What explains the decline of the Yenisseyan languages in Siberia?Research indicates that Yenisseyan languages have been in decline due to language shift towards Russian, prompted by increased socio-economic incentives for native Siberians, particularly post-1989.When did significant contact occur between Yenisseyan and Turkic languages?Direct contact likely dates back to the time of the Xiongnu nomadic confederation around the 4th century BCE, evidenced by phonological similarities and loanwords identified in early Turkic.How has toponymy contributed to understanding Yenisseyan language territories?Toponymic studies reveal that historical place-names in Central Siberia may link back to Yenisseyan origins, highlighting a substantial territory once dominated by speakers prior to the Russian conquest.