The importance of archaeology before population genomics

Recent paper First encounters in the north: cultural diversity and gene flow in Early Mesolithic Scandinavia, by Manninen et al. Antiquity (2021).

The authors criticize the model laid out in Günther et al. (2018), whereby the origin of the previously defined Mesolithic Scandinavian hunter-gatherer genetic group (SHG) was defined as an admixture between genetically defined WHG and EHG populations that migrated into Scandinavia from two separate Ice Age refugia: the south (WHG) and north (EHG). This dualistic model was further associated with two specific lithic blade technologies present in Early Mesolithic Scandinavia (Sørensen et al. 2013), as summarized by Skoglund (2018).

scandinavia-hunter-gatherer-admixture-events
Top left: Map of the Mesolithic European samples used in this study. The pie charts show the model-based [18,19] estimates of genetic ancestry for each SHG individual. Right: Maps showing potential migration routes into Scandinavia. Scenario (a) shows a migration related to the Ahrensburgian tradition from the south. Scenario (b) shows a possible route into Scandinavia for the EHG ancestry. Modified from Günther et al. (2018).

Interesting excerpts (emphasis mine):

Early to Middle Mesolithic in Fennoscandia

Experimental studies demonstrate that systematic lithic production requires theoretical knowledge, as well as a degree of expertise, which can only be acquired through practice and practical guidance via direct and repeated interaction with a skilled person (e.g. Pelegrin 1990). Consequently, tracing the spread of knowledge-intensive technological concepts, such as blade production, is a powerful tool for detecting social contact and the dispersal of technology. The introduction of complex lithic blade technology into an area suggests repeated encounters with populations that had already mastered the technology and/or with new groups migrating into an area (Pelegrin 2012).

Although our results strongly support the view that post-glacial human dispersal into Scandinavia took place from two general directions, the pre-7500 BC archaeological data support more complex processes than those proposed by two single-event gene-culture dispersal events (Günther et al. 2018).

The discovery of lithic tools and production waste characteristic of the eastern technological tradition at the Løkvika and Fállegoahtesajeguolbba sites in eastern Finnmark suggests that the wave of eastern dispersal was initiated much earlier than previously assumed (see Kleppe 2014, 2018), and probably before 9000 BC. (…)

There is no archaeological evidence for cultural mixing or the transmission of knowledge/ skills from this first millennium of coexistence. Although the groups visited the same landscape, any interaction did not result in lithic technological change. (…)

early-mesolithic-scandinavia-western-eastern-technology
Three archaeologically visible expansions of technology in pre-7500 BC Scandinavia that can be linked with population movement and/or gene flow. All three and the three from the map below pre-date the currently earliest aDNA sequence from Scandinavia (maps by M.A. Manninen & P. Persson). Image modified from Manninen et al. (2021).

Our data show the contemporaneous presence of both eastern and western technological concepts in the north after 8300 BC.(…) We therefore suggest that the processes that led to the increased archaeological visibility of the eastern technological tradition after 8300 BC and the genetic admixture detected in aDNA samples at c. 7500 BC can be traced back one millennium earlier than the expansion of the eastern technology from the north into Southern Scandinavia.

The sites around Hornborga Lake in south-eastern Sweden suggest that blade production employing the eastern concept was already in use in this area before c. 8500 BC. (…) Along the south-western coast of Scandinavia, a sudden technological change is observed at c. 8300 BC, as the eastern blade-production concept began to dominate; no sites or artefacts representing a mixed eastern/western technology are known in this area.

The data also demonstrate regional variation in the eastern technological tradition in Fennoscandia. In Finland, while ground macro-tool technology continued, blade production was completely replaced by a flake technology by c. 8000 BC, and in northern Sweden, quartz-flake technology was already dominant at the earliest sites. In eastern Finnmark and Kola, we observe a long period of coexistence of hunter-gatherer groups belonging to different cultural traditions, before a mostly eastern technology becomes prominent c. 8300 BC.

early-mesolithic-scandinavia-western-eastern-blade-technology
Three archaeologically visible expansions of technology in pre-7500 BC Scandinavia that can be linked with population movement and/or gene flow. All three and the three from the map above pre-date the currently earliest aDNA sequence from Scandinavia (maps by M.A. Manninen & P. Persson). Image modified from Manninen et al. (2021).

We conclude that the data on archaeological sites and technological change in Fennoscandia pre-dating the earliest aDNA, indicate at least six pre-7500 BC population events:

  1. The initial dispersal into southern Sweden from the south c. 11300– 10000 BC.
  2. The north-westward migration along the Norwegian coast from western Sweden c. 9500–9300 BC.
  3. The pre-9000 BC north-eastern migration into northern Norway and Kola.
  4. The eastern dispersal into Finland and Karelia c. 9000–8400 BC.
  5. The movement of quartz-using groups into northern Sweden from the east between 8900–8200 BC.
  6. The southward migration of groups using the eastern technology along the Norwegian coast and into central Sweden c. 8400–8000 BC.

Ancient Y-DNA

In support of the authors’ claims, and as a sign of the complex nature of Northern European Mesolithic, one can notice (at least) the following Y-DNA haplogroups related to ancient samples from Fennoscandia, which may or may not have been part of distinct bottlenecks associated to those described Mesolithic migrations:

NOTE. For detailed information on these samples, check the Ancient DNA Dataset. You can explore them visually in the ArcGIS Web App by period, but also in the easily searchable Haplotree Ancient DNA (by haplogroup or age), and (as registered users) in the Ancient Y-DNA Plot Maps of Genetic Homeland.

  • R1a-YP1301 of Veretye PES001 (ca. 10700 BC) – an EHG sample from NW Russia close to the time it was populated – found also later in Yuzhnyy Oleni Ostrov, and possibly behind an R1a Kunda sample from Spiginas, representing a lineage present around the Gulf of Finland until the arrival of Corded Ware.
  • R1b-P297, mostly R1b-M73* and R1b-Y13202(*), from samples of the Narva culture in Lithuania, Latvia, and Estonia, representing a lineage present in the South-Eastern Baltic until the arrival of Corded Ware, and at least up to ca. 2000 BC in north-eastern Norway. It was also present in the only available hunter-gatherer from Samara in the Middle Volga, and later among the Botai and similar WSHG-related populations.
  • J1-M267, found during the Mesolithic in Popovo2 and Yuzhnyy Oleni Ostrov, and also in the Eneolithic steppes and probably in the Caucasus.
  • NOTE. In particular, J1-FGC82833 subclades appear to be conspicuously associated with ancient Indo-Europeans or cultures in close contact with them around the Caucasus.

  • Q1b, found (before the Narva culture?) in Zvejnieki as a basal clade, and much later in Funnelbeaker samples of hg. Q1b(xL54) from Southern Sweden. Probably from a different migration wave is a Lyalovo sample of hg. Q1b-L54(pre-L804) from Berendeyevo.
  • Different I2 and I-Z2699* haplogroups, each potentially with its own wave of expansion from the west (see here).
  • NOTE. In turn, the expansion of I-Z2699* might not be related to a “local” split and spread of a full-fledged I1 with the Nordic Late Neolithic, but rather – like J2b-L283 or E1b-V13 – to the expansion of Yamnaya settlers into (and East Bell Beakers from) the Carpathian Basin (see here).

Of course, the specific subclades behind each sample are more relevant than general branches, but without a proper chronological and geographical transect – and a precise description of mediating cultural traits of each group and their relationship to others – it is almost impossible to say anything certain about them, despite the most accurate genomic analysis.

As the detailed description in Manninen et al. (2021) shows, even correct ancestry assessments offer but another one-dimensional glimpse into what was a constantly evolving chain of population changes, including migrations, resurgence events, infiltrations, founder effects, exogamy practices, etc. And that is without taking into account the much more complex cultural diffusion events – led by imitation of fashionable trends – among groups in contact, and other forms of complex population replacement events without radical cultural change.

“SHG”, “WHG”, or “EHG”, like “CHG”, “Anatolia Neolithic”, “Steppe”, “WSHG”, or “Siberian” ancestry components are clearly umbrella terms, useful mostly to paint broad strokes of likely admixture events among populations isolated from each other for millennia. Because of that, they also offer dangerously slippery models – if there is no careful evaluation of their limitations – when applied to infer fine-scale population movements; especially if all other relevant genetic and archaeological data accompanying published samples are not taken into account.

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