Ancient Sardinia hints at Mesolithic spread of R1b-V88, and Western EEF-related expansion of Vasconic

nuragic-sardinia-neolithic

New preprint Population history from the Neolithic to present on the Mediterranean island of Sardinia: An ancient DNA perspective, by Marcus et al. bioRxiv (2019)

Interesting excerpts (emphasis mine, edited for clarity):

On the high frequency of R1b-V88

Our genome-wide data allowed us to assign Y haplogroups for 25 ancient Sardinian individuals. More than half of them consist of R1b-V88 (n=10) or I2-M223 (n=7).

Francalacci et al. (2013) identi fied three major Sardinia-specifi c founder clades based on present-day variation within the haplogroups I2-M26, G2-L91 and R1b-V88, and here we found each of those broader haplogroups in at least one ancient Sardinian individual. Two major present-day Sardinian haplogroups, R1b-M269 and E-M215, are absent.

Compared to other Neolithic and present-day European populations, the number of identi fied R1b-V88 carriers is relatively high.

(…)ancient Sardinian mtDNA haplotypes belong almost exclusively to macro-haplogroups HV (n = 16), JT (n = 17) and U (n = 9), a composition broadly similar to other European Neolithic populations.

r1b-v88-europe
Geographic and temporal distribution of R1b-V88 Y-haplotypes in ancient European samples. We plot the geographic position of all ancient samples inferred to carry R1b-V88 equivalent markers. Dates are given as years BCE (means of calibrated 2s radio-carbon dates). Multiple V88 individuals with similar geographic positions are vertically stacked. We additionally color-code the status of the R1b-V88 subclade R1b-V2197, which is found in most present-day African R1b-V88 carriers.

On the origin of a Vasconic-like Paleosardo with the Western EEF

(…) the Neolithic (and also later) ancient Sardinian individuals sit between early Neolithic Iberian and later Copper Age Iberian populations, roughly on an axis that differentiates WHG and EEF populations and embedded in a cluster that additionally includes Neolithic British individuals. This result is also evident in terms of absolute genetic differentiation, with low pairwise FST ~ 0.005 +- 0.002 between Neolithic Sardinian individuals and Neolithic western mainland European populations. Pairwise outgroup-f3 analysis shows a very similar pattern, with the highest values of f3 (i.e. most shared drift) being with Neolithic and Copper Age Iberia, gradually dropping off for temporally and geographically distant populations.

In explicit admixture models (using qpAdm, see Methods) the southern French Neolithic individuals (France-N) are the most consistent with being a single source for Neolithic Sardinia (p ~ 0:074 to reject the model of one population being the direct source of the other); followed by other populations associated with the western Mediterranean Neolithic Cardial Ware expansion.

sardinians-ancient-eef
Principal Components Analysis based on the Human Origins dataset. A: Projection of ancient individuals’ genotypes onto principal component axes de fined by modern Western Eurasians (gray labels).

Pervasive Western Hunter-Gatherer ancestry in Iberian/French/Sardinian population

Similar to western European Neolithic and central European Late Neolithic populations, ancient Sardinian individuals are shifted towards WHG individuals in the top two PCs relative to early Neolithic Anatolians Admixture analysis using qpAdm infers that ancient Sardinian individuals harbour HG ancestry (~ 17%) that is higher than early Neolithic mainland populations (including Iberia, ~ 8%), but lower than Copper Age Iberians (~ 25%) and about the same as Southern French Middle-Neolithic individuals (~ 21%).

sardinia-modern-ancient-nuragic-pca
Principal Components Analysis based on the Human Origins dataset. B: Zoom into the region most relevant for Sardinian individuals.

Continuity from Sardinia Neolithic through the Nuragic

We found several lines of evidence supporting genetic continuity from the Sardinian Neolithic into the Bronze Age and Nuragic times. Importantly, we observed low genetic differentiation between ancient Sardinian individuals from various time periods.

A qpAdm analysis, which is based on simultaneously testing f-statistics with a number of outgroups and adjusts for correlations, cannot reject a model of Neolithic Sardinian individuals being a direct predecessor of Nuragic Sardinian individuals (…) Our qpAdm analysis further shows that the WHG ancestry proportion, in a model of admixture with Neolithic Anatolia, remains stable at ~17% throughout three ancient time-periods.

sardinians-modern-ancient-pca-admixture
Present-day genetic structure in Sardinia reanalyzed with aDNA. A: Scatter plot of the rst two principal components trained on 1577 present-day individuals with grand-parental ancestry from Sardinia. Each individual is labeled with a location if at least 3 of the 4 grandparents were born in the same geographical location (\small” three letter abbreviations); otherwise with \x” or if grand-parental ancestry is missing with \?”. We calculated median PC values for each Sardinian province (large abbreviations). We also projected each ancient Sardinian individual on to the top two PCs (gray points). B/C: We plot f-statistics that test for admixture of modern Sardinian individuals (grouped into provinces) when using Nuragic Sardinian individuals as one source population. Uncertainty ranges depict one standard error (calculated from block bootstrap). Karitiana are used in the f-statistic calculation as a proxy for ANE/Steppe ancestry (Patterson et al., 2012).

Steppe influx in Modern Sardinians

While contemporary Sardinian individuals show the highest affinity towards EEF-associated populations among all of the modern populations, they also display membership with other clusters (Fig. 5). In contrast to ancient Sardinian individuals, present-day Sardinian individuals carry a modest “Steppe-like” ancestry component (but generally less than continental present-day European populations), and an appreciable broadly “eastern Mediterranean” ancestry component (also inferred at a high fraction in other present-day Mediterranean populations, such as Sicily and Greece).

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Arrival of steppe ancestry with R1b-P312 in the Mediterranean: Balearic Islands, Sicily, and Iron Age Sardinia

steppe-balearic-sicily-sardinia

New preprint The Arrival of Steppe and Iranian Related Ancestry in the Islands of the Western Mediterranean by Fernandes, Mittnik, Olalde et al. bioRxiv (2019)

Interesting excerpts (emphasis in bold; modified for clarity):

Balearic Islands: The expansion of Iberian speakers

Mallorca_EBA dates to the earliest period of permanent occupation of the islands at around 2400 BCE. We parsimoniously modeled Mallorca_EBA as deriving 36.9 ± 4.2% of her ancestry from a source related to Yamnaya_Samara; (…). We next used qpAdm to identify “proximal” sources for Mallorca_EBA’s ancestry that are more closely related to this individual in space and time, and found that she can be modeled as a clade with the (small) subset of Iberian Bell Beaker culture associated individuals who carried Steppe-derived ancestry (p=0.442).

Suppl. Materials: The model used was with Bell_Beaker_Iberia_highsteppe, a group of outliers from Iberia buried in a Bell Beaker mortuary context who unlike most individuals from this context in that region had high proportions of Steppe ancestry (p=0.442).

Our estimates of Steppe ancestry in the two later Balearic Islands individuals are lower than the earlier one: 26.3 ± 5.1% for Formentera_MBA and 23.1 ± 3.6% for Menorca_LBA, but the Middle to Late Bronze Age Balearic individuals are not a clade relative to non-Balearic groups. Specifically, we find that f4(Mbuti.DG, X; Formentera_MBA, Menorca_LBA) is positive when X=Iberia_Chalcolithic (Z=2.6) or X=Sardinia_Nuragic_BA (Z=2.7). While it is tempting to interpret the latter statistic as suggesting a genetic link between peoples of the Talaiotic culture of the Balearic islands and the Nuragic culture of Sardinia, the attraction to Iberia_Chalcolithic is just as strong, and the mitochondrial haplogroup U5b1+16189+@16192 in Menorca_LBA is not observed in Sardinia_Nuragic_BA but is observed in multiple Iberia_Chalcolithic individuals. A possible explanation is that both the ancestors of Nuragic Sardinians and the ancestors of Talaiotic people from the Balearic Islands received gene flow from an unsampled Iberian Chalcolithic-related group (perhaps a mainland group affiliated to both) that did not contribute to Formentera_MBA.

This sample, like another one in El Argar, is of hg. R1b-P312. So there you are, the data that connects the Proto-Iberian expansion (replacing IE-speaking Bell Beakers) to the Iberian Chalcolithic population, signaled by the increase in Iberian Chalcolithic ancestry after the arrival of Bell Beakers, most likely connected originally to the Argaric and post-Argaric expansions during the MBA.

balearic-sicily-sardinia-pca
PCA with previously published ancient individuals (non-filled symbols), projected onto variation from present-day populations (gray squares).

Steppe in Sardinia IA: Phocaeans from Italy?

Most Sardinians buried in a Nuragic Bronze Age context possessed uniparental haplogroups found in European hunter-gatherers and early farmers, including Y-haplogroup R1b1a[xR1b1a1a] which is different from the characteristic R1b1a1a2a1a2 spread in association with the Bell Beaker complex. An exception is individual I10553 (1226-1056 calBCE) who carried Y-haplogroup J2b2a, previously observed in a Croatian Middle Bronze Age individual bearing Steppe ancestry, suggesting the possibility of genetic input from groups that arrived from the east after the spread of first farmers. This is consistent with the evidence of material culture exchange between Sardinians and mainland Mediterranean groups, although genome-wide analyses find no significant evidence of Steppe ancestry so the quantitative demographic impact was minimal.

Another interesting data, these (Mesolithic) remnant R1b-V88 lineages closely related to the Italian Peninsula, the most likely region of expansion of these lineages into Africa, in turn possibly connected to the expansion of Proto-Afroasiatic.

We detect definitive evidence of Iranian-related ancestry in an Iron Age Sardinian I10366 (391-209 calBCE) with an estimate of 11.9 ± 3.7.% Iran_Ganj_Dareh_Neolithic related ancestry, while rejecting the model with only Anatolian_Neolithic and WHG at p=0.0066 (Supplementary Table 9). The only model that we can fit for this individual using a pair of populations that are closer in time is as a mixture of Iberia_Chalcolithic (11.9 ± 3.2%) and Mycenaean (88.1 ± 3.2%) (p=0.067). This model fits even when including Nuragic Sardinians in the outgroups of the qpAdm analysis, which is consistent with the hypothesis that this individual had little if any ancestry from earlier Sardinians.

yamnaya-samara
Proportions of ancestry using a distal qpAdm framework on an individual basis (a), and based on qpWave clusters

Sicily EBA: The Lusitanian/Ligurian connection?

(…) While a previously reported Bell Beaker culture-associated individual from Sicily had no evidence of Steppe ancestry, (…) we find evidence of Steppe ancestry in the Early Bronze Age by ~2200 BCE. In distal qpAdm, the outlier Sicily_EBA11443 is parsimoniously modeled as harboring 40.2 ± 3.5% Steppe ancestry, and the outlier Sicily_EBA8561 is parsimoniously modeled as harboring 23.3 ± 3.5% Steppe ancestry. (…) The presence of Steppe ancestry in Early Bronze Age Sicily is also evident in Y chromosome analysis, which reveals that 4 of the 5 Early Bronze Age males had Steppe-associated Y-haplogroup R1b1a1a2a1a2. (Online Table 1). Two of these were Y-haplogroup R1b1a1a2a1a2a1 (Z195) which today is largely restricted to Iberia and has been hypothesized to have originated there 2500-2000 BCE. This evidence of west-to-east gene flow from Iberia is also suggested by qpAdm modeling where the only parsimonious proximate source for the Steppe ancestry we found in the main Sicily_EBA cluster is Iberians.

What’s this? An ancestral connection between Sicel Elymian and Galaico-Lusitanian or Ligurian (based on an origin in NE Iberia)? Impossible to say, especially if the languages of these early settlers were replaced later by non-Indo-European speakers from the eastern Mediterranean, and by Indo-European speakers from the mainland closely related to Proto-Italic during the LBA, but see below.

Regarding the comment on R1b-Z195, it is associated with modern Iberians, as DF27 in general, due to founder effects beyond the Pyrenees. It is a very old subclade, split directly from DF27 roughly at the same time as it split from the parent P312, i.e. it can be found anywhere in Europe, and it almost certainly accompanied the expansion of Celts from Central Europe under the subclade R1b-M167/SRY2627.

The connection is thus strong only because of the qpAdm modeling, since R1b-DF27 and subclade R1b-Z195 are certainly lineages expanded quite early, most likely with Yamna settlers in Hungary and East Bell Beakers.

In this case, if stemming from Iberia, it is most likely of subclade R1b-Z220 – or another Z195 (xM167) lineage – originally associated with the Old European substrate found in topo-hydronymy in Iberia, whose most likely remnants attested during the Iron Age were Lusitanians.

r1b-df27-z195
Left: Modern distribution of R1b-Z195 (YFull estimate 2700 BC); Right: Modern distribution of DF27. Both include later founder effects within Iberia, so the increase in the Basque country and the Crown of Aragon and the decrease in Portugal can safely be ignored. Contour maps of the derived allele frequencies of the SNPs analyzed in Solé-Morata et al. (2017).

We detect Iranian-related ancestry in Sicily by the Middle Bronze Age 1800-1500 BCE, consistent with the directional shift of these individuals toward Mycenaeans in PCA. Specifically, two of the Middle Bronze Age individuals can only be fit with models that in addition to Anatolia_Neolithic and WHG, include Iran_Ganj_Dareh_Neolithic. The most parsimonious model for Sicily_MBA3125 has 18.0 ± 3.6% Iranian-related ancestry (p=0.032 for rejecting the alternative model of Steppe rather than Iranian-related ancestry), and the most parsimonious model for Sicily_MBA has 14.9 ± 3.9% Iranian-related ancestry (p=0.037 for rejecting the alternative model).

The modern southern Italian Caucasus-related signal identified in Raveane et al. (2018) is plausibly related to the same Iranian-related spread of ancestry into Sicily that we observe in the Middle Bronze Age (and possibly the Early Bronze Age).

The non-Indo-European Sicanians and Elymians were possibly then connected to eastern Mediterranean groups before the expansion of the Sea Peoples.

For the Late Bronze Age group of individuals, qpAdm documented Steppe-related ancestry, modeling this group as 80.2 ± 1.8% Anatolia_Neolithic, 5.3 ± 1.6% WHG, and 14.5 ± 2.2% Yamnaya_Samara. Our modeling using sources more closely related in space and time also supports Sicily_LBA having Minoan-related ancestry or being derived from local preceding populations or individuals with ancestries similar to those of Sicily_EBA3123 (p=0.527), Sicily_MBA3124 (p=0.352), and Sicily_MBA3125 (p=0.095).

This increase in Steppe-related ancestry in a western site during the LBA most likely represents either an expansion from the Aegean or – maybe more likely, given the archaeological finds – a regional population similar to Sicily EBA re-emerging or rather being displaced from the eastern part of the island because of a westward movement from nearby Calabria.

Whether this population sampled spoke Indo-European or not at this time is questionable, since the Iron Age accounts show non-IE Elymians in this region.

Actually, Elymians seem to have spoken Indo-European, which fits well with the increase in steppe ancestry.

EDIT (21 MAR): Interesting about a proposed incoming Minoan-like ancestry is the potential origin of the Iran Neolithic-related ancestry that is going to appear in Central Italy during the LBA. This could then be potentially associated with Tyrsenians passing through the area, although the traditional description may be more more compatible with an arrival of Sea Peoples from the Adriatic.

Sad to read this:

This manuscript is dedicated to the memory of Sebastiano Tusa of the Soprintendenza del Mare in Palermo, who would have been an author of this study had he not tragically died in the crash of Ethiopia Airlines flight 302 on March 10.

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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.

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