Knowledge of them comes chiefly from that linguistic reconstruction, along with material evidence from archaeology and archaeogenetics. The Proto-Indo-Europeans likely lived during the late Neolithic, or roughly the 4th millennium BC. Mainstream scholarship places them in the Pontic–Caspian steppe zone in Eastern Europe (present day Ukraine and Russia). Some archaeologists would extend the time depth of PIE to the middle Neolithic (5500 to 4500 BC) or even the early Neolithic (7500 to 5500 BC), and suggest alternative location hypotheses.
By the early second millennium BC, offshoots of the Proto-Indo-Europeans had reached far and wide across Eurasia, including Anatolia (Hittites), the Aegean (the ancestors of Mycenaean Greece), the north of Europe (Corded Ware culture), the edges of Central Asia (Yamnaya culture), and southern Siberia (Afanasievo culture).
Using linguistic reconstruction, hypothetical features of the Proto-Indo-European language are deduced. Assuming that these linguistic features reflect culture and environment of the Proto-Indo-Europeans, the following cultural and environmental traits are widely proposed:
Researchers have made many attempts to identify particular prehistoric cultures with the Proto-Indo-European-speaking peoples, but all such theories remain speculative. Any attempt to identify an actual people with an unattested language depends on a sound reconstruction of that language that allows identification of cultural concepts and environmental factors associated with particular cultures (such as the use of metals, agriculture vs. pastoralism, geographically distinctive plants and animals, etc.).
The scholars of the 19th century who first tackled the question of the Indo-Europeans' original homeland (also called Urheimat, from German), had essentially only linguistic evidence. They attempted a rough localization by reconstructing the names of plants and animals (importantly the beech and the salmon) as well as the culture and technology (a Bronze Age culture centered on animal husbandry and having domesticated the horse). The scholarly opinions became basically divided between a European hypothesis, positing migration from Europe to Asia, and an Asian hypothesis, holding that the migration took place in the opposite direction.
In the early 20th century, the question became associated with the expansion of a supposed "Aryan race", a fallacy promoted during the expansion of European empires and the rise of "scientific racism". The question remains contentious within some flavours of ethnic nationalism (see also Indigenous Aryans).
A series of major advances occurred in the 1970s due to the convergence of several factors. First, the radiocarbon dating method (invented in 1949) had become sufficiently inexpensive to be applied on a mass scale. Through dendrochronology (tree-ring dating), pre-historians could calibrate radiocarbon dates to a much higher degree of accuracy. And finally, before the 1970s, parts of Eastern Europe and Central Asia had been off limits to Western scholars, while non-Western archaeologists did not have access to publication in Western peer-reviewed journals. The pioneering work of Marija Gimbutas, assisted by Colin Renfrew, at least partly addressed this problem by organizing expeditions and arranging for more academic collaboration between Western and non-Western scholars.
The Kurgan hypothesis, as of 2017 the most widely held theory, depends on linguistic and archaeological evidence, but is not universally accepted. It suggests PIE origin in the Pontic-Caspian steppe during the Chalcolithic. A minority of scholars prefer the Anatolian hypothesis, suggesting an origin in Anatolia during the Neolithic. Other theories (Armenian hypothesis, Out of India theory, Paleolithic Continuity Theory, Balkan hypothesis) have only marginal scholarly support.
In regard to terminology, in the 19th and early 20th centuries, the term Aryan was used to refer to the Proto-Indo-Europeans and their descendants. However, Aryan more properly applies to the Indo-Iranians, the Indo-European branch that settled parts of the Middle East and South Asia, as only Indic and Iranian languages explicitly affirm the term as a self-designation referring to the entirety of their people, whereas the same Proto-Indo-European root (*aryo-) is the basis for Greek and Germanic word forms which seem only to denote the ruling elite of Proto-Indo-European (PIE) society. In fact, the most accessible evidence available confirms only the existence of a common, but vague, socio-cultural designation of "nobility" associated with PIE society, such that Greek socio-cultural lexicon and Germanic proper names derived from this root remain insufficient to determine whether the concept was limited to the designation of an exclusive, socio-political elite, or whether it could possibly have been applied in the most inclusive sense to an inherent and ancestral "noble" quality which allegedly characterized all ethnic members of PIE society. Only the latter could have served as a true and universal self-designation for the Proto-Indo-European people.
By the early twentieth century this term had come to be widely used in a racist context referring to a hypothesized white, blonde and blue eyed master race, culminating with the pogroms of the Nazis in Europe. Subsequently, the term Aryan as a general term for Indo-Europeans has been largely abandoned by scholars (though the term Indo-Aryan is still used to refer to the branch that settled in Southern Asia).
According to some archaeologists, PIE speakers cannot be assumed to have been a single, identifiable people or tribe, but were a group of loosely related populations ancestral to the later, still partially prehistoric, Bronze Age Indo-Europeans. This view is held especially by those archaeologists who posit an original homeland of vast extent and immense time depth. However, this view is not shared by linguists, as proto-languages, like all languages before modern transport and communication, occupied small geographical areas over a limited time span, and were spoken by a set of close-knit communities—a tribe in the broad sense.
Researchers have put forward a great variety of proposed locations for the first speakers of Proto-Indo-European. Few of these hypotheses have survived scrutiny by academic specialists in Indo-European studies sufficiently well to be included in modern academic debate.
In 1956 Marija Gimbutas (1921–1994) first proposed the Kurgan hypothesis. The name originates from the kurgans (burial mounds) of the Eurasian steppes. The hypothesis suggests that the Indo-Europeans, a nomadic culture of the Pontic-Caspian steppe (now part of Eastern Ukraine and Southern Russia), expanded in several waves during the 3rd millennium BC. Their expansion coincided with the taming of the horse. Leaving archaeological signs of their presence (see battle-axe people), they subjugated the peaceful European neolithic farmers of Gimbutas' Old Europe. As Gimbutas' beliefs evolved, she put increasing emphasis on the patriarchal, patrilinear nature of the invading culture, sharply contrasting it with the supposedly egalitarian, if not matrilinear culture of the invaded, to a point of formulating essentially feminist archaeology. A modified form of this theory by JP Mallory (1945- ), dating the migrations earlier (to around 3500 BC) and putting less insistence on their violent or quasi-military nature, remains the most widely accepted view of the Proto-Indo-European expansion.[note 4]
The Armenian hypothesis, based on the glottalic theory, suggests that the Proto-Indo-European language was spoken during the 4th millennium BC in the Armenian Highland. This Indo-Hittite model does not include the Anatolian languages in its scenario. The phonological peculiarities of PIE proposed in the glottalic theory would be best preserved in the Armenian language and the Germanic languages, the former assuming the role of the dialect which remained in situ, implied to be particularly archaic in spite of its late attestation. Proto-Greek would be practically equivalent to Mycenean Greek and would date to the 17th century BC, closely associating Greek migration to Greece with the Indo-Aryan migration to India at about the same time (viz., Indo-European expansion at the transition to the Late Bronze Age, including the possibility of Indo-European Kassites). The Armenian hypothesis argues for the latest possible date of Proto-Indo-European (sans Anatolian), a full millennium later than the mainstream Kurgan hypothesis. In this, it figures as an opposite to the Anatolian hypothesis, in spite of the geographical proximity of the respective Urheimaten suggested, diverging from the time-frame suggested there by a full three millennia.
Bernard Sergent associates the Indo-European language family with certain archaeological cultures in Southern Russia, and he reconstructs an Indo-European religion (relying on the method of Georges Dumézil). He writes that the lithic assemblage of the first Kurgan culture in Ukraine (Sredni Stog II), originated from the Volga and South Urals, recalls that of the Mesolithic-Neolithic sites to the east of the Caspian sea, Dam Dam Chesme II and the cave of Djebel. Thus, he places the roots of the Gimbutas' Kurgan cradle of Indo-Europeans in a more southern cradle, and adds that the Djebel material is related to a Paleolithic material of Northwestern Iran, the Zarzian culture, dated 10,000-8,500 BC, and in the more ancient Kebarian of the Near East. He concludes that more than 10,000 years ago the Indo-Europeans were a small people grammatically, phonetically and lexically close to Semitic-Hamitic populations of the Near East.
The Anatolian hypothesis proposes that the Indo-European languages spread peacefully into Europe from Asia Minor from around 7000 BC with the advance of farming (wave of advance). The leading propagator of the theory is Colin Renfrew. The culture of the Indo-Europeans as inferred by linguistic reconstruction raises difficulties for this theory, since early neolithic cultures had neither the horse, nor the wheel, nor metal, terms for all of which are securely reconstructed for Proto-Indo-European. Renfrew dismisses this argument, comparing such reconstructions to a theory that the presence of the word "café" in all modern Romance languages implies that the ancient Romans had cafés too. The linguistic counter-argument to this[original research?] might state that whereas there can be no clear Proto-Romance reconstruction of the word "café" according to historical linguistic methodology, words such as "wheel" in the Indo-European languages clearly point to an archaic form of the protolanguage. Another argument[whose?] against Renfrew is the fact that ancient Anatolia is known to have been inhabited[when?] by non-Indo-European Caucasian-speaking peoples, namely the Hattians, the Chalybes, and the Hurrians.
The rise of archaeogenetic evidence which uses genetic analysis to trace migration patterns also added new elements to the origins puzzle.
According to three autosomal DNA studies, haplogroups R1b and R1a, now the most common in Europe (R1a is also very 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. Studies which analysed ancient human remains in Ireland and Portugal suggest that R1b was introduced in these places along with autosomal DNA from the Eastern European steppes.
The subclade R1a1a (R-M17 or R-M198) is most commonly associated with Indo-European speakers, although the subclade R1b1a (P-297) has also been linked to the Centum branch of Indo-European. Data so far collected indicate that there are two widely separated areas of high frequency, one in Eastern Europe, around Poland and the Russian core, and the other in South Asia, around Indo-Gangetic Plain. The historical and prehistoric possible reasons for this are the subject of on-going discussion and attention amongst population geneticists and genetic genealogists, and are considered to be of potential interest to linguists and archaeologists also.
A large, 2014 study by Underhill et al., using 16,244 individuals from over 126 populations from across Eurasia, concluded there was compelling evidence, that R1a-M420 originated in the vicinity of Iran. The mutations that characterize haplogroup R1a occurred ~10,000 years BP. Its defining mutation (M17) occurred about 10,000 to 14,000 years ago.
Ornella Semino et al. propose a postglacial (Holocene) spread of the 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.
According to Jones et al. (2015) and Haak et al. (2015), Yamnaya culture was exclusively R1b, autosomic tests indicate that the Yamnaya-people were the result of admixture between two different hunter-gatherer populations: distinctive "Eastern European hunter-gatherers" with high affinity to the Mal'ta-Buret' culture or other, closely related Ancient North Eurasian (ANE) people from Siberia and to Western Hunter Gatherers(WHG) and a population of "Caucasus hunter-gatherers" who probably arrived from somewhere in the Near East, probably the Caucasus or Iran.[web 1] Each of those two populations contributed about half the Yamnaya DNA.[web 1] According to co-author Dr. Andrea Manica of the University of Cambridge:
The question of where the Yamnaya come from has been something of a mystery up to now [...] we can now answer that, as we've found that their genetic make-up is a mix of Eastern European hunter-gatherers and a population from this pocket of Caucasus hunter-gatherers who weathered much of the last Ice Age in apparent isolation.[web 1]
According to Haak et al. (2015), "Eastern European hunter-gatherers" who inhabited Russia were a distinctive population of hunter-gatherers with high affinity to a ~24,000-year-old Siberian from Mal'ta-Buret' culture, or other, closely related Ancient North Eurasian (ANE) people from Siberia and to the Western Hunter Gatherers (WHG).[web 1] Remains of the "Eastern European hunter-gatherers" have been found in Mesolithic or early Neolithic sites in Karelia and Samara Oblast, Russia, and put under analysis. Three such hunter-gathering individuals of the male sex have had their DNA results published. Each was found to belong to a different Y-DNA haplogroup: R1a, R1b, and J. R1b is also the most common Y-DNA haplogroup found among both the Yamnaya and modern-day Western Europeans.
Jones et al. (2015) analyzed genomes from males from western Georgia, in the Caucasus, from the Late Upper Palaeolithic (13,300 years old) and the Mesolithic (9,700 years old). These two males carried Y-DNA haplogroup: J* and J2a. The researchers found that these Caucasus hunters were probably the source of the farmer-like DNA in the Yamnaya, as the Caucasians were distantly related to the Middle Eastern people who introduced farming in Europe.[web 1] Their genomes showed that a continued mixture of the Caucasians with Middle Eastern took place up to 25,000 years ago, when the coldest period in the last Ice Age started.[web 1]
According to Lazaridis et al. (2016), "a population related to the people of the Iran Chalcolithic contributed ~43% of the ancestry of early Bronze Age populations of the steppe." According to Lazaridis et al. (2016), these Iranian Chalcolithic people were a mixture of "the Neolithic people of western Iran, the Levant, and Caucasus Hunter Gatherers."[note 5] Lazaridis et al. (2016) also note that farming spread at two places in the Near East, namely the Levant and Iran, from where it spread, Iranian people spreading to the steppe and south Asia.
Haak et al. (2015) studied DNA from 94 skeletons from Europe and Russia aged between 3,000 and 8,000 years old. They concluded that about 4,500 years ago there was a major influx into Europe of Yamnaya culture people originating from the Pontic-Caspian steppe north of the Black Sea and that the DNA of copper-age Europeans matched that of the Yamnaya. The genetic basis of a number of features of the Yamnaya people were ascertained: they were genetically tall (phenotypic height is determined by both genetics and environmental factors), overwhelmingly dark-eyed (brown), dark-haired and had a skin colour that was moderately light, though somewhat darker than that of the average modern European:
The four Corded Ware people could trace an astonishing three-quarters of their ancestry to the Yamnaya, according to the paper. That suggests a massive migration of Yamnaya people from their steppe homeland into eastern Europe about 4500 years ago when the Corded Ware culture began, perhaps carrying an early form of Indo-European language.
From the Corded Ware culture the Indo-Europeans spread eastward again, forming the Andronovo culture. Most researchers associate the Andronovo horizon with early Indo-Iranian languages, though it may have overlapped the early Uralic-speaking area at its northern fringe. According to Allentoft et al. (2015), the Sintashta culture and Andronovo culture are derived from the Corded Ware culture. According to Keyser et al. (2009), out of 10 human male remains assigned to the Andronovo horizon from the Krasnoyarsk region, nine possessed the R1a Y-chromosome haplogroup and one had the C-M130 haplogroup (xC3). Furthermore, 90% of the Bronze Age period mtDNA haplogroups were of west Eurasian origin, and the study determined that at least 60% of the individuals overall (out of the 25 Bronze and Iron Age human-remains samples from the study that could be tested) had blue or green eyes.[note 6]
A 2004 study also established that during the Bronze Age/Iron Age period, the majority of the population of Kazakhstan (part of the Andronovo culture during Bronze Age), was of west Eurasian origin (with mtDNA haplogroups such as U, H, HV, T, I and W), and that prior to the 13th–7th centuries BC, all samples from Kazakhstan belonged to European lineages.
Luigi Luca Cavalli-Sforza and Alberto Piazza argue that Renfrew and Gimbutas reinforce rather than contradict each other. Cavalli-Sforza (2000) states that "It 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." Piazza and Cavalli-Sforza (2006) state that:
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 unfavourable 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.
Spencer Wells suggests in a 2001 study that the origin, distribution and age of the R1a1 haplotype points to an ancient migration, possibly corresponding to the spread by the Kurgan people in their expansion across the Eurasian steppe around 3000 BC.
About his old teacher Cavalli-Sforza's proposal, Wells (2002) states that "there is nothing to contradict this model, although the genetic patterns do not provide clear support either", and instead argues that the evidence is much stronger for Gimbutas' model:
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.
David Reich (2018) argues that the most likely location of the Proto-Indo-European homeland is south of the Caucasus, 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".