Corded Ware Culture (CWC) Genetics

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Corded Ware Culture (CWC) Genetics May 24, 2021 3:39:50 GMT

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Post by Admin on May 24, 2021 3:39:50 GMT

Figure 1. ADMIXTURE plot of select ancient individuals (data from Allentoft et al., 2015; Haak et al., 2015; Mathieson et al., 2015; Jones et al., 2017). CW = Corded Ware; MN = Middle Neolithic.

As Furholt continues his argument, much of his subsequent debate revolves around the term ‘migration’ and (as opposed to) ‘gene flow’ as, for example, when he writes, ‘The argument of Haak et al. (2015) rests on the assumption that the Corded Ware represents a single distinct population and that one would need evidence of Yamnaya affinity in an earlier archaeological culture to make a case for a continuous gene flow. This model seems to exclude the possibility that such a continuous gene flow could take place within the Corded Ware, which lasts for up to 800 years’ (p. 8); and, additionally, ‘the real issue here is that the authors do not make explicit what they mean by the term migration. The suggestion that continuous gene flow would be something different from migration is not consistent with the archaeological debates on the matter’ (p. 8).

I agree that there is no clear definition of migration in our manuscript, which, as the author admits, remains an elusive term. However, the model proposed in Haak et al. is based on the possibility of distinguishing between migration and continuous gene flow, wherein the latter becomes somewhat easier to demarcate. Under the assumption of continuous gene flow between the east (here, the north Pontic steppe) and the west (here, central Europe), we would not expect such a clear distinction between the genetic profiles of both. Instead, we would expect to see a gradient of shared ancestry in which the respective proportions would be maximized on one side (here ‘Early Farmer’ ancestry in the west and ‘Iranian Neolithic’ ancestry in the east), minimized in the opposite direction, but present nonetheless. However, this is not the case, as seen from individuals that span the time frame 8000-3000 bp. Ancestry profiles remain exclusive until the time of the Corded Ware.

Of note, new data from Globular Amphorae-associated individuals from Poland and the Ukraine show no steppe ancestry, that is, they very closely resemble the Middle Neolithic farmers in Figure 1 (Mathieson et al., 2017, available on biorxiv: biorxiv.org/content/early/2017/05/09/135616), which is intriguing given the geographical proximity and contemporaneity with Yamnaya individuals. Likewise, as also seen in Figure 1, one individual associated with the Corded Ware in the Baltic region lacks ‘farmer-ancestry’ (CW Latvia from Jones et al., 2017) and, thus, resembles the steppe ancestry profile of Yamnaya individuals.

Both observations narrow down the remaining time window for the expansion of steppe ancestry into central Europe to a few hundred years at best or perhaps five to ten generations. Given that we do not observe the signal of continuous gene flow over longer time periods (where the formation of steppe ancestry 5000–6000 years ago would pose a time constraint), we were inclined to call this process ‘migration’. Given the time window between the Globular Amphorae individuals with no ancestry and the earliest Corded Ware individuals with very large proportions, this process is still considered ‘rapid’ in biological terms and ‘massive’ in comparison.

As a further consideration, Furholt argues that, ‘this interpretation of the patterns seems to overstate the explanatory powers of the PCA. The notion of a generally closer connection of Corded Ware individuals to Yamnaya individuals than the other Late Neolithic samples is much less clear in a different study using different samples connected to Corded Ware (Allentoft et al., 2015)’ (p. 8). PCA and ADMIXTURE are qualitative methods that are used to characterize the ancestry profiles of prehistoric individuals. All observations from PCA and ADMIXTURE are backed by formal statistics (f- and D-statistic, etc.), which are quantitative methods and which were described in detail in the respective papers. As such, formal admixture tests were carried out to explain the genetic profiles of Corded Ware-associated individuals and the likely source populations (e.g. Haak et al., 2015: Supplementary Information 7, page 75 onwards and Supplementary Information 9, page 101 onwards). The observed ancestry components as well as the positioning of Corded Ware individuals in principal component space are reliable and remain stable in all subsequent studies, which include these datapoints (e.g. Günther & Jakobsson, 2016; Jones et al., 2017; Mittnik et al. 2017, biorxiv.org/content/early/2017/03/03/113241; Saag et al., 2017).

Finally, I would like to address Furholt's statement that ‘for example, in their Supplementary Information 2, Haak et al. (2015) demonstrate that three individuals connected to the Pitted Ware culture in Sweden (taken from Skoglund et al., 2012) are clearly under that eastern genetic influence’ (p. 10). Supplementary Information 2 describes the mitochondrial DNA data. Individuals associated with the Pitted Ware show high proportions of mtDNA U4 and U5 lineages (~74%), which are very common among all Holocene hunter-gatherer individuals reported so far. This mtDNA profile thus equates to the blue component of the autosomal data and not to ‘steppe ancestry’ per se.

Overall, I welcome this opportunity of interaction and open discussion. It is important that archaeologists shed a critical light on the recent findings of archaeogenetics in order to put these into a balanced and well-contextualized perspective. Likewise, I am grateful for the opportunity to clarify a few technical aspects of our genetic work, which might relativize some of Furholt's arguments.

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Corded Ware Culture (CWC) Genetics May 24, 2021 22:40:52 GMT

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Post by Admin on May 24, 2021 22:40:52 GMT

The Less Harmonious Past
Daniela Hofmann
Vor- und Frühgeschichtliche Archäologie, Universität Hamburg, Germany
Although this paper is focused on the Corded Ware, it makes several excellent points about aDNA data and their interpretation in archaeology generally. This is a topic of obvious interest both to researchers and to the wider public, but archaeologists have been uncertain how to react to the flood of new information and the associated interpretations. On the one hand, genetics have been enthusiastically embraced as part of a third science revolution which will finally free us from self-absorbed theorizing and mere ‘storytelling’ (e.g. Kristiansen, 2014; Gerbault et al., 2017), but alongside the explicit critical voices (see e.g. Niklasson, 2014) many colleagues have preferred to remain on the sidelines of the debate.

As Furholt points out, this is largely because they feel uncomfortable with the ‘Kossinna-like’ interpretative shorthand employed in such studies (see also Heyd, 2017). Also, assumptions inherent in the methodologies are often difficult to pinpoint and critique for those not familiar with statistical or genetic terminology. For instance, the closedness of the ‘populations’ under study, their internal homogeneity, and the timings and speed of gene flow are all far from proven (as Furholt recognizes), although they are written about with considerable assertiveness. Sometimes, the number of individuals taken as representative for a given ‘culture’ is extremely low and/or from a restricted area; and it is not yet possible to investigate trends over the whole duration of often long-lived cultural phenomena. As a result, we seem to be re-creating the internally homogenous and static ‘cultures’ which then need a revolutionary event to be transformed—the population revolution which goes with our science revolution in an increasingly hyperbolic rhetoric.

Furholt's paper takes an important and necessary step in highlighting the potential archaeological contribution to the mobility and migration debate. This is especially so because he does not stop at criticism, but sketches plausible alternatives to the scenarios proposed on the basis of genetic work. These can now be researched further. In particular, the idea that more mobile communities will be internally more heterogeneous and, therefore, materially more uniform is interesting and deserves to be compared with other case studies making similar points, for instance for the LBK (Hofmann, 2016) or the lake village horizon (Ebersbach et al., 2017), and probably well beyond the Neolithic, too.

But there remains a general sense of dissatisfaction with how archaeological interpretations are generated by those outside the discipline. Even in times of inter- and increasingly trans- or even meta-disciplinarity, communication does not appear to be working terribly well, at least not at the scale beyond individual research projects (see e.g. Bánffy et al., 2012). Indeed, as social/‘soft’ and natural/‘hard’ scientists, we have caricatures of each other firmly in mind: one lot are fluffy storytellers, obsessed with details, who only claim to be worried about new results because they don't understand the maths, the other lot are boors, unaware of their own inbuilt subjectivity, who just want the fame of solving an age-old mystery, ideally on the front page of the right magazine. I'll leave you to figure out who's who.

Thus, although the entrenched oppositions between the humanities and sciences have been declared over (e.g. Robb, 2014), the truce seems a little uneasy in places. This may not be a bad thing. Disagreements are, after all, fertile ground for new research endeavours. For the purposes of the present discussion, two aspects deserve to be drawn out.

First, to work together better, we need to find common concerns and vocabularies. From an archaeological perspective, if our theoretically aware models have been ignored, we are a little bit to blame ourselves. It is not just that, as Furholt outlines, some theoretically less enthusiastic archaeologists have continued to use cultures as an all-too-convenient shorthand. There has also been a tendency among some of those who do enjoy theorizing to remain aloof with regard to scientific approaches and to refrain from ‘big questions’ concerning ‘origins’, widespread material culture patterns, or convergent social trends at the continental or global scale. These topics brush over local nuance, which so many of us are accustomed to put centre-stage. Because geneticists, partly by training and partly due to the available data, tend to look at broad timescales and large regions, there is a mismatch of scales here.

This is only a problem if the genetic data as a palimpsest of timescales and regions are interpreted in terms of short-term ‘events’, but with a sketchy grasp of the details, or, indeed, if the increasingly detailed material entanglements archaeologists write about disregard a wider and potentially unsettling context. As Furholt points out, it should be possible for geneticists to write about scenarios other than an implicitly bloodthirsty replacement of one set of populations by another. Yet, by the same token, it should be possible to write narratives of power imbalance, exploitation, and upheaval within symmetrical, network, and similar approaches. As yet, the overwhelming majority of these (and I must admit this is largely an outsider's perspective) seem to prefer a cosier view. We have moved away from debates in which we passionately argued about the differences between people, things, and practices to writings in which all capacity for action is diffused across very complex but ultimately similar networks (or meshworks, etc.), largely ignoring the social constellations supporting them, including institutions, norms, and power relations (as criticized e.g. in Strathern, 1996; Glørstad, 2008; Burmeister, 2013). This lends itself most easily to narratives of sedate paces and steady flows, as for instance in Neolithisation debates (e.g. Cummings & Harris, 2011; Jones & Sibbesson, 2013) and recreates human actors as the ‘faceless blobs’ long critiqued in feminist writing (Tringham, 1991: 94). It is good to have this comfort challenged, also to reveal the full potential of these theoretical approaches.

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Corded Ware Culture (CWC) Genetics May 25, 2021 0:43:34 GMT

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Post by Admin on May 25, 2021 0:43:34 GMT

Second, power differentials are not just part of the pasts we study, but also of the research contexts within which we work. There is no point denying that, in the current climate, archaeologists feel very much like the junior partner, with funding and fame on the side of the geneticists. Joining in the debate more actively, therefore, holds the promise of considerable gains; but this does not mean that we have to act as mere sample providers and ‘culture consultants’. Instead, we must be genuinely interested in outcomes, find a vocabulary that makes sense to others and brings our concerns across clearly, and also stand by those concerns, even if they are temporarily unfashionable. Indeed, this kind of debate is something several archaeogeneticists explicitly value (e.g. see Haak's comments on this article).

One can only agree with Niklasson (2014: 59) that we need to question and critique the reasons archaeogenetics are so popular right now, and why these ‘facts’ are happily accepted within an otherwise allegedly facts-hostile climate. We must also continue to challenge the idea that greater simplification always makes better explanations (Gerbault et al., 2017; for criticism see e.g. Mizoguchi, 2017: 20). As we are no longer in a position in which choosing a bottom-up instead of a top-down approach will gain anything, we have to argue clearly why diversity and internal complexity is the more fascinating question, at whatever scale (local community or ‘culture’) we are seeking the answer.

Judging from the controversies surrounding other newly introduced techniques (for instance, 14C-dating or strontium isotopes), we can expect that, after an initial phase of unbridled enthusiasm, it will become clear that the new technique does not serve easy answers up on a plate. That is the point at which common ground can be found, and it is a process we can actively initiate and shape. Papers like Furholt's are key first steps. My hope is that this will inspire more people from across the theoretical spectrum to incorporate the results of genetics explicitly into their own writings, identifying and working through alternative perspectives and scenarios. Then we'll have plenty to talk about.

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Corded Ware Culture (CWC) Genetics May 25, 2021 22:24:56 GMT

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Post by Admin on May 25, 2021 22:24:56 GMT

Comment on: Massive Migrations? The Impact of Recent aDNA Studies on our View of Third Millennium Europe
Eva Fernández-Domínguez
Department of Archaeology, Durham University, United Kingdom

In the present manuscript, the author revisits the contribution of recent ancient DNA studies to the knowledge of third millennium cal bc societies in Europe while stressing their main conceptual flaws. The main critique revolves around the equation of archaeological cultures and biological/genetic population distinctiveness, and three main aspects are highlighted: a) the (lack of) representativeness of the studied samples; b) the lack of biological/genetic homogeneity of the members of a particular archaeological culture; and c) the ambiguous use of the term migration in those publications.

I find this paper both timely and necessary. It comes at a time when the popularity of ancient DNA studies has transcended the scientific community to seize the holders of popular media in a time of economic and political instability, where the debate on immigration and its subsequent ramifications are on the table. Hopefully, this manuscript will serve as inspiration for a constructive dialogue between geneticists and archaeologists in the search for a more holistic and realistic interpretation of the dynamics of prehistoric populations.

One of the practices criticized by the author of this manuscript is the use of a handful of samples as representative of a whole period or archaeological culture, and he cites the four individuals from Esperstedt that signify the whole Corded Ware culture in Haak et al. (2015) as an example. While this is a widespread practice in ancient DNA studies, it should be seen as a result of the limitations imposed by the small working sample size. It is important to highlight at this point that ancient DNA results are heavily constrained firstly by the availability of suitable samples and, ultimately, by their bio-molecular preservation. While this bias is insurmountable, it is our responsibility to recognize the limitations of the data, and I agree with the author that some of the cited papers have failed in adequately integrating the obtained genetic data with the evidence from other sources.

Turning into other sources of evidence to fill in the gaps and using the author's words ‘engagment with archaeological and anthropological theory’ (p. 4) is undoubtedly the right path to follow; however, I feel that much more can be done from the genetics side itself. Even with a limited sample size, two independent teams have reported that a new genetic component nearly absent in the preceding European populations appears in several individuals belonging to the Corded Ware culture, thus indicating an exogenous genomic influence during the third millennium cal bc (Allentoft et al., 2015; Haak et al., 2015). The questions to be answered are: 1) how much of the original genetic diversity that existed in these cultures has been captured by the studied samples; and 2) if a pan-cultural pattern can be inferred, as defended by the authors of these studies.

Ultimately, this leads us to the question of how the resolution of these studies can be improved. In my opinion, in a time where ancient genomic studies have gained considerable success due to new technical advances and a targeted sampling of certain skeletal elements, we should aim for a more complete chronological and geographical genetic dissection of the different cultural/populational sub-units as a way to assess the genetic substructure of these big cultural units (e.g. Corded Ware or Yamnaya). This can only be achieved through a combined effort of archaeologists and geneticists towards an informed sampling protocol followed by a holistic interpretation of the data.

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Corded Ware Culture (CWC) Genetics May 26, 2021 0:30:36 GMT

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Post by Admin on May 26, 2021 0:30:36 GMT

During the time of revision of the present paper, interesting additions to the debate have been published. The most significant one is the work of Kristiansen et al. (2017) in Antiquity. In this paper, some of the authors of Allentoff et al. (2015) re-theorize their original ‘massive migration’ hypothesis towards an integrative model that places more emphasis onto ‘social’ factors rather than on migration and assimilation to explain the observed connections between the Yamnaya and the Corded Ware people. This reworked version of the original paper incorporates some of the lacking “cultural and social elements to explain population history” and is more in line with the views of the author of this manuscript about a constant genetic flow between both cultural units, explained by Kristiansen et al. (2017) through a pattern of female exogamy.

However, the most revealing paragraph brings up a point that is also central to the present manuscript, the recognition that ‘the exact source [referring to the eastern genetic component found in the studied Corded Ware individuals] could have been another, yet unsampled group of people’ (Kristiansen et al., 2017: 335). This illustrates very well some of the limitations of genetic data as a single predictor of past population movements. Ultimately, human population genetics needs to feed more strongly on other disciplines to be able to disentangle the biological, social, and cultural mechanisms behind the observed genetic patterns.