Abin da wani giwa ta hakori ya koya mana game da juyin halitta

What an elephant’s tooth teaches us about evolution

Don tabbatar da cewa juyin canji ba ko da yaushe gangara zuwa genes, kawai bude wani giwa ta bakin ...


Powered by Guardian.co.ukWannan labarin mai taken “Abin da wani giwa ta hakori ya koya mana game da juyin halitta” aka rubuta ta hanyar Alice Roberts, for The Observer a ranar Lahadi 31st Janairu 2016 07.00 UTC

Long da suka wuce, watakila ma kafin bikin hazo lokaci, akwai wani babban iyali dabbobi da suka rayu a nahiyar Afirka. Labarin ya fara da wasu 10 miliyan years ago, sa'an nan kuma iyali girma da kuma yada daga. Around uku da miliyan da suka wuce, wani reshe na shi zube a cikin kasashen Turai da kuma Asiya. Kamar yadda dabbobi koma cikin sabon yankunan, suka saba da more arewacin climes. A ƙarshe, wasu haye gada daga Beringia, migrating daga arewa maso gabashin Asia cikin North America.

Yana sauti a saba story. Lalle ne, wannan shi ne duk game da kakanninmu - Afrika asalin a Miocene, da key burbushin bayyana daga zamanin d sediments a Kenya; wasu daga wannan rukuni colonizing Turai da Asia; da Maris a cikin sabuwar duniya. Amma wannan ba labarin hominins: na Australopithecines, paranthropines da Homo. Wannan shi ne labarin da elephantines: na mammoths, Loxodonta da kuma Elephas.

A mafi daukan hankali halaye na rayuwa giwaye - kututturan da giwa - ya bayyana a cikin gomphothere kakanninsu da 20 miliyan years ago. Ga wani babban dabba da wani ɗan gajeren wuyansa, gangar jikin wani musamman m ci gaban, kyale wadannan proboscideans fahimci ganye da kuma kawo su bakin, haka samar da wani juyin amfani.

A ci gaba da wani akwati da canji na incisors cikin giwa aka tare da wani canji a cikin siffar da kwanyar. Tu bakin, hakora aka kuma canza. A takaice muƙamuƙi bar kadan dakin cikakken sa na molars, yayin da hakora da ake bukata don ya sami damar raya dogon rayuwa ta daraja da nauyi lalacewa. Evolution azurta wani m warware dukan matsalolin. Maimakon da ciwon dukan sa na premolars da molars crammed a bakin a lokaci guda - kamar yadda a cikin bakinka - akwai m guda, babban hakori mamaye kowane gefe daga cikin manya da ƙananan muƙamuƙi a kowane lokaci. Kamar yadda wannan hakori sa saukar, wani za a girma a baya shi, shirye slide cikin wurin lokacin da sawa-fito hakori fadi daga, samar da dabba da har zuwa shida sets hakora a rayuwa.

An artist ta bugu na gomphotherium
An artist ta bugu na gomphotherium, hudu tusked m na giwa, da zuriya. M: Alamy

The haƙoran m gomphotheres da giwaye adana wani alama da abun da ake ci. A rabo daga daban-daban isotopes na carbon a hakori enamel nuna ko wani mutum da aka mayar da hankali a kan more lilo a kan ganye ko cin ciyawa. The grasslands Afrika na farko ya fara yada a kusa da 10 shekaru miliyan da suka wuce kuma isotope analysis bayyana cewa marigayi gomphotheres da farkon giwaye switched zuwa cin yafi ciyawa a kusa da miliyan takwas da suka wuce. a giwaye, wannan canji da aka nuna a cikin wani canji zuwa ga taban da ake hakora, wanda ya zama sau uku a matsayin m, tare da yaduwa na enamel ridges. amma wadannan adaptations zuwa wani abrasive rage cin abinci bayyana a kusa da miliyan biyar da suka wuce, miliyan uku bayan shekara da canza daga m ganye m ciyawa. Tare da mataki na ƙuduri da za mu iya cimma a lokacin da neman nisa baya cikin da, yana da sau da yawa wuya a san abin da ya zo na farko - a canji a hali ko a fannin Anatomy. Amma a wannan yanayin, yana da matukar bayyana: da canje-canje ga hakora aka miliyoyin shekara bayan canji a rage cin abinci.

A cikin juyin labarun, da kwayoyin da kanta sau da yawa alama taka m rawa: a m aka azabtar, kusan, canje-canje zuwa ga muhalli ko maye gurbi a cikin halittar. Amma labari na giwa ta hakori ne ko ta yaya daban-daban, wani canji a hali a fili ya biyo baya wani canji a fannin Anatomy (kuma tamkar kayyade umarnin don hakori ci gaba). Zai yiwu bai kamata mu yi mamaki da wannan: tsarin plasticity yana nufin cewa na karshe siffar dabba ta jiki ne m ba kawai ta hanyar DNA amma kuma daga waje dalilai. Kuma dabbobi ne mafi m, a cikin hanyar da suka hul] a da su muhallin daga gare mu, wani lokacin zaton. As giwaye nuna, tushen sabon abu a cikin juyin su iya zo daga hali maimakon daga kwayoyin halittu.

Hakora a Afrika giwa kwanyar.
Hakora a Afrika giwa kwanyar. M: Images of Africa Photobank / Alamy

Yana da kawai zai yiwu cewa wannan irin canji, originating da wani canji a hali, taka muhimmiyar rawa a juyin halittar mutum. Around shekaru miliyan biyu da suka wuce, akwai wani babban motsi a cikin jiki da kuma siffar daga m kafafu, wanda ya fara bayyana a cikin Homo erectus. Yana da m cewa da dama daga cikin sabon sifofin, daga tsawon kafafu don kara girman gluteal tsokoki da chunkier Achilles tendons, suna da alaka ta ƙara yadda ya dace a cikin Gudun. Idan wani rukuni na mutane suka fara gudu a kai a kai, watakila kyale su su farautar ko roron more yadda ya kamata, ilimin Halittar Jiki canje-canje zai bi, musamman a cikin m-tasowa majiya karfi. Da zarar Gudun zama wani muhimmin ɓangare na hali, wani maye gurbi wanda inganta shi za a yi falala a kansu. Amma hakikanin tushen sabon abu, watakila, shi ne cewa canji a hali da ba a kayyade maye gurbi.

Babban proboscideans cewa yawonta Afrika shimfidar wurare inda namu kakanninsa samo asali tunatar da mu cewa juyin halitta sabon abu ba ko da yaushe yake fãra a genes.

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