Proto-Indo-European (PIE) is the reconstructed common ancestor of the Indo-European language family. No direct record of Proto-Indo-European has been discovered; its proposed features have been derived by linguistic reconstruction from documented Indo-European languages. Far more work has gone into reconstructing PIE than any other proto-language. The majority of linguistic work during the 19th century was devoted to the reconstruction of PIE and its daughter languages, and many of the modern techniques of linguistic reconstruction (such as the comparative method) were developed as a result.
PIE is hypothesized to have been spoken as a single language from approximately 4500 BCE to 2500 BCE during the Late Neolithic to Early Bronze Age, though other estimates place the bounds of the period as much as more than a thousand years later. According to the prevailing Kurgan hypothesis, the original homeland of the Proto-Indo-Europeans may have been in the Pontic–Caspian steppe of eastern Europe and central Asia. The linguistic reconstruction of PIE has provided insight into the pastoral culture and patriarchal religion of its speakers. Recent studies of archaeogenetics (the study of ancient DNA) add to the evidence that these were not just isolated tribal movements but broad networks of both pastoral expansion and trade where the language spoken was a key marker of identity for the tribes involved. As speakers of Proto-Indo-European became isolated from each other through the Indo-European migrations, the regional dialects of Proto-Indo-European spoken by the various groups diverged, as each dialect underwent shifts in pronunciation, morphology, and vocabulary. Over many centuries, these dialects transformed into the known ancient Indo-European languages. From there, more linguistic divergence led to the evolution of their current descendants, the modern Indo-European languages.
PIE is believed to have had an elaborate system of morphology that included inflectional suffixes (analogous to English child, child's, children, children's) as well as ablaut (vowel alterations, as preserved in English sing, sang, sung, song) and accent. PIE nominals and pronouns had a complex system of declension, and verbs similarly had a complex system of conjugation. The PIE phonology, particles, numerals, and copula are also well-reconstructed. Asterisks are used by linguists as a conventional mark of reconstructed words, such as , , or ; these forms are the reconstructed ancestors of the modern English words water, hound, and three, respectively.
Development of the hypothesis
No direct evidence of the Proto-Indo-European language exists; scholars have reconstructed PIE from its present-day descendants using the comparative method. For example, compare the pairs of words in Italian and English: and foot, and father, and fish. Since there is a consistent correspondence of the initial consonants (p and f) that emerges far too frequently to be unrelated coincidence, one can infer that these languages stem from a common parent language. Detailed analysis suggests a system of sound laws to describe the phonetic and phonological changes from the hypothetical ancestral words to the modern ones. These laws have become so detailed and reliable as to support the Neogrammarian hypothesis: the Indo-European sound laws apply without exception.
William Jones, an Anglo-Welsh philologist and puisne judge in Bengal during early East India Company rule in India, caused an academic sensation when in 1786 he postulated the common ancestry of Sanskrit, Greek, Latin, Gothic, the Celtic languages, and Old Persian, but he was not the first to state such a hypothesis. In the 16th century, European visitors to the Indian subcontinent became aware of similarities between Indo-Iranian languages and European languages, and as early as 1653, Marcus Zuerius van Boxhorn had published a proposal for a proto-language ("Scythian") for the following language families: Germanic, Romance, Greek, Baltic, Slavic, Celtic, and Iranian. In a memoir sent to the in 1767, , a French Jesuit who spent most of his life in India, had specifically demonstrated the analogy between Sanskrit and European languages. According to current academic consensus, Jones's famous work of 1786 was less accurate than his predecessors', as he erroneously included Egyptian, Japanese and Chinese in the Indo-European languages, while omitting Hindi.
In 1818, Danish linguist Rasmus Christian Rask elaborated the set of correspondences in his prize essay ('Investigation of the Origin of the Old Norse or Icelandic Language'), where he argued that Old Norse was related to the Germanic languages, and even suggested a relation to the Baltic, Slavic, Greek, Latin and Romance languages. In 1816, Franz Bopp published On the System of Conjugation in Sanskrit, in which he investigated the common origin of Sanskrit, Persian, Greek, Latin, and German. In 1833, he began publishing the Comparative Grammar of Sanskrit, Zend, Greek, Latin, Lithuanian, Old Slavic, Gothic, and German.
In 1822, Jacob Grimm formulated what became known as Grimm's law as a general rule in his . Grimm showed correlations between the Germanic and other Indo-European languages and demonstrated that sound change systematically transforms all words of a language. From the 1870s, the Neogrammarians proposed that sound laws have no exceptions, as illustrated by Verner's law, published in 1876, which resolved apparent exceptions to Grimm's law by exploring the role of accent (stress) in language change.
August Schleicher's A Compendium of the Comparative Grammar of the Indo-European, Sanskrit, Greek and Latin Languages (1874–77) represented an early attempt to reconstruct the Proto-Indo-European language.
By the early 1900s, Indo-Europeanists had developed well-defined descriptions of PIE which scholars still accept today. Later, the discovery of the Anatolian and Tocharian languages added to the corpus of descendant languages. A subtle new principle won wide acceptance: the laryngeal theory, which explained irregularities in the reconstruction of Proto-Indo-European phonology as the effects of hypothetical sounds which no longer exist in all languages documented prior to the excavation of cuneiform tablets in Anatolian. This theory was first proposed by Ferdinand de Saussure in 1879 on the basis of internal reconstruction only, and progressively won general acceptance after Jerzy Kuryłowicz's discovery of consonantal reflexes of these reconstructed sounds in Hittite.
Julius Pokorny's ('Indo-European Etymological Dictionary', 1959) gave a detailed, though conservative, overview of the lexical knowledge accumulated by 1959. Jerzy Kuryłowicz's 1956 Apophonie gave a better understanding of Indo-European ablaut. From the 1960s, knowledge of Anatolian became robust enough to establish its relationship to PIE.
In The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World, Mallory and Adams illustrate the resemblance with the following examples of cognate forms (with the addition of Old English for further comparison): {| class="wikitable" style="vertical-align:center;" |+ Examples of cognate words in Indo-European languages |- style="vertical-align:bottom;" ! ! Modern English ! Old English ! Latin ! Greek ! Sanskrit |- style="vertical-align:center;" | *méh₂tēr | mother | mōdor | māter | mḗtēr | mātár- |- style="vertical-align:center;" | *ph₂tḗr | father | fæder | pater | patḗr | pitár- |- style="vertical-align:center;" | *bʰréh₂tēr | brother | brōþor | frāter | phrḗtēr | bhrā́tar- |- style="vertical-align:center;" | *swésōr | sister | sweostor | soror | éor | svásar- |- style="vertical-align:center;" | *suHnús, *suHyús | son | sunu | | huiús | sūnú- |- style="vertical-align:center;" | *dʰugh₂tḗr | daughter | dohtor | | thugátēr | duhitár- |- style="vertical-align:center;" | *gʷṓus | cow | cū | bōs | boûs | gáu-
Historical and geographical setting
Scholars have proposed multiple hypotheses about when, where, and by whom PIE was spoken. The Kurgan hypothesis, first put forward in 1956 by Marija Gimbutas, has become the most popular. It proposes that this proto-language was spoken by the Yamnaya culture in the general area of the Pontic steppe north of the Black Sea 3400 BCE.
Other theories include the Anatolian hypothesis, which posits that PIE spread out from Anatolia with agriculture beginning 7500–6000 BCE, the Armenian hypothesis, the Paleolithic continuity paradigm, and the indigenous Aryans theory. The last two of these theories are not regarded as credible within academia. Review of Out of all the theories for a PIE homeland, the Kurgan and Anatolian hypotheses are the ones most widely accepted, and also the ones most debated against each other. Following the publication of several studies on ancient DNA in 2015, Colin Renfrew, the original author and proponent of the Anatolian hypothesis, has accepted the reality of migrations of populations speaking one or several Indo-European languages from the Pontic steppe towards Northwestern Europe.
Descendants
The antiquity of the earliest attestation (in units of 500 years) of each Indo-European group is: 2000–1500 BCE for Anatolian; 1500–1000 BCE for Indo-Aryan and Greek; 1000–500 BCE for Iranic, Celtic, Italic, Phrygian, Illyric, Messapic, South Picene, and Venetic; 500–1 BCE for Thracian and Ancient Macedonian; 1–500 CE for Germanic, Armenian, Lusitanian, and Tocharian; 500–1000 CE for Slavic; 1500–2000 CE for Albanian and Baltic.
The table lists the main Indo-European language families, comprising the languages descended from Proto-Indo-European. CladeProto-languageDescriptionHistorical languagesModern descendantsAnatolianProto-AnatolianAll now extinct, the best attested being the Hittite language.Hittite, Luwian, Palaic, Lycian, Lydian, Carian, Pisidian, Sidetic, MilyanThere are no living descendants of Proto-Anatolian.TocharianProto-TocharianAn extinct branch known from manuscripts dating from the 6th to the 8th century CE and found in northwest China.Tocharian A, Tocharian BThere are no living descendants of Proto-Tocharian.ItalicProto-ItalicThis included many languages, but only descendants of Latin (the Romance languages) survive.Latin, Faliscan, Umbrian, Oscan, African Romance, Dalmatian, Volscian, Marsi, Pre-Samnite, Paeligni, SabinePortuguese, Galician, Spanish, Ladino, Catalan, Occitan, French, Italian, Friulian, Romansh, Romanian, Aromanian, Sardinian, Corsican, Venetian, Latin (as a liturgical language of the Catholic Church), Picard, Mirandese, Aragonese, Walloon, Piedmontese, Lombard, Neapolitan, Sicilian, Emilian-Romagnol, Ligurian, Ladin CelticProto-CelticOnce spoken across Europe and Anatolia (Asia Minor), but now mostly confined to Europe's northwestern edge.Gaulish, Lepontic, Noric, Pictish, Cumbric, Old Irish, Middle Welsh, Gallaecian, Galatian, CeltiberianIrish, Scottish Gaelic, Welsh, Breton, Cornish, ManxGermanicProto-GermanicBranched into three subfamilies: West Germanic, East Germanic (now extinct), and North Germanic.Old English, Old Norse, Gothic, Old High German, Old Saxon, Vandalic, Burgundian, Crimean Gothic, Norn, Greenlandic NorseEnglish, German, Afrikaans, Dutch, Yiddish, Norwegian, Danish, Swedish, Frisian, Icelandic, Faroese, Luxembourgish, Scots, Limburgish, Wymysorys, ElfdalianBalto-SlavicProto-Balto-SlavicBranched into the Baltic languages and the Slavic languages.Old Prussian, Old Church Slavonic, Sudovian, Semigallian, Selonian, Skalvian, Galindian, Polabian, KnaanicBaltic: Latvian, Latgalian and Lithuanian;