Origins of Greek Civilization: Minoans and Mycenaeans

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Origins of Greek Civilization: Minoans and Mycenaeans Feb 14, 2024 20:55:35 GMT

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Insights into sex bias, biological kinship and marital practices
Studies have shown that in some regions of Europe—like the Iberian Peninsula, Central Europe and Britain—the large-scale gene flow associated with the Eurasian Steppe during the BA resulted in the prevalence of the Y chromosome R1a and R1b haplogroups28 or even involved male-biased admixture33,39,40. For the Aegean, we also estimated a significantly lower WES-ancestry proportion on the X chromosomes of the male individuals compared to most of the autosomes, which is consistent with male-biased admixture (Extended Data Fig. 3). However, only four out of the 30 male individuals dating post-sixteenth century BC (LBA and IA) carry the R1b1a1b Y haplogroup. The remaining—as well as the EBA/MBA ones—attest to the high prevalence of Y haplogroups J and G/G2 (39 and 10 out of 59, respectively; Supplementary Table 2). These were already present in Early Holocene Iran/Caucasus and among Anatolian and European farmers41,42,43,44,45 and very common in the Chalcolithic Anatolia and the Levant as well42,46,47, further highlighting the importance of the contacts between the Aegean and southwest Asian populations since the Early Neolithic.

Biological relatedness and its representation in prehistoric collective burials has been poorly understood in the Aegean. Here, we present the first evidence for representation of biologically kin groups from a collective intramural infant grave dating to the LBA—a type of burial which existed since the Neolithic Aegean but became more common since the MBA48,49. Located within the Mycenaean (LBA) settlement in Mygdalia, a small cist grave was the primary inhumation of at least eight perinatal infants and one of the six child burials under the houses of the settlement (Supplementary Note 1). By estimating the degree of relatedness among seven of these infants (Methods; Extended Data Fig. 4 and Supplementary Note 3) and assigning the uniparental haplogroups (Supplementary Table 2), the relationship of the infants could be resolved in a single extended family tree whereby the six infants were the children and grandchildren of one couple (Fig. 5). The seventh individual (MYG004) was not a direct offspring of this family but related to MYG005 in the third degree through the maternal line, plausibly as first cousins.

Fig. 5: Reconstruction of the family tree for the infants from the burial in Mygdalia (MYG; solid colour shapes).

Additional evidence of biological relatedness comes from Aidonia, where pairs of first- to third-degree relatives were determined among individuals buried within the three chamber tombs and the ossuary of Hagios Charalambos at the Lasithi plateau (Supplementary Note 1 and Extended Data Fig. 4). The individuals studied from Hagios Charalambos represent a secondary deposition of intermingled skeletons but were all unearthed from a particular section of the cave (Supplementary Note 1). Besides some pairs of close relatives (first to second degree), many pairs represent distant relatives. In addition to this high frequency of distant genetic relatedness, we also report extraordinarily high levels of consanguinity (~50% of the 27 individuals) estimated from the runs of homozygosity (ROH) by performing hapROH on the genotyping data50 (Fig. 6a; Methods). The individual ROH histograms matched more with the expectations for parents being related to the degree of first cousins, half-siblings and aunt/uncle–nephew/niece (Extended Data Fig. 5). However, given the stochastic nature of genetic recombination and the often-compromised coverage of ancient samples, one individual’s genome might only noisily match the expectations. Therefore, we combined the possible first-cousins unions cases and the cumulative histogram this produced favoured the parental relationship of first cousins against other scenarios (Fig. 6b and Extended Data Fig. 6). Coupling the evidence for frequent distant relatives and cousin–cousin unions suggests that those individuals formed a small endogamous community that regularly practiced first-cousin intermarriages.

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Origins of Greek Civilization: Minoans and Mycenaeans Feb 16, 2024 19:36:40 GMT

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Post by Admin on Feb 16, 2024 19:36:40 GMT

Fig. 6: Runs of homozygosity estimated with hapROH.

Intriguingly, endogamy is not a unique feature of Hagios Charalambos. We applied the method on another 61 Aegean individuals from all the periods that met recommended SNP coverage thresholds. In total, we found that ~30% of the individuals have most of their ROH in the bin of the longest ROH blocks, consistent with being offspring of parents related to a degree equivalent to first and second cousins (Fig. 6a). Offspring of close-kin unions were identified from the Neolithic through the LBA but due to the uneven sampling no conclusions can be drawn regarding temporal trends. Consanguinity was also present in higher frequency in the smaller islands of Salamis, Lazarides, Koukounaries and Koufonisia (50%) but overall it seemed common throughout the Aegean. The observed high frequency of endogamy diachronically points to a rather common social practice in the prehistoric Aegean that is so far unattested in the rest of the global aDNA record50.

Finally, we observe a lowered genetic diversity among the Neolithic Aposelemis individuals, measured by a substantially reduced rate of mismatching alleles between pairs of samples (median P0 ≈ 0.22) (Extended Data Fig. 4; Methods). This signal can be due to several reasons. First, a lower P0 would be consistent with Aposelemis being a small endogamous community; however the absence of any long ROH in APO004, the single individual with sufficient coverage to infer long ROH, does not support this hypothesis. Second, the lowered pairwise diversity could represent multiple pairs of second-degree relatives. However, to fit all pairs into a single consistent pedigree would require that all six individuals are half-siblings from either the maternal or the paternal side, with the exception of a single pair of full siblings (APO004–APO028). Due to the low SNP coverage in all the individuals, uniparental markers can neither rule out nor confirm such a pedigree but its high specificity places it as a less likely scenario. Finally, long-term reduction of population size (bottlenecks) can cause lower population heterozygosity and such a signal has been previously reported for instance in hunter-gatherer groups and Cardial Neolithic Iberians51,52. Individuals from such drifted populations are expected to exhibit shorter ROH (4–8 cM), which are currently not detectable in low-coverage individuals such as APO004. Further supporting this scenario, the inferred heterozygosity (h) within the Aposelemis individuals was also reduced (mean h ≈ 0.1) and close to the expectation when assuming that the average pairwise diversity (P0 ≈ 0.2) represents the diversity of the population and not pairs of close relatives. Summarizing, the current evidence is most consistent with the scenario of the Aposelemis early farmers descending from a small-sized population.

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Origins of Greek Civilization: Minoans and Mycenaeans Feb 17, 2024 23:38:09 GMT

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Post by Admin on Feb 17, 2024 23:38:09 GMT

Discussion
Our large-scale archaeogenomic approach provides new evidence regarding the role of human mobility in Aegean prehistory. The unprecedented finding of high frequency of consanguinity reveals a cultural practice otherwise unattested in the archaeological record.

First, our analyses on the Neolithic cemetery of Aposelemis, postdating the earliest levels at Knossos by about 1,000 years, suggest an Anatolian origin of the first Neolithic settlers, consistent with architectural, palaeobotanical and lithic evidence53 and recent evaluation of wild and domestic fauna at those earliest levels that also suggest animal husbandry54. While a similar genetic connection was observed for coeval mainland populations24,25, the genetic impact of Mesolithic and Neolithic populations from the other Aegean Islands, remain unknown but the evidence of a pre-Neolithic island horizon of a seafaring tradition55 forces us to further elucidate the role of hunter-gatherers in the uptake of Neolithic subsistence practices in future studies. Thus, the reduced heterozygosity of the Aposelemis population might be interpreted as a coalescence of a small population of Anatolian farmers who settled the island in the early seventh millenium BC and remained biologically isolated for a period of time or as mobile small-sized populations arriving from nearby islands or a combination of both.

Subsequently, our findings indicate that the genetic landscape of Crete changed substantially since the early sixth millenium BC, marked by an influx of Anatolian populations inferred with our qpAdm modelling and admixture dating. Interestingly, eastern gene flow is also evident in other parts of Greece (Euboea, Aegina and Cyclades) since the LN but seems more episodic and oriented to populations from the Caucasus. In addition, although Y haplogroups are unresolved, male exogamy should be discussed as a plausible contributing factor to the heterogenous genetic profiles among the male individuals from Nea Styra, in line with evidence from biodistance on a neighbouring site35. Overall, while a more even sampling would be critical, current data seem to support that the eastern gene flow was not symmetric across the Aegean.

The disruption of life that is manifested in the Aegean and the Balkans via settlement dislocation during the late third millenium BC could be related to a breakdown of social structures and/or climatic challenges56. The finding of ‘northern’ ancestry in the MBA and LBA populations from the Greek mainland, does not support a large-scale population displacement but the north–south gradient indicates the directionality of this migration and population mingling. Some putatively proximal sources like ‘Serbia EBA’ or ‘Bulgaria BA’ failed to model this ‘incoming’ ancestry in many groups and R1b Y haplogroups were rather infrequent among LBA Aegean groups, all of which points to different migration dynamics in the BA Balkans and Greece, compared to other parts of Central and Western Europe.

A more direct demographic connection can be proposed regarding the LBA Cretan and Greek mainland populations. Following an horizon of destructions targeting palatial centres and elite symbols in Crete (Late Minoan IB)57, material culture, funerary architecture and burial practices are believed to express innovations with features traditionally ascribed to the Mycenaean culture. On these grounds, an invasion of the island by people from the Greek mainland (around fifteenth century BC) has been proposed but remains highly contested12,58,59,60. While unable to settle this debate decisively, the genetic analyses demonstrate that Cretan populations at larger port cities biologically mixed with populations coming to the island during the course of a few centuries. The presence of individuals with some of the highest WES-related ancestry proportions within LBA Aegean (Crete LBA group C), despite fitting with a scenario that the Greek mainland was the only source of incoming people, it could also suggest that populations from more distant areas (for example, Italy) contributed to the Crete LBA transition, a possibility that is supported in the material culture as well61,62,63.

All different migrations proposed here (to Crete during the Neolithic and EBA, to the Greek mainland before the LBA and from the mainland to Crete during the LBA) differ in their bioarchaeological evidence, which, therefore, must not be seen as a simple proof of an archaeological hypothesis but as an additional perspective enabling us to unravel the complexity of past mobilities.

Finally, the evidence for consanguinity adds another layer regarding human mobility and social practices. Since the fundamental work by ref. 64, the phenomenon of cross-cousin unions has been much debated in anthropology, whereby in present-day societies, the evidence for cross-cousin unions is diverse, ranging from a common practice via toleration up to prohibition65. Different social, economic and ecological arguments have been brought forward as underlying reasons, for example, geographic isolation, endemic pathogen stress, integrity of inherited land and so on66. A combination of several factors combined with subsistence-specific needs (for example, olive cultivation forcing local constancy) might have shaped this practice in the Aegean. However, small population size was probably not a major reason in the Aegean as the reduced short-range ROH shown in our analyses is consistent with larger population sizes. Moreover, cross-cousin unions were practiced in different geographic contexts—on islands of different sizes as well as the Greek mainland and are not evident at some places during the second millennium (for example, Chania). Future studies need to further elucidate the factors that were responsible for the emergence, continuity and disappearance of marital practices. So far, the importance of cross-cousin unions in the prehistoric Aegean is unique among the currently available data for prehistoric endogamy, which is otherwise rarely evidenced50,67,68,69. This might indicate different standpoints with respect to marital practices of rural versus urban societies and/or that those were amenable to cultural influences and changed over time. Studying the interplay between past mortuary practices and social structure—including marital or residence rules—from an integrative bioarchaeological perspective has just become possible and future studies will help to refine our understanding of past social belonging.