 By way of language shift, acculturation, adoption and religious conversion, it is sometimes possible for individuals or groups to leave one ethnic group and become part of another.The social construct that ethnic groups share a similar gene pool has been contradicted within the scientific community as evidenced by data finding more genetic variation within ethnic groups compared to between ethnic groups.The largest ethnic groups in modern times comprise more than one billion individuals each (Han Chinese being the single largest), while the smallest are limited to a few dozen individuals (numerous indigenous peoples worldwide).