There are several competing hypotheses about when and where PIE was spoken. The Kurgan hypothesis is "the single most popular" model, postulating that the Kurgan culture of the Pontic steppe were the hypothesized speakers of the reconstructed Proto-Indo-European language. However, alternative theories such as the Anatolian urheimat have also gained acceptance.
The satemization process that caused the separation between Centum and Satem languages probably started as early as the fourth millennium BC and the only thing known for certain is that the proto language must have been differentiated into unconnected daughter dialects by the late 3rd millennium BC.
Mainstream linguist estimates of the time between PIE and the earliest attested texts (ca. nineteenth century BC; see Kültepe texts) range around 1,500 to 2,500 years, with extreme proposals diverging up to another 100% on either side:
PIE as described in the early 1900s is still generally accepted today; subsequent work is largely refinement and systematization, as well as the incorporation of new information, notably the Anatolian and Tocharian branches unknown in the 19th century.
Notably, the laryngeal theory, in its early forms discussed since the 1880s, became mainstream after Jerzy Kuryłowicz's 1927 discovery of the survival of at least some of these hypothetical phonemes in Anatolian. Julius Pokorny's Indogermanisches etymologisches Wörterbuch (1959) gave an overview of the lexical knowledge accumulated until the early 20th century, but neglected contemporary trends of morphology and phonology, and largely ignored Anatolian and Tocharian.
The generation of Indo-Europeanists active in the last third of the 20th century (such as Calvert Watkins, Jochem Schindler and Helmut Rix) developed a better understanding of morphology and, in the wake of Kuryłowicz's 1956 Apophonie, understanding of the ablaut. From the 1960s, knowledge of Anatolian became certain enough to establish its relationship to PIE; see also Indo-Hittite.
As the Proto-Indo-European language broke up, its sound system diverged as well, according to various sound laws in the daughter languages. Notable among these are Grimm's law and Verner's law in Proto-Germanic, loss of prevocalic *p- in Proto-Celtic, reduction to h of prevocalic *s- in Proto-Greek, Brugmann's law and Bartholomae's law in Proto-Indo-Iranian, Grassmann's law independently in both Proto-Greek and Proto-Indo-Iranian, and Winter's law and Hirt's law in Balto-Slavic.
The existence of certain PIE typological features in Northwest Caucasian languages may hint at an early Sprachbund or substratum that reached geographically to the PIE homelands. This same type of languages, featuring complex verbs and of which the current Northwest Caucasian languages might have been the sole survivors, was cited by Peter Schrijver to indicate a local lexical and typological reminiscence in western Europe pointing to a possible Neolithic substratum.
Other proposals, further back in time (and correspondingly less accepted), link PIE and Uralic with Altaic and certain other families in Asia, such as Korean, Japanese, Chukotko-Kamchatkan and Eskimo-Aleut (representative proposals are Nostratic and Joseph Greenberg's Eurasiatic); or link some or all of these to Afro-Asiatic, Dravidian, etc., and ultimately to a single Proto-World family (nowadays mostly associated with Merritt Ruhlen). Various proposals, with varying levels of skepticism, also exist that join some subset of the putative Eurasiatic language families and/or some of the Caucasian language families, such as Uralo-Siberian, Ural-Altaic, Proto-Pontic, and so on.
|Fricative||*/s/||*/h₁/, */h₂/, */h₃/|
Other long vowels may have appeared already in the proto-language by compensatory lengthening: .
PIE was an inflected language, in which the grammatical relationships between words were signaled through inflectional morphemes (usually endings). The roots of PIE are basic morphemes carrying a lexical meaning. By addition of suffixes, they form stems, and by addition of desinences (usually endings), these form grammatically inflected words (nouns or verbs). PIE roots are understood to be predominantly monosyllabic with a basic shape CvC(C). This basic root shape is often altered by ablaut. Roots which appear to be vowel initial are believed by many scholars to have originally begun with a set of consonants, later lost in all but the Anatolian branch, called laryngeals (usually indicated H, and often specified with a subscript number h1, h2, h3). Thus a verb form such as the one reflected in Latin agunt, Greek ἄγουσι (ágousi), Sanskrit would be reconstructed as , with the element constituting the root per se.
One of the distinctive aspects of PIE was its ablaut sequence that contrasted the vowel phonemes o/e/Ø [no vowel] within the same root. Ablaut is a form of vowel variation which changed between these three forms perhaps depending on the adjacent sounds and placement of stress in the word. These changes are echoed in modern Indo-European languages where they have come to reflect grammatical categories. These ablaut grades are usually referred to as: e-grade and o-grade, sometimes collectively termed full grade; zero-grade (no vowel, Ø); and lengthened grade (ē or ō). Modern English sing, sang, sung is an example of such an ablaut set and reflects a pre-Proto-Germanic sequence sengw-, songw-, sngw-. Some scholars believe that the inflectional affixes of Indo European reflect ablaut variants, usually zero-grade, of older PIE roots. Often the zero-grade appears where the word's accent has shifted from the root to one of the affixes. Thus the alternation found in Latin est, sunt reflects PIE h1és-ti, h1s-ónti
Proto-Indo-European nouns were declined for eight cases (nominative, accusative, genitive, dative, instrumental, ablative, locative, vocative). There were three genders: masculine, feminine, and neuter.
There are two major types of declension, thematic and athematic. Thematic nominal stems are formed with a suffix -o- (in vocative -e) and the stem does not undergo ablaut. The athematic stems are more archaic, and they are classified further by their ablaut behaviour (acro-dynamic, protero-dynamic, hystero-dynamic and holo-dynamic, after the positioning of the early PIE accent (dynamis) in the paradigm).
PIE pronouns are difficult to reconstruct owing to their variety in later languages. This is especially the case for demonstrative pronouns. PIE had personal pronouns in the first and second person, but not the third person, where demonstratives were used instead. The personal pronouns had their own unique forms and endings, and some had two distinct stems; this is most obvious in the first person singular, where the two stems are still preserved in English I and me. According to Beekes (1995), there were also two varieties for the accusative, genitive and dative cases, a stressed and an enclitic form.
|Personal pronouns (Beekes 1995)|
|First person||Second person|
|Accusative||h₁mé, h₁me||nsmé, nōs||twé||usmé, wōs|
|Genitive||h₁méne, h₁moi||ns(er)o-, nos||tewe, toi||yus(er)o-, wos|
|Dative||h₁méǵʰio, h₁moi||nsmei, ns||tébʰio, toi||usmei|
As for demonstratives, Beekes (1995) tentatively reconstructs a system with only two pronouns: so/seh₂/tod "this, that" and h₁e/ (h₁)ih₂/(h₁)id "the (just named)" (anaphoric). He also postulates three adverbial particles ḱi "here", h₂en "there" and h₂eu "away, again", from which demonstratives were constructed in various later languages.
The Indo-European verb system is complex and, as the noun, exhibits a system of ablaut. Verbs have at least four moods (indicative, imperative, subjunctive and optative, as well as possibly the injunctive, reconstructible from Vedic Sanskrit), two voices (active and mediopassive), as well as three persons (first, second and third) and three numbers (singular, dual and plural). Verbs are conjugated in at least three "tenses" (present, aorist, and perfect), which actually have primarily aspectual value. Indicative forms of the imperfect and (less likely) the pluperfect may have existed. Verbs were also marked by a highly developed system of participles, one for each combination of tense and mood, and an assorted array of verbal nouns and adjectival formations.
|Buck 1933||Beekes 1995|
The Proto-Indo-European numerals are generally reconstructed as follows:
|Sihler 1995, 402–24||Beekes 1995, 212–16|
|three||*trei- (full grade)/*tri- (zero grade)||*treies|
|four||*kʷetwor- (o-grade)/*kʷetur- (zero grade), |
see also the kʷetwóres rule
|six||*s(w)eḱs; originally perhaps*weḱs||*(s)uéks|
|twenty||*wīḱm̥t-; originally perhaps*widḱomt-||*duidḱmti|
|thirty||*trīḱomt-; originally perhaps*tridḱomt-||*trih₂dḱomth₂|
|forty||*kʷetwr̥̄ḱomt-; originally perhaps*kʷetwr̥dḱomt-||*kʷeturdḱomth₂|
|fifty||*penkʷēḱomt-; originally perhaps*penkʷedḱomt-||*penkʷedḱomth₂|
|sixty||*s(w)eḱsḱomt-; originally perhaps*weḱsdḱomt-||*ueksdḱomth₂|
|seventy||*septm̥̄ḱomt-; originally perhaps*septm̥dḱomt-||*septmdḱomth₂|
|eighty||*oḱtō(u)ḱomt-; originally perhaps*h₃eḱto(u)dḱomt-||*h₃eḱth₃dḱomth₂|
|ninety||*(h₁)newn̥̄ḱomt-; originally perhaps*h₁newn̥dḱomt-||*h₁neundḱomth₂|
|hundred||*ḱm̥tom; originally perhaps*dḱm̥tom||*dḱmtóm|
As PIE was spoken by a prehistoric society, no genuine sample texts are available, but since the 19th century modern scholars have made various attempts to compose example texts for purposes of illustration. These texts are educated guesses at best; Calvert Watkins in 1969 observes that in spite of its 150 years' history, comparative linguistics is not in the position to reconstruct a single well-formed sentence in PIE. Nevertheless, such texts do have the merit of giving an impression of what a coherent utterance in PIE might have sounded like.
Published PIE sample texts:
Authors: Thomas V. Gamkrelidze and VV Ivanov. (Scientific American, March 1990)]