Umwana w’ihene atangira kugenda mu minota mike avutse. Mu minsi ibiri gusa, umutavu w’inka uba uri kwiruka. Ni mu gihe umwana w’umuntu amara amezi atatu adashobora no kwegura umutwe, akamara umwaka adashobora kugenda, n’imyaka hafi ibiri nta jambo azi kuvuga. Mu myaka irenga 10, aba ashobora gupfa aramutse abuze umwitaho.

None se ni iyihe mpamvu ikiremwa muntu gitinda gukura cyane ugereranyije n’izindi nyamabere? Igisubizo ni uko tuvuka imburagihe.

Mu myaka hafi miliyoni enye ishize, abakurambere bacu batangiye kugenda ku maguru abiri. Ibyo byatumye amagufa ya pelvis umwana acamo hagati yegerana, uwo mwanya uba muto. Mu myaka hafi miliyoni ebyiri ishize, ubwonko bw’umuntu bwatangiye kwaguka. Uko ubwonko bwagukaga ni ko umwanya ucamo umwana wagabanukaga.

Umubiri w’umuntu wahisemo gusohora umwana hakiri kare mbere y’uko ananirwa guca muri uwo mwanya.

Inguge ivukana ubwonko bungana na 40% bw’inguge nkuru mu gihe umuntu avukana ubwonko bungana na 25% by’ubwonko bw’umuntu mukuru. Kugira ngo umwana avukane ubwonko bungana na 40% by’ubwumuntu mukuru byasaba ko bamutwita imyaka ibiri, ariko icyo gihe ntabwo yabasha guca mu maguru ngo avuke.

Niyo mpamvu abana b’abantu bavuka igihe kitageze. Umuhanga muri siyansi Adolf Portmann yabyise "secondary altriciality," mu gihe abahanga mu by’imico n’amateka babyita the fourth trimester. Buriya umwaka wa mbere umwana avutse uba ari uwo kurangiza igihembwe cyo gutwita umwana yakabaye yaragiriye mu nda.

Ubwonko bw’umwana bwiga ku muvuduko uhambaye cyane. Mu kwezi kwa mbere, buba buri kurema inzira zibarirwa mu ma miliyoni. Ku myaka ibiri, buba bumaze kungana na 80% by’ubwonko bw’umuntu mukuru. Ureba uruhinja ukabona nta kintu na kimwe rushoboye gukora uretse kurira no kwinyarira, ariko ubwonko bwarwo buba buri gukura ku muvuduko utangaje.

Igice cy’ubwonko kitabashije kwiremera mu nda kiremwa n’ibikikije uwo mwana. Ibyo yumva byose, abantu areba, na buri makuru yose ubwonko bwe bwakira bigira uruhare mu kumurema nk’umuntu. Ni nk’uko wakora imashini itariho ikintu maze ugashyiramo windows ukoresheje flash disk.

Nta kindi kiremwa gikora ibyo bintu kuko nta kindi kiremwa gikenera kwiga ibintu byinshi nk’umuntu. Inyana ntabwo ikenera kumara imyaka yiga ngo ibe inka. Uruhinja ruba rukeneye kwita ururimi, umuco, imyitwarire, imyemerere, ubugeni, n’ibindi bintu byinshi cyane abantu bagezeho mu myaka ibihumbi amagana ishize.

Ubwo rero nujya kubyara igise kikakurya cyane, uzibuke ko uri kwishyura igiciro cyo kugenda ku maguru abiri. Inyamaswa hafi ya zose zivuka zuzuye, mu gihe umuntu avuka ari igice ngo yuzurire ku Isi.