Złota a GAC-CWC transitional group…but not the origin of Corded Ware peoples

koszyce-gac-zlota-cwc

Open access Unraveling ancestry, kinship, and violence in a Late Neolithic mass grave, by Schroeder et al. PNAS (2019).

Interesting excerpts of the paper and supplementary materials, about the Złota group variant of Globular Amphora (emphasis mine):

A special case is the so-called Złota group, which emerged around 2,900 BCE in the northern part of the Małopolska Upland and existed until 2,600-2,500 BCE. Originally defined as a separate archaeological “culture” (15), this group is mainly defined by the rather local introduction of a distinct form of burial in the area mentioned. Distinct Złota settlements have not yet been identified. Nonetheless, because of the character of its burial practices and material culture, which both retain many elements of the GAC and yet point forward to the Corded Ware tradition, and because of its geographical location, the Złota group has attracted significant archaeological attention (15, 16).

The Złota group buried their dead in a new, distinct type of funerary structure; so-called niche graves (also called catacomb graves). These structures featured an entrance shaft or pit and, below that, a more or less extensive niche, sometimes connected to the entrance area by a narrow corridor. Local limestone was used to seal off the entrance shaft and to pave the floor of the niche, on which the dead were usually placed along with grave goods. This specific and relatively sophisticated form of burial probably reflects contacts between the northern Małopolska Upland and the steppe and forest-steppe communities further to the east, who also buried their dead in a form of catacomb graves. Individual cases of the use of ochre and of deformation of skulls in Złota burials provide further indications of such a connection (15). At the same time, the Złota niche grave practice also retains central elements of the GAC funerary tradition, such as the frequent practice of multiple burials in one grave, often entailing redeposition and violation of the anatomical order of corpses, and thus differs from the catacomb grave customs found on the steppes which are strongly dominated by single graves. Nonetheless, at Złota group cemeteries single burial graves appear, and even in multiple burial graves the identity of each individual is increasingly emphasized, e.g. by careful deposition of the body and through the personal nature of grave goods (16).

globular-amphorae-corded-ware-zlota-amphorae
Correspondence analysis of amphorae from the Złota-graveyards reveals that there is no typological break between Globular Amphorae and Corded Ware Amphorae, including ‘Strichbündelamphorae’ (after Furholt 2008)

Just like its burial practices, the material culture and grave goods of the Złota group combine elements of the GAC, such as amber ornaments and central parts of the ceramic inventory, with elements also found in the Corded Ware tradition, such as copper ornaments, stone shaft-hole axes, bone and shell ornaments, and other stylistic features of the ceramic inventory. In particular, Złota group ceramic styles have been seen as a clear transitional phenomenon between classical GAC styles and the subsequent Corded Ware ceramics, probably playing a key role in the development of the typical cord decoration patterns that came to define the latter (17).

As briefly summarized above, the Złota group displays a distinct funerary tradition and combination of material culture traits, which give the clear impression of a cultural “transitional situation”. While the group also appears to have had long-distance contacts directed elsewhere (e.g. to Baden communities to the south), it is the combination of Globular Amphora traits, on the one hand, and traits found among late Yamnaya or Catacomb Grave groups to the east as well as the closely related Corded Ware groups that emerged around 2,800 BCE, on the other hand, that is such a striking feature of the Złota group and which makes it interesting when attempting to understand cultural and demographic dynamics in Central and Eastern Europe during the early 3rd millennium BCE.

catacomb-grave-ksiaznice
Catacomb grave no. 2a/06 from Książnice, Złota culture (acc. to Wilk 2013). Image from Włodarczak (2017)

Książnice (site 2, grave 3ZC), Świętokrzyskie province. This burial, a so-called niche grave of the Złota type (with a vertical entrance shaft and perpendicularly situated niche), was excavated in 2006 and contained the remains of 8 individuals, osteologically identified as three adult females and five children, positioned on limestone pavement in the niche part of the grave. Radiocarbon dating of the human remains indicates that the grave dates to 2900-2630 BCE, 95.4% probability (Dataset S1). The grave had an oval entrance shaft with a diameter of 60 cm and depth of 130 cm; the depth of the niche reached to 170 cm (both measured from the modern surface), and it also contained a few animal bones, a few flint artefacts and four ceramic vessels typical of the Złota group. Książnice is located in the western part of the Małopolska Upland, which only has a few Złota group sites but a stronger presence of other, contemporary groups (including variants of the Baden culture).

Wilczyce (site 90, grave 10), Świętokrzyskie province. A rescue excavation in 2001 uncovered a niche grave of the Złota type, which had a round entrance shaft measuring 90 cm in diameter. The grave was some 60-65 cm deep below the modern surface and the bottom of the niche was paved with thin limestone plates, on which remains of three individuals had been placed; two adults, one female and one male, and one child. Four ceramic vessels of Złota group type were deposited in the niche along with the bodies. Wilczyce is located in the Sandomierz Upland, an area with substantial presence of both the Globular Amphora culture and Złota group, as well as the Corded Ware culture from 2800 BCE.

zlota-gac-cwc
Genetic affinities of the Koszyce individuals and other GAC groups (here including Złota) analyzed in this study. (A) Principal component analysis of previously published and newly sequenced ancient individuals. Ancient genomes were projected onto modern reference populations, shown in gray. (B) Ancestry proportions based on supervised ADMIXTURE analysis (K = 3), specifying Western hunter-gatherers, Anatolian Neolithic farmers, and early Bronze Age steppe populations as ancestral source populations. LP, Late Paleolithic; M, Mesolithic; EN, Early Neolithic; MN, Middle Neolithic; LN, Late Neolithic; EBA, Early Bronze Age; PWC, Pitted Ware culture; TRB, Trichterbecherkultur/Funnelbeaker culture; LBK, Linearbandkeramik/Linear Pottery culture; GAC, Globular Amphora culture; Złota, Złota culture. Image modified to outline in red GAC and Złota groups.

To further investigate the ancestry of the Globular Amphora individuals, we performed a supervised ADMIXTURE (6) analysis, specifying typical western European hunter-gatherers (Loschbour), early Neolithic Anatolian farmers (Barcın), and early Bronze Age steppe populations (Yamnaya) as ancestral source populations (Fig. 2B). The results indicate that the Globular Amphora/Złota group individuals harbor ca. 30% western hunter-gatherer and 70% Neolithic farmer ancestry, but lack steppe ancestry. To formally test different admixture models and estimate mixture proportions, we then used qpAdm (7) and find that the Polish Globular Amphora/Złota group individuals can be modeled as a mix of western European hunter-gatherer (17%) and Anatolian Neolithic farmer (83%) ancestry (SI Appendix, Table S2), mirroring the results of previous studies.

zlota-steppe-ancestry-cwc
Table S2. qpADM results. The ancestry of most Globular Amphora/Złota group individuals
can be modelled as a two-way mixture of Mesolithic western hunter-gatherers (WHG), and early Anatolian Neolithic farmers (Barcın). The five individuals from Książnice (Złota group) show evidence for additional gene flow, most likely from an eastern source.

The lack of a direct genetic connection of Corded Ware peoples with the Złota group despite their common “steppe-like traits” – shared with Yamna – reveals, once more, how the few “Yamna-like” traits of Corded Ware do not support a direct connection with Indo-Europeans, and are the result of the expansion of the so-called steppe package all over Europe, and particularly among cultures closely related to the Khvalynsk expansion, and later under the influence of expanding Yamna peoples.

The results from Książnice may support that early Corded Ware peoples were in close contact with GAC peoples in Lesser Poland during the complex period of GAC-Trypillia-CWC interactions, and especially close to the Złota group at the beginning of the 3rd millennium BC. Nevertheless, patrilineal clans of Złota apparently correspond to Globular Amphorae populations, with the only male sample available yet being within haplogroup I2a-L801, prevalent in GAC.

NOTE. The ADMIXTURE of Złota samples in common with GAC samples (and in contrast with the shared Sredni Stog – Corded Ware “steppe ancestry”) makes the possibility of R1a-M417 popping up in the Złota group from now on highly unlikely. If it happened, that would complicate further the available picture of unusually diverse patrilineal clans found among Uralic speakers expanding with early Corded Ware groups, in contrast with the strict patrilineal and patrilocal culture of Indo-Europeans as found in Repin, Yamna and Bell Beakers.

Once again the traditional links between groups hypothesized by archaeologists – like Gimbutas and Kristiansen in this case – are wrong, as is the still fashionable trend in descriptive archaeology, of supporting 1) wide cultural relationships in spite of clear-cut inter-cultural differences (and intra-cultural uniformity kept over long distances by genetically-related groups), 2) peaceful interactions among groups based on few common traits, and 3) regional population continuities despite cultural change. These generalized ideas made some propose a steppe language shared between Pontic-Caspian groups, most of which have been proven to be radically different in culture and genetics.

gimbutas-kurgan-indo-european
The background shading indicates the tree migratory waves proposed by Marija Gimbutas, and personally checked by her in 1995. Image from Tassi et al. (2017).

Furthermore, paternal lines show once again marked bottlenecks in expanding Neolithic cultures, supporting their relevance to follow the ethnolinguistic identity of different cultural groups. The steppe- or EHG-related ancestry (if it is in fact from early Corded Ware peoples) in Książnice was thus probably, as in the case of Trypillia, in the form of exogamy with females of neighbouring groups:

The presence of unrelated females and related males in the grave is interesting because it suggests that the community at Koszyce was organized along patrilineal lines of descent, adding to the mounting evidence that this was the dominant form of social organization among Late Neolithic communities in Central Europe. Usually, patrilineal forms of social organization go hand in hand with female exogamy (i.e., the practice of women marrying outside their social group). Indeed, several studies (11, 12) have shown that patrilocal residence patterns and female exogamy prevailed in several parts of Central Europe during the Late Neolithic. (…) the high diversity of mtDNA lineages, combined with the presence of only a single Y chromosome lineage, is certainly consistent with a patrilocal residence system.

funnelbeaker-trypillia-corded-ware
Map of territorial ranges of Funnel Beaker Culture (and its settlement concentrations in Lesser Poland), local Tripolyan groups and Corded Ware Culture settlements (■) at the turn of the 4th/3rd millennia BC.

Since ancient and modern Uralians show predominantly Corded Ware ancestry, and Proto-Uralic must have been in close contact with Proto-Indo-European for a very long time – given the different layers of influence that can be distinguished between them -, it follows as logical consequence that the North Pontic forest-steppes (immediately to the west of the PIE homeland in the Don-Volga-Ural steppes) is the most likely candidate for the expansion of Proto-Uralic, accompanying the spread of Sredni Stog ancestry and a bottleneck under R1a-M417 lineages.

The early TMRCAs in the 4th millennium BC for R1a-M417 and R1a-Z645 support this interpretation, like the R1a-M417 sample found in Sredni Stog. On the other hand, the resurgence of typical GAC-like ancestry in late Corded Ware groups, with GAC lineages showing late TMRCAs in the 3rd millennium BC, proves the disintegration of Corded Ware all over Europe (except in Textile Ceramics- and Abashevo-related groups) as the culture lost its cohesion and different local patrilineal clans used the opportunity to seize power – similar to how eventually I2a-L621 infiltrated eastern (Finno-Ugrian) groups.

Related

Modern Sardinians show elevated Neolithic farmer ancestry shared with Basques

sardinia-europe-relation

New paper (behind paywall), Genomic history of the Sardinian population, by Chiang et al. Nature Genetics (2018), previously published as a preprint at bioRxiv (2016).

#EDIT (18 Sep 2018): Link to read paper for free shared by the main author.

Interesting excerpts (emphasis mine):

Our analysis of divergence times suggests the population lineage ancestral to modern-day Sardinia was effectively isolated from the mainland European populations ~140–250 generations ago, corresponding to ~4,300–7,000 years ago assuming a generation time of 30 years and a mutation rate of 1.25 × 10−8 per basepair per generation. (…) in terms of relative values, the divergence time between Northern and Southern Europeans is much more recent than either is to Sardinia, signaling the relative isolation of Sardinia from mainland Europe.

We documented fine-scale variation in the ancient population ancestry proportions across the island. The most remote and interior areas of Sardinia—the Gennargentu massif covering the central and eastern regions, including the present-day province of Ogliastra— are thought to have been the least exposed to contact with outside populations. We found that pre-Neolithic hunter-gatherer and Neolithic farmer ancestries are enriched in this region of isolation. Under the premise that Ogliastra has been more buffered from recent immigration to the island, one interpretation of the result is that the early populations of Sardinia were an admixture of the two ancestries, rather than the pre-Neolithic ancestry arriving via later migrations from the mainland. Such admixture could have occurred principally on the island or on the mainland before the hypothesized Neolithic era influx to the island. Under the alternative premise that Ogliastra is simply a highly isolated region that has differentiated within Sardinia due to genetic drift, the result would be interpreted as genetic drift leading to a structured pattern of pre-Neolithic ancestry across the island, in an overall background of high Neolithic ancestry.

sardinia-pca
PCA results of merged Sardinian whole-genome sequences and the HGDP Sardinians. See below for a map of the corresponding regions.

We found Sardinians show a signal of shared ancestry with the Basque in terms of the outgroup f3 shared-drift statistics. This is consistent with long-held arguments of a connection between the two populations, including claims of Basque-like, non-Indo-European words among Sardinian placenames. More recently, the Basque have been shown to be enriched for Neolithic farmer ancestry and Indo-European languages have been associated with steppe population expansions in the post-Neolithic Bronze Age. These results support a model in which Sardinians and the Basque may both retain a legacy of pre-Indo-European Neolithic ancestry. To be cautious, while it seems unlikely, we cannot exclude that the genetic similarity between the Basque and Sardinians is due to an unsampled pre-Neolithic population that has affinities with the Neolithic representatives analyzed here.

density-nuraghi-sardinia-genetics
Left: Geographical map of Sardinia. The provincial boundaries are given as black lines. The provinces are abbreviated as Cag (Cagliari), Cmp (Campidano), Car (Carbonia), Ori (Oristano), Sas (Sassari), Olb (Olbia-tempio), Nuo (Nuoro), and Ogl (Ogliastra). For sampled villages within Ogliastra, the names and abbreviations are indicated in the colored boxes. The color corresponds to the color used in the PCA plot (Fig. 2a). The Gennargentu region referred to in the main text is the mountainous area shown in brown that is centered in western Ogliastra and southeastern Nuoro.
Right: Density of Nuraghi in Sardinia, from Wikipedia.

While we can confirm that Sardinians principally have Neolithic ancestry on the autosomes, the high frequency of two Y-chromosome haplogroups (I2a1a1 at ~39% and R1b1a2 at ~18%) that are not typically affiliated with Neolithic ancestry is one challenge to this model. Whether these haplogroups rose in frequency due to extensive genetic drift and/or reflect sex-biased demographic processes has been an open question. Our analysis of X chromosome versus autosome diversity suggests a smaller effective size for males, which can arise due to multiple processes, including polygyny, patrilineal inheritance rules, or transmission of reproductive success. We also find that the genetic ancestry enriched in Sardinia is more prevalent on the X chromosome than the autosome, suggesting that male lineages may more rapidly trace back to the mainland. Considering that the R1b1a2 haplogroup may be associated with post-Neolithic steppe ancestry expansions in Europe, and the recent timeframe when the R1b1a2 lineages expanded in Sardinia, the patterns raise the possibility of recent male-biased steppe ancestry migration to Sardinia, as has been reported among mainland Europeans at large (though see Lazaridis and Reich and Goldberg et al.). Such a recent influx is difficult to square with the overall divergence of Sardinian populations observed here.

sardinian-admixture
Mixture proportions of the three-component ancestries among Sardinian populations. Using a method first presented in Haak et al. (Nature 522, 207–211, 2015), we computed unbiased estimates of mixture proportions without a parameterized model of relationships between the test populations and the outgroup populations based on f4 statistics. The three-component ancestries were represented by early Neolithic individuals from the LBK culture (LBK_EN), pre-Neolithic huntergatherers (Loschbour), and Bronze Age steppe pastoralists (Yamnaya). See Supplementary Table 5 for standard error estimates computed using a block jackknife.

Once again, haplogroup R1b1a2 (M269), and only R1b1a2, related to male-biased, steppe-related Indo-European migrations…just sayin’.

Interestingly, haplogroup I2a1a1 is actually found among northern Iberians during the Neolithic and Chalcolithic, and is therefore associated with Neolithic ancestry in Iberia, too, and consequently – unless there is a big surprise hidden somewhere – with the ancestry found today among Basques.

NOTE. In fact, the increase in Neolithic ancestry found in south-west Ireland with expanding Bell Beakers (likely Proto-Beakers), coupled with the finding of I2a subclades in Megalithic cultures of western Europe, would support this replacement after the Cardial and Epi-Cardial expansions, which were initially associated with G2a lineages.

I am not convinced about a survival of Palaeo-Sardo after the Bell Beaker expansion, though, since there is no clear-cut cultural divide (and posterior continuity) of pre-Beaker archaeological cultures after the arrival of Bell Beakers in the island that could be identified with the survival of Neolithic languages.

We may have to wait for ancient DNA to show a potential expansion of Neolithic ancestry from the west, maybe associated with the emergence of the Nuragic civilization (potentially linked with contemporaneous Megalithic cultures in Corsica and in the Balearic Islands, and thus with an Iberian rather than a Basque stock), although this is quite speculative at this moment in linguistic, archaeological, and genetic terms.

Nevertheless, it seems that the association of a Basque-Iberian language with the Neolithic expansion from Anatolia (see Villar’s latest book on the subject) is somehow strengthened by this paper. However, it is unclear when, how, and where expanding G2a subclades were replaced by native I2 lineages.

Related

Long-term matrilineal continuity in a nonisolated region of Tuscany

iron_age_europe_mediterranean

New paper (behind paywall) The female ancestor’s tale: Long‐term matrilineal continuity in a nonisolated region of Tuscany, by Leonardi et al. Am J Phys Anthr (2018).

EDIT (10 SEP 2018): The main author has shared an open access link to read the PDF.

Interesting excerpts:

Here we analyze North-western Tuscany, a region that was a corridor of exchanges between Central Italy and the Western Mediterranean coast.

We newly obtained mitochondrial HVRI sequences from 28 individuals, and after gathering published data, we collected genetic information for 119 individuals from the region. Those span five periods during the last 5,000 years: Prehistory, Etruscan age, Roman age, Renaissance, and Present-day. We used serial coalescent simulations in an approximate Bayesian computation framework to test for continuity between the mentioned groups.

In all cases, a simple model of a long-term genealogical continuity proved to fit the data better, and sometimes much better, than the alternative hypothesis of discontinuity.

The low number of samples analyzed requires some caution in the interpretation. Because we did not test for gene flow, it is at this stage impossible to reject it, but our results suggest at least significant levels of genealogical continuity. Moreover, as it has not been possible to obtain more precise information on the age of the Eneolithic samples, they were grouped together considering the average archaeological period of interest, which may cause a bias in the analyses. (…)

tuscany
Geographic location of the samples considered in this work

(…) clearly, our samples show high levels of continuity when considering the whole Tuscan region as a genetic reservoir during the Iron Age.

The posterior distributions of the parameters confirm a high degree of genetic isolation in the sampled population, with very small values for the female effective population sizes across time. Such values, in particular the Neolithic ones, are in accord with the estimates obtained in similar studies, both in Tuscany (Ghirotto et al., 2013) and in France (Rivollat et al., 2017).

tuscany-genetic-diversity

Taken at their face value, our results do not show any major shift in the composition of the maternal ancestry of the population, across 50 centuries. This does not mean that no demographic process of relevance has affected the population, and indeed the higher diversity accumulating in time is the likely consequence of immigrating people, enriching the mitochondrial gene pool.

(…) the population of the current Lucca province appears to have retained very ancient mitochondrial features, despite occupying a geographical corridor between the Ligurian and the Tyrrhenian coast, and despite not showing the persistence of unique cultural traits through the centuries.

tuscany-genetic-diversity-hap

Another possibility is that that the different populations passing through the area (Etruscans, Romans, and Lombards) had a consistent social and/or sex bias. An example of similar patterns has been observed several times. Between the Late Neolithic and the Early Bronze Age, female exogamy in patrilocal society has been observed in Southern Germany (Knipper et al., 2017); during the Bronze Age the migrations toward Europe from the steppes appears to have consisted prevalently of males (Goldberg, Günther, Rosenberg, & Jakobsson, 2017); and in more recent periods in the Canary Islands, the female ancestry maintains a significant amount of autochthonous lineages, while the male ancestry was strongly influenced by the European colonization (Fregel et al., 2009, b).

It is well known that military invasions may not have a significant genetic impact upon the invaded population (Schiffels et al., 2016; Sokal, Oden, Walker, Di Giovanni, & Thomson, 1996;Weale,Weiss, Jager, Bradman, & Thomas, 2002), especially at the mitochondrial level, because of the limited size of a sustainable army, and of the fact that armies are generally composed mostly or only of males. Even if a substantial share of invaders decided to remain and settle the region, this form of gene flow would affect mostly or only the paternal lineages, rather than the maternal ones. We can also hypothesize the immigration of a number of people (e.g., Romans, Lombards) that may have acted as ruler of the region, remaining socially (and so genetically) separated by the local population, and leaving few (if any) traces in the gene pools of the local population.

tuscany-mtdna-haplogroups
Supporting Information, Table S1 New ancient samples genotyped

We expect to see that certain migrations since the Iron Age – like the Celtic and Roman ones – were somehow different from previous ones, where, at least since the Neolithic, male-dominated expansions were the rule.

If, however, male-biased expansions are also seen during the Iron Age – probably driven by particular subclades then – , this would certainly justify the continuity of admixture in certain regions in spite of these population expansions, and thus the importance of Y-DNA to track more recent language changes.

One of the most interesting details of the upcoming paper of Italic peoples will be the Y-DNA (and admixture) of Etruscans compared to other neighbouring peoples, given the known conflicting theories regarding their recent vs. older origin in the East before the historical record.

Related

Bantu distinguished from Khoe by uniparental markers, not genome-wide autosomal admixture

bantu-expansion

The role of matrilineality in shaping patterns of Y chromosome and mtDNA sequence variation in southwestern Angola, by Oliveira et al. bioRxiv (2018).

Interesting excerpts (emphasis mine):

The origins of NRY diversity in SW Angola

In accordance with our previous mtDNA study9, the present NRY analysis reveals a major division between the Kx’a-speaking !Xun and the Bantu-speaking groups, whose paternal genetic ancestry does not display any old remnant lineages, or a clear link to pre-Bantu eastern African migrants introducing Khoe-Kwadi languages and pastoralism into southern Africa (cf. 15). This is especially evident in the distribution of the eastern African subhaplogroup E1b1b1b2b29, which reaches the highest frequency in the !Xun (25%) and not in the formerly Kwadi-speaking Kwepe (7%). This observation, together with recent genome-wide estimates of 9-22% of eastern African ancestry in other Kx’a and Tuu-speaking groups35, suggests that eastern African admixture was not restricted to present-day Khoe-Kwadi speakers. Alternatively, it is likely that the dispersal of pastoralism and Khoe-Kwadi languages involved a series of punctuated contacts that led to a wide variety of cultural, genetic and linguistic outcomes, including possible shifts to Khoe-Kwadi by originally Bantu-speaking peoples36.

Although traces of an ancestral pre-Bantu population may yet be found in autosomal genome-wide studies, the extant variation in both uniparental markers strongly supports a scenario in which all groups of the Angolan Namib share most of their genetic ancestry with other Bantu groups but became increasingly differentiated within the highly stratified social context of SW African pastoral societies11.

bantu-pastoralists
Y chromosome phylogeny, haplogroup distribution and map of the sampling locations. The phylogenetic tree was reconstructed in BEAST based on 2,379 SNPs and is in accordance with the known Y chromosome topology. Main haplogroup clades and their labels are shown with different colors. Age estimates are reported in italics near each node, with the TMRCA of main haplogroups shown with their corresponding color. A map of the sampling locations, re-used with permission from Oliveira et al. (2018) 9, is shown on the bottom left, and the haplogroup distribution per population is shown on the bottom right, with color-coding corresponding to the phylogenetic tree.

The influence of socio-cultural behaviors on the diversity of NRY and mtDNA

A comparison of the NRY variation with previous mtDNA results for the same groups 9 identifies three main sex-specific patterns. First, gene flow from the Bantu into the !Xun is much higher for male than for female lineages (31% NRY vs. 3% mtDNA), similar to the reported male-biased patterns of gene flow from Bantu to Khoisan-speaking groups33, and from non-Pygmies to Pygmies in Central Africa 37. A comparable trend, involving exclusive introgression of NRY eastern African lineages into the !Xun (25%) was also found. (…)

Secondly, the levels of intrapopulation diversity in the Bantu-speaking peoples from the Namib were found to be consistently higher for mtDNA than for the NRY, reflecting the marked association between the Bantu expansion and the relatively young NRY E1b1a1a1 haplogroup, which has no parallel in mtDNA25,39. (…)

In the context of the Bantu expansions, these patterns have been mostly interpreted as the result of polygyny and/or higher levels of assimilation of females from resident forager communities38,40. However, most groups from the Angolan Namib are only mildly polygynous11 and ethnographic data suggest that the actual rates of polygyny in many populations may be insufficient to significantly reduce Nem2,41. In addition, the finding of a large Nef/ Nem ratio in the Himba (Fig. S5), who have almost no Khoisan-related mtDNA lineages9, indicates that female biased introgression cannot fully explain the observed patterns.

An alternative explanation may be sought in the prevailing matrilineal descent rules, which might have created a sex-specific structuring effect, similar to that proposed for patrilineal groups from Central Asia (…)

bantu-xun-plot
Bayesian skyline plots (BSP) of effective population size change through time, based on mtDNA (red) and the NRY (black). Thick lines show the mean estimates and dashed lines show the 95% HPD intervals. The vertical line highlights the 2 ky before present mark. Effective sizes are plotted on a log scale. Generation times of 25 and 31 years were assumed for mtDNA and the NRY, respectively32.

The third important sex-specific pattern observed in this study is the much lower amount of between-group differentiation for NRY than for mtDNA among Bantu-speaking populations (4.4% NRY vs. 20.2% mtDNA), in spite of the patrilocal residence patterns of all ethnic groups (Table S5). This difference can hardly be explained by unequal levels of introgression of “Khoisan” mtDNA lineages into the Bantu, since the percentage of mtDNA variation remains high (18.8%) when the Kuvale, who have high frequencies of “Khoisan”-related mtDNA, are excluded from the comparisons. It therefore seems more plausible that differentiation is higher in the mtDNA simply because there is more ancestral mtDNA than NRY variation that can be sorted among different populations (see 45). Moreover, due to the matriclanic organization of all Bantu-speaking communities, factors enhancing inter-group differentiation, like kin-structured migration and kin-structured founder effects46, would have been restricted to mtDNA. Finally, it is also likely that the discrepancy between among-group divergence of mtDNA and NRY might have been influenced by higher migration rates in males than females. In fact, although all Bantu-speaking populations have patrilocal residence patterns, the observance of endogamy rules severely constrains the between-group mobility of females. In this context, the children from extramarital unions involving members from different populations tend to be raised in the mother’s group, effectively increasing male versus female migration rates. Moreover, it is likely that, in the highly hierarchized setting of the Namib, most intergroup extramarital unions would involve men from dominant groups and women from peripatetic communities. This hypothesis is indirectly supported by the finding that in NRY-based clusters (but not in mtDNA) pastoralist populations are grouped together with peripatetic communities that share their cultural traits (Figs. S6 and 3b), suggesting that migration of NRY lineages follows a path that is similar to horizontally transmitted cultural features.

Related:

Post-Neolithic Y-chromosome bottleneck explained by cultural hitchhiking and competition between patrilineal clans

Open access study Cultural hitchhiking and competition between patrilineal kin groups explain the post-Neolithic Y-chromosome bottleneck, by Zeng, Aw, and Feldman, Nature Communications (2018).

Abstract (emphasis mine):

In human populations, changes in genetic variation are driven not only by genetic processes, but can also arise from cultural or social changes. An abrupt population bottleneck specific to human males has been inferred across several Old World (Africa, Europe, Asia) populations 5000–7000 BP. Here, bringing together anthropological theory, recent population genomic studies and mathematical models, we propose a sociocultural hypothesis, involving the formation of patrilineal kin groups and intergroup competition among these groups. Our analysis shows that this sociocultural hypothesis can explain the inference of a population bottleneck. We also show that our hypothesis is consistent with current findings from the archaeogenetics of Old World Eurasia, and is important for conceptions of cultural and social evolution in prehistory.

Relevant excerpts:

y-dna-bottleneck
Tree of Y-chromosome genotypes from samples found among cultures with hunter-gatherer subsistence, and agropastoralist subsistence. The blue background represents hunter-gatherer subsistence while the green background represents agropastoralist subsistence. Letters in red circles match individuals from sites with their archaeological context. Note that R1b-P321 is synonymous with R1b-S116. Adapted from Figs. 3, 4, 5 and 6 of Kivisild67, with addition of information from Olalde et al.64. The vertical axis represents time; the position of branch points represent the ages of branch-defining mutations, with nomenclature and age from yfull (https://www.yfull.com/tree/)

Our hypothesis explains the bottleneck as a consequence of intergroup competition between patrilineal kin groups, which caused cultural hitchhiking between Y-chromosomes and cultural groups and reduction in Y-chromosomal diversity. Competition between demes can dramatically reduce genetic diversity within a population1, especially if the population is structured such that variation is greater between demes than within demes. Culturally transmitted kinship ideals and norms can cause homophilous sorting and limit interdemic gene flow, creating homogeneous demes that differ strongly from one another. Patrilineal corporate kin groups, with coresiding male group members descending from a common male ancestor, would produce such an effect on Y-chromosomes only, as patrilineal corporate kin groups generally coexist with female exogamy40, which would homogenize the mitochondrial gene pools of different groups41,42.

With intergroup competition between patrilineal corporate kin groups, two mechanisms would operate to reduce Y-chromosomal diversity. First, patrilineal corporate kin groups produce high levels of Y-chromosomal homogeneity within each social group due to common descent, as well as high levels of between-group variation. Second, the presence of such groups results in violent intergroup competition preferentially taking place between members of male descent groups, instead of between unrelated individuals. Casualties from intergroup competition then tend to cluster among related males, and group extinction is effectively the extinction of lineages.

There is evidence that other analogous situations involving gene-culture hitchhiking in culturally-defined social groups may have affected genetic diversity. Central Asian pastoralists, who are organized into patriclans, have high levels of intergroup competition and demonstrate ethnolinguistic and population-genetic turnover down into the historical period59. They also have a markedly lower diversity in Y-chromosomal lineages than nearby agriculturalists42,60. In fact, Central Asians are the only population whose male effective population size has not recovered from the post-Neolithic bottleneck; it remains disproportionately reduced, compared to female estimates using mtDNA4. Central Asians are also the only population to have star-shaped expansions of Y-chromosomes within the historical period, which may be due to competitive processes that led to the disproportionate political success of certain patrilineal clans60.

The simulation offers an interesting graphic. I had been thinking for some time about developing an interactive image with waves of expansion showing how only few haplogroups expand and thus their variability is reduced in successive migration waves, because a lot of people seemed not to be willing to accept this:

y-dna-bottleneck-simulation
Schematic of the steps in the simulation, according to the order described in the algorithm. a (i) Patrilineal (PT) starting conditions, where cultural groups strictly determine haplogroup type. a (ii) The non-patrilineal (NPT) condition where they are perfectly uncorrelated. b The killing step, with a more (PT) and less (NPT) patrilineal starting condition. The number of deaths in each group is inversely related to group size. The blue cultural group goes extinct in both cases. This causes the haplogroup represented by the diamonds to go extinct in PT, but no haplogroup extinction occurs in NPT. c The mutation step, where a small number of individuals in the largest haplogroup change their haplogroup. d The regeneration step, where (i) is a replica of (b) PT (iii), and (d) (ii) shows how the original number of individuals before the killing step is restored by proportionally increasing the number of individuals in all cells. e Group fission step. Where an empty row occurs, the largest cultural group splits, and half the individuals form a new cultural group in the empty row. The step in which we remove cultural groups that are too small—between (c, d) (see Methods)—is not shown

You only have to imagine this process happening in many successive waves of expansion (external as well as internal to each culture) since the first Neolithic expansions in the steppe in the late-6th millennium BC, even before the formation of the Khvalynsk-Sredni Stog cultural-historical community, to understand what happened in the next thousands of years with evolving patrilineal clans and their distinct cultures.

The whole paper is an interesting read. It’s great to see sociology and genetics finally catch up and interact to develop more complex anthropological hypotheses.

The fact that this paper appears in mid-2018 and geneticists are beginning to discuss this only now when their statistical methods fail to explain the obvious (see David Reich’s recent interview) seems anachronistic, though, because all this was quite clear already in 2015 – at least for those who were looking for mainstream Yamna – Bell Beaker connections, instead of inventing new migration pathways to justify the results of certain statistical analyses

Anyway, better late than never.

Also, they use YFull estimates, which vindicates my use of them in the Indo-European demic diffusion model (2017). On the other hand, their use of these estimates right now in 2018 for R1a-M417 and R1b-M269 – when we know of a R1a-Z93 case much older than YFull’s estimated 5,000 YBP for this subclade, and possibly for R1b-L23, too, is the biggest pitfall in their temporal assessment, although the bottlenecks seen in Chalcolithic expansions seem to have indeed began during the Mesolithic-Neolithic transition in the steppe.

So, say goodbye (if you haven’t already) to dat fantasy ‘steppe people’ of mixed R1a/R1b descent cooperating with the same mixed steppe language, all represented by the Yamnaya™ ancestral component, and say hello to distinct, competing ethnolinguistic steppe groups during the Neolithic.

Related:

Distribution of Southern Iberian haplogroup H indicates exchanges in the western Mediterranean

Recent open access paper The distribution of mitochondrial DNA haplogroup H in southern Iberia indicates ancient human genetic exchanges along the western edge of the Mediterranean, by Hernández, Dugoujon, Novelletto, Rodríguez, Cuesta and Calderón, BMC Genetics (2017).

Abstract (emphasis mine):

Background
The structure of haplogroup H reveals significant differences between the western and eastern edges of the Mediterranean, as well as between the northern and southern regions. Human populations along the westernmost Mediterranean coasts, which were settled by individuals from two continents separated by a relatively narrow body of water, show the highest frequencies of mitochondrial haplogroup H. These characteristics permit the analysis of ancient migrations between both shores, which may have occurred via primitive sea crafts and early seafaring. We collected a sample of 750 autochthonous people from the southern Iberian Peninsula (Andalusians from Huelva and Granada provinces). We performed a high-resolution analysis of haplogroup H by control region sequencing and coding SNP screening of the 337 individuals harboring this maternal marker. Our results were compared with those of a wide panel of populations, including individuals from Iberia, the Maghreb, and other regions around the Mediterranean, collected from the literature.

Results
Both Andalusian subpopulations showed a typical western European profile for the internal composition of clade H, but eastern Andalusians from Granada also revealed interesting traces from the eastern Mediterranean. The basal nodes of the most frequent H sub-haplogroups, H1 and H3, harbored many individuals of Iberian and Maghrebian origins. Derived haplotypes were found in both regions; haplotypes were shared far more frequently between Andalusia and Morocco than between Andalusia and the rest of the Maghreb. These and previous results indicate intense, ancient and sustained contact among populations on both sides of the Mediterranean.

Conclusions
Our genetic data on mtDNA diversity, combined with corresponding archaeological similarities, provide support for arguments favoring prehistoric bonds with a genetic legacy traceable in extant populations. Furthermore, the results presented here indicate that the Strait of Gibraltar and the adjacent Alboran Sea, which have often been assumed to be an insurmountable geographic barrier in prehistory, served as a frequently traveled route between continents.

mtdna-h1-h3-europe-frequency
a, b, c. Interpolated frequency surfaces of clade H and its main sub-clades (H1 and H3). Frequencies (%) are showed in a colour scale. See information about the populations used in Additional files 4 and 5. Map templates were taken from Natural Earth free map repository (http://www.naturalearthdata.com/)

I usually find mtDNA data, especially studies like this one based on modern populations, very difficult to interpret for anthropological purposes. It is well-known that there are important differences in the pattern of Y-DNA and mtDNA expansion and distribution.

A paragraph in this respect caught my attention:

The patterns of variation in the Y-chromosome between western and eastern Andalusians, based on 416 males, have also been investigated for a set of Y-Short Tandem Repeats (Y-STRs) and Y-SNPs [53, 54, 55], Calderón et al., unpublished data] in combination to mtDNA analyses ([18, 19] and present study). In general, for both uniparental makers, Andalusians exhibit a typical western European genetic background, with peak frequencies of mtDNA Hg H and Y-chromosome Hg R1b1b2-M269 (45% and 60%, respectively). Interestingly, our results have further revealed that the influence of African female input is far more significant when compared to male influence in contemporary Andalusians. The lack of correspondence between the maternal and paternal genetic profiles of human populations reflects intrinsic differences in migratory behavior related to sex-biased processes and admixture, as well as differences in male and female effective population sizes related to the variance in reproductive success affected, for example, by polygyny [56, 57].

I think that the greater reduction in patrilineal lineages compared to maternal lineages we usually see during and after prehistoric or historic migrations have more to do with the renown Uí Néill family case and with war-related casualties (since combatants were usually men) than with other more popular explanations, such as enslavement of women or polygyny.

The most successful paternal lines (anywhere in the world) were probably those who remained in power for a long time (be it a patriarchal society based on families, clans, or more complex organizational units), who were richer and thus more capable of having healthy offspring, who in turn were able to survive longer and have more children who inherited power, etc.

In case of recent migrations or population movements that disrupt the previously established organization, after a certain number of generations, successful patrilocal families (usually from incoming lineages) might slowly dominate over a whole region, with poorer families (usually of ‘indigenous’ lineages) suffering a greater – especially perinatal and child – mortality, without any obvious (pre)historic event associated to these gradual changes.

This gradual replacement of paternal lineages is compatible with the adoption of the native language by newcomers. If the number of migrants is greater that the native population, and especially if their technology is more advanced, then a more radical change including ethnolinguistic identification is more likely.

I don’t deny the (pre)historic existence of radical replacement of male populations with continuity of female lineages due to massacres of men, female slavery, or polygyny, but they are probably not the main explanation for most regional differences seen in paternal lineages, and should thus be used with caution.

Gradual replacement and founder effects are also the most logical explanation for why autochthonous continuity myths (that the modern regional prevalence of few successful lineages tended to create in the 2000s) haven’t been corroborated by ancient DNA; e.g. R1b-DF27 in Basques, N1c-M178 in Finnic populations, R1a-Z283 in Slavs, etc. There is nothing different in those areas from other recent founder effects and internal migratory flows seen everywhere in Europe in the past millennia.

Paper discovered via a link by Alberto Gonzalez on Facebook group Iberia ADN

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