Ikusasa lokuziphendukela kwemvelo komuntu

 Uma sicabanga ngokuziphendukela kwemvelo, sicabanga ngososayensi abadumile abafana noDarwin, Lamarck, Woese nabanye. Siyimikhiqizo emihle yezigidi zeminyaka yokukhethwa nokuguqulwa kwezakhi zofuzo, eyathuthukiswa yaba into eyodwa enamandla kakhulu, kodwa ingabe siqinisile uma sicabanga ukuthi siyisiphetho sakho konke? Kuthiwani uma simane siwuhlobo oluphakathi nendawo oluzoshintsha lube into ehluke ngokuphelele eminyakeni eyinkulungwane, noma siye sazenza indawo engenazo izingcindezi zokuzikhethela eziqhuba ukuziphendukela kwemvelo?  

Ufuzo nokuziphendukela kwemvelo  

Kunezifundo eziningi okwamanje ezihlola amandla abantu okuphendula izimo ezintsha. Ososayensi bakholelwa ukuthi lezi zimo zingabonakala ezakhini zethu zofuzo. Ngokulandela imvamisa ye-allele, ososayensi banganquma izingcindezi zokukhetha ezakhini zofuzo emphakathini jikelele.  

Wonke umuntu unamakhophi amabili ofuzo ngalunye, olubizwa ngokuthi ama-allele, futhi angahluka phakathi kwabantu. Ukuguqulwa kwelinye lamakhophi kungaholela ekwenyukeni noma ekwehleni kwesici esithile somzimba, noma isici, ufuzo olusijwayezayo. Uma indawo umuntu ahlala kuyo (okungukuthi, isimo sezulu, ukutholakala kokudla namanzi) ithandeka kakhulu ekuguqulweni kofuzo okukodwa kwalokhu okubili, abantu abanalokho kuguquka bazodlulisela ufuzo lwabo. Umphumela ungaholela ekuthi ukuguquguquka okukhethiwe kuvame kakhulu kubantu kunokuguqulwa okungazuzisi.  

Lesi isisekelo sedatha ye-genomic ebheka amashifu wokuziphendukela kwemvelo kusibalo sabantu. Uma sibheka abantu abavela emhlabeni wonke singabona ukuhlukahluka kwezinhlobo zabantu ngokubuka izici ezihlukene zomzimba; nokho, kubalulekile ukuqaphela ukuthi kunezinhlobonhlobo eziningi esingase singakwazi ukuzibona ngamehlo ethu. Zonke lezi zakhi zofuzo zihlangene zixoxa indaba yokuthi uhlobo noma inani labantu lafika kanjani lapho likhona namuhla. Esikhathini esithile esikhathini sempilo yesibalo sabantu, kufanele kube khona ukukhetha kwezici abazibonisayo manje. 

Kubukeka kanjani ukuziphendukela kwemvelo namuhla? 

Ukubheka nje ngokushesha kuzobonisa izici eziningi zobuntu esizizuze njengefa ngokuziphendukela kwemvelo. Eqinisweni, ziningi izakhi zofuzo ososayensi babonise ukuthi bakhona kuphela kubantu abangaphansi kweminyaka engu-40,000 ubudala. Lokhu kubonisa ubufakazi obuqondile bokuthi abantu basazuza ngofuzo olusha olusekelwe endaweni abahlala kuyo. Isibonelo, ukwethulwa kokuphila kwedolobha kwashintsha kakhulu izingcindezi zesigaba kubantu futhi kwashintsha ukwahluka kofuzo okukhethelwa kona kubantu.    

Amasosha ethu omzimba anawo ijwayele ukulwa nokutheleleka nge-HIV. Izinhlanganisela ezahlukene zamaprotheni omzimba zingasebenza kangcono ekuqedeni ukutheleleka kunabanye. Njengoba amaprotheni efakwe ku-DNA, ukuhlukahluka kwe-DNA kungashintsha inhlanganisela yamaprotheni akhona. Lezi zingabe sezitholwa yizizukulwane ezizayo, zidale isibalo sabantu abangenaso isifo. Isibonelo, i-HIV ayivamile kakhulu eNtshonalanga Yurophu kunase-Afrika. Kwaqondana nje, u-13% wabantu base-Europe baboniswe ukuthi baqukethe ukuhluka ekubhalweni kofuzo kwe-co-receptor ye-HIV; lokhu kwabenza bakwazi ukuzivikela ngokuphelele kulesi sifo.  

Siphinde sahlakulela ezinye izici eziningi ngenxa yokuziphendukela kwemvelo, njengokukwazi kwethu ukuphuza ubisi. Ngokuvamile, i- isakhi sofuzo esigaya i-lactose obisini luyavalwa ngemva kokuba umama eseqedile ukuncelisa. Lokhu kusho ukuthi wonke umuntu omdala kunosana kufanele alahlekelwe amandla okuphuza ubisi, kodwa lokhu akunjalo ngokusobala. Ngemva kokufuywa kwezimvu, izinkomo nezimbuzi, kwaba nenzuzo yokudla okunomsoco ekugayeni i-lactose, futhi labo abenza kanjalo babesemathubeni amaningi okudlulisela lesi sici ezinganeni zabo. Ngakho-ke, ezindaweni lapho ubisi luguquke lwaba umthombo omkhulu wokudla okunomsoco, kwaba khona nezingcindezi zokukhetha ezazinikeza inzuzo kulabo ababengaqhubeka nokugaya ubisi ngemva kobuntwana. Yingakho namuhla, ngaphezu kwama-95% enzalo yaseNyakatho Yurophu ephethe lolu fuzo. 

Ukuguquka kwezakhi zofuzo nakho kuye kwabangela amehlo aluhlaza kanye nezinye  izici osekulahleka manje, njengokuncipha kokuvama kwamazinyo ahlakaniphile ngenxa yosayizi womhlathi wethu oncishisiwe. Izici ezinjengalezi zisishiye izinkomba zokutholwa kokuziphendukela kwemvelo esimweni sanamuhla; kungenxa yalezi zici ezincishisiwe okuthi abanye ososayensi baphinde bakholelwe ukuthi ukuziphendukela kwemvelo akwenzeki kuphela, kodwa empeleni kwenzeka ngezinga elishesha kakhulu kunalokho okuke kwabonwa ngaphambilini.  

Kunalokho, uSolwazi Steven Jones, isazi sezakhi zofuzo sase-University College London, uthi "Ukukhetha kwemvelo, uma kungamile, kuye kwehlile okungenani". Uqhube wathi ngobuchwepheshe nezinto ezisunguliwe, sikwazile ukushintsha indlela yokuziphendukela kwemvelo esebenza kithi. Lokhu futhi kubangela ukwanda kobude bempilo yabantu. 

Phambilini besisemseni wokwakheka kwethu kofuzo nokuthi besiyosabela kanjani endaweni esihlala kuyo, kodwa namuhla siyakwazi ukweqa le mingcele nakuba kunezinyathelo zokwelapha nezobuchwepheshe. Cishe wonke umuntu usinda kuze kube yilapho esemdala ukuze adlulisele izakhi zofuzo, kungakhathaliseki ukuthi “amandla” ezakhi zawo zofuzo zingakanani. Ngaphezu kwalokho, akukho ukuhlobana phakathi kofuzo kanye nenani lezingane umuntu anazo. Eqinisweni, abaningi bakhetha ukungabi nabantwana nhlobo.   

U-Stephen Stearns, uprofesa we-Ecology and Evolutionary Biology e-Yale University, uchaza ushintsho endleleni yokudluliselwa kofuzo kuya ezizukulwaneni ezilandelayo luhlobene nokuncika kwethu ukusuka ekufeni njengendlela yokuziphendukela kwemvelo. Sesiqala ukubona ukuhlukahluka okuningi kokuzala okubangela izinguquko ekuziphendukeleni kwemvelo, esikhundleni sokufa. Izindlela zokuziphendukela kwemvelo ziyashintsha! 

Ukuziphendukela kwemvelo kuyobukeka kanjani esikhathini esizayo? 

Ngakho uma ukuziphendukela kwemvelo kusenzeka, izowushintsha kanjani umhlaba esiwaziyo  namuhla? 

Noma nini lapho kuba nokwehluka empumelelweni yokuzala, sinokuziphendukela kwemvelo. U-Stearns uthi ukuziphendukela kwemvelo “akunakumiswa”, futhi uma besazi ukuthi kanjani, besizokwazi ukumisa ukuvela kwezinto ezifana nokumelana nama-antibiotic; noma kunjalo, lezi zinhlobo zezinqubo azikho.  

Ekugcineni, u-Stearns ukholelwa ukuthi kunzima ngathi “ukusonga amakhanda ethu ezinqubweni ezinkulu kakhulu nezinyakazayo kuna[thi]; ukuziphendukela kwemvelo kuthatha isikhathi, futhi iningi lethu alikwazi ukuphuma ngaphandle bese libona inani labantu lishintsha kancane kancane”. Ukuziphendukela kwemvelo kwenzeka nsuku zonke ngamanani okunzima ngathi ukuwaqonda noma ukuwabona, kodwa lokhu akusho ukuthi akukona okwangempela. U-Stearns uthi ososayensi baqoqe idatha iminyaka eminingi ebonisa ukuziphendukela kwemvelo okwenzeka phambi kwamehlo ethu; sidinga kuphela ukwethemba inqubo njengoba yenzeka esikhathini esizayo.  

Nokho, ososayensi abanjengoSteven Jones kanye nesazi sesayensi yesintu u-Ian Tattersall we-American Museum of Natural History yaseNew York, bakholelwa okuphambene. I-Tattersall ithi “ngoba siye savela , kungokwemvelo ukucabanga ukuthi sizoqhubeka senza kanjalo, kodwa ngicabanga ukuthi lokho akulungile”.  

Isisekelo sikaTattersall yilapho ukuguqulwa kofuzo kudluliselwa kusuka esizukulwaneni kuya esizukulwaneni, kungenxa yokuthi kuzuzisa uhlobo lokuthola ifa loguquko. Uma ukuguqulwa kungasebenzisi njongo kubantu, ngeke kudluliswe ngemvamisa ephezulu kunanoma yikuphi okunye ukuguqulwa. Ngaphezu kwalokho, uTattersall uyachaza, “izinto ezintsha eziqanjiwe zofuzo kungenzeka zihlale kubantu abambalwa, abangabodwa”, njengaseziQhingini ezidumile zaseGalapagos zaseDarwin. UJones ulandelela ngokuthi “Umshini kaDarwin uphelelwe amandla… Iqiniso lokuthi wonke umuntu uhlala ephila, okungenani aze abe mdala ngokocansi, kusho ukuthi [ukusinda kwabanamandla kunabo bonke] akunalutho okusebenza ngalo.”  

Ukuziphendukela kwemvelo kwamasiko vs ukuziphendukela kwemvelo  

UStearns ukholelwa ukuthi umbono oyiphutha omkhulu kunayo yonke mayelana nokuziphendukela kwemvelo namuhla usuka ekudidekeni phakathi kokuziphendukela kwemvelo kwezinto eziphilayo, okuhlanganisa ufuzo lwethu, nokuziphendukela kwemvelo kwamasiko, okuhlanganisa izici zomzimba nengqondo, njengokufunda nokufunda. Kokubili kwenzeka ngokufana futhi kuveza imiphumela ehlukene, futhi njengoba isiko lishintsha ngokushesha, imiphumela yokuziphendukela kwemvelo kunzima ukuyibikezela.  

Eceleni kwalokhu kwanda kokuziphendukela kwemvelo kwamasiko, siyabona futhi ukukhetha ubulili ngokukhetha kwethu abangane bomshado. Lokhu kuyadingeka ukuze umuntu aphumelele kwezomnotho futhi akhulise izingane, ngokusho kaGeoffrey Miller, isazi sokusebenza kwengqondo esikholelwa ekuziphendukeleni kwemvelo eNyuvesi yaseNew Mexico. Ubuye achaze “lapho ubuchwepheshe buthuthuke kakhulu, kulapho ubuhlakani obujwayelekile buyoba nomthelela omkhulu empumelelweni yomuntu ngamunye kwezomnotho nezenhlalo, ngoba ubuchwepheshe buba nzima nakakhulu, udinga ukuhlakanipha okwengeziwe ukuze uphumelele.”   

Lezi zingcindezi zokukhetha ubulili cishe zizobona ukukhuphuka kwezici ezihambisanayo ezihilelekile ekuthandeni ngokomzimba, njengobude, amazinga emisipha namandla, kanye nempilo. UMiller uphawula ukuthi lokhu kunamandla okudala ukuhlukana kwabantu phakathi kwezigaba eziphakeme neziphansi, ngenxa yokuthi “abacebile nabanamandla” bazigcinela ukukhetha okwenziwayo. Ukukhetha okwenziwayo kuzovumela abazali ikhono lokukhetha iminikelo yofuzo enganeni yabo. Eziningi zalezi zingakhetha izici zomzimba nezengqondo. UMiller ukholelwa ukuthi, nokho, ngenxa yenzuzo yalezi zinhlobo zobuchwepheshe bofuzo, kungenzeka ukuthi lobu buchwepheshe buthengeke futhi butholakale kubo bobabili abacebile nabampofu.