The Caucasus is the most complex ethnographic region in all of Eurasia. It is home to three language families, North-West Caucasian, North-East Caucasian, and Kartvelian. While these three families reveal some areal commonalities, they also diverge radically in the details of their grammars. They show a degree of grammatical complexity that surpasses anything else on the continent. Caucasus folklore is also rich and shows many links with lore from Ireland to India. It seems to have preserved both a wealth of linguistic material antedating the great Indo-European and Altaic expansion of the last 5,000 years, and folkloric material from a host of peoples who have passed by the region on their way to present-day abodes or into the oblivion of history. Indo-European and Altaic languages and peoples have also penetrated the region, some, such as Ossetian at an early date, and others, such as Armenian and Russian within contemporary horizons.