Indo-European Languages

The Indo-European language family, one of the world's largest language families, encompasses a wide range of languages spoken across Europe, Asia; through much of the world by way of European colonization. Despite the significant diversity in the family, resulting from thousands of years of evolution, migration, and contact with unrelated languages, there are common traits that can be traced back to their shared ancestry. These commonalities, while sometimes abstract or obscured by language change, include phonological, morphological, syntactic, and lexical features.

The modern Indo-European languages with the most native speakers are Spanish, English, Hindi–Urdu, Bengali, Portuguese, Russian, Punjabi, French and German (each with over 100 million native speakers), while many others are small and in danger of extinction. Nine of its historical subfamilies are completely extinct.

In total, 46% of the world's population (3.2 billion people) speaks an Indo-European first language (by far the highest of any language family). There are about 445 currently spoken Indo-European languages, with over two-thirds (313) of them belonging to the Indo-Iranian branch.

The IE family has the second-longest written history of any known family, after the Afroasiatic languages (particularly Egyptian, ~3200 BCE and Akkadian, ~2500 BCE).

Common Traits

Indo-European languages split into two groups based on their treatment of certain velar consonants. Centum languages (like Latin, Greek, and Germanic languages) merged or kept these velars distinct, while Satem languages (like Indo-Iranian languages) palatalized them.

Certain phonological changes, such as Grimm's Law in Germanic languages (a systematic shift of consonant sounds) can be traced back to common Indo-European roots.

Many Indo-European languages utilize inflections to convey grammatical relationships. This includes the use of case endings in nouns to indicate their role in a sentence (nominative, accusative, genitive) and verb conjugations to express tense, mood, aspect, and voice. A common trait is the distinction between aspect (perfective versus imperfective) and mood (indicative, subjunctive, imperative) in verb systems, although the specifics can vary widely among the languages.

It is hypothesized that the Proto-Indo-European language might have predominantly used an SOV (Subject Object Verb) word order, which is still found in some modern Indo-European languages, although many have shifted to SVO (Subject Verb Object).

There are many cognates (words derived from a common ancestral word) across Indo-European languages in basic vocabulary such as family terms (mother, father), numbers, and body parts. The reconstruction of the Proto-Indo-European language has provided a basis for identifying these common roots. Similar processes for creating words from roots, including suffixation and prefixation, can be observed across the family.

Comparative mythology has found recurring themes and deities in the mythologies of various Indo-European cultures, suggesting a common proto-mythology. Similarities in poetic and metrical forms have been observed, indicating a shared tradition of oral literature.

It's important to note that while these traits can be identified across Indo-European languages, the extent and manner in which they are present can vary greatly due to the vast time scale of linguistic evolution, geographical dispersion, and contact with non-Indo-European languages. Additionally, the Indo-European family is a historical construct based on linguistic evidence; thus, the features of individual languages have diverged significantly from their proto-language over millennia.

Indo-European Language Branches

The family consists of several major subfamilies:

• Anatolian, an extinct branch of languages spoken in/around Anatolia, in modern Türkiye.
• Hellenic (the Ancient Greek dialects), spoken around the Aegean, Mediterranean, and Black Sea.
• Italic (including Latin), spoken by the peoples of the Italian peninsula.
• Germanic, initially spoken in Northern Europe and Scandinavia.
• Indo-Iranian, initially spoken around the Iranian plateau and then into Central Asia and South Asia.
• Balto-Slavic, spoken across Central Europe and Eastern Europe.
• Celtic, spoken across France, Belgium, Ireland, the British Isles, Iberia, and beyond.

There are also a number of languages that are within the Indo-European family but do not necessarily belong to a distinct branch of subfamily:

• Albanian
• Armenian
• Tocharian
• Thracian
• Illyrian
• Dacian
• Liburnian
• Ligurian
• Lusitanian
• Messapic
• Phrygian

Proto-Indo-European Roots

The Proto-Indo-European (PIE) language is the hypothetical common ancestor of the Indo-European language family. Despite the absence of direct records, linguists have reconstructed aspects of PIE based on systematic comparisons of its descendant languages, utilizing the comparative method. This reconstruction offers insights into its phonology, morphology, syntax, and lexicon, as well as aspects of the culture and environment of its speakers. The consensus on PIE, while robust in many areas, is still subject to ongoing research and debate.

PIE is believed to have had a complex system of consonants and vowels, with distinctions between voiced, voiceless, and aspirated stops, as well as sonorants (nasals, liquids) and sibilants. The existence of laryngeal sounds, which have left their trace primarily in the vowel system of descendant languages, is a significant aspect of PIE phonology that was uncovered through the analysis of anomalies in the phonetic patterns of these languages.

Most scholars now believe there were three distinct laryngeals, which can be written H₁, H₂, and H₃. Of these, H₁ may ha ve been h or a glottal stop; H₂ was perhaps a pharyngeal spirant like Arabic ḥ in ḥams ‘five’; H₃, whatever its other features, was probably voiced. When laryngeals between consonants disappeared a vowel sometimes remained, as in Greek stásis, Sanskrit sthitis, Old English stede ‘a standing (place)’ from Proto-Indo-European *stH₂tis. Before the advent of the laryngeal theory, a separate Proto-Indo-European vowel ə (called schwa indogermanicum) was reconstructed to account for these correspondences.

PIE nouns and adjectives are reconstructed with a system of declensions, including cases such as nominative, accusative, genitive, dative, and ablative; gender (masculine, feminine, and neuter) and number (singular, dual, and plural) distinctions were also present. The PIE verb system is believed to have included aspects (imperfect versus perfect), mood (indicative, subjunctive, optative, imperative), voice (active, middle, and possibly passive), and a rich set of conjugations to express tense (present, past, future).

The reconstructed syntax of PIE suggests a flexible word order with a tendency towards SOV (Subject-Object-Verb), similar to many of its ancient descendants such as Sanskrit and Ancient Greek. The use of cases allowed for this flexibility, as syntactic roles were marked on the nouns rather than determined by position.

Reconstruction of the PIE lexicon has provided insights into the culture and environment of its speakers. Terms related to family, animals, nature, agriculture, technology, and the divine suggest a pastoral-agrarian society. Thus is it supposed that the community knew and talked about dogs (*ḱwón-), horses (*H₁éḱwo-), sheep (*H₃éwi-), and almost certainly cows (*g^wów-) and pigs (*súH-), all of which were likely domesticated.

At least one cereal grain was known (*yéwo-), and at least one metal (*H₂éyos). There were vehicles (*wóǵho-) with wheels (*k^wék^wlo-), pulled by teams joined by yokes (*yugó-). Honey was known, and it probably formed the basis of an alcoholic drink (*mélit-, *médhu) related to the English mead. Numerals up through 100 (*ḱm̥tóm) were in use. All this suggests a people with a well-developed Neolithic or even Chalcolithic technology.

While more speculative, the reconstruction of PIE vocabulary has led scholars to infer aspects of PIE society, including its patrilineal and patriarchal structure, importance of kinship and hospitality, and practices related to agriculture, animal husbandry, and warfare. Mythological reconstructions point towards a religion that included sky father gods, earth mother goddesses, and a complex set of ritual practices.

Number	Proposed PIE Reconstruction
one	*Hoi-no-/*Hoi-wo-/*Hoi-k(ʷ)o-; *sem- *Hoi(H)nos ; sem-/sm̥-
two	*d(u)wo- *du̯oh
three	*trei- (full grade) / *tri- (zero grade) *trei̯es
four	*kʷetwor- (o-grade) / *kʷetur- (zero grade) *kʷétu̯ōr
five	*penkʷe
six	*s(w)eḱs; originally perhaps *weḱs *(s)u̯éks
seven	*septḿ̥ *séptm̥
eight	*oḱtō, *oḱtou or *heḱtō, *heḱtou *heḱteh
nine	*(h)newn̥ *(h₁)néun
ten	*déḱm̥(t) *déḱm̥t

Rather than specifically 'one hundred,' *ḱm̥tóm (*dḱm̥tóm) may originally have meant 'a large number.'

The reference to grade relates to the ablaut system, a type of vowel gradation that occurs in the root of a word. Ablaut is a fundamental aspect of PIE and many of its descendant languages, affecting how words are inflected and how their related forms are derived. The concept of grade in PIE linguistics refers to the variations in the root vowel that occur in different forms of a word, often corresponding to grammatical or semantic changes. There are typically three main grades recognized in PIE ablaut patterns:

• Full Grade (E-Grade or O-Grade): Includes the presence of a full vowel, either *e or *o, in the root of the word. It is often seen in the basic form or "strong" cases of a noun or the present tense of a verb. For example, the *e in *trei- ("three") represents a full grade.
• Zero Grade: The vowel of the root is absent or reduced, often resulting in the contraction of surrounding consonants. It occurs in various grammatical forms, such as in certain noun cases or in verb conjugations. The absence of the vowel in *tri- (a reduced form of 'three') and *kʷetur- ('four') illustrates the zero grade.
• Lengthened Grade: This involves the lengthening of the vowel in the root, which can appear in certain grammatical contexts or to indicate a semantic difference. It's represented by ē or ō in reconstructions.

The ablaut system is one reason for the complexity of PIE verb conjugations and noun declensions, as well as the formation of various grammatical moods and aspects.

Divergence of PIE into the IE Language Family

It is difficult, if not impossible, for linguists to date the divergence from PIE based on the existing evidence. The best that can be done is to estimate how different each language is to the others, and then comparing that degree of difference across the family (paying special attention to branches like the Romance subfamily, where dates of divergence have a stronger foundation).

Based on this, it is generally 'calculated' that the earliest branches of Indo-European languages (Anatolian, Indo-Iranian, and Hellenic) began to emerge ~3000 BCE, with the ancestral (PIE) language itself likely emerging up to a millennium before this. The initial PIE population was likely a small, homogenous Eurasian group that expanded and fragmented significantly around ~4000 BCE.

Many steppe cultures extended across the entire Black Sea to Caspian Sea region (the Caucasus; modern Russia; Georgia; Azerbaijan; Armenia; and NE Türkiye; it is believed that multiple migrations of these peoples moved outward from the core homeland in different time periods, possibly coming to dominate indigenous populations as a new warrior elite, possibly via 'elite recruitment'.

• Ciscaucasia lies within Russian territory and includes the foothills and plains extending northward from the primary range of the Caucasus Mountains. It is home to the North Caucasus Federal District, which encompasses several Russian republics.
• Transcaucasia is south of the Caucasus Mountains and includes the modern countries of Georgia, Armenia, and Azerbaijan.

According to the widely held Kurgan hypothesis (or renewed Steppe hypothesis), the oldest migration branch of steppe migrants produced the Anatolian languages (Hittite and Luwian) which split from the earliest proto-Indo-European speech community (archaic PIE) inhabiting the Volga basin. The second-oldest branch language group, Tocharian, was spoken in the Tarim Basin (now western China), after splitting from early PIE spoken on the eastern Pontic steppe. The bulk of the Indo-European languages developed from later PIE, which according to this hypothesis was spoken within the Yamnaya horizon on the Pontic–Caspian steppe around 3000 BCE.

'Elite recruitment' refers to a process where the social, political, or military elite of a migrating group exerts influence over the indigenous populations they encounter, leading to the adoption of the elite's language and cultural practices by the larger population. This influence does not necessarily require large-scale migration or displacement of the existing population; instead, the prestige or power of the elite group drives the adoption of their language and culture.

A remote relationship of Indo-European to the Uralic languages is possible; both families appear to have developed in relatively close proximity, and they share a number of similarities in terms of grammatical elements (particularly with pronouns, personal endings of verbs, the accusative case, and some terms). Both families also have many suffixes but few or no prefixes or infixes. Aside from these features, there are few other similarities - so if they are related, it would have been through an ancestor that existed thousands of years ago. Still, there are many more similarities between Indo-European and Uralic as compared to other language families such as Afro-Asiatic and Kartvelian, indicating a closer temporal proximity in terms of when they diverged from one another. The idea of any kind of reconstructed superfamily preceding them is bereft of evidence.

As PIE split into the dialects that would eventually spawn the family's first daughter languages, different regions developed distinct changes. Among the Central Asian and Eastern European dialects, the palatal stops (*ḱ, *ǵ, and *ǵh) favored by PIE were changed into fricatives (s, ś, th, et cetera) or affricates (ch, j). In this way, from the basic PIE element *H₂eḱ (meaning ‘sharp, pointed') we see the following transmutations:

• Sanskrit: aśri - 'edge.’ The change from PIE *ḱ to "ś" is characteristic.
• Old Church Slavonic: ostrŭ - ‘sharp.' Reflecting the common Slavic treatment of PIE *ḱ as 's' or 'st.'
• Armenian: asełn - ‘needle.'
• Albanian: athëtë - ‘bitter.’
• Greek: ákros meaning ‘tip.’ The change from *ḱ to 'k' is a feature of Greek phonology.
• Latin: acidus meaning ‘biting,' *ḱ becoming 'c' is a common Latin development.

Satem versus Centum

The languages that change the palatal stops into affricates are known as the satem languages - from the Avestan word satəm ‘hundred’ (from PIE *kmtóm), which illustrates the change. The languages that preserve the palatal stops as k-like sounds are known as centum languages, from centum (/kentum/), the corresponding word in Latin. Satem languages are not geographically separated from one another by any centum languages, which implies this change happened only once, but occurred across a contiguous language area of PIE.

Boundaries between Satem and Centum Languages

Generally, there is an east-west division within the family, with the satem languages predominantly situated in the east, and the centum languages occupying the west.

The boundary begins in Europe, where the Baltic and Slavic languages mark the westernmost extent of the satem languages. The division here separates the satem-speaking Slavic and Baltic regions from the centum-speaking Germanic and Romance-speaking areas of Western Europe.

The boundary continues, separating the Slavic languages in Eastern Europe from the Germanic languages to the northwest and the Romance languages to the southwest. The Satem-Centum divide here is not purely geographical but correlates with the linguistic landscape shaped by historical migrations and the Roman Empire's influence.

The boundary extends south, where the historical presence of satem-speaking Thracian, Dacian, and Illyrian languages differentiated these areas from the centum-speaking regions of ancient Italy and Greece. This area is more complex due to the historical movements of peoples and the eventual dominance of Slavic languages in much of the Balkans. To the northeast of the Black Sea, the boundary delineates the Indo-Iranian languages of the satem group from the Anatolian languages and the ancient Greek dialects, which were centum languages.

The boundary extends into Asia, encompassing the vast area of Iran and Central Asia, where Iranian languages are spoken, and further into South Asia, home to the Indo-Aryan languages. The boundary skirts around the Caucasus region, which is linguistically diverse and includes languages from both the Indo-European family (including Armenian, a satem language) and many non-Indo-European languages.

'bh' -> 'm'

In two families (Balto-Slavic and Germanic), certain cases that ended in 'bh' or a related phoneme in other Indo-European languages were replaced with an 'm' sound (including in English, a Germanic language, where the word 'them' is a key example). The same is true in Old Church Slavonic, where it becomes tě-mŭ ('to those ones'). In more easterly languages, it remains. In Sanskrit té-bhyas ‘to those ones,’ Armenian noro-vkʿ ‘with new ones,’ Albanian male-ve ‘to mountains,’ Greek ókhes-phin ‘with chariots,’ Latin omni-bus ‘for all.’

Balto-Slavic and Germanic are neighbors, so it's believed that this phonemic transition occurred only once in a proto-parent shared by these two branches. It exists in a partial, but not complete, overlap of the region affected by the satem change, above. Rarely do these sorts of changes in two branches of the family overlap the exact same territory.

Dialects into Families

No later than 2500 BCE in most cases, these developing dialects had differentiated enough to be called distinct languages. While each had become distinct, additional similarities developed throughout history on account of borrowing and other convergences.

A very common trait among descendant families is the reduction of syllables, usually showing up as the loss of final or unaccented syllables, or certain consonants sitting between vowels (often replaced by a contraction). Words in many Indo-European languages are significantly shorter than ancestral PIE forms: English ‘four,’ Armenian čʿorkʿ, colloquial Persian čar from *k^wetwóres; French vit ‘lives’ from *g^wíH₃weti; Russian dvestí ‘two hundred’ from *duwóyH₁ ḱm̥tóyH₁.

Final syllables were often meaningful in PIE, bearing inflectional markers; this change led to widespread grammatical consequences, causing the loss of case systems and gender systems, but usually preserving the marker for plurality. This is true even in verbs - in English, 'to love' has lost any indication of the subject (I/we/you all use the same form: love compared to Russian: ljubljú, ljúbish, ljúbit).

Noun systems have generally been simplified, and plurality has been reduced to eliminate differentiation for dual, and genders have reduced from three to two (French, Swedish, Lithuanian, Hindi-Urdu) or been eliminated completely (English, Armenian, Bengali). Slavic is an outlier, in that it has created an even more complicated gender system, adding distinctions of animacy and personal versus nonpersonal.

In almost all descendants, the eight PIE cases have been reduced, and in some languages (like French and Welsh) nouns are not inflected for case at all. Some languages built new cases atop the others - Old Lithuanian had in addition to seven cases inherited from PIE an illative (place into), made by adding -n(a) to the accusative (peklosna ‘into hell’), an allative (place to, toward), made by adding -p(i) to the genitive (Jesausp ‘to Jesus’), and an adessive (place at which), made by adding -p(i) to the locative (Joniep ‘in John’). In many other languages, forms have been added, lost, or changed their meanings or usages.

Very little actual vocabulary in any family actually descends noticeably from the ancestral language - no language has more than a few hundred examples; they are usually pronouns; numbers; and simple, easily understood adverbs, prepositions, nouns, verbs, or adjectives. This is complicated by the presence of geographically close non-Indo-European neighbors that are different for each branch or language, which have provided divergent loan-words and other borrowing.

In prehistory, most of the branches of Indo-European were carried into territories that are presumed to have been occupied by non-Indo-European-speaking peoples, and it is very likely that these indigenous languages also had an effect on the divergence of the family's constituents. In India, grammatical features have spread into Indo-European languages from Dravidian influences, and vice versa.