Patrilocality and hunter-gatherer-related ancestry of populations in East-Central Europe during the

There is another interesting new data about Central-East European genetics ( Poles)

https://www.nature.com/articles/s414...Kvz4msIis3jcc0

Genetic affinities of Early Bronze Age populations from East-Central Europe indicate the continuation of processes initiated in the onset of the epoch
The majority of the EBA individuals in this study (2200–1850 BCE) associated with the MC, IC and SC are genetically similar to their direct cultural predecessors (such as the BBC and CWC), as indicated by the principal component analysis (PCA) plot (Fig. 1D). The results of unsupervised admixture analysis (K = 7) of the selected populations (Fig. 1C) support these relationships as they indicate similar levels of admixture components (Fig. 1C). These findings are consistent with the general archaeological consensus and previous analyses of mitochondrial data28 Although the IC is believed to have the greatest cultural similarity to groups associated with the BBC, the one individual analysed here (poz929) exhibited closer affinity with individuals associated with various CWC groups rather than the BBC populations according to the f3 and D statistics (Supplementary Data 7, Supplementary Data 12 and Supplementary Fig. 2). A similar trend was observed in the case of individuals attributed to the MC, which displayed closer affinity to CWC individuals from Estonia over other EBA groups. However, the division between the BBC and CWC (and their definition as independent cultural entities associated with distinct populations) is contested7, and the majority of the above D statistics have low Z scores. Further studies are needed to fully understand the regional, cultural and genetic complexity of Central and Eastern Europe after the arrival of steppe pastoralists.

One IC-associated male from Łojewo (poz502) deviated from the general pattern, as he was genetically closest to the Middle and Late Neolithic populations, which occupied the same space on the PCA plot and displayed similar admixture proportions. The results of f3 statistics indicate that the population sharing the most genetic drift with this individual was the GAC, followed closely by the FBC (Supplementary Data 7). Such seemingly Neolithic individuals have occasionally been observed in populations postdating the arrival of steppe pastoralists and have been hypothesised to be foreigners who were incorporated into Bronze Age societies from isolated populations that retained a Middle Neolithic genetic makeup up to the end of the 3rd millennium BCE35. If this interpretation is applied to poz502, radiocarbon dated to the border between the EBA and MBA (2008-1750 BCE), it might indicate that such isolated populations lasted far longer than previously reported. This hypothesis is supported by the archaeological record, which shows that some Neolithic cultures, most notably the GAC, lasted well into the Bronze Age21.

Similar to poz502, two of the SC-associated males (poz794 and poz758) differed genetically from other EBA individuals. These two males were closer to the hunter-gatherer space in the PCA plot (Fig. 1D) and showed an increased proportion of genetic components that were maximised in various European hunter-gatherer populations in the admixture analysis (Fig. 1C). However, direct radiocarbon dating for one of these individuals (poz794, 1921–1697 BCE) as well as their genetic similarity to the MBA populations analysed in this study indicate that these two males should be discussed as a part of the genetic shifts observed in the MBA. Notably, the SC is generally thought to be a regional cultural phenomenon with mixed cultural traits, leading to frequent dispute over the association of individual burials or sites with this culture24,25,26. Therefore, the definition and associations of the SC with any genetically distinct population warrants further exploration targeting a broader selection of individuals attributed to this culture.

Increase in hunter-gatherer ancestry in East-Central Europe in the Middle Bronze Age
The MBA individuals analysed here were dated to a range between 1750 and 1200 BCE and were associated with the TCC, representing both the TC and KC. The majority of these individuals clustered together in PCA space and shared similar admixture proportions (Fig. 1C and D). This apparent genetic relation is further highlighted by f3 and D statistics, which indicate that when analysed separately, KC and TC individuals do not, in majority of cases, display any statistically significant closer genetic affinity to either of the two populations (Supplementary Data 7 and Supplementary Data 12, Supplementary Figs. 3C and 4B). These results are in accordance with the archaeological interpretation that questions the separation of the TC and KC, arguing in favour of treating them as regional variants of the same phenomenon27,36.

Interestingly compared to EBA populations, the MBA individuals were closer in the PCA space to various hunter-gatherer populations from Europe (Fig. 1D), something that previously was not detected in analyses of mitochondrial genome data alone28. Moreover, admixture analysis indicated elevated amounts of genetic components maximised in hunter-gatherers (Fig. 1C). This suggests an additional admixture event at the beginning of the MBA involving a population with relatively high proportions of this genetic component. However, there were notable deviations to this trend, with three individuals associated with TC from Pielgrzymowice site and poz643, a relatively early KC male from Beremiany, clustering closer to EBA populations in PCA space and displaying the lowest levels of shared genetic drift with both TC and hunter-gatherer populations (Supplementary Data 7). When using qpAdm to test for possible two-way admixture models that resulted in the formation of MBA populations, several models were determined to be plausible (Supplementary Data 13) with the highest p value (p = 0.21) obtained for pair consisting of IC and Neolithic Baltic hunter-gatherers (NBL). Similarly high pvalues were found for other pairs including IC and other hunter-gatherer populations: Western Hunter Gatherers (WHG), PWC hunter-gatherers from Gotland, hunter-gatherer buried in BKG context (BKGout) and hunter-gatherer populations predating the NBL (HGBL) (p = 0.207, 0.204, 0.164, 0.160 respectively). These results are in accordance with the archaeological hypothesis that the IC greatly contributed to the emergence of the TC27. However, this finding should be interpreted with caution, as only one individual associated with the IC had sufficient coverage for inclusion in qpAdm. High fit values were also obtained for pair of populations, containing individuals from modern day Estonia associated with the CWC, as the EBA predecessor and PWC, as the source of hunter-gatherer ancestry (p = 0.11).

The process of admixture was likely more complex, as indicated by the three-way admixture model with the addition of a Neolithic population. These models yielded even better fits than the two-way models. Multiple plausible scenarios were found, all displaying high fit values (p > 0.9) including CWCes in addition to various hunter-gatherer and Neolithic populations (Supplementary Data 14). The more discriminatory rotating outgroup approach to qpAdm37 used for both two- and three- way models helped to narrow down the number of plausible scenarios. After excluding the models containing sources consisting of one individual, only three-way scenarios including CWCes and either GAC or FBC as Neolithic and NBL or HGBL as hunter-gatherer population were found to be plausible (Supplementary Data 15 and Supplementary Data 16). Based on geographical and temporal proximity as well as results of D statistics directly comparing the potential ancestry sources for each MBA individual (Supplementary Data 12, Supplementary Fig. 3) we find CWCes, NBL and GAC to be the best proxies for populations involved in the admixture process. However high fit values and close genetic affinity to the individual with hunter-gatherer ancestry buried in BKG context, indicate that further studies might help to better define the populations involved in the process.

The most likely hypothesis is that these admixed MBA populations originated in the confluence of the sub-Neolithic forest zone, associated with populations with dominant WHG ancestry14,15 as well as post-CWC groups characterised by a large proportion of steppe ancestry. The sub-Neolithic forest zone” is a broad term that includes various archaeological cultures from north-eastern Europe, characterised by long-lasting preservation of a predominantly hunter-gatherer lifestyle, and the incorporation of cultural elements of Neolithic and Bronze Age origin38. These populations remained genetically distinct from the Neolithic and post-Neolithic populations, although they maintained some level of long lasting cultural and economic exchange14 It is possible that this lead to some degree of gene flow between those populations, similar to the one observed in the case of PWC in Gotland6,16 followed by subsequent contacts with EBA descendants of steppe pastoralists. Moreover, the TCC and sub-Neolithic forest zone exhibited similar cultural traits, mostly in the form of pottery and technologies12,13,39,40,41. These similarities have often been interpreted as signs of primarily cultural exchange. Our results, showing an increase in WHG ancestry during the MBA, indicate that at least some level of admixture occurred during these interactions.

Notably, the two EBA individuals (poz794 and poz758) associated with the SC, that displayed closer genetic affinity to the MBA populations both came from the south-eastern part of modern-day Poland (Supplementary Text); of these two, the individual with a direct date (poz794) predated the MBA samples analysed here. This observation suggests that the contact zone described above is not the only place where admixture took place and/or that the process was more geographically diffused. Either is plausible, given the range and duration of exchange networks seen in the EBA40. Individual poz794 might even signal the beginning of the observed gene flow, which would date it to approximately 1800 BCE.

The SC is usually seen as a continuation of CWC traditions with additional elements from steppe cultures such as the Catacomb Culture24,25. However, the genetic shift toward an increase in WHG ancestry cannot be explained by additional migration from the steppe, a notion that we previously proposed based solely on mitochondrial data28. This idea is not supported by any indication of increase of steppe ancestry as calculated by three-way qpAdm modelling including WHG, AN and YAM as best proxies of major ancestries in European gene pool (Supplementary Data 17, Supplementary Fig. 4A). Moreover, two-way qpAdm models that explored the scenarios resulting in the emergence of the MBA populations, including EBA individuals and hunter-gatherer populations, yielded higher probabilities than models including additional steppe populations such as Andronovo, Afanasievo, Sintashta, Poltavka, Karasuk, or Srubnaya (Supplementary Data 13).

The process of admixture, which began around 1800 BCE, appears to have been a continuous rather than a result of a single migratory event, as evidenced by the presence of individuals with very high or very low proportions of hunter-gatherer ancestry throughout the whole temporal range of MBA samples analysed here (Fig. 2C, Supplementary Data 17). However, gene flow was likely more extensive in the beginning, as both shared genetic drift (as identified by f3 statistics) and admixture proportions (calculated with qpAdm) show that the proportion of hunter-gatherer ancestry decreased slightly over time (Fig. 2A and Fig. 2C). The results of this event must have been long lasting, as Late Bronze Age individuals from modern-day Latvia and Lithuania14 retain the same genetic composition as our MBA individual despite living nearly half a century later and were found, based on f3 statistics, to have the closest genetic affinity to the MBA individuals presented here out of all Bronze Age populations (Supplementary Data 7 and Supplementary Fig. 3C).