjalo neenlwana.¹⁹

Amaqiniso. Iimhlobo eemnengi yesitjalo namtjhana yesilwana ihlukaniswa ziinqophiso ezimumethe izakhi zazo zefuzo, amano la agubuzeswe ma-nucleus weseli ngalinye.c Abarhubhululi bafumene bona amatjhuguluko wezakhi zefuzo angakghona ukukhiqiza iinzukulwana zeentjalo neenlwana. Kodwana kungenzeka bona amatjhuguluko wezakhi zefuzo kwamambala enze iimhlobo emitjha yezinto? Khuyini eyavezwako ngerhubhululo erherhweni lezakhi zefuzo ngekhulu leemnyaka?

Ekupheleni kwaka-1930 abososayensi bamukela umbono omutjha ngetjisakalo. Gade bacabanga bona imvelo izihlelele—ikambiso yezinto eziphilako ifanelekela kuhle khulu ibhoduluko kanengi iyaphuluka begodu iyazalanisa—kungakhiqiza iimhlobo yeentjalo ematjhugulukweni wezakhi zefuzo ngokuzenzakalelako. Ngalokho-ke nje bacabanga bona ukutjhuguluka kwezakhi zefuzo okunqophiswa mumuntu kufuze kukwazi ukwenza lokho kodwana ngendlela ebhedere khulu. “Zoke izazi zesayensi yezinto eziphilako nezazi zezakhi zefuzo nezokuzalanisa zathaba khulu,” kwatjho u-Wolf-Ekkehard Lönnig, usosayensi we-Max Planck Institute for Plant Breeding Research eJarimani.d Kubayini bathaba kangaka? ULönnig, okumthethe iimyaka ema-30 afunda ngokutjhuguluka kwezakhi zefuzo eentjalweni, wathi: “Abarhubhululaba bebacabanga bona sesifikile isikhathi sokobana basombulule indlela ejayelekileko yokuzalanisa iintjalo neenlwana. Bebacabanga bona ukukhulisa nokukhetha ukutjhugulula izakhi zefuzo gade bangakhiqiza iintjalo ezingcono neenlwana ezitja.”²⁰ Eqinisweni abanye bebathemba bona bazokukhiqiza iimhlobo emitjha-tjha yezinto eziphilako.

Abasosayensi e-United States, e-Asia, ne-Europe bathoma amahlelo werhubhululo asekelwe kuhle ngeemali baberegisa iindlela ezithembisa ukusombuluka kwemvelo okumsinyana. Ngemva kweemnyaka engaphezu kwama-40 werhubhululo lokuzimisela, yaba yini iimphumela? Umrhubhululi u-Peter von Sengbusch uthi: “Naphezu kwemali enengi eyaberegiswako, umzamo wokuveza iimhlobo ethileko ngeemsebe etjhisako [ukubangela amatjhuguluko wezakhi zefuzo], kubonakale kubhalelwa.”²¹ Godu uLönnig wathi: “Ngabo 1980 amathemba nethabo elikhulu hlangana nabososayensi besele kuphelile ephasini loke ngebanga lokubhalelwa. Eenarheni zeTjhingalanga igatja elizijameleko lerhubhululo yokutjhuguluka nokuzalanisa izakhi zefuzo yaliswa. Pheze zoke izinto ezitjhuguliliweko . . . zafa nofana bezibuthakathaka kuneemhlobo engokwemvelo.”e

Namtjhana kunjalo, imininingwana ekhona nje esele ibuthelelwe iimnyaka eyi-100 yerhubhululo letjhuguluko yezakhi zefuzo neemnyaka ema-70 yetjhuguluko lokuzalanisa irhelebha abasosayensi bona bafinyelele iimphetho malungana nekghono lokutjhugulula iimkhiqizo emitjha yeemhlobo yezinto eziphilako. Ngemva kokuhlola ubufakazi, uLönnig waphetha ngokuthi: “Ukutjhuguluka kwezakhi zefuzo ngekhe kutjhentjhe iimhlobo engokwemvelo yezinto eziphilako [yesitjalo namtjhana yesilwana] ibe mhlobo emitjha ngokupheleleko. Isiphethwesi sivumelana nakho koke abahlangabezane nakho neemphumela yerhubhululo lokutjhuguluka kwezakhi zefuzo ekhulwini lama-20 kuhlanganise neemthetho yokwenzeka nofana iimphumela yalokho.”

Ukutjhuguluka kwezakhi zefuzo kungakghona ukubangela iimhlobo eyodwa bona itjhuguluke ngokuzeleko ibe mhlobo omutjha wesibunjwa? Ubufakazi buyala! Irhubhululo yakaLönnig imdosele bona aphethe ngokuthi “iimhlobo yezinto eziphilako ehlukileko kunezinye ineemkhawulo engekhe yapheliswa namtjhana yeqiwe kutjhuguluka kwezakhi zefuzo ngengozi.”²²

Cabangela lokho okutjhiwo maqiniso angehla. Nengabe abasosayensi ababanduliweko babhalelwe ukuveza iimhlobo emitjha yezinto eziphilako ngokutjhugulula nokukhetha izakhi zefuzo ezifaneleko, bekungenzeka bona ikambiso engakahlakaniphi gade ingenza umberego ongcono? Nengabe irhubhululo itjengisa bona ukutjhuguluka kwezakhi zefuzo ngekhe kutjhentjhele izinto ezingokwemvelo eemhlobeni yezinto eziphilako ezitja, yeke, bekungenzeka njani bona ukusombuluka kwemvelo kwenzeke?

Iintolwana 2. Ukukhetha kwemvelo kudosela ekubunjweni kweemhlobo emitjha. U-Darwin gade akholelwa bona lokho abakubiza ngokobana kuzihlelela nokuvumelanisa kwemvelo gade kuzokuzuzisa izinto eziphilako ezivumelana bhedere nendawo eziyibhodileko, kanti iimhlobo engavumelani kuhle nendawo beyizokugcina ifile. Izazi zokusombuluka kwemvelo zesikhathi sanje zifundisa bona njengombana iimhlobo yezinto eziphilako yanda begodu irhatjheka, imvelo ikhethe lezo ezinezakhi zefuzo ezivumelana bhedere nendawazo etja. Ngebanga lalokho, izazi zokusombuluka kwemvelo zithi iinqhema ezirhatjhekilekwezi zigcina zitjhugulukile zaba mhlobo emitjha ngokupheleleko yezinto eziphilako.

Amaqiniso. Njengombana kutjhiwo ngaphambili, ubufakazi berhubhululo butjengisa ngamandla bona amatjhuguluko wezakhi zefuzo angekhe aveze iimhlobo yeentjalo neenlwana ezitjha ngokuphumeleleko. Nokho, ngibuphi ubufakazi obutjengiswe zizazi zokusombuluka kwemvelo obusekela ukukhuluma kwazo bona imvelo ikhetha izinto ezinezakhi zefuzo ezitjhugululiweko ezinenzuzo bonyana ziveze iimhlobo emitjha? Incwajana eyagadangiswa ngo-1999 yi-National Academy of Sciences (NAS) e-United States iqalisa “eemhlobweni eli-13 yeensakabula uDarwin azihlola eenhlengeleni zeGalápagos, nje ezaziwa ngokobana ma-Darwin’s finches.”²³

Ngabo-1970 isiqhema sabarhubhululi egade sidoswa ngu-Peter R. noB. Rosemary Grant be-University yePrinceton sathoma ukuhlola iinsakabulezi begodu safumana bona ngemva komnyaka woke wesomiso esihlengeleni, iinsakabula ezinomlomo omkhudlwana ziphila bhedere kunalezo ezinomlomo omncani. Njengombana ukuqala ubukhulu nokubumbeka komlomo wenyoni kungenye yeendlela eziyihloko zokuhlukanisa iimhlobo eyi-13 le yeensakabula, gade kucatjangwa bona iimphumela le iqakathekile. “Incwajana i-NAS iragela phambili ithi, Bakwa-Grant balinganisela bona nengabe kuba nesomiso qobe ngemva kweemyaka eli-10 esihlengeleneso, kungenzeka kuvele iimhlobo emitjha yeensakabula ngemva kweemnyaka epheze ibe ma-200.”²⁴

Nanyana kunjalo, incwajana i-NAS ayisitjeli bona eemnyakeni elandelako ngemva kwesomiso, iinyoni ezibizwa bona ziinsakabula ezineemlomo emncani zanda zaba zinengi. Abarhubhululi bafumene bona ubujamo bezulu esihlengeleni butjhugulukile, iinsakabula ezinomlomo omude beziba zinengi emnyakeni owodwa, kodwana ngemva kwesikhathi lezo ezinomlomo omncani ngizo ebeziba zinengi. Bayelela nokobana eminye “iimhlobo” ehlukileko yeensakabula beyizalaniselana begodu izala ezinye eziphila ngcono kunababelethi bazo. Baphetha ngokobana nengabe ukuzalanisana kuragela phambili, lokhu kungaphumela ekutheni ihlanganisela “yeemhlobo” eembili le iphethe ngokuba mhlobo owodwa.²⁵

Ukukhetha kwemvelo kwenza kube neemhlobo emitjha kwamambala na? Eemnyakeni eemnengi eyadlulako, isazi sezinto eziphilako uGeorge Christopher Williams wathoma ukubuza bona ukukhetha kwemvelo kungenzeka bona kunamandla anjalo.²⁶ Ngo-1999, isazi sefilosofi u-Jeffrey H. Schwartz watlola bona ukukhetha kwemvelo kungenzeka bona kurhelebha iimhlobo le bonyana ijayelane nobujamo bokuphila obutjhugulukako, kodwana akubangeli bona kubunjwe ezitja.²⁷

Kwamambala, iinsakabula ezahlolwa nguDarwin azibi “ngokuthileko okutjha.” Zisese yiinsakabula. Godu iqiniso kukobana ziyazalanisa okwenza zibe nokuzaza iinkambiso ezinye zezazi zokuziphendukela kwemvelo eziziberegisako zihlathulule bona uyini umhlobo othileko wento ephilako. Ukungezelela kilokhu, imininingwana malungana neenyonezi iveza iqiniso lokobana ngitjho neenhlangano eziphambili zezesayensi azinalo ilungelo lokubika ubufakazi ngendlela ekhethako.

Iintolwana 3. Imininingwana yeensalela efumanekileko efakazela ukusombuluka kwemvelo okunamatjhuguluko. Incwajana etjhiwo ngambili i-NAS itjhiye umfundi anombono wokobana iinsalela ezifunyenwe bososayansi zisekela ukusombuluka kwemvelo. Ithi: “Kuneemhlobo eemnengi efumaneke hlangana kweemfesi neenlwana, nahlangana kweenlwana ezirhurhubako, nahlangana nezimunyisako, begodu ngokujayelekileko kubudisi ukutjho ngokunembileko bona itjhuguluko lenzeke kuphi hlangana kweemhlobo ethileko.”²⁸

Amaqiniso. Isitatimende esenziwe yincwanjana ye-NAS sikhuluma ngesibindi siyarara. Kubayini kunjalo? UNiles Eldredge, osisazi esitjhisekela ukusombuluka kwemvelo, uyavuma bona iinsalela zitjengisa bonyana phakathi nesikhathi eside “liba lincani itjhuguluko elinengi namtjhana alibi khona nakancani eemhlobeni yezinto eziphilako.”f²⁹

Bekube nje, abososayensi ephasini loke barhubhulule begodu benza irhelo lezinto ezipheze zibe ziingidi ezima-200 weensalela ezikulu namabhiliyoni weensalela ezincani. Abarhubhululi abanengi bayavuma bona ubufakazi obukhulobu butjengisa bona zoke iinqhema zeenlwana zavela msinyana begodu kanengi zihlala zingatjhuguluki, kanti eminye iimhlobo yeenlwana inyamalala msinyana ngendlela ezivele ngayo.

Ukukholelwa ekusombulukeni kwemvelo—sisenzo “sekolo”

Kubayini izazi ezinengi ezaziwako zokusombuluka kwemvelo zikatelela bona ukusombuluka kwemvela kuliqiniso? Isazi esidumileko sokusombuluka kwemvelo u-Richard Lewontin watlola bona abososayensi abanengi bazimisele ukwamukela iimbono yesayensi engakaqinisekiswa ngombana “bazibophele entweni ethileko, bazibophele eentweni eziphathekako.”g Abososayensi abanengi bayala ngitjho nokucabanga bona kungenzeka bonyana kunoMenzi ohlakaniphileko njengombana uLewontin atlola, “angekhe sivumele bona uZimu angenele endabeni le.”³⁰

Malungana nalokhu isazi sezokuhlalisana kwabantu uRodney Stark udzubhulwe encwadini Scientific American athi: “Sekudlule iimnyaka ema-200 kukhuthazwa umbono wokobana nengabe ufuna ukuba ngusosayensi kufuze utjhaphulule umkhumbulwakho ungavumeli ikolo ibe nomthelela.” Waragela phambili wathi emayunivesithi wokwenza irhubhululo, “abantu bekolo kufuze bathule bangakhulumi ngoZimu.”³¹

Nengabe wamukela ifundiso yokusombuluka kwemvelo njengeliqiniso, kufuze ukholelwe bona abososayensi abaphika ukuba khona kwakaZimu namtjhana abathi akaziwa ngekhe bavumele iinkolelo zabo zibe nomthelela endleleni abahlathulula ngayo izinto. Kufuze ukholelwe bona ukutjhuguluka kwezakhi zefuzo nokukhetha okungokwemvelo kubangele bona kube khona yoke iimhlobo ehlukeneko yokuphila ebudisi ukuyizwisisa, naphezu kwekhulu leemnyaka lerhubhululo elitjengisa bona ukutjhuguluka kwezakhi zefuzo akukatjhugululi ngitjho nomhlobo owodwa onqophileko ekubeni yinto etja. Kufuze ukholelwe bona zoke izinto ezibunjiweko kancanikancani zatjhuguluka zisuka kukhokho oyedwa, naphezu kobufakazi beensalela obuqinileko obutjengisa bona iimhlobo eyihloko yeentjalo neenlwana zavela msinyana begodu akhenge zitjhugulukele kweminye iimhlobo, ngitjho nangemva kwesikhathi eside. Kodwana ukukholelwa kilokho kuzwakala kusekelwe eqinisweni namtjhana emaleni? Kwamambala ukukholelwa ekusombulukeni kwemvelo kusisenzo “sekolo.”