Proto-Indo-European homeland

The Steppe model, the Near Eastern (or Armenian) model, and the Anatolian model are the three leading solutions for the Indo-European homeland.[12] The former, placing the PIE homeland in the Pontic-Caspian steppe around 4000 BC,[13] is the theory supported by most scholars.[note 1]

According to linguist Allan R. Bomhard (2019), the steppe hypothesis, proposed by archeologists Marija Gimbutas and David W. Anthony, "is supported not only by linguistic evidence, but also by a growing body of archeological and genetic evidence. The Indo-Europeans have been identified with several cultural complexes existing in that area between 4,500—3,500 BCE. The literature supporting such a homeland is both extensive and persuasive [...]. Consequently, other scenarios regarding the possible Indo-European homeland, such as Anatolia, have now been mostly abandoned,"[14] although critical issues such as the way proto-Greek,[15] proto-Armenian,[16][17] proto-Albanian[18] and proto-Anatolian[19] languages became spoken in their attested homeland are still debated inside the steppe model.[12]

The Anatolian hypothesis proposed by archeologist Colin Renfrew places the pre-PIE homeland in Anatolia around 8000 BC,[7] and the homeland of Proto-Indo-European proper in the Balkans around 5000 BC, with waves of linguistic expansion following the progression of agriculture in Europe. Although it has attracted substantive attention and discussions, the datings it proposes are at odds with the linguistic timeframe for Proto-Indo-European[2] and with genetic data which do not find evidence for Anatolian origins in the Indian genepool.[20] In general, the progressive dominance of a specific language or dialect over others can be explained by the access to a natural resource unknown or unexploited until then by its speakers, which is thought to be horse-based pastoralism for Indo-European speakers rather than crop cultivation.[note 2][21][14]

A notable third possibility, which has gained renewed attention since the 2010s, is the "Near Eastern model",[12] also known as the Armenian hypothesis. It was proposed by linguists Tamaz V. Gamkrelidze and Vyacheslav Ivanov in the early 1980s, postulating connections between Indo-European and Caucasian languages based on the disputed glottalic theory and connected to archaeological findings by Grogoriev.[12] Some recent DNA-research has led to renewed suggestions of a Caucasian or Iranian homeland for archaic or 'proto-proto-Indo-European', the common ancestor of both Anatolian languages and early proto-IE (from which Tocharian and all other early branches split-off).[13][22][23][24][25]

A number of other theories have been proposed, most of which have little or no academic currency today (see discussion below):

• Modern nationalist doctrines:
  • Indigenous Aryans, which suggests a homeland in the Indian subcontinent in the 6th millennium BC, and is favored by Hindu nationalists
  • Arctic theory, with a 6th millennium BC or later origin in Northern Europe, according to Lothar Kilian's and, especially, Marek Zvelebil's models of a broader homeland,[26] which is favored by European and white ethnonationalists
• Paleolithic Continuity Theory, with an origin in the Upper Paleolithic
• Nikolai Trubetzkoy's theory of Sprachbund origin of Indo-European traits

Through comparative linguistics it is possible to reconstruct the vocabulary found in the proto-language, and in this way achieve knowledge of the cultural, technological and ecological context that the speakers inhabited. Such a context can then be compared with archaeological evidence. This vocabulary includes, in the case of (late) PIE, which is based on the post-Anatolian and post-Tocharian IE-languages:

• pastoralism, including domesticated cattle, horses, and dogs[27]
• agriculture and cereal cultivation, including technology commonly ascribed to late-Neolithic farming communities, e.g., the plow[28]
• a climate with winter snow[29]
• transportation by or across water[27]
• the solid wheel[27] used for wagons, but not yet chariots with spoked wheels[30]

Proto-Finno-Ugric and PIE have a lexicon in common, generally related to trade, such as words for "price" and "draw, lead". Similarly, "sell" and "wash" were borrowed in Proto-Ugric. Although some have proposed a common ancestor (the hypothetical Nostratic macrofamily), this is generally regarded as the result of intensive borrowing, which suggests that their homelands were located near each other. Proto-Indo-European also exhibits lexical loans to or from Caucasian languages, particularly Proto-Northwest Caucasian and Proto-Kartvelian, which suggests a location close to the Caucasus.[31][14]

Gramkelidze and Ivanov, using the now largely unsupported glottalic theory of Indo-European phonology, also proposed Semitic borrowings into Proto-Indo-European, suggesting a more southern homeland to explain these borrowings. According to Mallory and Adams, some of these borrowings may be too speculative or from a later date, but they consider the proposed Semitic loans *táwros 'bull' and *wéyh₁on- 'wine; vine' to be more likely.[30] Anthony notes that those Semitic borrowings may also have occurred through the advancement of Anatolian farmer cultures via the Danube valley into the steppe zone.[2]

According to Anthony, the following terminology may be used:[2]

• Archaic PIE for "the last common ancestor of the Anatolian and non-Anatolian IE branches";
• Early, or Post-Anatolian, PIE for "the last common ancestor of the non-Anatolian PIE languages, including Tocharian";
• Late PIE for "the common ancestor of all other IE branches".

The Anatolian languages are the first Indo-European language family to have split off from the main group. Due to the archaic elements preserved in the Anatolian languages, they may be a "cousin" of Proto-Indo-European, instead of a "daughter", but Anatolian is generally regarded as an early offshoot of the Indo-European language group.[2]

The Indo-Hittite hypothesis postulates a common predecessor for both the Anatolian languages and the other Indo-European languages, called Indo-Hittite or Indo-Anatolian.[2] Although PIE had predecessors,[32] the Indo-Hittite hypothesis is not widely accepted, and there is little to suggest that it is possible to reconstruct a proto-Indo-Hittite stage that differs substantially from what is already reconstructed for PIE.[33]

Anthony (2019) suggests a derivation of the proto-Indo-European language mainly from a base of languages spoken by Eastern European Hunter-Gatherers living at the Volga steppes, with influences from languages spoken by northern Caucasus hunter-gatherers who migrated from the Caucasus to the lower Volga basin, in addition to a possible later influence from the language of the Maikop culture to the south (which is hypothesized to have belonged to the North Caucasian family) in the later Neolithic or Bronze Age involving little genetic impact.[34]

Using a mathematical analysis borrowed from evolutionary biology, Don Ringe and Tandy Warnow propose the following tree of Indo-European branches:[2]

• Pre-Anatolian (before 3500 BC)
• Pre-Tocharian
• Pre-Italic and Pre-Celtic (before 2500 BC)
• Pre-Armenian and Pre-Greek (after 2500 BC)
• Pre-Germanic and Pre-Balto-Slavic;[2] proto-Germanic c. 500 BC[35]
• Proto-Indo-Iranian (2000 BC)

David Anthony, following the methodology of Ringe and Warnow, proposes the following sequence:[2]

• Pre-Anatolian (4200 BC)
• Pre-Tocharian (3700 BC)
• Pre-Germanic (3300 BC)
• Pre-Italic and Pre-Celtic (3000 BC)
• Pre-Armenian (2800 BC)
• Pre-Balto-Slavic (2800 BC)
• Pre-Greek (2500 BC)
• Proto-Indo-Iranian (2200 BC); split between Iranian and Old Indic 1800 BC

In the early 1980s,[36] a mainstream consensus had emerged among Indo-Europeanists in favour of the "Kurgan hypothesis" (named after the kurgans, burial mounds, of the Eurasian steppes) placing the Indo-European homeland in the Pontic–Caspian steppe of the Chalcolithic.[37][2] This was not least due to the influence of the Journal of Indo-European Studies, edited by J. P. Mallory, that focused on the ideas of Marija Gimbutas and offered some improvements.

Gimbutas had created a modern variation on the traditional invasion theory in which the Indo-Europeans were a nomadic tribe in Eastern Ukraine and Southern Russia and expanded on horseback in several waves during the 3rd millennium BC. Their expansion coincided with the taming of the horse. Leaving archaeological signs of their presence (see Corded Ware culture), they subjugated the peaceful European Neolithic farmers of Gimbutas' Old Europe. As Gimbutas' beliefs evolved, she put increasing emphasis on the patriarchal, patrilineal nature of the invading culture, sharply contrasting it with the supposedly egalitarian, if not matrilineal culture of the invaded, to the point of formulating essentially a feminist archaeology. Her interpretation of Indo-European culture found genetic support in remains from the Neolithic culture of Scandinavia, where DNA from bone remains in Neolithic graves indicated that the megalith culture was either matrilocal or matrilineal, as the people buried in the same grave were related through the women. Likewise, there is a tradition of remaining matrilineal traditions among the Picts.

The Gimbutas-Mallory Kurgan hypothesis seeks to identify the source of the Indo-European language expansion as a succession of migrations from the Pontic–Caspian steppe, originating in the area encompassed by the Sredny Stog culture (c. 4500 BC).[38] J. P. Mallory, dating the migrations later, to c. 4000 BC, and putting less insistence on their violent or quasi-military nature, essentially modified Gimbutas' theory making it compatible with a less gender-political narrative. David Anthony, focusing mostly on the evidence for the domestication of horses and the presence of wheeled vehicles, came to regard specifically the Yamna culture, which replaced the Sredny Stog culture around 3500 BC, as the most likely candidate for the Proto-Indo-European speech community.[2]

Anthony describes the spread of cattle-raising from early farmers in the Danube Valley into the Ukrainian steppes in the 6th–5th millennium BC, forming a cultural border with the hunter-gatherers[2] whose languages may have included archaic PIE.[2] Anthony notes that domesticated cattle and sheep probably didn't enter the steppes from the Transcaucasia, since the early farming communities there were not widespread, and separated from the steppes by the glaciated Caucasus.[2] Subsequent cultures developed in this area which adopted cattle, most notably the Cucuteni-Trypillian culture.[2]

Parpola regards the Tripolye culture as the birthplace of wheeled vehicles, and therefore as the homeland for Late PIE, assuming that Early PIE was spoken by Skelya pastoralists (early Sredny Stog culture[2]) who took over the Tripolye culture at c. 4300–4000 BC.[39] On its eastern border lay the Sredny Stog culture (4400–3400 BC),[2] whose origins are related to "people from the east, perhaps from the Volga steppes".[2] It plays a central role in Gimbutas' Kurgan hypothesis,[2] and coincides with the spread of early PIE across the steppes[2] and into the Danube valley (c. 4000 BC),[2] leading to the collapse of Old Europe.[2] Hereafter the Maykop culture suddenly arose, Tripolye towns grew strongly, and eastern steppe people migrated to the Altai mountains, founding the Afanasevo culture (3300 to 2500 BC).[2]

The core element of the steppe hypothesis is the identification of the proto-Indo-European culture as a nomadic pastoralist society that did not practice intensive agriculture. This identification rests on the fact that vocabulary related to cows, to horses and horsemanship, and to wheeled vehicles can be reconstructed for all branches of the family, whereas only a few agricultural vocabulary items are reconstructable, suggesting a gradual adoption of agriculture through contact with non-Indo-Europeans. If this evidence and reasoning is accepted, the search for the Indo-European proto-culture has to involve searching for the earliest introduction of domesticated horses and wagons into Europe.[4]

Responding to these arguments, proponents of the Anatolian hypothesis Russell Gray and Quentin Atkinson have argued that the different branches could have independently developed similar vocabulary based on the same roots, creating the false appearance of shared inheritance – or alternatively, that the words related to wheeled vehicle might have been borrowed across Europe at a later date. Proponents of the Steppe hypothesis have argued this to be highly unlikely, and to break with the established principles for reasonable assumptions when explaining linguistic comparative data.[4]

Another source of evidence for the steppe hypothesis is the presence of what appears to be many shared loanwords between Uralic languages and proto-Indo-European, suggesting that these languages were spoken in adjacent areas. This would have had to take place a good deal further north than the Anatolian or Near Eastern scenarios would allow.[4] According to Kortlandt, Indo-Uralic is the pre-PIE, postulating that Indo-European and Uralic share a common ancestor.[40] According to Kortlandt, "Indo-European is a branch of Indo-Uralic which was radically transformed under the influence of a North Caucasian substratum when its speakers moved from the area north of the Caspian Sea to the area north of the Black Sea."[40][note 3][note 4] Anthony notes that the validity of such deep relationships cannot be reliably demonstrated due to the time-depth involved, and also notes that the similarities may be explained by borrowings from PIE into proto-Uralic.[32] Yet, Anthony also notes that the North Caucasian communities "were southern participants in the steppe world".[2]

Three genetic studies in 2015 gave support to the Kurgan theory of Gimbutas regarding the Indo-European Urheimat. According to those studies, Y chromosome haplogroups R1b and R1a, now the most common in Europe (R1a is also common in South Asia) would have expanded from the Russian steppes, along with the Indo-European languages; they also detected an autosomal component present in modern Europeans which was not present in Neolithic Europeans, which would have been introduced with paternal lineages R1b and R1a, as well as Indo European Languages.[41][42][43]

Many geneticists consider Haplogroup R1a to be associated with the origins and spread of the Indo-Europeans.[44][45][46] R1a1 shows a strong correlation with the distribution of the Indo-European languages in Europe and South Asia, being most prevalent in Poland, Russia, and Ukraine, and in central Asia, Afghanistan, Pakistan and India.[45][46] Two specific subclades dominate, namely R1-Z282 in Eastern-Europe and R1-Z93 in South Asia and South-Siberia.[45][46] According to Underhill et al. (2014), the initial diversification of R1a took place in the vicinity of Iran,[47] while Pamjav et al. (2012) think that R1a diversified within the Eurasian Steppes or the Middle East and Caucasus region.[48]

Paternal lineages R1a and R1b (and paternal haplogroup I) have been found in Yamnaya remains, as well as in remains from the preceding mesolithic (hunter gatherer) and Neolithic peoples of the Eastern European Steppe.[49][50]

The subclade R1a1a (R-M17 or R-M198) is the R1a subclade most commonly associated with Indo-European speakers. Ornella Semino et al. propose a postglacial (Holocene) spread of the R1a R1a1 haplogroup from north of the Black Sea during the time of the Late Glacial Maximum, which was subsequently magnified by the expansion of the Kurgan culture into Europe and eastward.[51]

Late Neolithic and Bronze Central Europeans surveyed in ancient DNA studies conclusively showed a mix of Western Hunter-Gatherers (WHG), Anatolian Farmers, and Pontic Steppe Hunter-Gatherers ancestry.[52] Individuals from the Yamnaya culture had themselves a mix from Eastern Hunter-Gatherers (EHG) and Caucasus Hunter-Gatherer (CHG) ancestry (a mating network going from the Caucasus Mountains, parts of eastern Anatolia, and the western Iranian plateau).[24][13][53][54][note 5] In 2015, a large-scale ancient DNA study published in Nature[5] found evidence of a "massive migration" from the Pontic-Caspian steppe to Central Europe that took place about 4,500 years ago. It found that individuals from the Central European Corded Ware culture (3rd millennium BC) were genetically closely related to individuals from the Yamnaya culture. The authors concluded that their "results provide support for the theory of a steppe origin of at least some of the Indo-European languages of Europe",[20][55] in this case pre-Italo-Celtic and pre-Germanic.[14]

However, the folk migration model cannot be the only diffusion theory for all linguistic families, as the Yamnaya ancestry component is particularly concentrated in Europe in the northwestern parts of the continent. Other models for languages like proto-Greek are still debated. The steppe genetic component is more diffuse in studied Mycenaean populations: if they came from elsewhere, proto-Greek speakers were certainly a minority in a sea of populations which had been familiar with agriculture for 4000 years.[15] Some propose that they gained progressive prominence through a cultural expansion by elite influence.[14] But if high correlations can be proven in ethnolinguistic or remote communities, genetics does not always equate with language,[56] and archaeologists have argued that although such a migration might have taken place, it does not necessarily explain either the distribution of archaeological cultures or the spread of the Indo-European languages.[57]

An analysis by David Anthony (2019) suggests a genetic origin of proto-Indo-Europeans (associated with the Yamnaya culture) in the Eastern European steppe north of the Caucasus, deriving from a mixture of Eastern European hunter-gatherers and hunter-gatherers from the Caucasus. Anthony also suggests that the proto-Indo-European language formed mainly from a base of languages spoken by Eastern European hunter-gathers with influences from languages of northern Caucasus hunter-gatherers, in addition to a possible later influence from the language of the Maikop culture to the south (which is hypothesized to have belonged to the North Caucasian family) in the later Neolithic or Bronze age involving little genetic impact.[34]

The main competitor to the Kurgan hypothesis is the Anatolian hypothesis advanced by Colin Renfrew in 1987. It couples the spread of the Indo-European languages to the hard fact of the Neolithic spread of farming from the Near East, stating that the Indo-European languages began to spread peacefully into Europe from Asia Minor from around 7000 BC with the Neolithic advance of farming (wave of advance). The expansion of agriculture from the Middle East would have diffused three language families: Indo-European toward Europe, Dravidian toward Pakistan and India, and Afro-Asiatic toward Arabia and North Africa.

According to Renfrew (2004), the spread of Indo-European proceeded in the following steps:

• Around 6500 BC: Pre-Proto-Indo-European, located in Anatolia, splits into Anatolian and Archaic Proto-Indo-European, the language of those Pre-Proto-Indo-European farmers who migrate to Europe in the initial farming dispersal. Archaic Proto-Indo-European languages occur in the Balkans (Starčevo-Körös-Cris culture), in the Danube valley (Linear Pottery culture), and possibly in the Bug-Dniestr area (Eastern Linear pottery culture).
• Around 5000 BC: Archaic Proto-Indo-European splits into Northwestern Indo-European (the ancestor of Italic, Celtic, and Germanic), located in the Danube valley, Balkan Proto-Indo-European (corresponding to Gimbutas' Old European culture), and Early Steppe Proto-Indo-European (the ancestor of Tocharian).

Reacting to criticism, Renfrew revised his proposal to the effect of taking a pronounced Indo-Hittite position. Renfrew's revised views place only Pre-Proto-Indo-European in 7th millennium BC Anatolia, proposing as the homeland of Proto-Indo-European proper the Balkans around 5000 BC, explicitly identified as the "Old European culture" proposed by Marija Gimbutas. He thus still situates the original source of the Indo-European language family in Anatolia c. 7000 BC. Reconstructions of a Bronze Age PIE society based on vocabulary items like "wheel" do not necessarily hold for the Anatolian branch, which appears to have separated from PIE at an early stage, prior to the invention of wheeled vehicles.[58]

Following the publication of several studies on ancient DNA in 2015, Colin Renfrew has accepted the reality of migrations of populations speaking one or several Indo-European languages from the Pontic steppe towards Northwestern Europe.[59][21]

The main objection to this theory is that it requires an unrealistically early date.[4] According to linguistic analysis, the Proto-Indo-European lexicon seems to include words for a range of inventions and practices related to the Secondary Products Revolution, which post-dates the early spread of farming. On lexico-cultural dating, Proto-Indo-European cannot be earlier than 4000 BC.[60]

The idea that farming was spread from Anatolia in a single wave has been revised. Instead it appears to have spread in several waves by several routes, primarily from the Levant.[61] The trail of plant domesticates indicates an initial foray from the Levant by sea.[62] The overland route via Anatolia seems to have been most significant in spreading farming into south-east Europe.[63]

Farming developed independently in the eastern fertile crescent.[20] Non-Indo-European languages appear to be associated with the spread of farming from the Near East into North Africa and the Caucasus. According to Lazaridis et al. (2016), farming developed independently both in the Levant and in the eastern Fertile Crescent.[20] After this initial development, the two regions and the Caucasus interacted, and the chalcolithic north-west Iranian population appears to be a mixture of Iranian Neolithic, Levant, and Caucasus hunter-gatherers.[20] According to Lazaridis et al. (2016), "farmers related to those from Iran spread northward into the Eurasian steppe; and people related to both the early farmers of Iran and to the pastoralists of the Eurasian steppe spread eastward into South Asia".[64] They further note that ANI "can be modelled as a mix of ancestry related to both early farmers of western Iran and to people of the Bronze Age Eurasian steppe",[64] which makes it unlikely that the Indo-European languages in India are derived from Anatolia.[65] Mascarenhas et al. (2015) note that the expansion of Z93 from Transcaucasia into South Asia is compatible with "the archeological records of eastward expansion of West Asian populations in the 4th millennium BC culminating in the so-called Kura-Araxes migrations in the post-Uruk IV period".[66]

According to Alberto Piazza "[i]t is clear that, genetically speaking, peoples of the Kurgan steppe descended at least in part from people of the Middle Eastern Neolithic who immigrated there from Turkey."[67] According to Piazza and Cavalli-Sforza, the Yamna-culture may have been derived from Middle Eastern Neolithic farmers who migrated to the Pontic steppe and developed pastoral nomadism.:

...if the expansions began at 9,500 years ago from Anatolia and at 6,000 years ago from the Yamnaya culture region, then a 3,500-year period elapsed during their migration to the Volga-Don region from Anatolia, probably through the Balkans. There a completely new, mostly pastoral culture developed under the stimulus of an environment unfavorable to standard agriculture, but offering new attractive possibilities. Our hypothesis is, therefore, that Indo-European languages derived from a secondary expansion from the Yamnaya culture region after the Neolithic farmers, possibly coming from Anatolia and settled there, developing pastoral nomadism.[68]

Wells agrees with Cavalli-Sforza that there is "some genetic evidence for migration from the Middle East":

... while we see substantial genetic and archaeological evidence for an Indo-European migration originating in the southern Russian steppes, there is little evidence for a similarly massive Indo-European migration from the Middle East to Europe. One possibility is that, as a much earlier migration (8,000 years old, as opposed to 4,000), the genetic signals carried by Indo-European-speaking farmers may simply have dispersed over the years. There is clearly some genetic evidence for migration from the Middle East, as Cavalli-Sforza and his colleagues showed, but the signal is not strong enough for us to trace the distribution of Neolithic languages throughout the entirety of Indo-European-speaking Europe.[69]

Gamkrelidze and Ivanov held that the urheimat was south of the Caucasus, specifically, "within eastern Anatolia, the southern Caucasus and northern Mesopotamia" in the fifth to fourth millennia BC.[70] Their proposal was based on a disputed theory of glottal consonants in PIE. According to Gamkrelidze and Ivanov, PIE words for material culture objects imply contact with more advanced peoples to the south, the existence of Semitic loan-words in PIE, Kartvelian (Georgian) borrowings from PIE, some contact with Sumerian, Elamite and others. However, given that the glottalic theory never caught on and there was little archaeological support, the Gamkrelidze and Ivanov theory did not gain support until Renfrew's Anatolian theory revived aspects of their proposal.[4]

Gamkrelidze and Ivanov proposed that the Greeks moved west across Anatolia to their present location, a northward movement of some IE speakers that brought them into contact with the Finno-Ugric languages, and suggested that the Kurgan area, or better "Black Sea and Volga steppe," was a secondary homeland from which the western IE languages emerged.

Recent DNA-research, which shows that the steppe-people derived from a mix of Eastern Hunter-Gatherers (EHG) and Caucasian Hunter-Gatherers (CHG, native to the Caucasus and Northern Iran, but also found in northern Pakistan[71]), has led to renewed suggestions of a Caucasian, or even Iranian, homeland for an archaic or 'proto-proto-Indo-European', the common ancestor of both Anatolian languages and all other Indo-European languages.[13][22][23][24][25] It is argued that this may lend support to the Indo-Hittite hypothesis, according to which both proto-Anatolian and proto-Indo-European split-off from a common mother language "no later than the 4th millennium BCE."[19][note 6]

Haak et al. (2015) state that their findings of gene flow of a population that shares traits with modern-day Armenians into the Yamnaya pastoralist culture, lends some plausibility to the Armenian hypothesis. Yet, they also state that "the question of what languages were spoken by the 'Eastern European hunter-gatherers' and the southern, Armenian-like, ancestral population remains open."[73][note 7]

David Reich, in his 2018 publication Who We Are and How We Got Here, noting the presence of some Indo-European languages (such as Hittite) in parts of ancient Anatolia, states that "Ancient DNA available from this time in Anatolia shows no evidence of steppe ancestry similar to that in the Yamnaya [...] This suggests to me that the most likely location of the population that first spoke an Indo-European language was south of the Caucasus Mountains, perhaps in present-day Iran or Armenia, because ancient DNA from people who lived there matches what we would expect for a source population both for the Yamnaya and for ancient Anatolians." Yet, Reich also notes that "...the evidence here is circumstantial as no ancient DNA from the Hittites themselves has yet been published."[74]

According to Wang et al. (2019), the typical steppe-ancestry, as an even mix between EHG and CHG, may result from "an existing natural genetic gradient running from EHG far to the north to CHG/Iran in the south," or it may be explained as "the result of Iranian/CHG-related ancestry reaching the steppe zone independently and prior to a stream of AF [Anatolian Farmer] ancestry."[75] Wang et al. (2019) note that the Caucasus and the Steppes were genetically separated in the 4th millennium BCE,[76] but that the Caucasus served as a corridor for gene flow between cultures south of the Caucasus and the Maykop culture during the Copper and the Bronze Age, speculating that this "opens up the possibility of a homeland of PIE south of the Caucasus,"[77] which "could offer a parsimonious explanation for an early branching off of Anatolian languages, as shown on many PIE tree topologies."[77] However, Wang et al. also acknowledge that "the spread of some or all of the PIE branches would have been possible via the North Pontic/Caucasus region," as explained in the steppe hypothesis.[77][note 8]

Kristian Kristiansen, in an interview with Der Spiegel in may 2018, stated that the Yamnaya culture may have had a predecessor at the Caucasus, where "proto-proto-Indo-European" was spoken.[25] In a 2020 publication, Kristiansen writes that "...the origin of Anatolian should be located in the Caucasus, at a time when it acted as a civilizational corridor between south and north. Here the Maykop Culture of the northern Caucasus stands out as the most probable source for Proto-Anatolian, and perhaps even Proto-Indo-Anatolian."[78] Yet, the idea of Maykop-origins is incompatible with the genetic ancestry of the Maykop-culture, which was too rich in Anatolian farmer ancestry to be ancestral to Proto-Indo-Europeans.[note 9]

Bomhard's Caucasian substrate hypothesis proposes an origin (Urheimat) in a Central Asian or North Caspian region of the steppe for Indo-Uralic (a proposed common ancestor of Indo-European and Uralic).[79][web 1] Bomhard elaborates on Johanna Nichols "Sogdiana hypothesis," and Kortlandt's ideas of an Indo-Uralic proto-language, proposing an Urheimat north or east of the Caspian Sea, of an Eurasiatic language which was imposed on a population which spoke a Northwest Caucasian language.[web 1][79][note 10]

Anthony states that the validity of such deep relationships cannot be reliably demonstrated due to the time-depth involved, and also notes that the similarities may be explained by borrowings from PIE into proto-Uralic.[4] Yet, Anthony also notes that the North Caucasian communities "were southern participants in the steppe world".[2]</ref>[note 4]

David Anthony criticizes the Southern/Caucasian homeland hypothesis (including the proposals of Reich, Kristiansen, and Wang).[89][90] Anthony rejects the possibility that the Bronze Age Maykop people of the Caucasus were a southern source of language and genetics of Indo-European.[89][90] Referring to Wang et al (2019), he notes that the Anatolian Farmer component in the Yamnaya-ancestry came from European farmers, not from the Maykop, which had too much Anatolian farmer ancestry to be ancestral to the Yamnaya-population.[91] Anthony also notes that the paternal lingeages of the Yamnaya, which were rich in R1b, were related to those of earlier Eastern European hunter-gatherers, rather than those of southern or Caucasus peoples such as the Maykop.[92][note 9] He also criticises Bomhard's Caucasian substrate hypothesis, arguing that such deep relationships as between Indo-European and Uralic cannot be reliably demonstrated due to the time-depth involved.[89]

Anthony proposes that the Yamnaya derived mainly from Eastern European hunter-gatherers (EHG) from the steppes, and undiluted Caucasus hunter-gatherers (CHG) from northwestern Iran or Azerbaijan, similar to the Hotu cave population, who mixed in the Eastern European steppe north of the Caucasus. He suggests that the proto-Indo-European language formed mainly from a base of languages spoken by Eastern European hunter-gatherers, with some influences from the languages of Caucasus hunter-gatherers. According to Anthony, hunting-fishing camps from the lower Volga, dated 6200-4500 BCE, could be the remains of people who contributed the CHG-component, migrating westwards along the coast of the Caspian Sea, from an area south-east of the Caspian Sea. They mixed with EHG-people from the north Volga steppes, and the resulting culture contributed to the Sredny Stog culture, a predecessor of the Yamnaya c1ulture.[89]

Lothar Kilian and Marek Zvelebil have proposed a 6th millennium BC or later origin in Northern Europe.[26] The Steppe theory is compatible with the argument that the PIE homeland must have been larger,[38] because the "Neolithic creolisation hypothesis" allows the Pontic-Caspian region to have been part of PIE territory.

The "Paleolithic Continuity Paradigm" is a hypothesis suggesting that the Proto-Indo-European language (PIE) can be traced back to the Upper Paleolithic, several millennia earlier than the Chalcolithic or at the most Neolithic estimates in other scenarios of Proto-Indo-European origins. Its main proponents are Marcel Otte, Alexander Häusler,[2] and Mario Alinei.

The PCT posits that the advent of Indo-European languages should be linked to the arrival of Homo sapiens in Europe and Asia from Africa in the Upper Paleolithic.[93] Employing "lexical periodization", Alinei arrives at a timeline deeper than even that of Colin Renfrew's Anatolian hypothesis.[93][note 11]

Since 2004, an informal workgroup of scholars who support the Paleolithic Continuity hypothesis has been held online.[94] Apart from Alinei himself, its leading members (referred to as "Scientific Committee" in the website) are linguists Xaverio Ballester (University of Valencia) and Francesco Benozzo (University of Bologna). Also included are prehistorian Marcel Otte (Université de Liège) and anthropologist Henry Harpending (University of Utah).[93]

It is not listed by Mallory among the proposals for the origins of the Indo-European languages that are widely discussed and considered credible within academia.[95]

The Indigenous Aryans theory, also known as the Out of India theory, proposes an Indian origin for the Indo-European languages. The languages of northern India and Pakistan, including Hindi and the historically and culturally significant liturgical language Sanskrit, belong to the Indo-Aryan branch of the Indo-European language family.[96] The Steppe model, rhetorically presented as an "Aryan invasion", has been opposed by Hindu revivalists and Hindu nationalists,[97][98] who argue that the Aryans were indigenous to India, and some, such as B.B. Lal,[99] Koenraad Elst[100][101] and Shrikant Talageri,[102] have proposed that Proto-Indo-European itself originated in northern India, either with or shortly before the Indus Valley Civilisation.[98][103] This "Out of India" theory is not regarded as plausible in mainstream scholarship.[103][104][105]