Comparative linguistics, with historical linguistics, studies languages to establish connections between them. Connections may be genetic, meaning the languages have a common ancestral language and belong to the same language family, or may result from cultural contact between unrelated languages. Shared cognates may result from either source. To discern connections, comparative linguists compare and contrast languages' phonological and morphological systems, syntax, and vocabularies, increasingly relying on computers to detect symmetries. One tool of comparative linguists is evolutionary phonology, which posits that language changes in predictable ways, allowing parent or "proto-languages" to be reconstructed through reverse engineering. A famous early success of comparative linguistics was proving that Indian Sanskrit is part of the same Indo-European language family as most contemporary European languages, showing a common origin.