of the knowledge on the Indo-European migrations and their purported homeland, new questions arise, and that "it is evident that we still have a very long way to go." One of those questions is the origin of the shared agricultural vocabulary, and the earliest dates for agriculturalism in areas settled by the Indo-Europeans. Those dates seem to be too late to account for the shared vocabulary, and raise the question what their origin is. Linguistics: relationships between languages Linguistic research traces the connections between the various Indo-European languages, and reconstructs proto-Indo-European. Accumulated linguistic evidence points to the Indo-Aryan languages as intrusive into the Indian subcontinent, some time in the 2nd millennium BCE. The language of the Rigveda, the earliest stratum of Vedic Sanskrit, is assigned to about 1500–1200 BCE. Comparative method Connections between languages can be traced because the processes that change languages are not random, but follow strict patterns. Especially sound shifts, the changing of vowels and consonants, are important, although grammar (especially morphology) and the lexicon (vocabulary) may also be significant. Historical-comparative linguistics thus makes it possible to see great similarities between languages which at first sight might seem very different. Linguistics use the comparative method to study the development of languages by performing a feature-by-feature comparison of two or more languages with common descent from a shared ancestor, as opposed to the method of internal reconstruction, which analyses the internal development of a single language over time. Ordinarily both methods are used together to reconstruct prehistoric phases of languages, to fill in gaps in the historical record of a language, to discover the development of phonological, morphological, and other linguistic systems, and to confirm or refute hypothesized relationships between languages. The comparative method aims to prove that two or more historically attested languages are descended from a single proto-language by comparing lists of cognate terms. From them, regular sound correspondences between the languages are established, and a sequence of regular sound changes can then be postulated, which allows the proto-language to be reconstructed. Relation is deemed certain only if at least a partial reconstruction of the common ancestor is feasible, and if regular sound correspondences can be established with chance similarities ruled out. The comparative method was developed over the 19th century. Key contributions were made by the Danish scholars Rasmus Rask and Karl Verner and the German scholar Jacob Grimm. The first linguist to offer reconstructed