The dissimilarity of the inhabitants of different regions may be attributed to modification through variation and natural selection, and probably in a subordinate degree to the definite influence of different physical conditions.
Herrialde ezberdinetako biztanleen arteko ezberdintasuna hautespen naturalaren bidezko eraldaketari iratxeki dakioke, eta ziurrenik, neurri txikiagoan, baldintza fisikoen eragin zehatzari.