Native Americans from the Amazon, Andes, and coastal geographic regions of South America have a rich cultural heritage but are genetically understudied, therefore leading to gaps in our knowledge of their genomic architecture and demographic history. In this study, we sequence 150 genomes to high coverage combined with an additional 130 genotype array samples from Native American and mestizo populations in Peru. The majority of our samples possess greater than 90% Native American ancestry, which makes this the most extensive Native American sequencing project to date. Demographic modeling reveals that the peopling of Peru began ∼12,000 y ago, consistent with the hypothesis of the rapid peopling of the Americas and Peruvian archeological data. We find that the Native American populations possess distinct ancestral divisions, whereas the mestizo groups were admixtures of multiple Native American communities that occurred before and during the Inca Empire and Spanish rule. In addition, the mestizo communities also show Spanish introgression largely following Peruvian Independence, nearly 300 y after Spain conquered Peru. Further, we estimate migration events between Peruvian populations from all three geographic regions with the majority of between-region migration moving from the high Andes to the low-altitude Amazon and coast. As such, we present a detailed model of the evolutionary dynamics which impacted the genomes of modern-day Peruvians and a Native American ancestry dataset that will serve as a beneficial resource to addressing the underrepresentation of Native American ancestry in sequencing studies.
The high frequency of Native American mitochondrial haplotypes suggests that European males were the primary source of European admixture with Native Americans, as previously found (23, 24, 41, 42). The only Peruvian populations that have a proportion of the Central American component are in the Amazon (Fig. 2A). This is supported by Homburger et al. (4), who also found Central American admixture in other Amazonian populations and could represent ancient shared ancestry or a recent migration between Central America and the Amazon.
Following the peopling of Peru, we find a complex history of admixture between Native American populations from multiple geographic regions (Figs. 2B and 3 A and C). This likely began before the Inca Empire due to Native American and mestizo groups sharing IBD segments that correspond to the time before the Inca Empire. However, the Inca Empire likely influenced this pattern due to their policy of forced migrations, known as “mitma” (mitmay in Quechua) (28, 31, 37), which moved large numbers of individuals to incorporate them into the Inca Empire. We can clearly see the influence of the Inca through IBD sharing where the center of dominance in Peru is in the Andes during the Inca Empire (Fig. 3C).
A similar policy of large-scale consolidation of multiple Native American populations was continued during Spanish rule through their program of reducciones, or reductions (31, 32), which is consistent with the hypothesis that the Inca and Spanish had a profound impact on Peruvian demography (25). The result of these movements of people created early New World cosmopolitan communities with genetic diversity from the Andes, Amazon, and coast regions as is evidenced by mestizo populations’ ancestry proportions (Fig. 3A). Following Peruvian independence, these cosmopolitan populations were those same ones that predominantly admixed with the Spanish (Fig. 3B). Therefore, this supports our model that the Inca Empire and Spanish colonial rule created these diverse populations as a result of admixture between multiple Native American ancestries, which would then go on to become the modern mestizo populations by admixing with the Spanish after Peruvian independence.
Further, it is interesting that this admixture began before the urbanization of Peru (26) because others suspected the urbanization process would greatly impact the ancestry patterns in these urban centers (25). (…)
In accordance with our previous mtDNA study9, the present NRY analysis reveals a major division between the Kx’a-speaking !Xun and the Bantu-speaking groups, whose paternal genetic ancestry does not display any old remnant lineages, or a clear link to pre-Bantu eastern African migrants introducing Khoe-Kwadi languages and pastoralism into southern Africa (cf. 15). This is especially evident in the distribution of the eastern African subhaplogroup E1b1b1b2b29, which reaches the highest frequency in the !Xun (25%) and not in the formerly Kwadi-speaking Kwepe (7%). This observation, together with recent genome-wide estimates of 9-22% of eastern African ancestry in other Kx’a and Tuu-speaking groups35, suggests that eastern African admixture was not restricted to present-day Khoe-Kwadi speakers. Alternatively, it is likely that the dispersal of pastoralism and Khoe-Kwadi languages involved a series of punctuated contacts that led to a wide variety of cultural, genetic and linguistic outcomes, including possible shifts to Khoe-Kwadi by originally Bantu-speaking peoples36.
Although traces of an ancestral pre-Bantu population may yet be found in autosomal genome-wide studies, the extant variation in both uniparental markers strongly supports a scenario in which all groups of the Angolan Namib share most of their genetic ancestry with other Bantu groups but became increasingly differentiated within the highly stratified social context of SW African pastoral societies11.
The influence of socio-cultural behaviors on the diversity of NRY and mtDNA
A comparison of the NRY variation with previous mtDNA results for the same groups 9 identifies three main sex-specific patterns. First, gene flow from the Bantu into the !Xun is much higher for male than for female lineages (31% NRY vs. 3% mtDNA), similar to the reported male-biased patterns of gene flow from Bantu to Khoisan-speaking groups33, and from non-Pygmies to Pygmies in Central Africa 37. A comparable trend, involving exclusive introgression of NRY eastern African lineages into the !Xun (25%) was also found. (…)
Secondly, the levels of intrapopulation diversity in the Bantu-speaking peoples from the Namib were found to be consistently higher for mtDNA than for the NRY, reflecting the marked association between the Bantu expansion and the relatively young NRY E1b1a1a1 haplogroup, which has no parallel in mtDNA25,39. (…)
In the context of the Bantu expansions, these patterns have been mostly interpreted as the result of polygyny and/or higher levels of assimilation of females from resident forager communities38,40. However, most groups from the Angolan Namib are only mildly polygynous11 and ethnographic data suggest that the actual rates of polygyny in many populations may be insufficient to significantly reduce Nem2,41. In addition, the finding of a large Nef/ Nem ratio in the Himba (Fig. S5), who have almost no Khoisan-related mtDNA lineages9, indicates that female biased introgression cannot fully explain the observed patterns.
An alternative explanation may be sought in the prevailing matrilineal descent rules, which might have created a sex-specific structuring effect, similar to that proposed for patrilineal groups from Central Asia (…)
The third important sex-specific pattern observed in this study is the much lower amount of between-group differentiation for NRY than for mtDNA among Bantu-speaking populations (4.4% NRY vs. 20.2% mtDNA), in spite of the patrilocal residence patterns of all ethnic groups (Table S5). This difference can hardly be explained by unequal levels of introgression of “Khoisan” mtDNA lineages into the Bantu, since the percentage of mtDNA variation remains high (18.8%) when the Kuvale, who have high frequencies of “Khoisan”-related mtDNA, are excluded from the comparisons. It therefore seems more plausible that differentiation is higher in the mtDNA simply because there is more ancestral mtDNA than NRY variation that can be sorted among different populations (see 45). Moreover, due to the matriclanic organization of all Bantu-speaking communities, factors enhancing inter-group differentiation, like kin-structured migration and kin-structured founder effects46, would have been restricted to mtDNA. Finally, it is also likely that the discrepancy between among-group divergence of mtDNA and NRY might have been influenced by higher migration rates in males than females. In fact, although all Bantu-speaking populations have patrilocal residence patterns, the observance of endogamy rules severely constrains the between-group mobility of females. In this context, the children from extramarital unions involving members from different populations tend to be raised in the mother’s group, effectively increasing male versus female migration rates. Moreover, it is likely that, in the highly hierarchized setting of the Namib, most intergroup extramarital unions would involve men from dominant groups and women from peripatetic communities. This hypothesis is indirectly supported by the finding that in NRY-based clusters (but not in mtDNA) pastoralist populations are grouped together with peripatetic communities that share their cultural traits (Figs. S6 and 3b), suggesting that migration of NRY lineages follows a path that is similar to horizontally transmitted cultural features.
Human populations often exhibit contrasting patterns of genetic diversity in the mtDNA and the non-recombining portion of the Y-chromosome (NRY), which reflect sex-specific cultural behaviors and population histories. Here, we sequenced 2.3 Mb of the NRY from 284 individuals representing more than 30 Native-American groups from Northwestern Amazonia (NWA) and compared these data to previously generated mtDNA genomes from the same groups, to investigate the impact of cultural practices on genetic diversity and gain new insights about NWA population history. Relevant cultural practices in NWA include postmarital residential rules and linguistic-exogamy, a marital practice in which men are required to marry women speaking a different language. We identified 2,969 SNPs in the NRY sequences; only 925 SNPs were previously described. The NRY and mtDNA data showed that males and females experienced different demographic histories: the female effective population size has been larger than that of males through time, and both markers show an increase in lineage diversification beginning ~5,000 years ago, with a male-specific expansion occurring ~3,500 years ago. These dates are too recent to be associated with agriculture, therefore we propose that they reflect technological innovations and the expansion of regional trade networks documented in the archaeological evidence. Furthermore, our study provides evidence of the impact of postmarital residence rules and linguistic exogamy on genetic diversity patterns. Finally, we highlight the importance of analyzing high-resolution mtDNA and NRY sequences to reconstruct demographic history, since this can differ considerably between males and females.
Looking more precisely at the different groups (even with the resampling approach), there are no significant differences between matrilocal and patrilocal groups. At best, as the study proposes, “this is just one of the factors at play in structuring the observed genetic variation”.
(…) we found evidence that the patterns of genetic differentiation depend on the geographical scale of the study. The magnitude of between-population differentiation in the NRY compared to the mtDNA is smaller when looking at the continental scale than in NWA (Figure 6). This is in agreement with the findings of Wilkins and Marlowe (2006), who showed that the excess of between-population differentiation for the NRY in comparison to the mtDNA decreases when comparing more geographically distant populations. Heyer et al. (2012) and Wilkins and Marlowe (2006) have proposed that at a local scale the patterns of genetic diversity reflect cultural practices over a relatively small number of generations, whereas at a larger geographic scale the genetic diversity reflects old migration and/or old common ancestry patterns(Heyer et al. 2012; Wilkins and Marlowe 2006).
The BSP plots and the diversity statistics indicate that overall the Ne of males has been smaller than that of females. One tentative explanation for this difference is that it reflects larger differences in reproductive success among males than among females. Some support for this explanation comes from the shape of the phylogenies (Supplementary Figures 1 and 6), since differences in reproductive success and the cultural transmission of fertility lead to imbalance phylogenies (Blum et al. 2006; Heyer et al. 2015). We estimated a common index of tree imbalance (Colless index) and calculated whether the mtDNA and NRY trees were more unbalanced than 1000 simulated trees generated under a Yule process (Bortolussi et al. 2006) (i.e. a simple pure birth process that assumes that the birth rate of new lineages is the same along the tree). We found that the NRY tree is more unbalanced than predicted by the Yule model (p-value=0.001), whereas the mtDNA tree is not significantly different from trees generated by the Yule model (p-value=0.628). It has been suggested that highly mobile hunter-gatherer societies, such as those typical of most of human prehistory, were polygynous bands (Dupanloup et al. 2003); similarly, nomadic horticulturalist Amazonian societies exhibit strong differences in reproductive success due to the common practice of polygyny, especially among community chiefs, whose offspring also enjoy a high fertility (Neel 1970; 1980; Neel and Weiss 1975).
Furthermore, a more recent expansion can be observed in the BSP based on the NRY, but not in the mtDNA BSP (Figure 5), indicating an expansion specifically in the paternal line. The reasons behind this recent male-biased population expansion, which starts ~3.5 kya, are as yet unclear. However, similar male-biased expansions have been observed in other studies using high-resolution NRY sequences (Batini et al. 2017; Karmin et al. 2015).
Archaeogenomic studies have largely elucidated human population history in West Eurasia during the Stone Age. However, despite being a broad geographical region of significant cultural and linguistic diversity, little is known about the population history in North Asia. We present complete mitochondrial genome sequences together with stable isotope data for 41 serially sampled ancient individuals from North Asia, dated between c.13,790 BP and c.1,380 BP extending from the Palaeolithic to the Iron Age. Analyses of mitochondrial DNA sequences and haplogroup data of these individuals revealed the highest genetic affinity to present-day North Asian populations of the same geographical region suggesting a possible long-term maternal genetic continuity in the region. We observed a decrease in genetic diversity over time and a reduction of maternal effective population size (Ne) approximately seven thousand years before present. Coalescent simulations were consistent with genetic continuity between present day individuals and individuals dating to 7,000 BP, 4,800 BP or 3,000 BP. Meanwhile, genetic differences observed between 7,000 BP and 3,000 BP as well as between 4,800 BP and 3,000 BP were inconsistent with genetic drift alone, suggesting gene flow into the region from distant gene pools or structure within the population. These results indicate that despite some level of continuity between ancient groups and present-day populations, the region exhibits a complex demographic history during the Holocene.
Although highly dependent on sample size and thus prone to generalization, haplotype sharing analysis between three spatial groups and other modern and ancient populations (Supplementary Table S15) revealed that the TRAB group shared most lineages with ancient Kazakh Altai (KA) and modern Nganasan (NGN)39,40,41,42. The CISB group shared most lineages with Tubalar39,42, KA43 and Early Bronze Age groups of Russia (BO)12, which might reflect the Siberian roots of BO, consistent with MDS based on Fst (Fig. 3b). The YAK group shared most lineages with the CISB, BO and Tubalar groups. These results showed that despite being from different sides of the Lake Baikal, the CISB and YAK groups shared most lineages with the Tubalar and also both of them were to a certain degree affiliated to the BO of the Cis-Baikal region, thus, reflecting a shared common ancestry. Furthermore, the CISB and YAK groups share lineages supporting the hypothesis of a lasting continuity in this large geographical territory. However, the TRAB group may have different legacy with affinities to ancient Kazakh Altai and modern Nganasan groups (that, actually, may have relocated from the Trans-Baikal region in times post-dating our sample).
Two findings, however, were intriguing. One was the discovery of only weak support for a single regional population in comparisons between Early vs. Late as well as Middle vs. Late groups in the region. This may be explained by population structure, as the Late group comprised geographically very distant individuals, such as individuals from Krasnoyarsk Krai and Amur Oblast, not represented in the other diachronic groups (Table S9). Another explanation for rejecting the null hypothesis of continuity between the Middle and Late (4,800–3,000 BP) groups might be due to an interruption and the arrival of pastoralists at the beginning of the Iron Age between 3,670 to 2,760 BP as suggested by the archaeological record32. Thus, the introduction of the new lifeways, technologies and material culture expressions might also here be associated to an increased mobility into the area.
The second point was the estimated reduction in maternal effective population size and haplotype diversity around 7,000 BP. Intriguingly, climate modelling and radiocarbon dating studies53 suggest that climatic change and a collapse of the riverine ecosystems might have affected the human populations in Cis Baikal between 7,000–6,000 BP in line with our results. This finding was further supported by archaeological studies pointing to a possible hiatus38,54,55.
Although our results provide a first glimpse into population structure and diversity in North Asia during the Holocene which link to trend in the archaeological record, complete genome sequences will provide a higher resolution of more complex demographic events in the region.
The retrieval of ancient DNA from osteological material provides direct evidence of human genetic diversity in the past. Ancient DNA samples are often used to investigate whether there was population continuity in the settlement history of an area. Methods based on the serial coalescent algorithm have been developed to test whether the population continuity hypothesis can be statistically rejected by analysing DNA samples from the same region but of different ages. Rejection of this hypothesis is indicative of a large genetic shift, possibly due to immigration occurring between two sampling times. However, this approach is only able to reject a model of full continuity model (a total absence of genetic input from outside), but admixture between local and immigrant populations may lead to partial continuity. We have recently developed a method to test for population continuity that explicitly considers the spatial and temporal dynamics of populations. Here we extended this approach to estimate the proportion of genetic continuity between two populations, by using ancient genetic samples. We applied our original approach to the question of the Neolithic transition in Central Europe. Our results confirmed the rejection of full continuity, but our approach represents an important step forward by estimating the relative contribution of immigrant farmers and of local hunter‐gatherers to the final Central European Neolithic genetic pool. Furthermore, we show that a substantial proportion of genes brought by the farmers in this region were assimilated from other hunter‐gatherer populations along the way from Anatolia, which was not detectable by previous continuity tests. Our approach is also able to jointly estimate demographic parameters, as we show here by finding both low density and low migration rate for pre‐Neolithic hunter‐gatherers. It provides a useful tool for the analysis of the numerous aDNA datasets that are currently being produced for many different species.
Our results are in general accordance with two distinct ancestry components that have previously been detected at the continental scale by Lazaridis, Patterson et al. (2014): the “early European farmer” (EEF), which corresponds here to the NFA from Anatolia (zone C in Figure 3), and the “West European hunter-gatherer” (WHG), which corresponds here to the PHG from zones A and B in Figure 3. Notably, the contribution of an Ancient North Eurasians (ANE) component is not included in our model as we did not consider potential post-Neolithic immigration waves, which could have contributed to the modern European genetic pool, such as the wave that came from the Pontic steppes and was associated with the Yamnaya culture (Haak, Lazaridis et al. 2015). Without considering the ANE ancestry component, our estimate of the autosomal genetic contribution of Early farmers to the gene pool of Central European populations (25%) tends to be lower than the EEF ancestry estimated in most modern Western European populations, but is of the same order than the estimations in modern Estonians and in the ancient Late Neolithic genome “Karsdorf” from Germany (Lazaridis, Patterson et al. 2014, Haak, Lazaridis et al. 2015). Note that the contribution of hunter-gatherers to Neolithic communities appears to be variable in different regions of Europe (Skoglund, Malmstrom et al. 2012, Brandt, Haak et al. 2013, Lazaridis, Patterson et al. 2014), while we computed an average value for Central Europe. Moreover, we computed the ancestry of the two groups at the end of the Neolithic period while previous studies estimated it in modern times. Finally, previous studies used molecular information to directly estimate admixture proportions, while we use molecular information to estimate the model parameters and, then, we computed the expected genetic contributions of both groups using the best parameters, without using molecular information during this second step. Model assumptions may thus influence the inferences on the relative genetic contribution of both groups. In particular, we made the assumption of a uniform expansion of NFA with constant and similar assimilation of PHG over the whole continent but spatio-temporally heterogeneous environment, variable assimilation rate and long distance dispersal may have played an important role. The effects of those factors should be investigated in future studies.
An interesting observation is that steppe zone individuals directly north of the Caucasus (Eneolithic Samara and Eneolithic steppe) had initially not received any gene flow from Anatolian farmers. Instead, the ancestry profile in Eneolithic steppe individuals shows an even mixture of EHG and CHG ancestry, which argues for an effective cultural and genetic border between the contemporaneous Eneolithic populations in the North Caucasus, notably Steppe and Caucasus. Due to the temporal limitations of our dataset, we currently cannot determine whether this ancestry is stemming from an existing natural genetic gradient running from EHG far to the north to CHG/Iran in the south or whether this is the result of farmers with Iranian farmer/ CHG-related ancestry reaching the steppe zone independent of and prior to a stream of Anatolian farmer-like ancestry, where they mixed with local hunter-gatherers that carried only EHG ancestry.
Concerning the influences from the south, our oldest dates from the immediate Maykop predecessors Darkveti-Meshoko (Eneolithic Caucasus) indicate that the Caucasus genetic profile was present north of the range ~6500 BP, 4500 calBCE. This is in accordance with the Neolithization of the Caucasus, which had started in the flood plains of the great rivers in the South Caucasus in the 6th millennium BCE from where it spread to the West and Northwest Caucasus during the 5th millennium BCE9, 49. It remains unclear whether the local CHG ancestry profile (represented by Late Upper Palaeolithic/Mesolithic individuals from Kotias Klde and Satsurblia in today’s Georgia) was also present in the North Caucasus region before the Neolithic. However, if we take the Caucasus hunter-gatherer individuals from Georgia as a local baseline and the oldest Eneolithic Caucasus individuals from our transect as a proxy for the local Late Neolithic ancestry, we notice a substantial increase in Anatolian farmer-related ancestry. This in all likelihood is linked to the process of Neolithization, which also brought this type of ancestry to Europe. As a consequence, it is possible that Neolithic groups could have reached the northern flanks of the Caucasus earlier50 (Supplementary Information 1) and in contact with local hunter gatherers facilitated the exploration of the steppe environment for pastoralist economies. Hence, additional sampling from older individuals is needed to fill this temporal and spatial gap.
The newest paper of the Reich/Jena group has brought samples (probably) much nearer to the actual CHG and ANE contribution seen in Eneolithic steppe peoples than the previously available Kotias Klde, Satsurblia, Afontova Gora 3, or Mal’ta.
It is impossible to say without direct access to the samples, but it is very likely that we will soon be able to break down different gross contributions from groups similar to these Steppe/Caucasus Neolithic ancestral groups into the diverse Eneolithic cultures of the Pontic-Caspian steppe, and thus trace more precisely each of these cultures to their genetic (and thus ethnolinguistic) heirs.
Some more representative samples from Eneolithic steppe, steppe-forest and forest zone cultures of Eastern Europe will probably help with the fine-scale structure of different Chalcolithic groups, especially the homeland of early Corded Ware groups.
These new samples seem another good reason (like the Botai and R1b-M73) to rethink the role of (what I assumed were) different westward Mesolithic Eurasian waves of expansion influencing the formation of an Indo-Uralic and Indo-European community in Eastern Europe, and return to the simpler idea of local contributions from North Caucasus and steppe peoples absorbed by expanding EHG-like groups.
Nevertheless, because I keep reading the same comments no matter what gets published, even in mid-2018 – the latest ones in our Facebook page (“was haplogroup X Indo-European?”), and in this very blog (“I see it very difficult to link Bell Beaker with Balto-Slavic, when now Balto-Slavic people are strikingly R1a-dominated”); and because I see even more misunderstandings and personal attacks, I have decided to publish them.
This way I will be able to explain my “R1b-L23/Proto-Indo-Europeans” theory with simplistic maps (however badly I hate such maps when I find them on Google searches), and I will also have a page to redirect those who don’t want to dismiss the “R1a – Indo-European association”, instead of answering comments about this question each time they pop up…
Here you have the links to the posts – and also on the menu above (there is a lot of rambling, because they are from a period of less clear data on Yamna and Corded Ware; today I would have never written such long discussions, they are mostly unnecessary):
The indigenous populations of inner Eurasia, a huge geographic region covering the central Eurasian steppe and the northern Eurasian taiga and tundra, harbor tremendous diversity in their genes, cultures and languages. In this study, we report novel genome-wide data for 763 individuals from Armenia, Georgia, Kazakhstan, Moldova, Mongolia, Russia, Tajikistan, Ukraine, and Uzbekistan. We furthermore report genome-wide data of two Eneolithic individuals (~5,400 years before present) associated with the Botai culture in northern Kazakhstan. We find that inner Eurasian populations are structured into three distinct admixture clines stretching between various western and eastern Eurasian ancestries. This genetic separation is well mirrored by geography. The ancient Botai genomes suggest yet another layer of admixture in inner Eurasia that involves Mesolithic hunter-gatherers in Europe, the Upper Paleolithic southern Siberians and East Asians. Admixture modeling of ancient and modern populations suggests an overwriting of this ancient structure in the Altai-Sayan region by migrations of western steppe herders, but partial retaining of this ancient North Eurasian-related cline further to the North. Finally, the genetic structure of Caucasus populations highlights a role of the Caucasus Mountains as a barrier to gene flow and suggests a post-Neolithic gene flow into North Caucasus populations from the steppe.
On North Eurasians
In a PCA of Eurasian individuals, we find that PC1 separates eastern and western Eurasian populations, PC2 splits eastern Eurasians along a north-south cline, and PC3 captures variation in western Eurasians with Caucasus and northeastern European populations at opposite ends (Figure 2A and Figures S1-S2). Inner Eurasians are scattered across PC1 in between, largely reflecting their geographic locations. Strikingly, inner Eurasian populations seem to be structured into three distinct west-east genetic clines running between different western and eastern Eurasian groups, instead of being evenly spaced in PC space. Individuals from northern Eurasia, speaking Uralic or Yeniseian languages, form a cline connecting northeast Europeans and the Uralic (Samoyedic) speaking Nganasans from northern Siberia (“forest-tundra” cline). Individuals from the Eurasian steppe, mostly speaking Turkic and Mongolic languages, are scattered along two clines below the forest-tundra cline. Both clines run into Turkic- and Mongolic-speaking populations in southern Siberia and Mongolia, and further into Tungusic-speaking populations in Manchuria and the Russian Far East in the East; however, they diverge in the west, oneheading to the Caucasus and the other heading to populations of the Volga-308 Ural area (the “southern steppe” and “steppe-forest” clines, respectively; Figure 2 and Figure S2).
(…) The forest-tundra cline populations derive most of their eastern Eurasian ancestry from a component most enriched in Nganasans, while those on the steppe-forest and southern steppe clines have this component together with another component most enriched in populations from the Russian Far East, such as Ulchi and Nivkh. The southern steppe cline groups are distinct from the others in their western Eurasian ancestry profile, in the sense that they have a high proportion of a component most enriched in Mesolithic Caucasus hunter-gatherers (“CHG”) and Neolithic Iranians (“Iran_N”) and frequently harbor another component enriched in South Asians (Figure S4).
For the forest-tundra cline populations, for which currently no relevant Holocene ancient genomes are available, we took a more generalized approach of using proxies for contemporary Europeans: WHG, WSH (represented by “Yamnaya_Samara”), and early Neolithic European farmers (EEF; represented by “LBK_EN”; Table S2). Adding Nganasans as the fourth reference, we find that most Uralic-speaking populations in Europe (i.e. west of the Urals) and Russians are well modeled by this four-way admixture model (χ 2 p ≥ 0.05 for all but three groups; Figure 5 and Table S8). Nganasan-related ancestry substantially contributes to their gene pools and cannot be removed from the model without a significant decrease in model fit (4.7% to 29.1% contribution; χ 2 p ≤ 1.12×10-8; Table S8). The ratio of contributions from three European references varies from group to group, probably reflecting genetic exchange with neighboring non-Uralic groups. For example, Saami from northern Fennoscandia contain a higher WHG and lower WSH contribution (16.1% and 41.3%, respectively) than Udmurts or Besermyans from the Volga river region do (4.9-6.6% and 50.7-53.2%, respectively), while the three groups have similar amounts of Nganasan-related ancestry (25.5-29.1%).
The Caucasus Mountains form a barrier to gene flow
By applying EEMS to the Caucasus region, we identify a strong barrier to gene flow separating North and South Caucasus populations. This genetic barrier coincides with the Greater Caucasus mountain ridge even to small scale: a weaker barrier in the middle, overlapping with Ossetia, matches well with the region where the ridge also becomes narrow. We also observe weak barriers running in the north-south direction that separate northeastern populations from northwestern ones. Together with PCA, EEMS results suggest that the Caucasus Mountains have posed a strong barrier to human migration.
On the Botai individuals
The Y-chromosome of the male Botai individual (TU45) belongs to the haplogroup R1b (Table 411 S6). However, it falls into neither a predominant European branch R1b-L5165 nor into a R1b-GG400 branch found in Yamnaya individuals. Thus, phylogenetically this Botai individual should belong to the R1b-M73 branch which is frequent in the Eurasian steppe (Figure S9). This branch was also found in Mesolithic samples from Latvia as well as in numerous modern southern Siberian and Central Asian groups.
The Botai genomes provide a critical snapshot of the genetic profile of pre-Bronze Age steppe populations. Our admixture modeling positions Botai primarily on an ancient genetic cline of the pre-Neolithic western Eurasian hunter-gatherers: stretching from the post-Ice Age western European hunter-gatherers (e.g. WHG) to EHG in Karelia and Samara to the Upper Paleolithic southern Siberians (e.g. AG3). Botai’s position on this cline, between EHG and AG3, fits well with their geographic location and suggests that ANE-related ancestry in the East did have a lingering genetic impact on Holocene Siberian and Central Asian populations at least till the time of Botai.
The most recent clear connection with the Botai ancestry can be found in the Middle Bronze Age Okunevo individuals (Figure S6C). In contrast, additional EHG-related ancestry is required to explain the forest-tundra populations to the east of the Urals (Figure 5 and Table S8). Their multi-way mixture model may in fact portrait a prehistoric two-way mixture of a WSH population and a hypothetical eastern Eurasian one that has an ANE-related contribution higher than that in Nganasans. Botai and Okunevo individuals prove the existence of such ANE ancestry-rich populations. Pre-Bronze Age genomes from Siberia will be critical for testing this hypothesis.
So, to sum up:
Northern Eurasia forms a Uralic – Yeniseian cline from east to west, with contribution from Steppe, WHG, and Siberian ancestry. Siberian ancestry is represented by Palaeo-Siberian Nganasans, who adopted Samoyedic quite late. It was already known that the different waves of Siberian ancestry are too late and do not represent the spread of Uralic languages, so that leaves us with Steppe and WHG.
The Botai sample (ca. 3632-3100 BC) represents thus the furthest east that R1b-P297 subclades had expanded (we did know that, and that they didn’t have close genetic links with Khvalynsk, so the haplogroup spread there probably much earlier). It expanded R1b-M269’s sister clade R1b-M73 (also found in the Baltic region), and the Botai are on the ‘eastern’ end of an ancient genetic cline stretching from WHG to EHG to Afontova Gora.
EDIT (23 MAY 2018) Both samples share mtDNA, and the male one shares Y-DNA, with those reported in Damgaard et al. (Nature 2018); although dates are slightly different (3371-3354 calBC for BOT 14), it is within the range given for this one; for the female, the dates are similar (3521-3377 calBC for BOT2016, 3517-3367 cal. BCE for this one). The lack of data on their origin may point to the fact that we only have different bone samples from the same two Botai individuals. So probably still 50% R1b-M73 (with the other 50% being N2* from BOT15)…
It seems therefore not only that R1b-M269 is bound to split from the parent haplogroup in or around the steppe or forest-steppe: the Mesolithic spread of haplogroup R1b in North Eurasia is wider and its relevance thus greater than previously thought.
Featured image, from the supplementary materials: Frequency distribution map of the Y-chromosomal haplogroup R1b-P343(xM269) identified in the Eneolithic Botai individual. All modern Eurasian samples with this haplogroup tested to date for the downstream markers fall into R1b-M73 branch, suggesting Botai sample be one of its earliest representatives.
This post should probably read “Consequences of Narasimhan et al. (2018),” too, since there seems to be enough data and materials published by the Copenhagen group in Nature and Science to make a proper interpretation of the data that will appear in their corrected tables.
The finding of late Khvalynsk/early Yamna migrations, identified with early LPIE migrants almost exclusively of R1b-L23 subclades is probably one of the most interesting findings in the recent papers regarding the Indo-European question.
Although there are still few samples to derive fully-fledged theories, they begin to depict a clearer idea of waves that shaped the expansion of Late Proto-Indo-European migrants in Eurasia during the 4th millennium BC, i.e. well before the expansion of North-West Indo-European, Palaeo-Balkan, and Indo-Iranian languages.
Late Khvalynsk expansions and archaic Late PIE
Like Anatolian, Tocharian has been described as having a more archaic nature than the rest of Late PIE. However, Pre-Tocharian belongs to the Late PIE trunk, clearly distinguishable phonetically and morphologically from Anatolian.
It is especially remarkable that – even though it expanded into Asia – it has more in common with North-West Indo-European, hence its classification (together with NWIE) as part of a Northern group, unrelated to Graeco-Aryan.
The linguistic supplement by Kroonen et al. accepts that peoples from the Afanasevo culture (ca. 3000-2500 BC) are the most likely ancestors of Tocharians.
NOTE. For those equating the Tarim Mummies (of R1a-Z93 lineages) with Tocharians, you have this assertion from the linguistic supplement, which I support:
An intermediate stage has been sought in the oldest so-called Tarim Mummies, which date to ca. 1800 BCE (Mallory and Mair 2000; Wáng 1999). However, also the language(s) spoken by the people(s) who buried the Tarim Mummies remain unknown, and any connection between them and the Afanasievo culture on the one hand or the historical speakers of Tocharian on the other has yet to be demonstrated (cf. also Mallory 2015; Peyrot 2017).
New samples of late Khvalynsk origin
These are are the recent samples that could, with more or less certainty, correspond to migration waves from late Khvalynsk (or early Yamna), from oldest to most recent:
The Namazga III samples from the Late Eneolithic period (in Turkmenistan), dated ca. 3360-3000 BC (one of haplogroup J), potentially showing the first wave of EHG-related steppe ancestry into South Asia. Not related to Indo-Iranian migrations.
NOTE. A proper evaluation with further samples from Narasimhan et al. (2018) is necessary, though, before we can assert a late Khvalynsk origin of this ancestry.
Afanasevo samples, dated ca. 3081-2450 BC, with all samples dated before ca. 2700 BC uniformly of R1b-Z2103 subclades, sharing a common genetic cluster with Yamna, showing together the most likely genomic picture of late Khvalynsk peoples.
NOTE 1. Anthony (2007) put this expansion from Repin ca. 3300-3000 BC, while his most recent review (2015) of his own work put its completion ca. 3000-2800. While the migration into Afanasevo may have lasted some time, the wave of migrants (based on the most recent radiocarbon dates) must be set at least before ca. 3100 BC from Khvalynsk.
NOTE 2. I proposed that we could find R1b-L51 in Afanasevo, presupposing the development of R1b-L51 and R1b-Z2103 lineages with separating clans, and thus with dialectal divisions. While finding this is still possible within Khvalynsk regions, it seems we will have a division of these lineages already ca. 4250-4000 BC, which would require a closer follow-up of the different inner late Khvalynsk groups and their samples. For the moment, we don’t have a clear connection through lineages between North-West Indo-European groups and Tocharian.
Subsequent and similar migration waves are probably to be suggested from the new sample of Karagash, beyond the Urals (attributed to the Yamna culture, hence maintaining cultural contacts after the migration waves), of R1b-Z2103 subclade, ca. 3018-2887 BC, potentially connected then to the event that caused the expansion of Yamna migrants westward into the Carpathians at the same time. Not related to Indo-Iranian migrations.
The isolated Darra-e Kur sample, without cultural adscription, ca. 2655 BC, of R1b-L151 lineage. Not related to Indo-Iranian migrations.
The Hajji Firuz samples: I4243 dated ca. 2326 BC, female, with a clear inflow of steppe ancestry; and I2327 (probably to be dated to the late 3rd millennium BC or after that), of R1b-Z2103 lineage. Not related to Indo-Iranian migrations.
NOTE. A new radiocarbon dating of I2327 is expected, to correct the currently available date of 5900-5000 BC. Since it clusters nearer to Chalcolithic samples from the site than I4243 (from the same archaeological site), it is possible that both are part of similar groups receiving admixture around this period, or maybe I2327 is from a later period, coinciding with the Iron Age sample F38 from Iran (Broushaki et al. 2016), with which it closely clusters. Also, the finding of EHG-related ancestry in Maykop samples dated ca. 3700-3000 BC (maybe with R1b-L23 subclades) offers another potential source of migrants for this Iranian group.
NOTE. Samples from Narasimhan et al. (2018) still need to be published in corrected tables, which may change the actual subclades shown here.
These late Khvalynsk / early Yamna migration waves into Asia are quite early compared to the Indo-Iranian migrations, whose ancestors can only be first identified with Volga-Ural groups of Yamna/Poltavka (ca. 3000-2400 BC), with its fully formed language expanding only with MLBA waves ca. 2300-1200 BC, after mixing with incoming Abashevo migrants.
While the authors apparently forget to reference the previous linguistic theories whereby Tocharian is more archaic than the rest of Late PIE dialects, they refer to the ca. 1,000-year gap between Pre-Tocharian and Proto-Indo-Iranian migrations, and thus their obvious difference:
The fact that Tocharian is so different from the Indo-Iranian languages can only be explained by assuming an extensive period of linguistic separation.
Potential linguistic substrates in the Middle East
A few words about relevant substrate language proposals.
What Gordon Whittaker proposes is a North-West Indo-European-related substratum in Sumerian language and texts ca. 3500 BC, which may explain some non-Sumerian, non-Semitic word forms. It is just one of many theories concerning this substratum.
This is a summary of his findings from his latest writing on the subject (a chapter of a book on Indo-European phonetics, from the series Copenhagen Studies in Indo-European):
In Sumerian and Akkadian vocabulary, the cuneiform writing system, and the names of deities and places in Southern Mesopotamia a body of lexical material has been preserved that strongly suggests influence emanating from a superstrate of Indo-European origin. his Indo-European language, which has been given the name Euphratic, is, at present, attested only indirectly through the filters of Sumerian and Akkadian. The attestations consist of words and names recorded from the mid-4th millennium BC (Late Uruk period) onwards in texts and lexical lists. In addition, basic signs that originally had a recognizable pictorial structure in proto-cuneiform preserve (at least from the early 3rd millennium on) a number of phonetic values with no known motivation in Sumerian lexemes related semantically to the items depicted. This suggests that such values are relics from the original logographic values for the items depicted and, thus, that they were inherited from a language intimately associated with the development of writing in Mesopotamia. Since specialists working on proto-cuneiform, most notably Robert K. Englund of the Cuneiform Digital Library Initiative, see little or no evidence for the presence of Sumerian in the corpus of archaic tablets, the proposed Indo-European language provides a potential solution to this problem. It has been argued that this language, Euphratic, had a profound influence on Sumerian, not unlike that exerted by Sumerian and Akkadian on each other, and that the writing system was the primary vehicle of this influence. he phonological sketch drawn up here is an attempt to chart the salient characteristics of this influence, by comparing reconstructed Indo-European lexemes with similarly patterned ones in Sumerian (and, to a lesser extent, in Akkadian).
His original model, based on phonetic values in basic proto-cuneiform signs, is quite imaginative and a very interesting read, if you have the time. His Academia.edu account hosts most of his papers on the subject.
We could speculate about the potential expansion of this substrate language with the commercial contacts between Uruk and Maykop (as I did), now probably more strongly supported because of the EHG found in Maykop samples.
NOTE. We could also put it in relation with the Anatolian language of Mari, but this would require a new reassessment of its North-West Indo-European nature.
Nevertheless, this theory is far from being mainstream, anywhere. At least today.
NOTE. The proposal remains still hypothetic, because of the flaws in the Indo-European parallels – similar to Koch’s proposal of Indo-European in Tartessian inscriptions. A comprehensive critic approach to the theory is found in Sylvie Vanséveren’s A “new” ancient Indo-European language? On assumed linguistic contacts between Sumerian and Indo-European “Euphratic”, in JIES (2008) 36:3&4.
References to Gutian are popping up related to the Hajji Firuz samples of the mid-3rd millennium.
The hypothesis was put forward by Henning (1978) in purely archaeological terms.
This is the relevant excerpt from the book:
(…) Comparativists have asserted that, in spite of its late appearance, Tokharian is a relatively archaic form of Indo-European.3 This claim implies that the speakers of this group separated from their Indo-European brethren at a comparatively early date. They should accordingly have set out on their migrations rather early, and should have appeared within the Babylonian sphere of influence also rather early. Earlier, at any rate, than the Indo-Iranians, who spoke a highly developed (therefore probably later) form of Indo-European. Moreover, as some of the Indo-Iranians after their division into Iranians and Indo-Aryans4 appeared in Mesopotamia about 1500 B.C., we should expect the Proto-Tokharians about 2000 B.C. or even earlier.
If, armed with these assumptions as our working hypothesis, we look through the pages of history, we find one nation – one nation only – that perfectly fulfills all three conditions, which, therefore, entitles us to recognize it as the “Proto-Tokharians”. Tis name was Guti; the intial is also spelled with q (a voiceless back velar or pharyngeal), but the spelling with g is the original one. The closing -i is part of the name, for the Akkadian case-endings are added to it, nom. Gutium etc. Guti (or Gutium, as some scholars prefer) was valid for the nation, considered as an entity, but also for the territory it occupied.
The text goes on to follow the invasion of Babylonia by the Guti, and further eastward expansions supposedly connected with these, to form the attested Tocharians.
Among the Gutian rulers is one Elulumesh, whose name is evidently Akkadian Elulum slightly “Gutianized” by the Gutian case(?) ending -eš.40 This Gutian ruler Elulum is obviously the same man whom we find participating in the scramble for power after the death of Shar-kali-sharrii; his name appears there in Sumerian form without mimation as Elulu.
The Gutian dynasty, from ca. 22nd c. BC appears as follows:
I don’t think we could derive a potential relation to any specific Indo-European branch from this simple suffix repeated in Gutian rulers, though.
The hypothesis of the Tocharian-like nature of the Guti (apart from the obvious error of considering them as the ancestors of Tocharians) remains not contrasted in new works since. It was cited e.g. by Gamkrelidze and Ivanov (1995) to advance their Armenian homeland, and by Mallory and Adams in their Encyclopedia (1997).
It lies therefore in the obscurity of undeveloped archaeological-linguistic hypotheses, and its connection with the attested R1b-Z2103 samples from Iran is not (yet) warranted.
This is part I of two posts on the most recent data concerning the earliest known Indo-European migrations.
Anatolian in Armi
I am reading in forums about “Kroonen’s proposal” of Anatolian in the 3rd millennium. That is false. The Copenhagen group (in particular the authors of the linguistic supplement, Kroonen, Barjamovic, and Peyrot) are merely referencing Archi (2011. “In Search of Armi”. Journal of Cuneiform Studies 63: 5–34) in turn using transcriptions from Bonechi (1990. “Aleppo in età arcaica; a proposito di un’opera recente”. Studi Epigrafici e Linguistici sul Vicino Oriente Antico 7: 15–37.), who asserted the potential Anatolian origin of the terms. This is what Archi had to say about this:
Most of these personal names belong to a name-giving tradition different from that of Ebla; Arra-ti/tulu(m) is attested also at Dulu, a neighbouring city-state (Bonechi 1990b: 22–25).28 We must, therefore, deduce that Armi belonged to a marginal, partially Semitized linguistic area different from the ethno-linguistic region dominated by Ebla. Typical are masculine personal names ending in -a-du: A-la/li-wa-du/da, A-li/lu-wa-du, Ba-mi-a-du, La-wadu, Mi-mi-a-du, Mu-lu-wa-du. This reminds one of the suffix -(a)nda, -(a)ndu, very productive in the Anatolian branch of Indo-European (Laroche 1966: 329). Elements such as ali-, alali-, lawadu-, memi-, mula/i- are attested in Anatolian personal names of the Old Assyrian period (Laroche 1966: 26–27, 106, 118, 120).
This was used by Archi to speculatively locate the state of Armi, in or near Ebla territory, which could correspond with the region of modern north-western Syria:
The onomastic tradition of Armi, so different from that of Ebla and her allies (§ 5), obliges us to locate this city on the edges of the Semitized area and, thus, necessarily north of the line running through Hassuwan – Ursaum – Irritum – Harran. If Armi were to be found at Banat-Bazi, it would have represented an anomaly within an otherwise homogenous linguistic scenario.34
Taken as a whole, the available information suggests that Armi was a regional state, which enjoyed a privileged relationship with Ebla: the exchange of goods between the two cities was comparable only to that between Ebla and Mari. No other state sent so many people to Ebla, especially merchants, lú-kar. It is only a hypothesis that Armi was the go-between for Ebla and for the areas where silver and copper were extracted.
This proposal is similar to the one used to support Indo-Aryan terminology in Mittanni (ca. 16th-14th c. BC), so the scarce material should not pose a problem to those previously arguing about the ‘oldest’ nature of Indo-Aryan.
NOTE. On the other hand, the theory connecting ‘mariannu‘, a term dated to 1761 BC (referenced also in the linguistic supplement), and put in relation with PIIr. *arya–, seems too hypothetical for the moment, although there is a clear expansion of Aryan-related terms in the Middle East that could support one or more relevant eastern migration waves of Indo-Aryans from Asia.
Potential routes of Anatolian migration
Once we have accepted that Anatolian is not Late PIE – and that only needed a study of Anatolian archaisms, not the terminology from Armi – , we can move on to explore the potential routes of expansion.
On the Balkan route
A current sketch of the dots connecting Khvalynsk with Anatolia is as follows.
Then we have Cernavoda I (ca. 3850-3550 BC), a culture potentially derived from the earlier expansion of Suvorovo chiefs, as shown in cultural similarities with preceding cultures and Yamna, and also in the contacts with the North Pontic steppe cultures (read a a recent detailed post on this question).
We also have proof of genetic inflow from the steppe into populations of cultures near those suggested to be heirs of those dominated by Suvorovo chiefs, from the 5th millennium BC (in Varna I ca. 4630 BC, and Smyadovo ca. 4500 BC, see image below).
If these neighbouring Balkan peoples of ca. 4500 BC are taken as proxies for Proto-Anatolians, then it becomes quite clear why Old Hittite samples dated 3,000 years after this migration event of elite chiefs could show no or almost no ancestry from Europe (for this question, read my revision of Lazaridis’ preprint).
NOTE. A full account of the crisis in the lower Danube, as well as the Suvorovo-Novodanilovka intrusion, is available in Anthony (2007).
The southern Balkans and Anatolia
The later connection of Cernavoda II-III and related cultures (and potentially Ezero) with Troy, on the other hand, is still blurry. But, even if a massive migration of Common Anatolian is found to happen from the Balkans into Anatolia in the late 4th / beginning of the 3rd millennium, the people responsible for this expansion could show a minimal trace of European ancestry.
Earlier third millennium cal BCE is the period of development of interconnected Early Bronze Age societies in Eurasia, which economic and social structures expressed variants of pre-state political structures, named in the specialized literature tribes and chiefdoms. In this work new arguments will be added to the chiefdom model of third millennium cal BC societies of Yunatsite culture in the Central Balkans from the perspectives of the interrelations between Dubene (south central Bulgaria) and Troy (northwest Turkey) wealth expression.
Possible explanations of the similarity in the wealth expression between Troy and Yunatsite chiefdoms is the direct interaction between the political elite. However, the golden and silver objects in the third millennium cal BCE in the Eastern Mediterranean are most of all an expression of economic wealth. This is the biggest difference between the early state and chiefdoms in the third millennium cal BCE in Eurasia and Africa. The literacy and the wealth expression in the early states was politically centralized, while the absence of literacy and wider distribution of the wealth expression in the chiefdoms of the eastern Mediterranean are indicators, that wider distribution of wealth and the existed stable subsistence layers prevented the formation of states and the need to regulate the political systems through literacy.
The only way to link Common Anatolians to their Proto-Anatolian (linguistic) ancestors would therefore be to study preceding cultures and their expansions, until a proper connecting route is found, as I said recently.
These late commercial contacts in the south-eastern Balkans (Nikolova also offers a simplified presentation of data, in English) are yet another proof of how Common Anatolian languages may have further expanded into Anatolia.
NOTE. One should also take into account the distribution of modern R1b-M269* and L23* subclades (i.e. those not belonging to the most common subclades expanding with Yamna), which seem to peak around the Balkans. While those may just belong to founder effects of populations preceding Suvorovo or related to Yamna migrants, the Balkans is a region known to have retained Y-DNA haplogroup diversity, in contrast with other European regions.
On a purely linguistic aspect, there are strong Hattic and Hurrian influences on Anatolian languages, representing a unique layer that clearly differentiates them from LPIE languages, pointing also to different substrates behind each attested Common Anatolian branch or individual language:
Phonetic changes, like the appearance of /f/ and /v/.
Split ergativity: Hurrian is ergative, Hattic probably too.
Increasing use of enclitic pronoun and particle chains after first stressed word: in Hattic after verb, in Hurrian after nominal forms.
Almost obligatory use of clause initial and enclitic connectors: e.g. semantic and syntactic identity of Hattic pala/bala and Hittite nu.
It seems that the Danish group is now taking a stance in favour of a Maykop route (from the linguistic supplement):
The period of Proto-Anatolian linguistic unity can now be placed in the 4th millennium BCE and may have been contemporaneous with e.g. the Maykop culture (3700–3000 BCE), which influenced the formation and apparent westward migration of the Yamnaya and maintained commercial and cultural contact with the Anatolian highlands (Kristiansen et al. 2018).
In fact, they have data to support this:
The EHG ancestry detected in individuals associated with both Yamnaya (3000–2400 BCE) and the Maykop culture (3700–3000 BCE) (in prep.) is absent from our Anatolian specimens, suggesting that neither archaeological horizon constitutes a suitable candidate for a “homeland” or “stepping stone” for the origin or spread of Anatolian Indo- European speakers to Anatolia. However, with the archaeological and genetic data presented here, we cannot reject a continuous small-scale influx of mixed groups from the direction of the Caucasus during the Chalcolithic period of the 4th millennium BCE.
It will not be surprising to find not only EHG, but also R1b-L23 subclades there. In my opinion, though, the most likely source of EHG ancestry in Maykop (given the different culture shown in other steppe groups) is exogamy.
The question will still remain: was this a Proto-Anatolian-speaking group?
My opinion in this regard – again, without access to the study – is that you would still need to propose:
A break-up of Anatolian ca. 4500 BC represented by some early group migrating into the Northern Caucasus area.
For this group – who were closely related linguistically and culturally to early Khvalynsk – to remain isolated in or around the Northern Caucasus, i.e. somehow ‘hidden’ from the evolving LPIE speakers in late Khvalynsk/early Yamna peoples.
Then appear as Old Hittites without showing EHG ancestry (even though they show it in the period 3700-3000 BC), near the region of the Armi state, where Anatolian was supposedly spoken already in the mid-3rd millennium.
Not a very convincing picture, right now, but indeed possible.
Also, we have R1b-Z2103 lineages and clear steppe ancestry in the region probably ca. 2500 BC with Hajji Firuz, which is most likely the product of the late Khvalynsk migration waves that we are seeing in the recent papers.
These migrations are then related to early LPIE-speaking migrants spreading after ca. 3300 BC – that also caused the formation of early Yamna and the expansion of Tocharian-related migrants – , which leaves almost no space for an Anatolian expansion, unless one supports that the former drove the latter.
NOTE. In any case, if the Caucasus route turned out to be the actual Anatolian route, I guess this would be a way as good as any other to finally kill their Indo-European – Corded Ware theory, for obvious reasons.
On the North Iranian homeland
A few thoughts for those equating CHG ancestry in IE speakers (and especially now in Old Hittites) with an origin in North Iran, due to a recent comment by David Reich:
In the paper it is clearly stated that there is no Neolithic Iranian ancestry in the Old Hittite samples.
Ancestry is not people, and it is certainly not language. The addition of CHG ancestry to the Eneolithic steppe need not mean a population or linguistic replacement. Although it could have been. But this has to be demonstrated with solid anthropological models.
NOTE. On the other hand, if you find people who considered (at least until de Barros Damgaard et al. 2018) steppe (ancestry/PCA) = Indo-European, then you should probably confront them about why CHG in Hittites and the arrival of CHG in steppe groups is now not to be considered the same, i.e why CHG / Iran_N ≠ PIE.
Since there has been no serious North Iranian homeland proposal made for a while, it is difficult to delineate a modern sketch, and I won’t spend the time with that unless there is some real anthropological model and genetic proof of it. I guess the Armenian homeland hypothesis proposed by Gamkrelidze and Ivanov (1995) would do, but since it relies on outdated data (some of which appears also in Gimbutas’ writings), it would need a full revision.
NOTE. Their theory of glottalic consonants (or ejectives) relied on the ‘archaism’ of Hittite, Germanic, and Armenian. As you can see (unless you live in the mid-20th century) this is not very reasonable, since Hittite is attested quite late and after heavy admixture with Middle Eastern peoples, and Germanic and Armenian are some of the latest attested (and more admixed, phonetically changed) languages.
This would be a proper answer, indeed, for those who would accept this homeland due to the reconstruction of ‘ejectives’ for these languages. Evidently, there is no need to posit a homeland near Armenia to propose a glottalic theory. Kortlandt is a proponent of a late and small expansion of Late PIE from the steppe, and still proposes a reconstruction of ejectives for PIE. But, this was the main reason of Gamkrelidze and Ivanov to propose that homeland, and in that sense it is obviously flawed.
Those claiming a relationship of the North Iranian homeland with such EHG ancestry in Maykop, or with the hypothetic Proto-Euphratic or Gutian, are obviously not understanding the implications of finding steppe ancestry coupled with (likely) early Late PIE migrants in the region in the mid-4th millennium.