Russian is an East Slavic language of the Indo-European family. All Indo-European languages are descendants of a single prehistoric language, reconstructed as Proto-Indo-European, spoken sometime in the Neolithic era. Although no written records remain, much of the culture and religion of the Proto-Indo-European people can also be reconstructed based on their daughter cultures traditionally and continuing to inhabit most of Europe and South Asia, areas to where the Proto-Indo-Europeans migrated from their original homeland. External history Kievan Rus' period (9th–12th century) The common ancestor of the modern East Slavic languages, Old East Slavic, operated throughout Kievan Rus' ( 9th–13th century) as a spoken language. The earliest written record of the language, an amphora found at Gnezdovo, may date from the mid-10th century. In writing, Old Church Slavonic was the standard, although from the 11th century Rus' variations became distinguishable from Serb ones. Also in the 11th century, differences in written sources point to the slow emergence of distinct East Slavic languages. During the pre-Kievan period, the main sources of borrowings were Germanic languages, particularly Gothic and Old Norse. In the Kievan period, however, loanwords and calques entered the vernacular primarily from Old Church Slavonic and from Byzantine Greek: Feudal and linguistic breakup (13th–14th century) Kievan Rus' began to decline and fragment in the 12th century. From the 12th and 13th centuries, regional phonetic and grammatical variations within Rus' Church Slavonic texts could be detected, indicating the divergence of what would eventually become the Russian and Ukrainian languages from the 14th through 18th centuries. Around 1200, and especially after the Sack of Kiev (1240) when Mongols and Tatars established the Golden Horde in Central and Northern Rus', an autonomous spoken Russian language, largely independent from written Church Slavonic, began to develop. Nevertheless, Church Slavonic remained the literary standard in these central and northern regions for several more centuries. After the Mongol invasion of Kievan Rus' in the 13th century, the vernacular language of the conquered peoples remained firmly Slavic. Turko-Mongol borrowings in Russian relate mostly to commerce and the military: On the other hand, Ruthenian or Chancery Slavonic developed as a separate written form out of Old Church Slavonic, influenced by various local dialects and used in the chancery of the Grand Duchy of Lithuania, which came to dominate the western and southern lands of former Kievan Rus'. The Moscow period (15th–17th centuries) After the Golden Horde gradually disintegrated in the