Experienced researchers, particularly those interested in population structure and historical inference, typically present STRUCTURE results alongside other methods that make different modelling assumptions. These include TreeMix, ADMIXTUREGRAPH, fineSTRUCTURE, GLOBETROTTER, f3 and D statistics, amongst many others. These models can be used both to probe whether assumptions of the model are likely to hold and to validate specific features of the results. Each also comes with its own pitfalls and difficulties of interpretation. It is not obvious that any single approach represents a direct replacement as a data summary tool. Here we build more directly on the results of STRUCTURE/ADMIXTURE by developing a new approach, badMIXTURE, to examine which features of the data are poorly fit by the model. Rather than intending to replace more specific or sophisticated analyses, we hope to encourage their use by making the limitations of the initial analysis clearer.
The default interpretation protocol
Most researchers are cautious but literal in their interpretation of STRUCTURE and ADMIXTURE results, as caricatured in Fig. 1, as it is difficult to interpret the results at all without making several of these assumptions. Here we use simulated and real data to illustrate how following this protocol can lead to inference of false histories, and how badMIXTURE can be used to examine model fit and avoid common pitfalls.
STRUCTURE and ADMIXTURE are popular because they give the user a broad-brush view of variation in genetic data, while allowing the possibility of zooming down on details about specific individuals or labelled groups. Unfortunately it is rarely the case that sampled data follows a simple history comprising a differentiation phase followed by a mixture phase, as assumed in an ADMIXTURE model and highlighted by case study 1. Naïve inferences based on this model (the Protocol of Fig. 1) can be misleading if sampling strategy or the inferred value of the number of populations K is inappropriate, or if recent bottlenecks or unobserved ancient structure appear in the data. It is therefore useful when interpreting the results obtained from real data to think of STRUCTURE and ADMIXTURE as algorithms that parsimoniously explain variation between individuals rather than as parametric models of divergence and admixture.
For example, if admixture events or genetic drift affect all members of the sample equally, then there is no variation between individuals for the model to explain. Non-African humans have a few percent Neanderthal ancestry, but this is invisible to STRUCTURE or ADMIXTURE since it does not result in differences in ancestry profiles between individuals. The same reasoning helps to explain why for most data sets—even in species such as humans where mixing is commonplace—each of the K populations is inferred by STRUCTURE/ADMIXTURE to have non-admixed representatives in the sample. If every individual in a group is in fact admixed, then (with some exceptions) the model simply shifts the allele frequencies of the inferred ancestral population to reflect the fraction of admixture that is shared by all individuals.
Several methods have been developed to estimate K, but for real data, the assumption that there is a true value is always incorrect; the question rather being whether the model is a good enough approximation to be practically useful. First, there may be close relatives in the sample which violates model assumptions. Second, there might be “isolation by distance”, meaning that there are no discrete populations at all. Third, population structure may be hierarchical, with subtle subdivisions nested within diverged groups. This kind of structure can be hard for the algorithms to detect and can lead to underestimation of K. Fourth, population structure may be fluid between historical epochs, with multiple events and structures leaving signals in the data. Many users examine the results of multiple K simultaneously but this makes interpretation more complex, especially because it makes it easier for users to find support for preconceptions about the data somewhere in the results.
In practice, the best that can be expected is that the algorithms choose the smallest number of ancestral populations that can explain the most salient variation in the data. Unless the demographic history of the sample is particularly simple, the value of K inferred according to any statistically sensible criterion is likely to be smaller than the number of distinct drift events that have practically impacted the sample. The algorithm uses variation in admixture proportions between individuals to approximately mimic the effect of more than K distinct drift events without estimating ancestral populations corresponding to each one. In other words, an admixture model is almost always “wrong” (Assumption 2 of the Core protocol, Fig. 1) and should not be interpreted without examining whether this lack of fit matters for a given question.
Because STRUCTURE/ADMIXTURE accounts for the most salient variation, results are greatly affected by sample size in common with other methods. Specifically, groups that contain fewer samples or have undergone little population-specific drift of their own are likely to be fit as mixes of multiple drifted groups, rather than assigned to their own ancestral population. Indeed, if an ancient sample is put into a data set of modern individuals, the ancient sample is typically represented as an admixture of the modern populations (e.g., ref. 28,29), which can happen even if the individual sample is older than the split date of the modern populations and thus cannot be admixed.
This paper was already available as a preprint in bioRxiv (first published in 2016) and it is incredible that it needed to wait all this time to be published. I found it weird how reviewers focused on the “tone” of the paper. I think it is great to see files from the peer review process published, but we need to know who these reviewers were, to understand their whiny remarks… A lot of geneticists out there need to develop a thick skin, or else we are going to see more and more delays based on a perceived incorrect tone towards the field, which seems a rather subjective reason to force researchers to correct a paper.
A potential hindrance to our advice to upgrade from PCA graphs to PCA biplots is that the SNPs are often so numerous that they would obscure the Items if both were graphed together. One way to reduce clutter, which is used in several figures in this article, is to present a biplot in two side-by-side panels, one for Items and one for SNPs. Another stratagem is to focus on a manageable subset of SNPs of particular interest and show only them in a biplot in order to avoid obscuring the Items. A later section on causal exploration by current methods mentions several procedures for identifying particularly relevant SNPs.
One of several data transformations is ordinarily applied to SNP data prior to PCA computations, such as centering by SNPs. These transformations make a huge difference in the appearance of PCA graphs or biplots. A SNPs-by-Items data matrix constitutes a two-way factorial design, so analysis of variance (ANOVA) recognizes three sources of variation: SNP main effects, Item main effects, and SNP-by-Item (S×I) interaction effects. Double-Centered PCA (DC-PCA) removes both main effects in order to focus on the remaining S×I interaction effects. The resulting PCs are called interaction principal components (IPCs), and are denoted by IPC1, IPC2, and so on. By way of preview, a later section on PCA variants argues that DC-PCA is best for SNP data. Surprisingly, our literature survey did not encounter even a single analysis identified as DC-PCA.
The axes in PCA graphs or biplots are often scaled to obtain a convenient shape, but actually the axes should have the same scale for many reasons emphasized recently by Malik and Piepho . However, our literature survey found a correct ratio of 1 in only 10% of the articles, a slightly faulty ratio of the larger scale over the shorter scale within 1.1 in 12%, and a substantially faulty ratio above 2 in 16% with the worst cases being ratios of 31 and 44. Especially when the scale along one PCA axis is stretched by a factor of 2 or more relative to the other axis, the relationships among various points or clusters of points are distorted and easily misinterpreted. Also, 7% of the articles failed to show the scale on one or both PCA axes, which leaves readers with an impressionistic graph that cannot be reproduced without effort. The contemporary literature on PCA of SNP data mostly violates the prohibition against stretching axes.
The percentage of variation captured by each PC is often included in the axis labels of PCA graphs or biplots. In general this information is worth including, but there are two qualifications. First, these percentages need to be interpreted relative to the size of the data matrix because large datasets can capture a small percentage and yet still be effective. For example, for a large dataset with over 107,000 SNPs for over 6,000 persons, the first two components capture only 0.3693% and 0.117% of the variation, and yet the PCA graph shows clear structure (Fig 1A in ). Contrariwise, a PCA graph could capture a large percentage of the total variation, even 50% or more, but that would not guarantee that it will show evident structure in the data. Second, the interpretation of these percentages depends on exactly how the PCA analysis was conducted, as explained in a later section on PCA variants. Readers cannot meaningfully interpret the percentages of variation captured by PCA axes when authors fail to communicate which variant of PCA was used.
Five simple recommendations for effective PCA analysis of SNP data emerge from this investigation.
Use the SNP coding 1 for the rare or minor allele and 0 for the common or major allele.
Use DC-PCA; for any other PCA variant, examine its augmented ANOVA table.
Report which SNP coding and PCA variant were selected, as required by contemporary standards in science for transparency and reproducibility, so that readers can interpret PCA results properly and reproduce PCA analyses reliably.
Produce PCA biplots of both Items and SNPs, rather than merely PCA graphs of only Items, in order to display the joint structure of Items and SNPs and thereby to facilitate causal explanations. Be aware of the arch distortion when interpreting PCA graphs or biplots.
Produce PCA biplots and graphs that have the same scale on every axis.
I read the referenced paper Biplots: Do Not Stretch Them!, by Malik and Piepho (2018), and even though it is not directly applicable to the most commonly available PCA graphs out there, it is a good reminder of the distorting effects of stretching. So for example quite recently in Krause-Kyora et al. (2018), where you can see Corded Ware and BBC samples from Central Europe clustering with samples from Yamna:
NOTE. This is related to a vertical distorsion (i.e. horizontal stretching), but possibly also to the addition of some distant outlier sample/s.
The so-called ‘Yamnaya’ ancestry
Every time I read papers like these, I remember commenters who kept swearing that genetics was the ultimate science that would solve anthropological problems, where unscientific archaeology and linguistics could not. Well, it seems that, like radiocarbon analysis, these promising developing methods need still a lot of refinement to achieve something meaningful, and that they mean nothing without traditional linguistics and archaeology… But we already knew that.
Also, if this is happening in most peer-reviewed publications, made by professional geneticists, in journals of high impact factor, you can only wonder how many more errors and misinterpretations can be found in the obscure market of so many amateur geneticists out there. Because amateur geneticist is a commonly used misnomer for people who are not geneticists (since they don’t have the most basic education in genetics), and some of them are not even ‘amateurs’ (because they are selling the outputs of bioinformatic tools)… It’s like calling healers ‘amateur doctors’.
NOTE. While everyone involved in population genetics is interested in knowing the truth, and we all have our confirmation (and other kinds of) biases, for those who get paid to tell people what they want to hear, and who have sold lots of wrong interpretations already, the incentives of ‘being right’ – and thus getting involved in crooked and paranoid behaviour regarding different interpretations – are as strong as the money they can win or loose by promoting themselves and selling more ‘product’.
As a reminder of how badly these wrong interpretations of genetic results – and the influence of the so-called ‘amateurs’ – can reflect on research groups, yet another turn of the screw by the Copenhagen group, in the oral presentations at Languages and migrations in pre-historic Europe (7-12 Aug 2018), organized by the Copenhagen University. The common theme seems to be that Bell Beaker and thus R1b-L23 subclades do represent a direct expansion from Yamna now, as opposed to being derived from Corded Ware migrants, as they supported before.
NOTE. Yes, the “Yamna → Corded Ware → Únětice / Bell Beaker” migration model is still commonplace in the Copenhagen workgroup. Yes, in 2018. Guus Kroonen had already admitted they were wrong, and it was already changed in the graphic representation accompanying a recent interview to Willerslev. However, since there is still no official retraction by anyone, it seems that each member has to reject the previous model in their own way, and at their own pace. I don’t think we can expect anyone at this point to accept responsibility for their wrong statements.
I love the newly invented arrows of migration from Yamna to the north to distinguish among dialects attributed by them to CWC groups, and the intensive use of materials from Heyd’s publications in the presentation, which means they understand he was right – except for the fact that they are used to support a completely different theory, radically opposed to those defended in Heyd’s model…
Now added to the Copenhagen’s unending proposals of language expansions, some pearls from the oral presentation:
Corded Ware north of the Carpathians of R1a lineages developed Germanic;
R1b borugh [?] Italo-Celtic;
the increase in steppe ancestry on north European Bell Beakers mean that they “were a continuation of the Yamnaya/Corded Ware expansion”;
“Corded Ware groups  stopped their expansion and took over the Bell Beaker package before migrating to England” [yep, it literally says that];
Italo-Celtic expanded to the UK and Iberia with Bell Beakers [I guess that included Lusitanian in Iberia, but not Messapian in Italy; or the opposite; or nothing like that, who knows];
2nd millennium BC Bronze Age Atlantic trade systems expanded Proto-Celtic [yep, trade systems expanded the language]
1st millennium BC expanded Gaulish with La Tène, including a “Gaulish version of Celtic to Ireland/UK” [hmmm, datBritish Gaulish indeed].
You know, because, why the hell not? A logical, stable, consequential, no-nonsense approach to Indo-European migrations, as always.
Also, compare still more invented arrows of migrations, from Mikkel Nørtoft’s Introducing the Homeland Timeline Map, going against Kristiansen’s multiple arrows, and even against the own recent fantasy map series in showing Bell Beakers stem from Yamna instead of CWC (or not, you never truly know what arrows actually mean):
I really, really loved that perennial arrow of migration from Volosovo, ca. 4000-800 BC (3000+ years, no less!), representing Uralic?, like that, without specifics – which is like saying, “somebody from the eastern forest zone, somehow, at some time, expanded something that was not Indo-European to Finland, and we couldn’t care less, except for the fact that they were certainly not R1a“.
This and Kristiansen’s arrows are the most comical invented migration routes of 2018; and that is saying something, given the dozens of similar maps that people publish in forums and blogs each week.
It’s hard to accept that this is a series of presentations made by professional linguists, archaeologists, and geneticists, as stated by the official website, and still harder to imagine that they collaborate within the same professional workgroup, which includes experienced geneticists and academics.
I propose the following video to close future presentations introducing innovative ideas like those above, to help the audience find the appropriate mood:
I find it interesting that many geneticists would question the simplistic approach to the Out of Africa model as it is often enunciated, but they would at the same time consider the current simplistic model of Yamna expansion essentially right; a model – if anyone is lost here – based on proportions of the so-called Yamnaya™ ancestral component, as found in a small number of samples, from four or five Eneolithic–Chalcolithic cultures spanning more than a thousand years.
These wrong interpretations have been now substituted by data from two new early samples from the Baltic, which cluster closely to Yamna, and which – based on the Y-DNA and PCA cluster formed by all Corded Ware samples – are likely the product of female exogamy with Yamna peoples from the neighbouring North Pontic region (as we are seeing, e.g. in the recent Nikitin et al. 2018).
NOTE. There is also another paper from Nikitin et al. (2017), with more ancient mtDNA, “Subdivisions of haplogroups U and C encompass mitochondrial DNA lineages of Eneolithic-Early Bronze Age Kurgan populations of western North Pontic steppe”. Link to paper (behind paywall). Most interesting data is summarized in the following table:
Even after the publication of Olalde et al. (2018) and Wang et al. (2018) – where expanding Yamna settlers and Bell Beakers are clearly seen highly admixed within a few generations, and are found spread across a wide Eurasian cline (sharing one common invariable trait, the paternally inherited haplogroup, as supported by David Reich) – fine-scale studies of population structure and social dynamics is still not a thing for many, even though it receives more and more advocates among geneticists (e.g. Lazaridis, or Veeramah).
NOTE. I have tried to explain, more than once, that the nature and origin of the so-called “Yamnaya ancestry” (then “steppe ancestry”, and now subdivided further as Steppe_EMBA and Steppe_MLBA) is not known with precision before Yamna samples of ca. 3000 BC, and especially that it is not necessarily a marker of Indo-European speakers. Why some people are adamant that steppe ancestry and thus R1a must be Indo-European is mostly related to a combination of grandaddy’s haplogroup, the own modern ethnolinguistic attribution, and an aversion to sharing grandpa with other peoples and cultures.
In the meantime, we are seeing the “Yamnaya proportion” question often reversed: “how do we make Corded Ware stem from Yamna, now that we believed it?”. This is a funny circular reasoning, akin to the one used by proponents of the Franco-Cantabrian origin of R1b, when they look now at EEF proportions in Iberian R1b-L23 samples. It seems too comic to be true.
R1a and steppe ancestry
The most likely origin of haplogroup R1a-Z645 is to be found in eastern Europe. Samples published in the last year support this region as a sort of cradle of R1a expansions:
I1819, Y-DNA R1a1-M459, mtDNA U5b2, Ukraine Mesolithic ca. 8825-8561 calBCE, from Vasilievka.
I0061, hg R1a1-M459 (xR1a1a-M17), mtDNA C1, ca. 6773-6000 calBCE (with variable dates), from Yuzhnyy Oleni Ostrov in Karelia.
Samples LOK_1980.006 and LOK_1981.024.01, of hg MR1a1a-M17, mtDNA F, Baikalic cultures, dated ca. 5500-5000 BC.
Sample I0433, hg R1a1-M459(xM198), mtDNA U5a1i, from Samara Eneolithic, ca. 5200-4000 BCE
Samples A3, A8, A9, of hg R1a1-M459, mtDNA H, from sub-Neolithic cultures (Comb Ware and Zhizhitskaya) at Serteyea, although dates (ca. 5th-3rd millennium BC) need possibly a revision (from Chekunova 2014).
NOTE. The fact that Europe is better sampled than North Asia, coupled with the finding of R1a-M17 in Baikalic cultures, poses some problems as to the precise origin of this haplogroup and its subclades. While the first (Palaeolithic or Mesolithic) expansion was almost certainly from Northern Eurasia to the west – due to the Mal’ta sample – , it is still unknown if the different subclades of R1a in Europe are the result of local developments, or rather different east—west migrations through North Eurasia.
Y-Full average estimates pointed to R1a-M417 formation ca. 6500 BC, TMRCA ca. 3500 BC, and R1a-Z645 formation ca. 3300 BC, TMRCA ca. 2900 BC, so the most likely explanation was that R1a-Z645 and its subclades – similar to R1b-L23 subclades, but slightly later) expanded quickly with the expansion of Corded Ware groups.
The presence of steppe ancestry in Ukraine Eneolithic sample I6561, of haplogroup R1a-M417, from Alexandria, dated ca. 4045-3974 calBCE, pointed to the forest steppe area and late Sredni Stog as the most likely territory from where the haplogroup related to the Corded Ware culture expanded.
However, the more recent Y-SNP call showing R1a-Z93 (L657) subclade rendered Y-Full’s (at least formation) estimates too young, so we have to rethink the actual origin of both subclades, R1a-Z93 (formation ca. 2900 BC, TMRCA ca 2700 BC), and R1a-Z283 (formation ca. 2900 BC, TMRCA ca. 2800 BC).
Contrary to what we thought before this, then, it is possible that the expansion of Khvalynsk-Novodanilovka chieftains through the steppes, around the mid-5th millennium BC, had something to do with the expansion of R1a-Z645 to the north, in the forest steppe.
We could think that the finding of Z93 in Alexandria after the expansion of Khvalynsk-Novodanilovka chiefs would make it more likely that R1a-Z645 will be found in the North Pontic area. However, given that Lower Mikhailovka and Kvitjana seem to follow a steppe-related cultural tradition, different to forest steppe cultures (like Dereivka and Alexandria), and that forest steppe cultures show connections to neighbouring northern and western forest regions, the rest of the expanding R1a-Z645 community may not be related directly to the steppe at all.
Adding a hypothetical split and expansion of Z645 subclades to the mid-/late-5th millennium could place the expansion of this haplogroup to the north and west, pushed by expanding Middle PIE-speaking steppe peoples from the east:
This is what Włodarczak (2017) says about the emergence of Corded Ware with ‘steppe features’ after the previous expansion of such features in Central Europe with Globular Amphorae peoples. He refers here to the Złota culture (appearing ca. 2900-2800 BC) in Lesser Poland, believed to be the (or a) transitional stage between GAC and Corded Ware, before the emergence of the full-fledged “Corded Ware package”.
So far, to the north of the Carpathian Mountains, including Polish lands, no graves indicating their relationship with communities of the steppe zone have been found. On the contrary, the funeral rites always display a local, central European nature. However, individual elements typical of steppe communities do appear, such as the “frog-like” arrangement of the body (Fig. 20), or items associated with Pit Grave milieux (cf. Klochko, Kośko 2009; Włodarczak 2014). A spectacular example of the latter is the pointed-base vessel of Pit Grave culture found at the cemetery in Święte, site 11 near Jarosław (Kośko et al. 2012). These finds constitute a confirmation of the importance of the relationships between communities of Pit Grave culture and Corded Ware culture. They are chronologically diverse, although most of them are dated to 2600-2400 BC – that is, to the “classic” period of Corded Ware culture.
However, when discussing the relationships with the steppe communities, Polish lands deserve particular attention since part of the groups inhabiting it belonged to the eastern province of Corded Ware culture (cf. Häusler 2014), which neighboured Pit Grave culture both from the east and south. In addition, there was a tradition of varied relationships with the north Pontic zone, which began to intensify from the second half of the 4th millennium BC (Kośko, Szmyt, 2009; Kośko, Klochko, 2009). These connections are especially readable in Małopolska and Kujawy (Kośko 2014; Włodarczak 2014). The emergence of the community of Globular Amphora culture in the north Pontic zone at the end of the 4th and the beginnings of the 3rd millennium BC (Szmyt 1999) became a harbinger of a cultural closening between the worlds of central Europe and the steppe.
The second important factor taking place at that time was the expansion of the people of Pit Grave culture in a westerly direction, along the Danube thoroughfare. As a result of this, also to the south of the Carpathian Mountains, e.g., along the upper Tisza River, a new “kurgan” cultural system was formed. As one outcome, the areas of central Europe, above all Małopolska, found themselves in the vicinity of areas inhabited by communities characterized by new principles of social organization and a new funeral rite. Around 2800 BC these changes became evident in different regions of Poland, with the most numerous examples being documented in south-eastern Poland and Kujawy. The nature of the funeral rite and the features of the material culture perceptible at that time do not have straight forward analogies in the world of north Pontic communities. In this respect, the “A-horizon” is a phenomenon of local, central European origin. The events preceding the emergence of the said horizon (that is, the expansion of the people of Pit Grave culture into the area north of the arc of the Carpathians) are nowadays completely unidentifiable and remain merely an interesting theoretical matter (cf. e.g., Kośko 2000). Therefore, analysis of the archaeological sources cannot confirm the first archaeogenetic analysis suggesting a bond between the communities of the Pit Grave culture and Corded Ware culture (e.g., Haak et al. 2015).
Artefacts of the “A-horizon”, i.e., shaft-hole axes, amphorae (Fig. 21), beakers, and pots with a plastic wavy strip (Fig. 7) are found in different funerary and settlement contexts, sometimes jointly with finds having characteristics of various cultures (e.g., in graves of Złota culture, or at settlements of Rzucewo culture). Hence, they primarily represent a chronological phase (c. 2800-2600 BC), one obviously related to the expansion of a new ideology.
Eastern CWC expansion
Before continuing tracing the Corded Ware culture’s main features, it is worth it to trace first their movement forward in time, as Corded Ware settlers, from Poland to the east.
The colonizing Neolithic waves are continued by the Circum-Baltic Corded Ware culture, closely related to the traditions of the Single Grave culture and traditions of the Northern European Lowlands. After ca. 2900 BC, certain cultural systems with ‘corded’ traits –genetically related to the catchment area of the south-western Baltic – appear in the drainages of the Nemen, Dvina, Upper Dnieper, and even the Volga. These communities are considered the vector of Neolithisation in the Forest Zone.
The picture in the Baltic (Pamariu / Rzucewo) and Finland (Battle Axe) is thus more or less clearly connected with early dates ca. 2900-2800 BC:
There is a clear interaction sphere between the eastern Gulf of Finland area – reaching from Estonia to the areas of present-day Finland and the Karelian Isthmus in Russia –, evidenced e.g. by the sharp-butted axes, derived from the Estonian Karlova axe.
Interesting in this regard is the expansion of the Corded Ware culture in Finland, into a far greater territory than previously thought, that is poorly represented in most maps depicting the extent of the culture in Europe. Here is summary of CWC findings in Finland, using images from Nordqvist and Häkäla (2014):
Middle Dnieper and Fatyanovo
The earliest Middle Dnieper remains are related to CWC graves between the Upper Vistula and the Bug, containing pottery with Middle Dnieper traits, dated probably ca. 2700 BC, which links it with the expansion of the A-horizon. In fact, during the period ca. 2800-2400 BC, the area of Lesser Poland (with its numerous kurgans and catacomb burials) is considered the western fringe of an area spreading to the east, to the middle Dniester and middle Dnieper river basins, i.e. regions bordering the steppe oecumene. This ‘eastern connection’ of funeral ritual, raw materials, and stylistic traits of artefacts is also identified in some graves of the Polish Lowlands (Włodarczak 2017).
The Fatyanovo (or Fatyanovo-Balanovo) culture was the easternmost group of the Corded Ware culture, and occupied the centre of the Russian Plain, from Lake Ilmen and the Upper Dnieper drainage to the Wiatka River and the middle course of the Volga. From the few available dates, the oldest ones from the plains of the Moskva river, and from the late Volosovo culture containing also Fatyanovo materials, and in combination they show a date of ca. 2700 BC for its appearance in the region. The Volosovo culture of foragers eventually disappeared when the Fatyanovo culture expanded into the Upper and Middle Volga basin.
The origin of the culture is complicated, because it involves at its earliest stage different Corded Ware influences in neighbouring sites, at least on the Moskva river plains (Krenke et al. 2013): some materials (possibly earlier) show Circum-Baltic and Polish features; other sites show a connection to western materials, in turn a bridge to the Middle Dnieper culture. This suggests that groups belonging to different groups of the corded ware tradition penetrated the Moscow region.
The split of subclades Z93 – Z283
If we take into account that the split between R1-Z93 and R1a-Z283 must have happened during the 5th millennium BC, we have R1a-Z93 likely around the middle Dnieper area (as supported by the Alexandria sample), and R1a-Z283 possibly to the north(-west), so that it could have expanded easily into Central Europe, and – through the northern, Baltic region – to the east.
Where exactly lies the division is unclear, but for the moment all reported Circum-Baltic samples with Z645 subclades seem to belong to Z282, while R1a samples from Sintashta/Potapovka (including the Poltavka outlier) point to Abashevo being dominated by R1a-Z93 subclades.
We have to assume, then, that an original east-west split betwen R1a-Z283 and R1a-Z93 turned, in the eastern migrations, into a north-south split between Z282 and Z93, where Finland and Battle Axe in general is going to show Z282, and Middle Dnieper – Abashevo Z93 subclades.
I can think of two reasons why this is important:
Depending on how Proto-Corded Ware peoples expanded, we may be talking about one community overcoming the other and imposing its language. Because either
clans of both Z93 and Z283 were quite close and kept intense cultural contacts around Dnieper-Dniester area; or
if the split is as early as the 5th millennium BC, and both communities separated then without contact, we are probably going to see a difference in the language spoken by both of them.
In any case, the main north-south division of eastern Corded Ware groups is pointing to an important linguistic division within the Uralic-speaking communities, specifically between a Pre-Finno-Ugric and a Pre-Samoyedic one, and potentially between Pre-Finno-Permic and Pre-Ugric.
These may seem irrelevant questions – especially for people interested only in Indo-European migrations. However, for those interested in the history of Eurasian peoples and languages as a whole, they are relevant: even those who support an ‘eastern’ origin of Proto-Uralic, like Häkkinen, or Parpola (who are, by the way, in the minority, because most Uralicists would point to eastern Europe well before the Yamna expansion), place the Finno-Ugric expansion with the Netted Ware culture as the latest possible Finno-Ugric immigrants in Fennoscandia.
The Netted Ware culture
The image below shows the approximate expansion of Corded Ware peoples of Battle Axe traditions in Finland, as well as neighbouring Fennoscandian territories, from ca. 2800 BC until the end of the 3rd millennium. A controversial 2nd (late) wave of the so-called Estonian Corded Ware is popular in texts about this region, but has not been substantiated, and it seems to be a regional development, rather than the product of migrations.
As we have seen, Fatyanovo represents the most likely cultural border zone between Circum-Baltic peoples reaching from the Russian Battle Axe to the south, and Middle Dnieper peoples reaching from Abashevo to the north. In that sense, it also represents the most likely border culture between north-western (mainly R1a-Z282) and south-eastern (R1a-Z93) subclades.
With worsening climatic conditions (cooler seasons) at the end of the 3rd millennium, less settlements are apparent in the archaeological record in Finland. After ca. 2000 BC, two CWC-related cultures remain: in the coast, the Kiukainen culture, derived from the original Circum-Baltic Corded Ware settlers, reverts to a subsistence economy which includes hunting and fishing, and keeps mainly settlements (from the best territories) along the coast. In the inland, Netted Ware immigrants eventually appear from the south.
The Netted Ware culture emerged in the Upper Volga–Oka region, derived from the Abashevo culture and its interaction with the Seima-Turbino network, and spread ca. 1900-1800 BC to the north into Finland, spreading into eastern regions previously occupied by cultures producing asbestos and organic-tempered wares (Parpola 2018).
NOTE. Those ‘contaminated’ by the Copenhagen fantasy map series may think that Volosovo hunter-gatherers somehow survived the expansion of Fatyanovo-Balanovo and Abashevo, hidden for hundreds of years in the forest, and then reappeared and expanded the Netted Ware culture. Well, they didn’t. At least not in archaeological terms, and certainly not with the genetic data we have.
If we combine all this information, and we think about these peoples in terms of Pre-Finno-Permic and Pre-Ugric languages developing side by side, we get a really interesting picture (see here for Proto-Fennic estimates):
The Battle Axe around the Baltic Sea – including the Gulf of Finland and Scandinavia – would be the area of expansion of Pre-Finno-Permic peoples, of R1a-Z283 subclades, which became later concentrated mainly on coastal regions;
the southern areas may correspond to Pre-Ugric peoples, which expanded later to the north with Netted Ware (see image below) – their precise subclades may be dependent on what will be found in Fatyanovo;
and Pre-Samoyedic peoples (of R1a-Z93 subclades) would have become isolated somewhere in the Cis- or (more likely) Trans-Urals region after 2000 BC, possibly from the interaction of the latest Balanovo stages and the Seima-Turbino phenomenon.
These communities in contact would have allowed for:
the known Indo-Iranian loanwords in Finno-Ugric to spread through a continuum of early dialects formed by Abashevo – Fatyanovo – Battle Axe groups;
the important Palaeo-Germanic loanwords in Finno-Saamic spreading with long-term contacts (from Pre-Germanic to the Proto-Germanic, and later North Germanic period) through the Baltic Sea, between Scandinavia and the Gulf of Finland;
and Tocharian contacts with Samoyedic (although limited, and in part controversial), which point to its early expansion to the east of the Ural Mountains.
On the other hand, if one is inclined to believe that R1a and steppe ancestry do represent Indo-European speakers… which language was spoken from the Gulf of Finland well into the north, the inland, and Karelia, and in Northern Russia, by Corded Ware peoples and their cultural heirs (like Kiukainen or Netted Ware) for almost three thousand years?
After the expansion of Bell Beaker peoples, the geographic distribution of late Corded Ware groups in the second half of the 3rd millennium, just before their demise – and before the expansion of Netted Ware to the north – , can be depicted thus as follows:
Territories in cyan must then represent, for some people who believe in an archaic Indo-Slavonic of sorts, the famous Fennoscandian Balto-Slavic to the north (before they were displaced by incoming Finno-Saamic peoples of hg N1c during the Iron Age and up to the Middle Ages); and the also famous Tundra-Forest Indo-Iranian in the Upper Volga area, a great environment for the development of the two-wheeled chariot…
But let’s leave the discussion on imaginary IE dialects for another post, and continue with the real question at hand.
A steppe funerary connection?
Back to Złota as a transitional culture, we have already seen how the corded ware vessels characteristic of the Classic CWC are related to Globular Amphora tradition, and show no break with this culture. It is usually believed that the funerary rites were adopted from steppe influence, too. That is probably right; but it does not mean that it came from Yamna or other coeval (or previous) steppe culture; at least not directly.
NOTE. A similar problem is seen when we read that Mierzanowice or Trzciniec show “Corded Ware” traits from a neighbouring CWC group, when CWC groups disappeared long before these cultures emerged. For cultural groups that are separated centuries from each other, an assertion as to their relationship needs specifics in terms of dates and material connection, or it is plainly wrong.
These are the funerary ritual features from Złota (later specialized in Corded Ware), as described by Włodarczak (2017):
Single burial graves; along with the habit of interring the deceased in multiple burial graves, but emphasizing their individual character by careful deposition of the body and personal nature of the grave goods.
Grave goods with materials and stylistiscs belonging to an older system (e.g. amber products); and others correlated to the ‘new world’ of the CWC, such as flint products made of the raw materials tipical of Lesser Poland’s CWC, copper ornaments, stone shaft-hole axes, bone and shell ornaments, and characteristic forms of vessels like beakers and amphoras.
Military goods, which would become prevalent in later periods, are present in a moderate number, compatible with their lesser importance.
There are also cases of the characteristic catacomb (“niche”) graves – with an entrance pit, a more extensive niche, and a narrow corridor leading to a vault – , as well as some individual cases of application of ochre and deformation of skulls.
It seems that the Złota funerary tradition was also “transitional”, like corded ware vessels, into the classical Corded Ware ideology. But “transitional” from what exactly? Yamna? Probably not.
The Lublin-Volhynia culture
One needs not look for a too distant culture to find similarities. Włodarczak (2017) points to CWC in south-eastern Poland and Kuyavia showing, by the time of the Yamna expansion, a funeral rite and features of the material culture without straightforward analogies in the world of north Pontic communities, and thus suggests that the “A-horizon” is a local phenomenon of central European origin.
This assertion is interesting, in so far as most Corded Ware samples investigated to date seem to come precisely from an East-Central territory near the Ukraine forest steppe, with a cluster already established by the end of the 5th millennium:
The following text is from Stanisław Wilk (2018), about the Lublin-Volhynian (and related) cemeteries at Wyciąże and Książnice:
Regardless of the differences between the two necropolises (such as the number of burials, the area which has been explored, the orientation and layout of burials), it seems that they have several key elements in common:
concentration of graves in separate cemeteries;
differentiation of burials with regard to sex (the principle of the ‘left ̶ right’ side, different burial goods for males and females);
stratification of graves with regard to the richness of their inventories (this mainly applied to copper artefacts);
occurrence of indicators of the richest male burials (a copper dagger in Wyciąże, a copper battle axe, a small axe and a chisel in Książnice);
allocation of a separate area for elite burials (the eastern burial area in Książnice, and the southeastern and north-central part of the necropolis in Wyciąże), as well as one for egalitarian burials (the western area in Książnice, and the south-central and western part of the cemetery in Wyciąże).
The above-mentioned characteristics prove that the patterns of social and religious behaviours from areas lying beyond the Carpathian Mountains exerted a strong influence on the two societies living in Lesser Poland.
Anna Zakościelna, while describing the similarities between the burial ritual of the late Polgár groups and cultures from areas on the Tisza river and the Lublin-Volhynia culture, claimed that:
a characteristic feature of the burial ritual of both cultures was practicing various group norms, which required different treatment of the deceased depending on their sex, age and social rank. As in the Lublin-Volhynia culture, the opposition ‘male – female’ can the most clearly be observed ̶ particularly, in the consistent positioning of males on the right, and females, on the left side. And, there is much indication that this ritual norm divided the deceased from early childhood (Sofaer Derevensky 1997: 877, Tab. 1; Lichter 2001: 276- 280, 322-323) (Zakościelna 2010: 227-228).
It seems that these observations can also be extended to the Wyciąże-Złotniki group.
Another question is whether the evidence of the influences of the copper civilization observed in both cemeteries emerged as a result of the literal copying of patterns from the south, or whether the latter were only a source of inspiration for local solutions.
Looking at this problem form the perspective of the details of burial ritual, between the Carpathian Basin and Lesser Poland, we can observe clear differences, among others, in the size of cemeteries and orientation of burials. While, in the Carpathian Basin there were large necropolises, consisting of several dozen burials located in rows, with the dominant orientation along the SE-NW and E-W axis (Lichter 2001: Abb. 123, 143; Kadrow 2008: 87); in Lesser Poland there were small cemeteries of several to a dozen or so burials, mostly oriented along the S-N axis (in the Lublin-Volhynia culture; Zakościelna 2010: 66), as well as S-E and NE-SW (in the Wyciąże-Złotniki group; Kaczanowska 2009: 77). Similarly, there are differences in the details of the burial goods. North of the Carpathians, there is a much smaller frequency of copper artefacts, particularly in the group of prestigious, heavy items (battle axes, axes and daggers), as well as a complete lack of objects made of gold. Want is more, the pottery found in the graves has a distinct local character, only supplemented by imitating or imports from areas beyond the Carpathians (Zakościelna 2006: 85; Nowak 2014: 273; a different opinion Kozłowski 2006: 57). Therefore, the suggestion made by Nowak seems right ̶ namely, that these influences were not caused by migrations of groups of the population living on the Tisza river to Lesser Poland, but were rather due to processes of selective cultural transmission (Nowak 2014: 273).
Therefore, the sharing of a similar funerary rite (as happened later between Lublin-Volhynia and Złota), although it shows a strong cultural connection with autochthonous cultures, is obviously not the same as sharing ancestors; and even if it were so, they would not need to be paternal ancestors. But it shows that important Corded Ware cultural traits are local developments, and it disconnects thus still more supposed CWC ‘steppe traits’ from steppe cultures, and connects them with the first steppe-related cultural wave that reached central Europe in the 5th millennium BC.
Prehistoric Pontic—Caspian links
How would a Lublin-Volhynia culture be related to the North Pontic area ca. 4500-3000 BC? We can enjoy the map series of Baltic—Pontic migrations by Viktor Klochko (2009), and make a wild guess:
In the second half of the 5th millennium BC (horizon 1), communities of the Tripolye culture, phases BI-BII, had contacts with the population of the late (IIa) phase of the Malice culture. The areas settled by both cultural complexes were located at a great distance from each other. The communities of the Tripolye culture adopted selected features of Malice ceramic production (fig 2). This seems to have resulted from marital exchange: on a moderate scale, Tripolye men sought out their wives in the area of the Malice culture and, according to patrilocal marriage customs, the women then moved to the Tripolye settlements, sporadically transferring ready-made ceramic products, so-called imports, to the Tripolye culture. Thus, the wives were responsible for the considerably more numerous imitations of the Malice ceramics and the long-lasting, though selective, traditions of Malice pottery passed down in their new environment. The patrilocal marriage customs involving the Malice women and the Tripolye men (never the other way round), and the fact that pottery was women’s domain, led to the unidirectional transfer of vessels, technology and norms of ceramic production from the Malice culture to the Tripolye culture.
The turn of the 5th and the 4th millennia and the early 4th millennium BC (horizon 2) witnessed the deepening interaction between the populations of the youngest (IIb) phase of the Malice culture and the classic (II) phase of the Lublin-Volhynia culture on the one hand and the communities of phase BII of the Tripolye culture on the other. The Danube and the Tripolye settlement complexes came into contact on the upper Dniester and between the Styr and the Horyn rivers in Volhynia. This helped to continue the previous forms of marital exchange, which resulted in further popularisation of the ceramics and the traditions of ceramic production typical of the Danube cultures, i.e. the Malice and the Lublin-Volhynia cultures, and also the Polgár culture, in the areas settled by the Tripolye cultural complex.
As the civilizational norms of the Eneolithic (Copper) Age became widespread in that period, the forms of interaction described above acquired new elements. The deepening internal diversification of the early Eneolithic communities of the Lublin-Volhynia culture led to a growing demand for prestige objects, which was met with import or imitation of copper artefacts, mainly those from the Carpathian Basin, and with flint tools produced from long blades. That type of flint production depended largely on new technologies derived from the Tripolye culture, as proven by such borrowings as troughlike retouch or the very idea and technology for the production of long flint blades in the Lublin-Volhynia culture. It seems that the influx of Tripolye settlers into flintbearing areas in Volhynia and on the upper Dniester, adjacent to the settlement centres of the late phase of the Malice culture and the Lublin-Volhynia culture, created sufficient conditions for the expanding influence of the Tripolye flint working on the communities of the Eneolithic Lublin-Volhynia culture.
In the mid-4th millennium BC (horizon 3), those forms of interaction between the Danube communities (the late phase of the Lublin-Volhynian culture) and the Tripolye communities (phase CI)were continued. Elements of the Danube pottery still grew in popularity in the Tripolye population, while selected features of the Tripolye flint working were adopted by the Lublin-Volhynia culture.
In that period, the population of the Funnel Beaker culture of the pre-classic and early classic phases (the beginnings of Gródek 1 and Bronocice III), until then absent from those areas, quite quickly drove out and replaced the Danube population in western Volhynia and the upper Dniester basin. This caused significant changes in the forms and intensity of the intercultural interaction, which became fully apparent already in the 2nd half of the 4th millennium BC.
In the following period (horizon 4), the population of the classic phase of the Funnel Beaker culture (Gródek 1, Bronocice III) settled more and more intensively the upper Dniester basin, up to the Hnyla Lypa river, and western Volhynia, up to the Styr river. East of those rivers, the Funnel Beaker settlers created considerable areas where they mixed with settlers from early phase CII of the Tripolye culture. Their coexistence, lasting there for many generations, resulted in deepening the interactions between members of both cultural complexes and in developing entirely new forms of relationships.
The intensifying interaction between the communities of the Funnel Beaker culture and the Tripolye culture, early phase CII, in the 2nd half of the 4th millennium BC (horizon 4) was an introduction to, and perhaps a condition for, even more frequent contacts in the next period, the first centuries of the 3rd millennium BC (horizon 5). In that case, the interaction was mainly triggered by multidirectional migrations of larger human groups, involving a significant part of the population of all cultures from the areas discussed here. The Tripolye communities of younger phase CII settled Volhynia, its eastern areas in particular, from the south and the south-east, while groups representing the younger phases of the Funnel Beaker culture (Gródek 2), often with Baden features (Bronocice IV and V), moved increasingly into the western part of that region. The Yamna communities expanded along the lower and central Danube to the west, whereas the populations of the late phase of the Baden culture took the opposite direction, reaching as far as Kiev in the northeast, and contributed to the cultural character of the Sofievka group.
The communities of the Globular Amphora culture migrated from the north-west, from eastern Poland, towards the Danube Delta and as far as the Dnieper in the east, while the multicultural population from the areas around the mouth of the Danube moved in the opposite direction, carrying with them cultural elements from Thrace, or even from Anatolia. Some of them returned to the starting point (to south-eastern Poland), bringing with them a new form of pottery, so-called Thuringian amphora, borrowed from the late Trypillian Usatovo group. This resulted in origins of the Złota culture, a cultural phenomenon that gave beginnings to the oldest Corded Ware culture. Inventories of both cultures contained the already mentioned Thuringian amphorae.
Here is a more recent assessment (2017) of the latest radiocarbon analyses of the available settlements of cultures in the area, published by Marek Novak (announced in a previous post), which gives the following data on Wyciąże-Złotniki, Lublin-Volhynia, and Wyciąże/Niedźwiedź:
This scheme unambiguously suggests both the overlapping and contiguous nature of cultural development in western Lesser Poland within the Middle Neolithic. The basic elements of this development are: 1) the Wyciąże-Złotniki group and the Lublin-Volhynian culture, until c. 3650–3550 cal BC; 2) the Funnel Beaker culture proper, which appeared c. 3750–3700c al BC, and existed until c. 3300–3250 cal BC, perhaps accompanied by the Wyciąże/Niedźwiedź materials from c. 3650–3550 cal BC; and 3) the Baden culture and the Funnel Beaker/Baden assemblages from 3100 and 3300–3100 cal BC, respectively, until 2850–2750 and 2850 cal BC, with – possibly – later Funnel Beaker culture and Wyciąże/ Niedźwiedź materials, existing until c. 3100 cal BC.
The final scheme shows that the Lublin-Volhynian culture could have coincided with the Wyciąże-Złotniki group. In view of the territorial relationship between them, relations from the point of view of material culture, primarily in the field of pottery, become particularly interesting. It is relatively easy to see clear similarities between these units. However, the most evident similarities apply only to some categories of ceramics, including, for example, vessels with Scheibenhenkel handles. What is more, in the period between the late 38th and early 36th centuries BC, the early Funnel Beaker and possibly early Baden influences are superimposed on this Lublin-Volhynian/Wyciąże-Złotniki ‘mix’.
[About Corded Ware: The] development of this unit in central Europe, including western Lesser Poland,  usually point to c. 2800 cal BC (Włodarczak 2006a). (…) the calibration curve makes it possible to alternatively refer several dates earlier than c. 3100 to c. 2850–2800 cal BC.
There is no direct archaeological link of Lublin-Volhynia-related groups with Corded Ware, beyond the fact that they shared homeland and Central European (‘steppe-related’) traits, as found in the Złota culture. But there is no direct link of Yamna with Corded Ware, either, whether in terms of culture or population.
So, given the evident link of R1a-Z93 and steppe ancestry with the forest steppe ca. 4000 BC, the surrounding North Pontic areas in contact along the Dniester, Dnieper, Bug, and Prut are the best candidates for the appearance of R1a-Z283: steppe cultures to the south and south-west; sub-Neolithic (Comb Ware) groups to the north in the forest zone; and Eneolithic groups to the west and north-west.
Seeing how ‘ancestral components’ and PCA cluster can change within a few generations, the question of the spread of R1a-Z645 subclades is still not settled by a single sample in Alexandria. However, based on the explosive expansions we are seeing from small territories, it would not be surprising to find R1a-Z93 and R1a-Z283 side by side in the same small area within the forest steppe.
NOTE. An archaeological link may not mean anything relevant in genetics, especially – as in this case – when no clear migration event has been traced to date. We have seen exactly that with Kristiansen’s proposal of a long-term genetic admixture of Yamna with Trypillia and GAC to form Corded Ware, which didn’t happen. The cultural and ideological connection of CWC peoples with Lublin-Volhynian tradition may be similar to the already known connection with GAC, and not mean anything in genetic finds; at least in terms of Y-DNA haplogroup.
We believed in the 2000s that Corded Ware represented the expansion of Late Proto-Indo-European, because the modern map of haplogroup R1a showed a distribution similar to how we thought the European and Indo-Iranian languages could have expanded. This has been proven wrong, and that’s what ancient DNA is for; not to confirm the own ideas or models, or to support modern ideologies.
It is impossible to know if R1a-Z645 comes from the steppe, forest steppe, or forest zone, until more samples are published. I don’t think there will be any big surprise, no matter where it is eventually found. By now, adding linguistic reconstruction to archaeological traits, and to the genetic data from Yamna and Corded Ware settlers, the only clear pattern is that patrilineal clans expanded, during the Final Eneolithic / Chalcolithic:
Late Proto-Indo-European with Yamna and R1b-L23 subclades, given the known genomic data from Khvalynsk, Yamna, Afanasevo, Bell Beaker, Catacomb, and Poltavka—Sintashta/Potapovka.
Uralic with Corded Ware and R1a-Z645 subclades, given the known genomic data from Fennoscandia and the Forest Zone.
Everything else is just wishful thinking at this moment.
Chapter The Sea and Bronze Age Transformations, by Christopher Prescott, Anette Sand-Eriksen, and Knut Ivar Austvoll, In: Water and Power in Past Societies (2018), Emily Holt, Proceedings of the IEMA Postdoctoral Visiting Scholar Conference on Theories and Methods in Archaeology, Vol. 6.
Along the western Norwegian coast, in the northwestern region of the Nordic Late Neolithic and Bronze Age (2350–500 BCE) there is cultural homogeneity but variable expressions of political hierarchy. Although new ideological institutions, technology (e.g., metallurgy and boat building), intensified agro‑pastoral farming, and maritime travel were introduced throughout the region as of 2350 BCE, concentrations of expressions of Bronze Age elites are intermittently found along the coast. Four regions—Lista, Jæren, Karmøy, and Sunnmøre—are examined in an exploration of the establishment and early role of maritime practices in this Nordic region. It is argued that the expressions of power and material wealth concentrated in these four regions is based on the control of bottlenecks, channels, portages, and harbors along important maritime routes of travel. As such, this article is a study of prehistoric travel, sources of power, and maritime landscapes in the Late Neolithic and Early Bronze Age of Norway.
(…)The [Corded Ware culture (CWC)] in Norway (or Battle Axe Culture, 2750–2400/2350 BCE) is primarily represented in Eastern Norway, with a patchy settlement pattern along the Oslo fjord’s coast through the inland valleys to Trøndelag in Central Norway (Hinsch 1956). The CWC represents an enigmatic period in Norwegian prehistory (Hinsch 1956; Østmo 1988:227–231; Prescott and Walderhaug 1995; Shetelig 1936); however the data at the moment suggests the following patterns:
Migration: The CWC was the result of a small‑scale immigration, but did not trigger substantial change.
Eastern and limited impact: The CWC was primarily located in small settlement patches in eastern Norway.
Terrestrial: In terms of maritime practices, the CWC does not represent a significant break from older traditions, though it seems to have a more pronounced terrestrial bearing. It is conceivable that pastures and hunting grounds were a more important political‑economic resource than waterways.
The mid‑third millennium in Norway, around 2400 BCE, represents a significant reorientation. Bell Beaker Culture (BBC) settlements in western Denmark and Norway archaeologically mark the instigation of the Nordic LN, though much of the historical process leading from the Bell Beaker to the Late Neolithic, 2500 to 2350 BCE, remains unclear (Prescott 2012; Prescott and Melheim 2009; Prieto‑Martinez 2008:116; Sarauw 2007:66; Vandkilde 2001, 2005). Still, the outcome is the establishment of the Nordic region of interaction in the Baltic, Northern Germany, Sweden, Denmark, and Norway. The distribution of artifact materials such as Bell Beakers and flint daggers attests to the far‑flung network of regular exchange and communication. This general region of interaction was reproduced through the Late Neolithic and Bronze Age.
The transition from the preceding Neolithic period hunter‑gatherer societies was rapid and represents a dramatic termination of hunter‑gatherer traditions. It has been argued that the transformation is tied to initial migrations of people to the western coast of Norway from BBC areas, possibly from northern Jutland (Prescott 2011; Prescott and Walderhaug 1995:273). Bifacial tanged‑and‑barbed points, often referred to as “Bell Beaker points,” probably represent an early, short phase of the BBC‑transition around 2400 BCE. In Norway these points have a predominantly western and coastal distribution (Østmo 2012:64), underscoring the maritime nature of the initial BBC‑expansion.
(…) In response to the question about what attracted people from Bell Beaker groups to western Norway, responses have hypothesized hunting products, political power, pastures, and metals. Particularly the latter has been emphasized by Lene Melheim (2012, 2015:37ff).
A recent study by Melheim and Prescott (2016) integrated maritime exploration with metal prospecting to explain initial excursions of BBC‑people along the western coast and into the fjords. Building on the archaeological concept of traveling metal prospectors as an element in the expansion of the Bell Beaker phenomenon, in combination with anthropological perspectives on prospecting, the article explores how prospecting for metal would have adjusted to the landscapes of western Scandinavia. Generally speaking, prospecting seldom leads to successful metal production, and it is difficult to study archaeologically. However, it will often create links between the prospectors’ society and indigenous groups, opening new territories, and have a significant transformative impact—on both the external and indigenous actors and societies.
This CWC language would thus still form the common substrate to both Germanic and Balto-Slavic, both being North-West Indo-European dialects, which spread with Bell Beakers over previous Corded Ware territory.
NOTE. This pre-LPIE nature could be in turn related to Kortlandt’s controversial proposal of an ealier PIE dative *-mus shared by both branches. However, that would paradoxically be against Kortlandt’s own assumption that the substrate was in fact of a non-Indo-European nature…