According to Kortlandt, Indo-Uralic is the pre-PIE, postulating that Indo-European and Uralic share a common ancestor.
According to Kortlandt, "Indo-European is a branch of Indo-Uralic which was radically transformed under the influence of a North Caucasian substratum when its speakers moved from the area north of the Caspian Sea to the area north of the Black Sea." Anthony notes that the validity of such deep relationships cannot be reliably demonstrated due to the time-depth involved, and also notes that the similarities may be explained by borrowings from PIE into proto-Uralic.
The Proto-Indo-European language (PIE) is the linguistic reconstruction of a common ancestor of the Indo-European languages spoken by the Proto-Indo-Europeans.
PIE was the first proposed proto-language to be widely accepted by linguists.
Several disputed proposals link Indo-European to other major language families.
The similarities between various European languages, Sanskrit and Persian were noted by Sir William Jones when learning Sanskrit in India, concluding that all these languages originated from the same source.
Archaeological research has unearthed a broad range of historical cultures which can be related to the spread of the Indo-European languages.
Various steppe-cultures show strong similarities with the Yamna-horizon at the Pontic steppe, while the time-range of several Asian cultures also coincides with the proposed trajectory and time-range of the Indo-European migrations.
Of the 20 languages with the largest numbers of native speakers according to SIL Ethnologue, 12 are Indo-European: Spanish, English, Hindi, Portuguese, Bengali, Russian, German, Punjabi, Marathi, French, Urdu, Italian, accounting for over 1.7 billion native speakers.
Linguistics describes the similarities between various languages, and the linguistic laws at play in the changes in those languages.
Archaeological data, describes the spread of the Proto-Indo-European language and culture in several stages from the Proto-Indo-European Eurasian homeland in the Pontic–Caspian steppe, into Western Europe and Central and South Asia, Recent genetic research has a growing contribution to the understanding of the historical relations between various historical cultures.
According to the widely accepted Kurgan hypothesis c.q.
Steppe theory, the Indo-European language and culture spread in several stages from the Proto-Indo-European Eurasian homeland in the Pontic steppes, into Western Europe, Central and South Asia, through folk migrations and so-called elite recruitment.