Many of the modern ideas in this field involve the unsettled Indo-European homeland debate about the precise origins of the language itself. There are four main approaches researchers have employed in their attempts to study this culture:
Domesticated cattle were introduced around 4700 BC from the Danube valley to the Volga-Ural steppes where the Early Khvalynsk culture (4900-3900) had emerged, associated by Anthony with early proto-Indo-European. Cattle and sheep were more important in ritual sacrifices than in diet, suggesting that a new set of cults and rituals had spread eastward across the Pontic-Caspian steppes, with domesticated animals at the root of the Proto-Indo-European conception of the universe. Anthony attributed the first and progressive domestication of horses, from taming to actually working with the animal, to that period. Copper, exotic ornamental shells and polished stone maces were exchanged across the Pontic-Caspian steppes from Varna, in the eastern Balkans, to Khvalynsk, near the Volga river, between 4500-4200 BCE. Around 4500 BCE, a minority of richly decorated single graves, partly enriched by imported copper items, began to appear in the steppes, contrasting with the remaining outfitted graves.
The Anatolian distinctive sub-family may have emerged from a first wave of migration into southeastern Europe that occurred about 4200-4000 BCE, coinciding with the Suvorovo-to-Cernavoda I migration, in the context of a progression of the Khvalynsk culture towards the Danube, from which had also emerged the Novodanilovka (4400-3800) and Late Sredny Stog (4000-3500) cultures.
Steppe economies underwent a revolutionary change between 4200-3300 BCE, in a shift from a partial reliance on herding, when domesticated animals were probably used principally as a ritual currency for public sacrifices, to a later regular dietary dependence on cattle, and either sheep or goat meat and dairy products. The Late Khvalynsk and Repin cultures (3900-3300), associated with classic (post-Anatolian) Proto-Indo-European, showed the first traces of cereal cultivation after 4000 BC, in the context of a slow and partial diffusion of farming from the Western parts of the steppes. Around 3700-3300, a second migration wave of proto-Tocharian speakers towards South Siberia led to the Afanasievo culture (3300-2500). The spoke-less wheeled wagon was introduced to the Pontic-Caspian steppe around 3500 BC from the neighboring North Caucasian Maykop culture (3700-3000), with which Proto-Indo-Europeans traded wool and horses. The interaction with the hierarchical Maykop culture, itself influenced by the Mesopotamian Uruk culture, had notable effects on the Proto-Indo-European steppe cultures. Meanwhile, the Khvalynsk-influenced cultures that had emerged in the Danube-Donets region after the first migration gave way to the Cernavod? (4000-3200), Usatovo (3500-2500), Mikhaylovka (3600-3000) and Kemi Oba (3700--2200) cultures, from west to east.
The Yamnaya horizon, associated with the late proto-Indo-European language (following both the Anatolian and the Tocharian splits), grew in the Don-Volga region and spread westwards after 3300 BC to establish a cultural horizon founded on kurgan funerals over a vast steppic area between the Dnieper and the Volga rivers. It was originally a herding-based society, with limited crop cultivation in the eastern part of the steppes, while the Dnieper-Donets region was more influenced by the agricultural Tripolye culture. Paleolinguistics likewise postulates Proto-Indo-European speakers as a semi-nomadic and pastoral population with subsidiary agriculture.
Bronze was introduced to the Pontic-Caspian steppes during this period, and long-distance trade in metals and other valuables like salt in the hinterlands probably brought prestige and power to Yamana societies after 3300 BCE. The Yamnaya funeral sacrifice of wagons, carts, sheep, cattle, and horse was probably related to a cult of ancestors requiring specific rituals and prayers, a connection between language and cult that introduced late Proto-Indo-European to new speakers. Yamnaya chiefdoms had institutionalized differences in prestige and power, and the society was organized along patron-client reciprocity, a mutual exchange of gifts and favors between their patrons, the gods, and human clients. The average life expectancy was fairly high, with many individuals living to 50-60 years old. The language itself appeared as a dialect continuum during this period. The tradition of pottery making was weakly developed.
As the steppe became dryer and colder between 3500 and 3000 BCE, herds needed to be moved frequently to feed them sufficiently. Yamnaya distinctive identity was thus founded on mobile pastoralism, permitted by two innovations: the earlier introduction of the wheeled wagon and the domestication of the horse. Yamnaya herders likely watched over their cattle and raided on horseback, while driving wagons for the bulk transport of water or food. Light-framework dwellings could easily be assembled and disassembled and transported on pack animals.
Another climate change that occurred after 3000 BCE led to a more favourable climate allowing grassland productivity, and Yamnaya new pastoral economy experienced first waves of rapid demographic expansion towards Central and Northern Europe. Expansions of Usatovo people towards southeastern Poland through the Old European Tripolye culture from around 3300 BCE, followed by Yamnya migrations towards the Pannonian Basin in between 3100 and 2800 BCE, are regarded as movements of pre-Italic, Celtic and Germanic speakers. The Proto-Indo-European language probably ceased to be spoken after 2500 BC, as its various dialects had already evolved into non-mutually intelligible languages that spread across western Eurasia during the third wave of Indo-European migrations. Indo-Iranian languages spread into Central Asia, present-day Iran, and South Asia after 2000 BCE.
It is generally agreed that Proto-Indo-European society was hierarchical, with some form of social ranking and various degrees of social status. It is unlikely however that they had a rigidly stratified structure, or castes such as are found in historical India. There was a general distinction between free persons and slaves, typically prisoners of war or debtors unable to repay a debt. The free part of society was composed of an elite class of priests, kings and warriors, along with the commoners, with each tribe following a chief (*wi?pots) sponsoring feasts and ceremonies and eventually immortalized in praise poetry.
The presence of kurgan graves prominently decorated with dress, body ornaments and weaponry, along with well-attested roots for concepts such as "wealth" (*h?ép-), "to be in need" (*h?eg-) or "servant" (*h?entb?i-k?olos, "one who moves about on both sides"; and *h?upo-sth?-i/o-, "one standing below"), indicate that a hierarchy of wealth and poverty was recognized. Some graves, larger than the average and necessitating a considerable number of people to be built, likewise suggest a higher status given to some individuals. These prestigious funerals were not necessarily reserved to the wealthiest person. Smiths in particular were given sumptuous graves, possibly due to the association of smithery with magic during the early Bronze Age. In general, such graves were mostly occupied by males in the eastern Don-Volga steppes, while they were more egalitarian in the western Dnieper-Donets region.
Linguistics has allowed for the reliable reconstruction of a large number of words relating to kinship relations. These all agree in exhibiting a patriarchal, patrilocal and patrilineal social fabric. Patrilocality is confirmed by lexical evidence, including the word *h2u?edh-, "to lead (away)", being the word that denotes a male wedding a female. Rights, possessions, and responsibilities were consequently reckoned to the father, and wives were to reside after marriage near the husband's family, after the payment of a bride-price.
The household (*domos) was generally ruled by the senior male of the family, the *dems-potis ("master of the household"), and could also consist of his children, grandchildren, and perhaps unrelated slaves or servants. His wife probably also played a complementary role: some evidence suggest that she would have kept her position as the mistress (*pot-n-ih?) of the household in the event her husband dies, while the eldest son would have become the new master.
Once established, the family lasted as long as the male stock of its founder endured, and clan or tribal founders were often portrayed as mythical beings stemming from a legendary past in Indo-European traditions. In this form of kinship organization, the individual's genetic distance from the clan's founding ancestor determined his social status. But if he was of exceptional prowess or virtue, the same individual could in his turn gain social prestige among the community and eventually found his own descent-group.
In the reconstructed lexicon linking the individual to the clan, *h?erós meant a "member of one's own group", "one who belongs to the community" (in contrast to an outsider), and gave way to the Indo-Iranian árya (an endonym), the Celtic *aryos ("noble, freeman"), and probably to the Hittite ar?- ("peer, companion") and the Germanic *arjaz ("noble, distinguished"). It is unlikely however that the word had an ethnic connotation, and we do not know if Proto-Indo-European speakers had a term to designate themselves as a group. Another word, *h?leudhos, meant "people", "freemen" in a more general way.
Proto-Indo-European had several words for "leader": *tagós was a general term derived from *tg- ("set in place, arrange"); *h?rs meant a ruler who also had religious functions, with the Roman rex sacrorum ("king of the sacred") as an heritage of the priestly function of the king; *w(n?)nákts designated a "lord" and possessed a feminine equivalent,*wnáktih? (a "queen"); while the *wi?pots (or *wi?-potis) was the chief of the settlement (*wei?s), the seat of a tribe, clan or family.
Public feasts sponsored by such patrons were a way for them to promote and secure a political hierarchy built on the unequal mobilization of labor and resources, by displaying their generosity towards the rest of the community. Rivals competed publicly through the size and complexity of their feasts, and alliances were confirmed by gift-giving and promises made during those public gatherings. The host of the feast was called the *ghosti-potis, the "lord of the guests", who honoured the immortal gods and his mortal guests with gifts of food, drink, and poetry.
Vertical power differences were partly balanced by horizontal mutual obligations of hospitality between guest and hosts. According to David W. Anthony, the domestication of horses and the introduction of the wagon in the Pontic-Caspian steppe between 4500 and 3500 BC led to an increase in mobility across the Yamnaya horizon, and eventually to the emergence of a guest-host political structure. As various herding clans began to move across the steppes, especially in harsh seasons, it became necessary to regulate local migrations on the territories of tribes which had likely restricted these obligations to their kins or co-residents (*h?erós) until then. In Proto-Indo-European, the term *ghós-ti-, whose original meaning must have been "table companion", could either mean a host or a guest. The connotation of an obligatory reciprocity between both guests and hosts has persisted in descendant cognates: Latin hosp?s ("foreigner, guest; host"), Old English ?iest ("stranger, guest"), or Old Church Slavonic gost? ("guest") and gospod? ("master").
Guests and hosts were indeed involved in a mutual and reciprocal relationship bound by oaths and sacrifices. The giving and receiving of favors was accompanied by a set of ritual actions that indebted the guest to show hospitality to his host at any time in the future. The obligation could even be heritable: Homer's warriors, Glaukos and Diomedes, stopped fighting and presented gifts to each other when they learned that their grandfathers had shared a guest-host relationship. Violations of the guest-host obligations were immoral, illegal and unholy: in Irish law, refusing hospitality was deemed a crime as serious as murder. The killing of a guest was also greeted with a singular revulsion, as was the abuse of hospitality.
Because of the archaic nature of traditional legal phraseology--which preserves old forms and meaning for words--and the necessity for legal sentences to be uttered precisely the same way each time to remain binding, it is possible to securely reconstruct some elements of the Proto-Indo-European legal system. For instance, the word *serk- ("to make a circle, complete") designated a type of compensation where the father (or the master) had to either pay for the damages caused by his son (or slave), or surrender the perpetrator to the offended party. It is attested by a common legal and linguistic origin in both Roman and Hittite laws. Another root denoting a compensation, *kwey-, also had the meanings of "blood-price", "vengeance" or "guilt" in daughter languages, suggesting that it was specifically applied to the restitution for theft or violence.
Law was apparently designed to preserve the "order" (*h?értus) of the universe, with the underlying concept that harmony should be maintained, be it in the physical universe or the social world. There was however probably no public enforcement of justice in Proto-Indo-European society, nor were there formal courts as we know them today. Contractual obligations were protected by private individuals acting as sureties: they pledged to be responsible for payments of debts incurred by someone else if the latter defaulted. In case of litigation, one could either take matter into their own hands, for instance by barring someone from accessing their property to compel payment, or bring the case before judges (perhaps kings) that featured witnesses. The word for "oath", *h?óitos, derives from the verb *h?ei- ("to go"), after the practice of walking between slaughtered animals as part of taking an oath.
The root *h?értus (from *h?er-, "to fit") is associated with the concept of a cosmic order, i.e. which is "fitting, right, ordered". It is one of most securely reconstructed Proto-Indo-European words, with cognates in most sub-families: Latin artus ("joint"); Middle High German art ("innate feature, nature, fashion"); Greek artús ("arrangement"), possibly arete ("excellence"); Armernian ard ("ornament, shape"); Avestan ar?ta- ("order") and ?tá ("truth"); Sanskrit ?tú- ("right time, order, rule"); Hittite ?ra ("right, proper"); Tocharian A ?rt- ("to praise, be pleased with").
The trifunctional hypothesis, proposed by Georges Dumézil, postulates a tripartite ideology reflected in a threefold division between a clerical class (encompassing both the religious and social functions of the priests and rulers), a warrior class (connected with the concepts of violence and braveness), and a class of farmers or husbandmen (associated with fertility and craftsmanship), on the basis that many historically known groups speaking Indo-European languages show such a division. Dumézil initially contended that it derived from an actual division in Indo-European societies, but later toned down his approach and represented the system as fonctions or general organizing principles. Dumézil's theory has been influential and some scholars continue to operate under its framework, although it has also been criticized as aprioristic and too inclusive, and thus impossible to be proved or disproved.
The reconstructed cosmology of the proto-Indo-Europeans shows that the ritual sacrifice of cattle, cows in particular, was at the root of their beliefs, as the primordial condition of the world order. The myth of *Trito, the first warrior, involves the liberation of a cattle stolen by a three-headed serpent named *Ngwhi. After recovering the wealth of the people, Trito eventually offered the cattle to the priest in order to ensure the continuity of the cycle of giving between gods and humans. The creation myth could have rationalized raiding as the recovery of cattle that the gods had intended for the people who sacrificed properly. Many Indo-European cultures preserved the tradition of cattle raiding, which they often associated with epic myths. Georges Dumézil suggested that the religious function was represented by a duality, one reflecting the magico-religious nature of priesthood, while the other is involved in religious sanction to human society (especially contracts), a theory supported by common features in Iranian, Roman, Scandinavian and Celtic traditions. The study of astronomy was not much developed among Proto-Indo-Europeans, and they probably had established names for only a few individual stars and star-groups (e.g. Sirius, Ursa Major).
The basic word for "god" in proto-Indo-European is *deiwós ("celestial"), itself a derivative of *dei- ("to shine, be bright"). On the other hand, the word for "earth" (*d?ém) is at root of both "earthly" and "human", as it is notably attested in the Latin cognates humus and homo. This suggests a hierarchical conception of the status of mankind regarding the gods, confirmed by the use of the term "mortal" (*mr?tós) as a synonym of "human" as opposed to the never-dying gods in Indo-European traditions. The idea is expressed in the Homeric phrase "of the immortal gods and of men who walk on earth".
Proto-Indo-European beliefs were influenced by a resistant animistic substratum, and the few names that can be reconstructed based upon both linguistic (cognates) and thematic (reflexes) evidence are the cosmic and elemental deities: the 'Daylight-Sky' (*Dy?us), his partner 'Earth' (*D?ém), his daughter the 'Dawn' (*H?éws?s), and his Twin Sons, the 'Sun' (*Séh?ul) and the Sun-Maiden, and deities of winds, waters, fire, rivers and springs. The Proto-Indo-European creation myth tells of a primordial sacrifice performed by the first man *Manu ("Man") on his twin brother *Yemo ("Twin"), from whom emerged the cosmological elements. Other deities, such as the weather-god *Perk?unos and the guardian of roads and herds, *Péh?us?n, are probably late innovations since they are attested in a restricted number of traditions, Western (European) and Graeco-Aryan, respectively.
Proto-Indo-Europeans practiced a polytheistic religion centered on sacrificial rites of cattle and horses, probably administered by a class of priests or shamans. Animals were slaughtered (*gn?tós) and dedicated to the gods (*déiwos) in the hope of winning their favor. The king as the high priest would have been the central figure in establishing good relations with the other world. The Khvalynsk culture, associated with early Proto-Indo-European, had already shown archeological evidence for the sacrifice of domesticated animals. Proto-Indo-Europeans also had a sacred tradition of horse sacrifice for the renewal of kinship involving the ritual mating of a queen or king with a horse, which was then sacrificed and cut up for distribution to the other participants in the ritual.
Although we know little about the role of magic in Proto-Indo-European society, there is no doubt that it existed as a social phenomenon, as several branches attest the use of similarly worded charms and curses, such as ones against worms. Furthermore, incantations and spells were one of the three categories of medicine, along with the use of surgical instruments and herbs or drugs. Since the earliest evidence for the burning of the plant was found in Romanian kurgans dated 3,500 BC, some scholars suggest that cannabis was first used as a psychoactive drug by Proto-Indo-Europeans during ritual ceremonies, a custom they eventually spread throughout western Eurasia during their migrations. Descendant cognates of the root *kanna ("cannabis") have been proposed in Sanskrit ?aná, Greek kánnabis (), Germanic *hanipa (German Hanf, English hemp), Russian konopljá, Albanian kanëp, Armenian kanap and Old Prussian knapios. Other linguists suggest that the common linguistic inheritance does not date back to the Indo-European period, and the word cannabis may have spread later across Europe as a Wanderwort ultimately borrowed from a non-Indo-European language.
Poetry and songs were central to Proto-Indo-European society. The poet-singer was the society's highest-paid professional, possibly a member of a hereditary profession that ran in certain families, the art passing from father to son as the poet had to acquire all the technical aspects of the art and master an extensive body of traditional subject matter. He performed against handsome rewards--like gifts of horses, cattle, wagons and women--and was held in high esteem. In some cases, the poet-singer had a stable relationship with a particular noble prince or family. In other cases, he travelled about with his dependants, attaching himself to one court after another.
A transmitter of inherited cultural knowledge, the poet sang as a recall of the old heroic times, entrusted with telling the praises of heroes, kings and the gods. Composing sacred hymns ensured the gods would in turn bestow favourable fate to the community, and for kings that their memory would live on many generations. A lexeme for a special song, the *erkw ("praise of the gift") have been identified in early Proto-Indo-European. Such praise poems proclaimed the generosity of the gods (or a patron) and enumerated their gifts, expanding the patron's fame, the path to immortality otherwise attainable for mortals only through conspicuous acts of war or piety.
The concept of fame (*?léwos) was central to Proto-Indo-European poetry and culture. Many poetic dictions built on this term can be reconstituted: *?léwos wéru ("wide fame"), *?léwos me?h? ("great fame"), *?léuesh? h?nróm ("the famous deeds of men, heroes"), or *dus-?lewes ("having bad repute"). Indo-European poetic tradition is oral-formulaic: stock formulas, such as the imperishable fame (*?léwos d?gitom), the swift horses (*héwes h?é?w?s), the eternal life (*h?iu-g?ih?), the metaphor of the wheel of the sun (*sh?uens k?ek?los), or the epithet man-killer (*h?nr?-g?hen), attached to Hektor and Rudra alike, were transmitted among poet-singers to fill out verse-lines in epic song lyrics. The task of the Indo-European poet was to preserve over the generations the famous deeds of heroes. He would compose and retell poems based on old and sometimes obscure formulations, reconnecting the motifs with his own skills and improvisations. Poetry was therefore associated with the acts of weaving words (*wék?os webh-) and crafting speech (*wék?os te?s-).
Although Proto-Indo-Europeans have been often cast as warlike conquerors, their reconstructed arsenal is not particularly extensive. There is no doubt that they possessed archery, as several words with the meaning of "spear" (*g?éru ; *?úh?los), "pointed stick" (*h?ei?smo) or "throwing spear" (*ai-só-s) are attested. The term *w?ben meant a "cutting weapon", probably a knife, and *h?/?n?sis a "large offensive knife", probably similar to bronze daggers found across Eurasia ca. 3300-3000 BCE. Proto-Indo-Europeans certainly did not know swords which appeared later around 2000-1500. The axe was *h?ed?és, while the word *spelo/eh? designated a wooden or leather shield. The term *leh?wós meant "military unit" or "military action", while *teutéh?- might have referred to the "adult male with possession" who would mobilize in warfare, perhaps originally a Proto-Indo-European term meaning "the people under arms".
A number of scholars propose that Proto-Indo-European rituals included a requirement that young unmarried men initiate into manhood by joining a warrior-band named *kóryos. They were led by a senior male and lived off the country by hunting and engaging in raiding and pillaging. They served in such brotherhoods (Männerbunden) for a number of years before returning home to adopt more respectable identities as mature men. During their initiation period, the boys engaged in the *kóryos wore the skins and bore the names of wild animals like wolves (*wl?k?o) and dogs (*?w?n) to assume their nature and escape the rules and taboos of their host society.
Most kurgan stelae found in Pontic-Caspian steppe feature a man along with a belt and weapons carved on the stone. In later Indo-European traditions, such as the warrior figures found in Germanic and Celtic art, *kóryos raiders wore a belt that bound them to their leader and the gods, and little else. The tradition of kurgan stelae featuring warriors with a belt is also common in Scythian cultures. A continuity of an "animal-shaped raid culture" has been also postulated in various elements attested in later Indo-European cultures, such as the Germanic Berserkers, the Italic Ver Sacrum, and the Spartan Crypteia, in the mythical Celtic fianna and Vedic Maruts, and in the legend of the werewolf ("man-wolf"), found in Greek, Germanic, Baltic and Slavic traditions alike.
In a mostly patriarchal economy based on bride competition, the escalation of bride-prices in periods of climate change could have resulted in an increase in cattle raiding by unmarried men. Scholars also suggest that, alongside the attractiveness of the patron-client and the guest-host relationships, the *kóryos could have played a key role in diffusing Indo-European languages across a great part of Eurasia.
The use of two-word compound words for personal names, typically but not always ascribing some noble or heroic feat to their bearer, is so common in Indo-European languages that it is certainly an inherited feature. These names often belonged in early dialects to the class of compound words that in the Sanskrit tradition are called bahuvrihi. As in Vedic bahuvrihi (literally "much-rice", meaning "one who has much rice"), those compounds are formed as active structures indicating possession and do not require a verbal root. From the Proto-Indo-European personal name *?léwos-wésu (lit. "good-fame", meaning "possessing good fame") derive the Illyrian Vescleves, the Greek Eukle?s (?), the Old Persian Huçavah, the Avestan Haosravah- and the Sanskrit Su?ráva.
A second type of compound consists of a noun followed by a verbal root or stem, describing an individual performing an action. Compounds more similar to synthetics are found in the Sanskrit Trasá-dasyus ("one who causes enemies to tremble"), the Greek Archelaus (, "one who rules people"), and the Old Persian X?ay?r?an ("one who rules men").
Many Indo-European personal names are associated with the horse (*h?é?wos) in particular, which expressed both the wealth and nobility of their bearer, such as the Avestan Hwaspa ("owning good horses"), the Greek Hippónikos ("winning by his horses"), or the Gaulish Epomeduos ("master of horses"). Since domestic animals also served to sacrifice, there were often used as exocentric structures in compound names (the bearers are not 'horses' themselves but 'users of horses' in some way), in contrast to endocentric personal names rather associated with wild animals like the wolf, for instance in the German Adolf ("a noble wolf") or the Serbian Dobrovuk ("a good wolf").
Proto-Indo-Europeans possessed a Neolithic mixed economy based on livestock and subsidiary agriculture, with a wide range of economic regimes and various degrees of mobility that could be expected across the large Pontic-Caspian steppe. Tribes were typically more influenced by farming in the western Dnieper-Donets region, where cereal cultivation was practised, while the eastern Don-Volga steppes were inhabited by semi-nomadic and pastoral populations mostly relying on herding.
Proto-Indo-European distinguished between unmovable and movable wealth (*pé?u, the "livestock"). As for the rest of society, economy was founded on reciprocity. A gift always entailed a counter-gift, and each party was bound to the other in a mutual relationship cemented by trust.
The early Khvalynsk culture, located in the Volga-Ural steppes and associated with early Proto-Indo-European, had trade relationship with Old European cultures. Domesticated cattle, sheep and goats, as well as copper, were introduced eastward from the Danube valley around 4700-4500. Copper objects show an artistic influence from Old Europe, and the appearance of sacrificed animals suggest that a new set of rituals emerged following the introduction of herding from the west. The Old European Tripolye culture continued to influence the western part of the steppes, in the Dnieper-Donets region, where the Yamnaya culture was more agricultural and less male-centered.
Proto-Indo-European speakers also had indirect contacts with Uruk around 3700-3500 through the North Caucasian Maikop culture, a trade route that introduced the wheeled wagon into the Caspian-Pontic steppes. Wheel-made pottery imported from Mesopotamia were found in the Northern Caucasus, and Maikop chieftain was buried wearing Mesopotamian symbols of power--the lion paired with the bull. The late Khvalynsk and Repin cultures probably traded wool and domesticated horses in exchange, as suggested by the widespread appearance of horses in archeological sites across Transcaucasia after 3300. Socio-cultural interactions with Northwest Caucasians have been proposed, on the ground that the Proto-Indo-European language shows a number of lexical parallels with Proto-Northwest Caucasian. Proto-Indo-European also exhibits lexical loans to or from other Caucasian languages, particularly Proto-Kartvelian.
Proto-Indo-European probably also had trade relationships with Proto-Uralic speakers around the Ural Mountains. Words for "sell" and "wash" were borrowed in Proto-Uralic, and words for "price" and "draw, lead" were introduced in the Proto-Finno-Ugric language. James P. Mallory suggested that the expansion of the Uralic languages across the northern forest zone might have been stimulated by organizational changes within Uralic forager societies, resulting partly from interaction with more complex, hierarchical Proto-Indo-European and (later) Indo-Iranian pastoral societies at the steppe/forest-steppe ecological border.
From the reconstructable lexicon, it is clear that Proto-Indo-Europeans were familiar with wheeled vehicles--certainly horse-drawn wagons (*wenos)--as they knew the wheel (*k?ek?lóm), the axle (*h?e?s-), the shaft (*h?/?éih?os), and the yoke (*yugóm). Although wheels were most likely not invented by Proto-Indo-Europeans, the word *k?ek?lóm is a native derivation of the root *k?el- ("to turn") rather than a borrowing, suggesting short contacts with the people who introduced the concept to them.
The technology used was a solid wheel made of three planks joined together with their outer edges trimmed to a circle. The swift chariot with spoked wheels, which made the mode of transport much more rapid and lighter, appeared later within the Sintashta culture (2100-1800), associated with the Indo-Iranians. As the word for "boat" (*néh?us) is widely attested across the language groups, the means of transport (likely a dugout canoe) was certainly known by Proto-Indo-Europeans.
The vocabulary associated with metallurgy is very restricted and at best we can attest the existence of copper/bronze, gold, and silver. The basic word for "metal" (*h?ey-es) is generally presumed to mean "copper" or a copper-tin alloy of "bronze". "Gold" is reliably reconstructed as *h?eusom, and *h?er?-n?t-om designated a "white metal" or "silver". Proto-Indo-Europeans were also familiar with the sickle (*sr?po/eh?), the awl (*h?óleh?) for working leather or drilling wood, and used a primitive plough (*h?érh?ye/o) made of a curved and forked branch.
The term for "oven" or "cooking vessel" (*h?/?uk?) has been reconstructed based on four branches, as for "baking" (*bg-) and "boiling" (*yes-). They certainly drank beer (*h?elut) and mead (*méd?u), and the word for "wine" (*wóinom) has been proposed, although this remains a debated issue. Proto-Indo-Europeans produced textile, as attested by the reconstruct roots for wool (*w?h?neh?), flax (*linom), sewing (*syuh?-), spinning (*(s)pen-), weaving (*h?/?web?-) and plaiting (*ple?-), as well as needle (*skis) and thread (*pe/oth?mo). They were also familiar with combs (*kes) and ointments with salve (*h?eng?-).
Animals (mammals in particular) are fairly abundant in the reconstructed lexicon. We can ascribe about seventy-five names to various animal species, but it hardly recovers all the animals to have been distinguished in the proto-language. While *k?etwor-pod designated a four-footed animal (tetrapod), *g?yéh?wyom seems to have been the general term for animals, derived from the root *g?yeh?-, "to live". Proto-Indo-European speakers also made a distinction between wild animals (*w?r) and the livestock (*pé?u).
The reconstructed lexicon suggests a Neolithic economy with extensive references to domesticated animals. They were familiar with cows (*gus), sheep (*h?ówis), goats (*díks, or *h?ei?s) and pigs (*s?s ; also *pór?os, "piglet").
They knew dogs (*?w?n), milk (*?l?ákt; also *h?mel?-, "to milk") and dairy foods, wool (*w?h?neh?) and woollen textiles, agriculture, wagons, and honey (*mélit). The domestication of the horse (*h?é?wos), thought to be an extinct Tarpan species, have probably originated with these peoples, and scholars invoke this innovation as a factor contributing to their increased mobility and rapid expansion.
The dog was perceived as a symbol of death and depicted as the guardian of the Otherworld in Indo-European cultures (Greek Cerberus, Indic ?arvar?, Norse Garmr). The mytheme possibly stems from an older Ancient North Eurasian belief, as evidenced by similar motifs in Native American and Siberian mythology, in which case it might be one of the oldest mythemes recoverable through comparative mythology. In various Indo-European traditions, the worst throw at the game of dice was named the "dog", and the best throw was known as the "dog-killer". Canine teeth of dogs were frequently worn as pendants in Yamnaya graves in the western Pontic steppes, particularly in the Ingul valley.
Linguistic evidence suggests that Proto-Indo-European speakers were also in contact with various wild animals like red foxes (*wl(o)p), wolves (*wl?k?o), bears (*ht?os), red deers (*h?elhn), elks (moose) (*h?ól?is), eagles (*h?or), otters (*udrós), snakes (*h?ógis), mice (*m?s ; from *mus-, "to steal") or trouts (*ló?s).
Some of them were included in mythological and folkloric motifs. Goats draw the chariots of the Norse and Indic gods Thor and Pushan, and they are associated with the Baltic god Perk?nas and the Greek god Pan. The words for both the wolf and the bear underwent taboo deformation in a number of branches, suggesting they were feared as symbols of death in Proto-Indo-European culture.
In Indo-European culture, the term "wolf" is generally applied to brigands and outlaws who live in the wild. Ritual and mythological concepts connected with wolves, in some cases similar with Native American beliefs, may represent a common Ancient North Eurasian heritage: mai-coh meant both "wolf" and "witch" among Navajos, and shunk manita tanka a "doglike powerful spirit" among Sioux, while the Proto-Indo-European root *?eid ("knowledge, clairvoyance") designated the wolf in both Hittite (?etna) and Old Norse (witnir), and a "werewolf" in Slavic languages (Serb vjedo-gonja, Slovenian vedanec, Ukrainian viun).
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