Ukuziphendukela Kwemvelo—Izinganekwane Namaqiniso

“Ukuziphendukela kwemvelo kuyiqiniso njengoba nje nokushisa kwelanga kuyiqiniso,” kugomela uProfesa Richard Dawkins, usosayensi odumile osekela ukuziphendukela kwemvelo.¹⁶ Yiqiniso, ucwaningo nalokho esikubonayo kufakazela ukuthi ilanga liyashisa. Kodwa ingabe ucwaningo nalokho esikubonayo kuyifakazela ngendlela efanayo engenakuphikiswa imfundiso yokuziphendukela kwemvelo?

Ngaphambi kokuba siphendule lowo mbuzo, kukhona okuthile okufanele sikucacise. Ososayensi abaningi baye baphawula ukuthi ngokuhamba kwesikhathi inzalo yezinto eziphilayo ingase ishintshe kancane. Ngokwesibonelo, abantu bangazalanisa izinja zezinhlobo ezithile ukuze ekugcineni kuvele ezinemilenze emifushane noma uboya obude kunobabazali bazo.a Ososayensi babiza ushintsho olunjalo oluncane ngokuthi “ukuziphendukela kwemvelo okubangelwa izinguquko ezincane ezakhini zofuzo.”

Izazi zokuziphendukela kwemvelo zifundisa ukuthi izinguquko ezincane zavela kancane kancane ezigidigidini zeminyaka futhi zaveza ushintsho olukhulu olwaludingeka ukuze izinhlanzi ziphenduke izilwane zasemhlabeni, nezinkawu zibe abantu. Lezi zinguquko ezinkulu ezisikiselwayo kuthiwa “ukuziphendukela kwemvelo okubangelwa izinguquko ezinkulu.”

Ngokwesibonelo, uCharles Darwin wafundisa ukuthi izinguquko ezincane esizibonayo zifakazela ukuthi izinguquko ezinkulu—ezingakaze zibonwe muntu—nazo zingaba khona.¹⁷ Wayecabanga ukuthi ngemva kwesikhathi eside, izinto ezithile eziphilayo zokuqala, zashintsha kancane kancane—“ngokushintsha okuncane kakhulu kwezakhi zofuzo”—zaba izigidi zezinto ezihlukahlukene eziphila emhlabeni.¹⁸

Kwabaningi, lo mbono uzwakala unengqondo. Bayazibuza, ‘Uma kungaba noshintsho oluncane ohlotsheni oluthile lwento ephilayo, kungani ukuziphendukela kwemvelo kungenakuveza ushintsho olukhulu ngemva kwesikhathi eside?’b Eqinisweni imfundiso yokuziphendukela kwemvelo isekelwe ezinganekwaneni ezintathu. Cabanga ngalokhu okulandelayo.

Inganekwane 1. Ukuguquka kwezakhi zofuzo kuveza izinhlobo ezintsha zezinto eziphilayo. Imfundiso yokuziphendukela kwemvelo okubangelwa izinguquko ezinkulu isekelwe emcabangweni wokuthi ukuguquka kwezakhi zofuzo akuvezi nje izinhlobo ezintsha zezinto eziphilayo kuphela kodwa kuveza nezigaba ezintsha ngokuphelele zezitshalo nezilwane.¹⁹

Amaqiniso. Ukwakheka kwesitshalo noma isilwane kunqunywa iziyalezo ezisezakhini zaso zofuzo, amapulani atholakala kuyi-nucleus yengqamuzana ngayinye.c Abacwaningi baye bathola ukuthi ukuguquka kwezakhi zofuzo kungabangela ushintsho enzalweni yezitshalo nezilwane. Kodwa ingabe izinguquko ezakhini zofuzo ziyaziveza ngempela izinto eziphilayo ebezingekho nhlobo? Ukucwaninga kweminyaka eyikhulu emkhakheni wezakhi zofuzo kwembuleni?

Ngasekupheleni kwawo-1930, ososayensi bamukela umbono omusha ngesasasa. Kakade babekholelwa ukuthi inqubo yokuchuma kwezinto eziphilayo ngoba zivunywa indawo ingaveza izinhlobo ezintsha zezitshalo nezilwane ngokuguqula izakhi zofuzo. Base bephetha ngokuthi ukushintsha izakhi zofuzo okuqondiswa umuntu kufanele kukwazi ukwenza lokho ngendlela ephumelela kangcono. “Zonke izazi zesayensi yezinto eziphilayo zaba nesasasa, ikakhulukazi izazi zezakhi zofuzo nabazalanisi,” kusho uWolf-Ekkehard Lönnig, usosayensi e-Max Planck Institute for Plant Breeding Research eJalimane.d Kungani kwakunesasasa? ULönnig, osechithe iminyaka engaba ngu-30 ecwaninga ngokuguquka kwezakhi zofuzo ezitshalweni, wathi: “Laba bacwaningi babecabanga ukuthi kwase kufike isikhathi sokushintsha indlela evamile yokuzalanisa izitshalo nezilwane. Babecabanga ukuthi ngokukhuthaza nangokukhetha ukuguqula izakhi zofuzo ezikahle, babengakhiqiza izitshalo nezilwane ezintsha futhi ezingcono.”²⁰ Empeleni abanye babenethemba lokukhiqiza izinhlobo ezintsha ebezingekho.

Ososayensi e-United States, e-Asia naseYurophu baqala izinhlelo zocwaningo ezazixhaswe ngezimali ezishisayo, besebenzisa izinqubo ezazithembisa ukusheshisa ukuziphendukela kwemvelo. Ngemva kweminyaka engaphezu kwengu-40 yokucwaninga kanzulu, yini abayithola? Umcwaningi uPeter von Sengbusch uthi: “Naphezu kwemali eningi eyachithwa, umzamo wokuveza izinhlobo zezitshalo ezithela kakhulu ngokuzishisa ngemisebe [ukuze kuguqulwe izakhi zofuzo], wabonakala uhluleka ngendlela edabukisayo.”²¹ ULönnig wathi: “Ngawo-1980, amathemba nesasasa lososayensi kwase kushabalele emhlabeni wonke. Emazweni aseNtshonalanga, umkhakha ozimele wokucwaninga ngokuzalanisa izitshalo nezilwane ngokuguqula izakhi zofuzo wayekwa. Cishe zonke izinto ezaziguqulwe izakhi zofuzo . . . zafa noma zaba ntekenteke kunezinhlobo zasendle.”e

Noma kunjalo, ukwaziswa osekuqoqiwe ngemva kweminyaka engaba ikhulu yokucwaninga ngokuguqula izakhi zofuzo kanye neminyaka engu-70 yokuzalanisa izinto ngokuguqula izakhi, kusiza ososayensi ukuba bafinyelele iziphetho ngokuthi izinto ezishintshwe izakhi ziyakwazi yini ukukhiqiza izinhlobo ezintsha. Ngemva kokuhlola ubufakazi, uLönnig waphetha: “Ukuguqula izakhi zofuzo ngeke kulushintshe uhlobo oluthile [lwesitshalo noma lwesilwane] lube uhlobo olusha obelungekho. Lesi siphetho sivumelana nakho konke esiye sakubona nemiphumela yokucwaninga ngokuguqula izakhi ekhulwini lama-20 lilonke.”

Ngakho, ingabe ukuguqulwa kwezakhi zofuzo kungashintsha uhlobo oluthile lwento ephilayo lube uhlobo olusha obelungekho? Ubufakazi buyaphika! Ucwaningo lukaLönnig lumenze waphetha ngokuthi “izinhlobo zezinto eziphilayo ezinezakhi zofuzo ezihlukile kwezezinye zinemingcele engenakususwa noma yeqiwe ukuguquka ngengozi kwezakhi zofuzo.”²²

Cabangela okushiwo amaqiniso angenhla. Uma ososayensi abagogodile behluleka ukuveza izinhlobo ezintsha zezinto eziphilayo ngokushintsha nokukhetha izakhi zofuzo ezikahle, inqubo engenakuhlakanipha ingakwenza yini lokho? Uma ucwaningo lubonisa ukuthi ukuguqula izakhi zofuzo ngeke kulushintshe uhlobo oluthile lube uhlobo olusha obelungekho, khona-ke kwakungenzeka kanjani ngempela ukuziphendukela kwemvelo okubangelwa izinguquko ezinkulu?

Inganekwane 2. Inqubo yokuchuma kwezinto eziphilayo ngoba zivunywa indawo yabangela ukuba khona kwezinhlobo ezintsha zezinto eziphilayo. UDarwin wayekholelwa ukuthi inqubo yokuchuma kwezinto eziphilayo ngoba zivunywa indawo yayiyozuzisa izinto eziphilayo ezizivumelanisa kangcono nendawo eziphila kuyo, kanti izinhlobo ezingazivumelanisi kahle nendawo zaziyogcina zifile. Izazi zanamuhla zokuziphendukela kwemvelo zifundisa ukuthi njengoba izinhlobo zazanda futhi zisakazeka, le nqubo yakhetha lezo ezinezakhi zofuzo ezivumelana kangcono nendawo yazo entsha. Ngenxa yalokho, izazi zokuziphendukela kwemvelo zithi lezi zinhlobo zezinto eziphilayo ezisakazekile zagcina seziphenduke izinhlobo ezintsha zezinto eziphilayo ezazingakaze zibe khona.

Amaqiniso. Njengoba sekuphawuliwe, ubufakazi bocwaningo bubonisa ngokunamandla ukuthi ukuguquka kwezakhi zofuzo akunakuveza izinhlobo zezitshalo noma zezilwane ezintsha ebezingekho. Noma kunjalo, ibuphi ubufakazi obuvezwa izazi zokuziphendukela kwemvelo obusekela lokho abakushoyo ukuthi inqubo yokuchuma kwezinto eziphilayo ngoba zivunywa indawo ikhetha izinto ezinezakhi eziguquliwe ukuze iveze izinhlobo ezintsha zezinto eziphilayo? Incwajana eyanyatheliswa yi-National Academy of Sciences (NAS) ngo-1999 e-United States ikhuluma “ngezinhlobo ezingu-13 zezintaka uDarwin azihlola eziQhingini ZaseGalápagos, ezaziwa ngokuthi izintaka zikaDarwin.”²³

Ngawo-1970, iqembu labacwaningi elaliholwa uPeter R. noB. Rosemary Grant basePrinceton University laqala ukuhlola lezi zintaka futhi lathola ukuthi ngemva konyaka wonke wesomiso, izintaka ezinoqhwaku olukhudlwana zaziphila kangcono kunezinoqhwaku oluncane. Njengoba ukubheka ubukhulu nokwakheka koqhwaku kungenye yezindlela eziyinhloko yokuhlukanisa lezi zinhlobo ezingu-13 zezintaka, kwakucatshangwa ukuthi le miphumela yayisho lukhulu. Le ncwajana iyaqhubeka: “AbakwaGrant baye basikisela ukuthi uma kungaba nesomiso kanye ngemva kweminyaka eyishumi kulezi ziqhingi, uhlobo olusha lwentaka lungase luvele ngemva kweminyaka engaba ngu-200.”²⁴

Nokho, le ncwajana ye-NAS ayisho ukuthi eminyakeni eyalandela isomiso, izintaka ezinoqhwaku oluncane zaphinde zanda. Abacwaningi bathole ukuthi lapho isimo sezulu sishintsha, kwakwanda izintaka ezinoqhwaku olukhulu ngomunye unyaka, kuthi kamuva kwande ezinoqhwaku oluncane. Baphawula nokuthi ezinye zalezi “zinhlobo” ezihlukile zezintaka zazizalana futhi ziveze inzalo eyaphila kangcono kunabazali. Baphetha ngokuthi uma lezi zinyoni ziqhubeka zizalana, kwakungaphumela ekuxubaneni “kwezinhlobo” ezimbili zibe uhlobo olulodwa.²⁵

Ngakho, ingabe inqubo yokuchuma kwezinto eziphilayo ngoba zivunywa indawo iyaziveza ngempela izinhlobo ezintsha zezinto eziphilayo? Emashumini eminyaka adlule, isazi sokuziphendukela kwemvelo uGeorge Christopher Williams saqala ukungabaza ukuthi le nqubo ingakwenza yini lokhu.²⁶ Ngo-1999, umhlaziyi wemfundiso yokuziphendukela kwemvelo uJeffrey H. Schwartz wathi inqubo yokuchuma kwezinto eziphilayo ngoba zivunywa indawo kungenzeka iyazisiza izinto eziphilayo ukuba zizivumelanise nezimo ezishintshashintshayo zokuphila, kodwa ayidali lutho olusha.²⁷

Ngempela, izintaka ezahlolwa uDarwin azibi “okuthile okusha.” Ziseyizintaka. Futhi iqiniso lokuthi ziyazalana lenza zingabazeke izindlela ezinye izazi zokuziphendukela kwemvelo ezizisebenzisayo ukuze zichaze ukuthi luyini uhlobo oluthile lwento ephilayo. Ngaphezu kwalokho, ulwazi oluye lwatholakala ngalezi zinyoni lwembula ukuthi ngisho nezinhlangano eziphambili zezesayensi zingayibika indaba ngendlela evumelana nombono wazo.

Inganekwane 3. Izinsalela zezitshalo nezilwane zifakazela ukuziphendukela kwemvelo okubangelwa izinguquko ezinkulu. Incwajana ye-NAS eshiwo ngaphambili ishiya umfundi enombono wokuthi izinsalela ezitholwa ososayensi zisekela ukuziphendukela kwemvelo okubangelwa izinguquko ezinkulu ngaphandle kokungabaza. Ithi: “Kuye kwatholakala izinhlobo eziningi eziphakathi kwezinhlanzi nezilwane eziphila ezweni, phakathi kwezilwane eziphila ezweni nezilwane ezihuquzelayo, phakathi kwezilwane ezihuquzelayo nezilwane ezincelisayo, naphakathi kwabantu nezimfene, kangangokuba ngokuvamile kunzima ukusho ngokuqondile ukuthi lolu shintsho lwenzeka nini phakathi kwezinhlobo ezithile.”²⁸

Amaqiniso. La mazwi ashiwo yile ncwajana ye-NAS ayamangalisa ngempela. Ngani? UNiles Eldredge, oyisazi esishisekayo sokuziphendukela kwemvelo, uthi lezi zinsalela azibonisi ukuthi kuba khona ushintsho olwenzeka kancane kancane, kodwa zibonisa ukuthi phakathi nesikhathi eside “luba luncane ushintsho olwenzekayo ezinhlotsheni eziningi zezinto eziphilayo noma lungabi khona nhlobo.”f²⁹

Kuze kube manje, ososayensi emhlabeni wonke baye bathola futhi babhala uhlu lwezinsalela ezinkulu zezinto ezaziphila ezingaba yizigidi ezingu-200 kanye nezigidigidi zezinsalela ezincane. Abacwaningi abaningi bayavuma ukuthi lolu hlu olude oluningilizayo lubonisa ukuthi zonke izilwane ezinkulu zavela ngokuphazima kweso futhi azizange zishintshe, futhi izinhlobo eziningi zanyamalala ngokuzuma ngendlela ezazivele ngayo.

Ukukholelwa Ekuziphendukeleni Kwemvelo Kuyisinqumo Esibonisa Lokho Okukholelwayo

Kungani izazi eziningi ezivelele zokuziphendukela kwemvelo ziphikelela nokuthi ukuziphendukela kwemvelo kuyiqiniso? Isazi esidumile sokuziphendukela kwemvelo uRichard Lewontin sabhala ukuthi ososayensi abaningi bazimisele ukwamukela imibono yesayensi engenabo ubufakazi ngoba “basuke sebezibophezele kokuthile kusengaphambili, bezibophezele emfundisweni yokuthi konke okusendaweni yonke, kuhlanganise nazo zonke izinto eziphilayo, kwaba khona ngaphandle kokungenela kwamandla angaphezu kwawemvelo.” Ososayensi abaningi benqaba ngisho nokucabangela ukuthi kungenzeka kunoMklami ohlakaniphile, ngoba, njengoba uLewontin esho, “asikwazi ukuvumela uNkulunkulu angene kule ndaba.”³⁰

Sikhuluma ngalokhu, isazi sezokuhlalisana kwabantu uRodney Stark sicashunwa kuyi-Scientific American sithi: “Sekuyiminyaka engu-200 kukhuthazwa umbono wokuthi uma ufuna ukuba usosayensi, khohlwa indaba yenkolo.” Siphawula nokuthi emayunivesithi ezocwaningo, “abantu abathanda inkolo abathi vú ngenkolo.”³¹

Uma uzokhetha ukukholelwa ukuthi ukuziphendukela kwemvelo kuyiqiniso, kumelwe ukholelwe ukuthi ososayensi abaphika ubukhona bukaNkulunkulu noma abathi akaziwa ngeke bavumele izinkolelo zabo zithonye indlela abazichaza ngayo izinto abazithole ngesayensi. Kumelwe ukholelwe ukuthi izinto eziguqulwe izakhi zofuzo nenqubo yokuchuma kwezinto eziphilayo ngoba zivunywa indawo kwakhiqiza zonke izinto eziphilayo eziyinkimbinkimbi, naphezu kocwaningo oluthathe ikhulu lonke leminyaka olubonisa ukuthi ukuguqulwa kwezakhi zofuzo akuzange kushintshe ngisho nohlobo olulodwa lwento ephilayo lwaba uhlobo olusha obelungekho. Kumelwe ukholelwe ukuthi zonke izinto eziphilayo zavela kancane kancane entweni eyodwa, naphezu kweqiniso lokuthi izinsalela ezitholakele zibonisa ukuthi izinhlobo eziyinhloko zezitshalo nezilwane zavela ngokuphazima kweso futhi azizange ziphenduke zibe ezinye izinhlobo, ngisho nangemva kweminyaka eminingi. Ingabe inkolelo enjalo izwakala sengathi isekelwe eqinisweni noma ezinganekwaneni? Ngempela, ukukholelwa ekuziphendukeleni kwemvelo kuyisinqumo esibonisa lokho okukholelwayo.