Kubera iki abantu badafise ubwoya nk’ibindi bikoko?

Ibikoko hafi vyose, harimwo n’ibitwegereye, bifise urushato ruriko ubwoya. None ni kubera iki twebwe bitameze uko?

Hagize ikiremwa gishasha kiza kw’isi hanyuma kikadushira hamwe n’ibindi bikoko, kimwe mu bintu vya mbere bidutandukanya – hampande y’uko duhagaze ku maguru abiri n’uburyo bwihariye bwo kuyaga – ni imibiri yacu isa n’iyitagira ubwoya.

Mu bisanzwe, ubigereranije n’ibindi bikoko, abantu muri rusangi nta bwoya bafise (havuyemwo bamwe bamwe, nabo nyene badakunze kuboneka). Hariho ibikoko bike cane navyo nyene bisangiye iyi ndangamubiri ya kiremwamuntu - muri vyo harimwo nk’imvubu, inzovu, rhinoceros, ifuku zitagira ubwoya [rats-taupe], baleine [ibifi binini cane bivyara], n’ibindi bike cane.

None vyoba vyagenze gute neza na neza kugira ngo twisange dusa n’aho turi gusa? Hari akarusho bifise muri kino gihe? Hanyuma wosigura gute ukungene ku bice bimwe bimwe vy’umubiri usanga bifise ubwoya bwinshi?

Ni vyo, abantu bafise ubwoya bwinshi: ugereranije, dufise udutoboro tw’ubwoya twababa imiriyoni zitanu ku mubiri wacu. Ariko utwo dutoboro hafi twose turimwo utwoya tw’utumerera, tworoshe cane, duto cane, tugufi cane, tumerera muri utu dutoboro tudashika kure mu mubiri. Utu twoya dutandukanye n’ubwoya burebure bumera ku bice bimwe bimwe nk’umushatsi ku mutwe, n’ubusakwaha, ubwoya bw'iruhande y'ibice vy'igitsina, n’ubwanwa ku bagabo hafi bose (inyuma y’imyaka y’ubuyabaga).

Tina Lasisi, umuhinga mu bijanye n’ibinyabuzima muri kaminuza ya California y’ubumanuko, akaba ariko yiga ibijanye n’ubwoya n’uruhu, agira ati: "Mu bisanzwe dufise ubwoya ku mubiri wose, ni utwoya duto cane. Ni duto cane ku buryo tutagishobora kudukingira nk’uko twategerezwa”.

Abahinga ntibazi neza na neza igituma ubu bwoya bwari bwinshi kandi bugumye bwagiye guhinduka bukaba utwoya duto cane, kandi ntibazi neza na neza igihe ibi vyabaye. N’ubwo bimeze uko, hari vyinshi bivugwa ku vyerekeye ivyatumye umuntu atakaza ubwoya.

Igisumba ibindi vyose ni igishingiye ku “kugenzura ubushuhe bw’umubiri”, kizwi nka hypothèse de la "savane"/ "savannah" hypothesis. Iki ciyumviro cerekana ko vyabaye nkenerwa ku bantu ba mbere ko imibiri yabo igira ubushobozi bwo kugenzura ubushuhe, maze bituma batakaza ubwoya.

Mu gihe kizwi nka Pleistocene, aba-Homo erectus bagiye mu nyuma kwitwa aba-hominidés/hominins boba batanguye gukora uruhigi rwabaruhisha cane mw’ishamba, biruka ku bikoko amasaha menshi kugira ngo babiruhishe batanakoresheje ibikoresho vy’uruhigi bihanitse vyagiye kuboneka mu nyuma mu bikoresho vy’aho hambere.

Ibi bikorwa biruhisha vyoba vyatumye bagira ibibazo vy’ubushuhe burenze urugero- ivyavuyemwo gutakaza ubwoya gushobora kuba kwabashoboje kubira icuya cinshi no guta ubushuhe ningoga batarinze no kuruhuka.

Ibi kandi bishingiye ku bushakashatsi bwerekana ihindagurika ry’uduce ndangakamere (genes) tumwe tumwe dutuma uturemangingo tumwe tumwe tuvamwo uduhimba dutanga indugumba canke tumeramwo ubwoya.

Lasisi ati: "Rero ibi bintu vyose birafise uruhara mw’ihindagurika ry’umubiri. Turavye ibi vyose tukabifatanya n’ibindi twashoboye gutora ku bijanye n’uduce ndangakamere twongereje ihindagurika ry’ibara ry’uruhu rw’umuntu, turashobora kwemeza tudakekeranya ko kuva mu myaka imiriyoni zibiri gushika ku miriyoni imwe n’inusu iheze…abantu bashobora kuba baratakaje ubwoya ku mubiri wabo”.

Iciyumviro gifitaniye isano n’iki cashizwe ahabona mu myaka ya 1980 cerekana ko impinduka zabaye zigatuma umuntu ahagarara agororotse ku maguru abiri zagabanije akamaro k’ubwoya. Kubera dushobora kubira icuya neza ata bwoya, ibi vyabaye akarusho gusumba kugira ubwoya.

Mark Pagel, umwigisha kw’ihindagurika ry’ibinyabuzima kw’ishure kaminuza rya Reading, avuga ko nubwo iciyumviro co kugabanya ubushuhe bw’umubiri gisa n’icumvikana cane kandi gishobora no kuba ari co cizewe, kirafise agahaze mu bice bimwe bimwe.

Avuga ati: "Wihweje ubushuhe bw’umubiri wacu mu kiringo c’amasaha 24, usanga dutakaza ubushuhe mw’ijoro gusumba uko twabishaka, rero ibi bigasigura ko inkurikizi yo gutakaza ubwoya ari uko twama dutakaza inguvu buri mwanya”.

Avuga kandi ko hari abantu benshi bamaze imyaka ibihumbi n’ibihumbi batiruka mu buryo buruhisha, ariko nta n’umwe yasuburiye kumera ubwoya, kandi benshi ubu baba mu turere dukanye cane kuri ino si.

Hagati aho, Lasisi avuga ko ubushuhe bw’umubiri burenze urugero (hyperthermia) bushobora kuba bwarabaye ikibazo kinini cane gusumba ubushuhe bw’umubiri buke cane (hypothermia) mu karere ka Afrika yo ku murongo uca hagati na hagati mu mubumbe w'isi (Afrique équatoriale), ari naho kiremwamuntu catanguriye. "Kuri jewe bisa n’uko hari urugamba rwo kurwanya ubushuhe burenze, gusumba umuntu kugira ubushuhe bugereranye”.

Avuga kandi ko uduce ndangakamere twinshi dushobora guhinduka mu buryo ntasubira inyuma – ku buryo bigoye gusubira uko twari tumeze nka kera. Hanyuma kandi, yongerako ko igihe abantu bashika mu turere tw’ubukonje burenze urugero, bari bamaze gutora ubundi buhinga bwo kwisusurutsa, nk’umuriro n’impuzu. Basa kandi n’abari batoye n’ubundi buhinga bwo kumenyereza umubiri imbeho, nk’akarorero amavuta agenzura ubushuhe bw’umubiri (adaptation de la graisse brune/brown fat adaptation).

Mu 2003, Pagel na mugenziwe Walter Bodmer kw’ishure kaminuza ya Oxford baratanze iyindi nsiguro ku catumye abantu ba mbere batakaza ubwoya, iciyumviro gishingiye ku vyonyi (parasites) bitera umubiri, ico bise hypothèse de l’ectoparasite/ectoparasite hypothesis. Basigura ko inguge itagira ubwoya yoba itatewe n’ivyonyi, ibi bikaba vyayibereye akarusho kadasanzwe.

Pagel ati: "Uravye hirya no hino kw’isi, ivyonyi biracari ikibazo gikomeye, nk’akarorero isazi ziryana zitera ingwara. Izo sazi zifise ubuhinga budasanzwe bwo gutura no kuba mu bwoya zigata amagi mu bwoya…rero, ivyonyi bishobora kuba ari kimwe mu bintu vyateje ihinduka rya kiremwamuntu, kandi n’ubu biracari uko”.

Pagel avuga ko "ata kintu na kimwe kiza kivuguruza” iki ciyumviro kuva aho we na Bodmer bavyerekaniye ubwa mbere.

Lasisi avuga ko adashobora gushira ku ruhande ibintu bifise uruhara mw’itakaza ry’ubwoya. Ku bwiwe, "utegerezwa kwibaza igituma ibi biba ku bantu ariko ntibibe ku nguge, ku nkende”.

"Nsa n’uwitaho gusumba ibintu bishobora kwerekana inyifato canke imyimukira yatandukanije abantu n’inguge ku buryo vyasaba ko umuntu atakaza ubwoya”.

Kimwe muri ibi bintu gishobora kuba cabaye guhingura impuzu mu bwoya bw’ibindi bikoko bashobora kwambura no kumesa.

Hagati aho, Charles Darwin, yibaza ko ugutakaza ubwoya kwacu kwavuye ku mahitamwo mu bijanye n’ugukora imibonano mpuzabitsina – abakurambere bacu bahisemwo kuyikorana n’abafise ubwoya buke. Abenshi mu bashakashatsi ntibemera ko iki ari co kintu nyamukuru catumye umuntu atakaza ubwoya.

Ariko iyo turiko tuvuga ivyerekeye kuba abantu batagira ubwoya, hari ikibazo kimwe kibandanya kigaruka: kubera iki tugifise umushatsi ku mutwe, mu micungararo y’ibice vy'igitsina no mu kwaha?

Lasisi yakoze ubushakashatsi kuri iki kibazo, mu misi ivyo yatoye bikaba bigiye gushirwa ahabona, avuga ati: "Ikigaragara ko cumvikana ni uko abantu bashobora kuba baragumije imishatsi yabo ku mutwe kandi mu bisanzwe ikaba yarakuze, ariko kandi cane cane yitsivye kugira ngo igabanye ubukari bw’imishwarara iva ku zuba”.

Avuga ko cane cane umushatsi w’abantu utsivye ukuntu ku buryo usigaza inzira n’impemu, ibituma ugabanya neza ubukari bw’ubushuhe ukanagabanya n’urugero ubwo bushuhe bushikana ku mutwe.

Naho ku vyerekeye ubwoya bwo ku bice vy'igitsina canke ubusakwaha, Lasisi abona ko ari ibintu vyaje bitewe n’ibindi vyari bije, canke bugashobora kuba ibisigarira vy’imisemburo abakurambere bakoresha mu kuyaga hagati yabo (nta cemezo nyaco cerekana ko abantu ubu bagikoresha ubu bwoko bw’imisemburo).

Caba ico ari co cose catumye dutakaza ubwoya, hari ikintu kimwe gishoboka cane: vyahuriranye n’ingene urukoba rw’abantu ba mbere rwahinduye ibara, aho ubwoya bwari kirumara mu gukingira umubiri imishwarara y’izuba.

Lasisi ati: "Ni wo mwanzuro wumvikana twofata. Bishobora kuba vyarangiye bamwe mu bantu bavuka batagira urwoya na rumwe, hanyuma mu nyuma bakagenda barahinduka uko uruhu rw’abantu rwagenda ruhinduka. Canke naho hashobora kuba hagiye haba bukebuke igabanuka ry’ubwoya ryagenda riba uko uruhu rwagenda ruhinduka”.

N’ubwo ari ikintu ciza kwihweza ingene twatakaje ubwoya bwacu, bishobora kuba ari ibintu ataco bimaze ku buzima bwacu ubu. Ariko ubushakashatsi bwerekana ko gutahura iki kibazo bishobora kugira ingaruka ku bantu batakaje umushatsi batabishaka biciye mu kumera ubuhanza, mu buryo bwa chimiothérapie/chemotherapy bwo kuvura kanseri (cancer) , canke indwara zituma umuntu atakaza umushatsi.

Mu ntango za 2023, Nathan Clark, umuhinga mu bijanye n’uduce ndangakamere kw’ishure kaminuza ya Utah, ari kumwe na bagenzibe Amanda Kowalczyk na Maria Chikina kw’ishure kaminuza ya Pittsburgh, barihweje utwo duce ndangakamere tw’ibikoko 62 bivyara harimwo n'abantu kugira ngo barabe impinduka z’uduce ndangakamare ibikoko bivyara bitagira ubwoya vyoba bihurirako bibitandukanya na bigenzi vyavyo bifise ubwoya.

Basanze abantu basa n’abafise uduce ndangakamere dutuma uruhu rwomera ubwoya bufuka umubiri wose, ariko inginganizo ndangakamere (genomes) ikabuza ubwo bwoya kumera ngo bugaragare.