The rest of the Jews lived among other peoples, mainly in the Ukrainian and Russian-Lithuanian environments. The numerical increase was due to mass migration of Yiddish-speaking Ashkenazi Jews from Central Europe to Eastern Europe beginning from the Middle Ages to the 16th century, as well as a high birth rate among these immigrants.[4] Genetic evidence also indicates that Yiddish-speaking Eastern European Jews largely descended from Ashkenazi Jews who migrated from central Europe and subsequently experienced high birthrates and genetic isolation.[5]