Post by Admin on Apr 6, 2022 19:50:26 GMT
Discussion
We have investigated genomic variation in BA and IA Orkney and compared it with the available evidence for the preceding Orcadian Neolithic, in the context of Mesolithic, Neolithic, BA, and IA variation from across Europe. Both the mtDNA and Y-DNA variation of Neolithic Orkney point to settlement primarily from the Mediterranean/Rhône/Atlantic dispersal route, via the British mainland, in line with genome-wide analyses for Neolithic Britain as a whole (13, 39). Although this process was largely one of colonization, we find some evidence for potential assimilation and survival of indigenous Mesolithic maternal lineages. The presence of an apparently ancient local branch of mtDNA haplogroup U5b complements genome-wide observations of hunter-gatherer assimilation in western Scotland (39) and Ireland (41).
This study confirms that the drastic shift in the British population in the BA, evident in both the genome-wide (13) and mtDNA patterns, also occurred in Orkney. Orkney was largely resettled from the British mainland by people of substantially recent continental ancestry. Although this demographic shift may have taken place over centuries, it was likely sustained relatively unchanged into the IA; although we have analyzed only three IA samples, they all show a similar pattern.
Unexpectedly, despite this wave of immigration, local Neolithic male lineages persisted well into the BA, at least in Westray. While we do see evidence for male newcomers, in the presence of a single R1b-M269 Y-DNA lineage (in an infant burial), the other males all carry the indigenous I2a1b-M423 lineage. This lineage survived in a single fifth or sixth century Pictish sample from Birsay, northwest Mainland (46), but is only seen in a single family (among 407 males tested) in Orkney today.
The I2a1b-M423 lineage almost vanished elsewhere in western Europe after the end of the Neolithic. None are seen in post-Neolithic European archaeological remains. It is seen at only ∼1% in modern Britain and is almost absent in most of modern western Europe, although one recent subclade of I2a1b2-S392 has undergone dramatic expansion with Slavic populations in the Balkans (Figs. 2–4 and SI Appendix, Fig. S13) (47).
A possible explanation can be found in the continuity, stability, and self-sufficiency of farming settlements, such as LoN. These successful household groups, while undoubtedly participating in an Orkney-wide Neolithic society, also developed strong local identities, manifested in locally variant art styles, material culture, architecture, and ritual activity. They may, for example, have pursued their own long-range contacts, as suggested, for example, by the importation of aurochs and local tomb art, distinctive within Orkney and most directly comparable with that found at Brú na Bóinne in Ireland, where patrilineal descent has recently also been inferred from genetic data (41). From a position of strength during the Neolithic, such settlements may have been better placed to mediate inward migration and to make specific choices with regards to the management of lineage.
We propose that we may be seeing the surviving remnants of well-established Neolithic household groups in BA Orkney: a number of distinct male lineages that have persisted when almost the whole of the rest of the population (and genome) has been replaced. While the archaeological signs of these groups may not have been especially ostentatious, the persistence of their lineages for at least a thousand years beyond the point when the vast majority of male lineages elsewhere in Britain were replaced by newcomers might imply a more protracted and perhaps more negotiated process of assimilation than elsewhere, as well as pointing to much less insularity than has often been assumed for the Orcadian BA (25).
There are several caveats to this suggestion. Firstly, we are describing the situation in one of the most remote parts of the Orkney archipelago and at a particular moment in time. It is a snapshot and may not be representative of Orkney as a whole. While the single Lop Ness sample (from another island in the archipelago) confirms the overall pattern of continental immigration, the individual is female and therefore provides no information on the male lineage. Further investigations can help to fill out the picture.
Secondly, there are numerous cremation burials at the site for which DNA analysis cannot be carried out. Is it possible that newcomer R1b-M269 males were mostly cremated? This seems unlikely; substantial numbers of BBC and EBA inhumation burials have been analyzed from England and Scotland, and the males carried almost exclusively R1b-M269 Y-DNA lineages. However, even if this were the case, the persistence in inhumations of the I2a1b-M423 lineage, in the face of an almost 95% replacement at the genome-wide (and probably also the mtDNA) level, remains extraordinary.
Within the European context, the Orkney BA stands in stark contrast as a location, at the northwestern extreme of the continent, where the majority of the genome was overwritten between the Late Neolithic and the end of the EBA but the male lineages somehow persisted. Even so, we can understand this phenomenon in terms of the same patrilocal marriage practices that we see throughout west Eurasia. The ancestral distribution in Orkney demonstrates deliberate marriage patterns involving local men and incoming women. This process of preferential assimilation seems likely to have continued for many generations, given the extent of replacement of the remainder of the Orcadian Neolithic genome.
The existence of a powerful and likely strongly hierarchical strand in Neolithic society has been proposed on the basis of the discovery of an incestuous first-degree union at Newgrange in Ireland (41) and was prefigured by earlier analyses of Ireland and other megalithic cultures in both northwest and central Europe (32, 48). Cassidy et al. (41) argue that it encompassed the whole of Ireland, adding that it may have incorporated the similar megalithic communities of Wales and Orkney, most likely originating in Brittany (1, 49). I2a1b-M423 is seen in both Mesolithic and Neolithic Ireland, and the main cluster seen in Late Neolithic Ireland, I2a2a1a1-M284—found in the putative elite lineage at Newgrange—matches an Orcadian Neolithic lineage from the Isbister Chambered Cairn (“Tomb of the Eagles”) on South Ronaldsay (Fig. 3 and SI Appendix, Fig. S13) (13). Both our data from BA Orkney and the Neolithic circumcoastal distribution of the Y-chromosome I2a1b-M423 haplogroup lend further support to this suggestion. European Neolithic society, at one extreme (but hardly peripheral) edge of its distribution, may have been patrilineal, patrilocal, and hierarchical long before the arrival of the Beaker complex and (most likely) Indo-European speech (27, 28, 31, 50).
Our data suggest that Neolithic lineages persisted within particular farming households, which, although not obviously elite, appear to have retained control of specific landholdings over many generations. This linkage of lineage with specific place is strongly suggestive of preferential inheritance along the male line. The continuity which this engendered is likely to have contributed significantly to the longevity of settlements between the third and first millennia BC. The indigenous male lineages remained in place while their people, their culture, their language, and even their genomes were transformed to resemble more and more those of the European mainland from which the newcomers had come.
Our findings both demonstrate EBA migration into Orkney and amplify the recognition that “the expansion of the Beaker complex cannot be described by a simple one-to-one mapping of an archaeologically defined material culture to a genetically homogenous population” (51). They also highlight that population influx may have occurred even where few archaeological traces have been identified. This prompts a critical reassessment of the origins of Orcadian BA practices, which have hitherto been viewed either as insular development, imitative of distant elites, or the result of gradual filtering-in of influences. The circumstances surrounding the emergence of novel monument types such as barrows and burnt mounds, for example, will need to be reconsidered.
If more widely borne out, these findings suggest that BA Orkney is likely to have seen regular and sustained migration, engaged in long-distance exchange networks, and adopted novel practices. The perseverance of Neolithic lineages—and, potentially, identities—into this period adds a further layer of cultural complexity, the implications of which remain to be fully explored.
Supporting Information
Materials/Methods, Supplementary Text, Tables, Figures, and/or References
Appendix 01 (PDF)
www.pnas.org/doi/suppl/10.1073/pnas.2108001119/suppl_file/pnas.2108001119.sapp.pdf
We have investigated genomic variation in BA and IA Orkney and compared it with the available evidence for the preceding Orcadian Neolithic, in the context of Mesolithic, Neolithic, BA, and IA variation from across Europe. Both the mtDNA and Y-DNA variation of Neolithic Orkney point to settlement primarily from the Mediterranean/Rhône/Atlantic dispersal route, via the British mainland, in line with genome-wide analyses for Neolithic Britain as a whole (13, 39). Although this process was largely one of colonization, we find some evidence for potential assimilation and survival of indigenous Mesolithic maternal lineages. The presence of an apparently ancient local branch of mtDNA haplogroup U5b complements genome-wide observations of hunter-gatherer assimilation in western Scotland (39) and Ireland (41).
This study confirms that the drastic shift in the British population in the BA, evident in both the genome-wide (13) and mtDNA patterns, also occurred in Orkney. Orkney was largely resettled from the British mainland by people of substantially recent continental ancestry. Although this demographic shift may have taken place over centuries, it was likely sustained relatively unchanged into the IA; although we have analyzed only three IA samples, they all show a similar pattern.
Unexpectedly, despite this wave of immigration, local Neolithic male lineages persisted well into the BA, at least in Westray. While we do see evidence for male newcomers, in the presence of a single R1b-M269 Y-DNA lineage (in an infant burial), the other males all carry the indigenous I2a1b-M423 lineage. This lineage survived in a single fifth or sixth century Pictish sample from Birsay, northwest Mainland (46), but is only seen in a single family (among 407 males tested) in Orkney today.
The I2a1b-M423 lineage almost vanished elsewhere in western Europe after the end of the Neolithic. None are seen in post-Neolithic European archaeological remains. It is seen at only ∼1% in modern Britain and is almost absent in most of modern western Europe, although one recent subclade of I2a1b2-S392 has undergone dramatic expansion with Slavic populations in the Balkans (Figs. 2–4 and SI Appendix, Fig. S13) (47).
A possible explanation can be found in the continuity, stability, and self-sufficiency of farming settlements, such as LoN. These successful household groups, while undoubtedly participating in an Orkney-wide Neolithic society, also developed strong local identities, manifested in locally variant art styles, material culture, architecture, and ritual activity. They may, for example, have pursued their own long-range contacts, as suggested, for example, by the importation of aurochs and local tomb art, distinctive within Orkney and most directly comparable with that found at Brú na Bóinne in Ireland, where patrilineal descent has recently also been inferred from genetic data (41). From a position of strength during the Neolithic, such settlements may have been better placed to mediate inward migration and to make specific choices with regards to the management of lineage.
We propose that we may be seeing the surviving remnants of well-established Neolithic household groups in BA Orkney: a number of distinct male lineages that have persisted when almost the whole of the rest of the population (and genome) has been replaced. While the archaeological signs of these groups may not have been especially ostentatious, the persistence of their lineages for at least a thousand years beyond the point when the vast majority of male lineages elsewhere in Britain were replaced by newcomers might imply a more protracted and perhaps more negotiated process of assimilation than elsewhere, as well as pointing to much less insularity than has often been assumed for the Orcadian BA (25).
There are several caveats to this suggestion. Firstly, we are describing the situation in one of the most remote parts of the Orkney archipelago and at a particular moment in time. It is a snapshot and may not be representative of Orkney as a whole. While the single Lop Ness sample (from another island in the archipelago) confirms the overall pattern of continental immigration, the individual is female and therefore provides no information on the male lineage. Further investigations can help to fill out the picture.
Secondly, there are numerous cremation burials at the site for which DNA analysis cannot be carried out. Is it possible that newcomer R1b-M269 males were mostly cremated? This seems unlikely; substantial numbers of BBC and EBA inhumation burials have been analyzed from England and Scotland, and the males carried almost exclusively R1b-M269 Y-DNA lineages. However, even if this were the case, the persistence in inhumations of the I2a1b-M423 lineage, in the face of an almost 95% replacement at the genome-wide (and probably also the mtDNA) level, remains extraordinary.
Within the European context, the Orkney BA stands in stark contrast as a location, at the northwestern extreme of the continent, where the majority of the genome was overwritten between the Late Neolithic and the end of the EBA but the male lineages somehow persisted. Even so, we can understand this phenomenon in terms of the same patrilocal marriage practices that we see throughout west Eurasia. The ancestral distribution in Orkney demonstrates deliberate marriage patterns involving local men and incoming women. This process of preferential assimilation seems likely to have continued for many generations, given the extent of replacement of the remainder of the Orcadian Neolithic genome.
The existence of a powerful and likely strongly hierarchical strand in Neolithic society has been proposed on the basis of the discovery of an incestuous first-degree union at Newgrange in Ireland (41) and was prefigured by earlier analyses of Ireland and other megalithic cultures in both northwest and central Europe (32, 48). Cassidy et al. (41) argue that it encompassed the whole of Ireland, adding that it may have incorporated the similar megalithic communities of Wales and Orkney, most likely originating in Brittany (1, 49). I2a1b-M423 is seen in both Mesolithic and Neolithic Ireland, and the main cluster seen in Late Neolithic Ireland, I2a2a1a1-M284—found in the putative elite lineage at Newgrange—matches an Orcadian Neolithic lineage from the Isbister Chambered Cairn (“Tomb of the Eagles”) on South Ronaldsay (Fig. 3 and SI Appendix, Fig. S13) (13). Both our data from BA Orkney and the Neolithic circumcoastal distribution of the Y-chromosome I2a1b-M423 haplogroup lend further support to this suggestion. European Neolithic society, at one extreme (but hardly peripheral) edge of its distribution, may have been patrilineal, patrilocal, and hierarchical long before the arrival of the Beaker complex and (most likely) Indo-European speech (27, 28, 31, 50).
Our data suggest that Neolithic lineages persisted within particular farming households, which, although not obviously elite, appear to have retained control of specific landholdings over many generations. This linkage of lineage with specific place is strongly suggestive of preferential inheritance along the male line. The continuity which this engendered is likely to have contributed significantly to the longevity of settlements between the third and first millennia BC. The indigenous male lineages remained in place while their people, their culture, their language, and even their genomes were transformed to resemble more and more those of the European mainland from which the newcomers had come.
Our findings both demonstrate EBA migration into Orkney and amplify the recognition that “the expansion of the Beaker complex cannot be described by a simple one-to-one mapping of an archaeologically defined material culture to a genetically homogenous population” (51). They also highlight that population influx may have occurred even where few archaeological traces have been identified. This prompts a critical reassessment of the origins of Orcadian BA practices, which have hitherto been viewed either as insular development, imitative of distant elites, or the result of gradual filtering-in of influences. The circumstances surrounding the emergence of novel monument types such as barrows and burnt mounds, for example, will need to be reconsidered.
If more widely borne out, these findings suggest that BA Orkney is likely to have seen regular and sustained migration, engaged in long-distance exchange networks, and adopted novel practices. The perseverance of Neolithic lineages—and, potentially, identities—into this period adds a further layer of cultural complexity, the implications of which remain to be fully explored.
Supporting Information
Materials/Methods, Supplementary Text, Tables, Figures, and/or References
Appendix 01 (PDF)
www.pnas.org/doi/suppl/10.1073/pnas.2108001119/suppl_file/pnas.2108001119.sapp.pdf