 Ubacwaningi abavela eNyuvesi yasePrinceton eMelika kanye naseNyuvesi yase-Uppsala eSweden babike ukuthi izidalwa ezintsha ziziphendukele ngezizukulwane ezimbili kuphela, nakuba lenqubo bekukholelwa ukuthi ithatha isikhathi eside, ngenxa yokuzalela phakathi kwezintaka zika-Darwin ezitholakala kuleyo ndawo kuphela, ama-Geospiza fortes, kanye nezintaka ze-cactus ezithuthele lapho, ama-Geospiza conirostris. 