The steppe hypothesis seeks to identify the source of the Indo-European language expansion which resulted in a succession of migrations from the
Pontic–Caspian steppe between the 5th and 3rd millennia BCE. During the early 1980s, 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.
Gimbutas's Kurgan hypothesis According to the Kurgan hypothesis as formulated by Gimbutas, Indo-European speaking
nomads from Eastern
Ukraine and Southern
Russia expanded on horseback in several waves during the 3rd millennium BCE, invading and subjugating supposedly peaceful European Neolithic farmers of Gimbutas's
Old Europe. Later versions of Gimbutas's hypothesis increasingly emphasized the
patriarchal and
patrilineal nature of the invading culture, in contrast with the supposedly egalitarian and
matrilineal culture of the invaded.
Archaeology The archaeologist
J. P. Mallory, dating the migrations to c. 4000 BCE, and having less insistence on their violent or quasi-military nature, essentially modified Gimbutas's theory making it compatible with a less gender-political narrative. David Anthony, emphasizing mostly the evidence for the domestication of horses and the presence of wheeled vehicles, came to regard specifically the
Yamnaya culture, which replaced the
Sredny Stog culture about 3500 BCE, as the most likely candidate for the Proto-Indo-European speech community. Anthony describes the spread of cattle-raising from early farmers in the Danube Valley into the Ukrainian steppes in the 6th–5th millennium BCE, forming a cultural border with the hunter-gatherers whose languages may have included archaic PIE. 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. Subsequent cultures developed in this area which adopted cattle, most notably the
Cucuteni-Trypillian culture. The Indologist
Asko Parpola regards the
Cucuteni-Trypillian 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) who took over the Tripillia culture at c. 4300–4000 BCE. On its eastern border lay the
Sredny Stog culture (4400–3400 BCE), whose origins are related to "people from the east, perhaps from the Volga steppes". It plays the main role in Gimbutas's Kurgan hypothesis, and coincides with the spread of early PIE across the steppes and into the Danube valley (c. 4000 BCE), resulting in the end of Old Europe. Hereafter the
Maykop culture suddenly began, Tripillia towns grew strongly, and eastern steppe people migrated to the Altai mountains, founding the
Afanasevo culture (3300 to 2500 BCE).
Vocabulary 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. 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 unlikely, and to violate the established principles for reasonable assumptions when explaining linguistic comparative data. 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 occur much further north than the Anatolian or Near Eastern scenarios would allow. According to Kortlandt,
Indo-Uralic is the common ancestor of the Indo-European and Uralic language families. Kortlandt argues that "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." 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. Yet, Anthony also notes that the North Caucasian communities "were southern participants in the steppe world". Kloekhorst argues that the Anatolian languages have preserved archaisms which are also found in proto-Uralic, providing strong evidence for a steppe-origin of PIE.
Human genetics The
subclade R1a1a (R-M17 or R-M198) is the R1a subclade associated most commonly with Indo-European speakers. In 2000, Ornella Semino et al. proposed a postglacial (
Holocene) period spread of the R1a1a 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. In 2015, a large-scale
ancient DNA study by Haak et al. published in
Nature found evidence of a "massive migration" from the Pontic-Caspian steppe to central Europe that occurred about 4,500 years ago. It found that individuals from the central European
Corded Ware culture (3rd millennium BCE) were closely related genetically 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". Two other genetic studies in 2015 gave support to the steppe hypothesis regarding the Indo-European
Urheimat. According to those studies, specific subclades of
Y chromosome haplogroups
R1b and
R1a, which are found in Yamnaya and other proposed early Indo-European cultures such as Sredny Stog and Khvalynsk, and are now the most common in Europe (R1a is also common in South Asia) would have expanded from the Ukrainian and Russian steppes, along with the Indo-European languages; these studies also detected an
autosomal component present in modern Europeans that was not present in Neolithic Europeans, which would have been introduced with paternal lineages R1b and R1a, as well as Indo-European languages. 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 that had been familiar with agriculture for 4,000 years. and archaeologists have argued that although such a migration might have occurred it does not necessarily explain either the distribution of archaeological cultures or the spread of the Indo-European languages. Russian archaeologist
Leo Klejn (2017) noted that in the Yamnaya population, R1b-L23 is predominant, whereas Corded Ware males belong mostly to R1a, as well as far-removed R1b clades not found in Yamnaya. In his opinion, this does not support a Yamnaya origin for the Corded Ware culture. British archaeologist
Barry Cunliffe describes this inconsistency as "disconcerting for the model as a whole". Klejn has also suggested that the autosomal evidence does not support a proposed Yamnaya migration, as Western Steppe Herder ancestry is lesser in the area from which the Yamnaya were proposed to have expanded, in both contemporary populations and Bronze Age specimens. Furthermore, Balanovsy et al. (2017) found that the majority of the Yamnaya genomes studied by Haak and Mathieson belonged to the "eastern" R-GG400 subclade of R1b-L23, which is not common in western Europe, and none belonged to the "western" R1b-L51 branch. The authors conclude that the Yamnaya could not have been an important source of modern western European male haplogroups. An analysis by
David Anthony (2019) suggested 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 (EHG) and hunter-gatherers from the Caucasus (CHG). Anthony also suggested 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 and more minor influence from the language of the
Maykop culture to the south (which is hypothesized to have belonged to the
North Caucasian languages) during the later Neolithic or Bronze Age, involving little genetic effect. In 2020, David Anthony offered a new hypothesis, with the intent of resolving the questions concerning the apparent absence of haplogroup R1a in Yamnaya. He speculates that haplogroup R1a must have been present in the Yamnaya, but that it was initially extremely rare, and that the Corded Ware culture are the descendants of this wayward population that migrated north from the Pontic steppe and greatly expanded in size and influence, later returning to dominate the Pontic-Caspian steppe. ==Anatolian hypothesis==