Bavuga ko ibi bishyigikira igitekerezo cyuko, ku bantu bamwe, kugira urubavu ruto biterwa ahanini no kuba baragize "amahirwe" yo kugira ingirabuzima-fatizo (genes) bakuye ku bo bakomokaho, kurusha kuba byaterwa n'indyo iboneye yabo cyangwa se imibereho yabo.
