Post by Admin on Jun 3, 2020 6:32:05 GMT
Discussion
Our results provide a comprehensive genetic picture of the primary inhabitants of the Southern Levant during the 2nd millennium BCE, known in the historical record and based on shared material culture as “Canaanites.” We carried out a detailed analysis aimed at answering three basic questions: how genetically homogeneous were these people, what were their plausible origins with respect to earlier peoples, and how much change in ancestry has there been in the region since the Bronze Age?
Earlier genetic analyses modeled the genomes of Middle-to-Late Bronze Age people of the Southern Levant as having almost equal shares of earlier local populations (Levant_N) and populations that are related to the Chalcolithic Zagros (Feldman et al., 2019, Haber et al., 2017, Lazaridis et al., 2016), suggesting a movement from the northeast into the Southern Levant. Here, we provide more details on this process, taking into account evidence from both archaeology and our temporally and geographically diverse genetic data. Because there is little archaeological evidence of a direct cultural connection between the Southern Levant and the Zagros region in this period, the Caucasus is a more likely source for this ancestry. We used our data to compare these two scenarios and concluded that the genetic data are compatible with both.
The Megiddo outliers, which we inferred to be relative newcomers to the region, are particularly important in demonstrating that the gene flow continued throughout the Bronze Age and that at least some of the gene flow likely came from the Caucasus rather than the Zagros. These two individuals have the highest proportions of Zagros- or Caucasian-related ancestry in our dataset. Analysis of these outliers gave significantly stronger evidence of a Caucasus source compared with a Zagros one, although this conclusion might be revised once ancient DNA data from the Middle-to-Late Bronze Age in the Zagros region become available. The two Megiddo individuals with the next lowest Neolithic Levant component (I10769 and I10770, brothers) were found near the monumental tomb that was likely related to the palace at Megiddo, raising the possibility that they might be associated with the ruling caste. Indeed, a ruler of Taanach (a town located immediately to the south of Megiddo) mentioned in a 15th century BCE cuneiform tablet found at the site and the rulers of Megiddo and Taanach mentioned in the 14th century BCE Amarna letters (found in Egypt) carry Hurrian names (a language spoken in the northeast of the ancient Near East, possibly including the Caucasus) (Na’aman, 1994b). This provides some evidence—albeit so far only suggestive—that at least some of the ruling groups in these (and other) cities might have originated from the northeast of the ancient Near East.
The Caucasus is represented in this study by ancient groups from the present-day country of Armenia, but the region known to have had cultural ties with the Southern Levant is much broader. Evidence of cultural effects on the Southern Levant is mainly focused on the Kura-Araxes culture during the Early Bronze Age (archaeology) and on the Hurrians during the Middle-to-Late Bronze Age (linguistic testimony). These two complexes were spread over the Caucasus, Eastern Anatolia, and neighboring regions. The Armenian sites we analyzed are the best representatives to date of these cultures. The Early Bronze Age individuals from Armenia (Armenia_EBA) come from an Early Bronze Age Kura-Araxes burial ground, and the later Middle-to-Late Bronze Age individuals (Armenia_MLBA) come from the Aragatsotn Province in northwestern Armenia. It is important to note that the Neolithic and Chalcolithic Anatolian individuals analyzed in this study come from the northwestern part of Anatolia, which is not part of the Caucasus. The Chalcolithic Zagros individuals come from the Kangavar Valley in Iran, which is located on the border of the Kura-Araxes influence.
The term “Canaanites” is loosely defined, referring to a collection of groups (which in the Bronze Age were organized in a city-state system) and thus in principle could lack genetic coherence. The individuals examined here cover a wide geographic span—coming from nine sites in present-day Lebanon, Israel, and Jordan. Our analyses revealed that, with the exception of Sidon (and to a smaller extent the individuals of the Baq‛ah), they are homogeneous in the sense of being closer to each other than to other contemporary and neighboring populations. This suggests that the archaeological and historical category of “Canaanites” correlates with shared ancestry (Eisenmann et al., 2018). This resembles the pattern observed in the Aegean basin during the 2nd millennium BCE, where the cultural categories of “Minoan” and “Mycenaean” show evidence of genetic homogeneity across multiple sites albeit with potentially subtle ancestry differences within these groupings (Lazaridis et al., 2017). Another example is the “Yamnaya” pastoralists of late 3rd and early 2nd millennium BCE in the western Eurasian Steppe (Allentoft et al., 2015, Haak et al., 2015). This contrasts with the pattern seen in other places, such as for the Bell Beaker cultural complex of the 2nd millennium BCE (Olalde et al., 2018), where people sharing similar cultural practices had widely varying ancestry. In any case, the detection of such associations—as we do here—cannot by itself prove that group identities in the past were related to genetics.
From the groups we have examined, the only one that is somewhat diverged from the rest is Sidon. We provide evidence against the possibility that this observation is a batch effect (Methods S1C). Rather, we suggest that the relative remoteness of Sidon stems from the fact that this population is genetically heterogeneous and has different individuals showing resemblance to different Southern Levantine groups (Methods S1C). During the 2nd millennium BCE, Sidon was a major port city and was connected in trading relations with the eastern Mediterranean basin, which could have led to a significant genetic inflow, making its population more heterogeneous than that of inland cities. This might also be the reason that the site that most resembles Sidon is Ashkelon, which is another coastal site. The only inland population that resembles Sidon is Abel Beth Maacah, perhaps because of its geographic proximity (Figures 1A and 2). Apart from Sidon, Baq‛ah also shows some minor deviations from the rest when taking a richer set of outgroup populations (Figure 3). The Baq‛ah is located on the fringe of the Syrian desert, therefore this population might be admixed with more eastern groups, which are not yet genetically sampled. This might be reflected by the fact that the individuals of the Baq‛ah also show some degree of variability in their ancestry patterns (Table S2).
Although this study focuses on the Bronze Age, it also reports two new samples from the Iron Age—one from Megiddo and the other from Abel Beth Maacah. These two individuals show ancestry patterns that are very similar to those observed in the Middle and Late Bronze Age individuals (Figure 4), suggesting that the destruction at the end of the Bronze Age in the region did not necessarily lead to genetic discontinuity in each and every site. Notably, both Abel Beth Maacah and Megiddo are inland cities, and their genetic continuity throughout the transition from the Bronze Age to the Iron Age might not be representative of other sites in the region. For example, one of the two Iron Age populations in the Philistine coastal city of Ashkelon (ASH_IA1) showed evidence of mobility of populations related to southern Europe around the Bronze Age to Iron Age transition (Feldman et al., 2019).
Estimating the ancestry proportions in present-day Middle Eastern populations with substantial sub-Saharan African admixture (as well as multiple sources of admixture from different parts of the Mediterranean), is difficult. We addressed the problem by developing two statistical techniques and then testing the robustness of our inference on the basis of a comparison between these methods, simulations, and perturbations of the input (see STAR Methods; Methods S1F–S1K). We examined 14 present-day populations that are historically or geographically linked to the Southern Levant and tested the contributions of East Africa, Europe, and the Middle East (combining Southern Levant Bronze Age populations and Zagros-related Chalcolithic ones) to their ancestry. We found that both Arabic-speaking and Jewish populations are compatible with having more than 50% Middle-Eastern-related ancestry. This does not mean that any these present-day groups bear direct ancestry from people who lived in the Middle-to-Late Bronze Age Levant or in Chalcolithic Zagros; rather, it indicates that they have ancestries from populations whose ancient proxy can be related to the Middle East. The Zagros- or Caucasian-related ancestry flow into the region apparently continued after the Bronze Age. We also see an Eastern-African-related ancestry entering the region after the Bronze Age with an approximate south-to-north gradient. In addition, we observe a European-related ancestry with the opposite gradient (north-to-south). Given the difficulties in separating the ancestry components arriving from the Southern Levant and the Zagros, an important direction for future work will be to reconstruct in high resolution the ancestry trajectories of each present-day group, and to understand how people from the Southern Levant Bronze Age mixed with other people in later periods in the context of processes known from the rich archaeological and historical records of the last three millennia.
STAR★Methods
Our results provide a comprehensive genetic picture of the primary inhabitants of the Southern Levant during the 2nd millennium BCE, known in the historical record and based on shared material culture as “Canaanites.” We carried out a detailed analysis aimed at answering three basic questions: how genetically homogeneous were these people, what were their plausible origins with respect to earlier peoples, and how much change in ancestry has there been in the region since the Bronze Age?
Earlier genetic analyses modeled the genomes of Middle-to-Late Bronze Age people of the Southern Levant as having almost equal shares of earlier local populations (Levant_N) and populations that are related to the Chalcolithic Zagros (Feldman et al., 2019, Haber et al., 2017, Lazaridis et al., 2016), suggesting a movement from the northeast into the Southern Levant. Here, we provide more details on this process, taking into account evidence from both archaeology and our temporally and geographically diverse genetic data. Because there is little archaeological evidence of a direct cultural connection between the Southern Levant and the Zagros region in this period, the Caucasus is a more likely source for this ancestry. We used our data to compare these two scenarios and concluded that the genetic data are compatible with both.
The Megiddo outliers, which we inferred to be relative newcomers to the region, are particularly important in demonstrating that the gene flow continued throughout the Bronze Age and that at least some of the gene flow likely came from the Caucasus rather than the Zagros. These two individuals have the highest proportions of Zagros- or Caucasian-related ancestry in our dataset. Analysis of these outliers gave significantly stronger evidence of a Caucasus source compared with a Zagros one, although this conclusion might be revised once ancient DNA data from the Middle-to-Late Bronze Age in the Zagros region become available. The two Megiddo individuals with the next lowest Neolithic Levant component (I10769 and I10770, brothers) were found near the monumental tomb that was likely related to the palace at Megiddo, raising the possibility that they might be associated with the ruling caste. Indeed, a ruler of Taanach (a town located immediately to the south of Megiddo) mentioned in a 15th century BCE cuneiform tablet found at the site and the rulers of Megiddo and Taanach mentioned in the 14th century BCE Amarna letters (found in Egypt) carry Hurrian names (a language spoken in the northeast of the ancient Near East, possibly including the Caucasus) (Na’aman, 1994b). This provides some evidence—albeit so far only suggestive—that at least some of the ruling groups in these (and other) cities might have originated from the northeast of the ancient Near East.
The Caucasus is represented in this study by ancient groups from the present-day country of Armenia, but the region known to have had cultural ties with the Southern Levant is much broader. Evidence of cultural effects on the Southern Levant is mainly focused on the Kura-Araxes culture during the Early Bronze Age (archaeology) and on the Hurrians during the Middle-to-Late Bronze Age (linguistic testimony). These two complexes were spread over the Caucasus, Eastern Anatolia, and neighboring regions. The Armenian sites we analyzed are the best representatives to date of these cultures. The Early Bronze Age individuals from Armenia (Armenia_EBA) come from an Early Bronze Age Kura-Araxes burial ground, and the later Middle-to-Late Bronze Age individuals (Armenia_MLBA) come from the Aragatsotn Province in northwestern Armenia. It is important to note that the Neolithic and Chalcolithic Anatolian individuals analyzed in this study come from the northwestern part of Anatolia, which is not part of the Caucasus. The Chalcolithic Zagros individuals come from the Kangavar Valley in Iran, which is located on the border of the Kura-Araxes influence.
The term “Canaanites” is loosely defined, referring to a collection of groups (which in the Bronze Age were organized in a city-state system) and thus in principle could lack genetic coherence. The individuals examined here cover a wide geographic span—coming from nine sites in present-day Lebanon, Israel, and Jordan. Our analyses revealed that, with the exception of Sidon (and to a smaller extent the individuals of the Baq‛ah), they are homogeneous in the sense of being closer to each other than to other contemporary and neighboring populations. This suggests that the archaeological and historical category of “Canaanites” correlates with shared ancestry (Eisenmann et al., 2018). This resembles the pattern observed in the Aegean basin during the 2nd millennium BCE, where the cultural categories of “Minoan” and “Mycenaean” show evidence of genetic homogeneity across multiple sites albeit with potentially subtle ancestry differences within these groupings (Lazaridis et al., 2017). Another example is the “Yamnaya” pastoralists of late 3rd and early 2nd millennium BCE in the western Eurasian Steppe (Allentoft et al., 2015, Haak et al., 2015). This contrasts with the pattern seen in other places, such as for the Bell Beaker cultural complex of the 2nd millennium BCE (Olalde et al., 2018), where people sharing similar cultural practices had widely varying ancestry. In any case, the detection of such associations—as we do here—cannot by itself prove that group identities in the past were related to genetics.
From the groups we have examined, the only one that is somewhat diverged from the rest is Sidon. We provide evidence against the possibility that this observation is a batch effect (Methods S1C). Rather, we suggest that the relative remoteness of Sidon stems from the fact that this population is genetically heterogeneous and has different individuals showing resemblance to different Southern Levantine groups (Methods S1C). During the 2nd millennium BCE, Sidon was a major port city and was connected in trading relations with the eastern Mediterranean basin, which could have led to a significant genetic inflow, making its population more heterogeneous than that of inland cities. This might also be the reason that the site that most resembles Sidon is Ashkelon, which is another coastal site. The only inland population that resembles Sidon is Abel Beth Maacah, perhaps because of its geographic proximity (Figures 1A and 2). Apart from Sidon, Baq‛ah also shows some minor deviations from the rest when taking a richer set of outgroup populations (Figure 3). The Baq‛ah is located on the fringe of the Syrian desert, therefore this population might be admixed with more eastern groups, which are not yet genetically sampled. This might be reflected by the fact that the individuals of the Baq‛ah also show some degree of variability in their ancestry patterns (Table S2).
Although this study focuses on the Bronze Age, it also reports two new samples from the Iron Age—one from Megiddo and the other from Abel Beth Maacah. These two individuals show ancestry patterns that are very similar to those observed in the Middle and Late Bronze Age individuals (Figure 4), suggesting that the destruction at the end of the Bronze Age in the region did not necessarily lead to genetic discontinuity in each and every site. Notably, both Abel Beth Maacah and Megiddo are inland cities, and their genetic continuity throughout the transition from the Bronze Age to the Iron Age might not be representative of other sites in the region. For example, one of the two Iron Age populations in the Philistine coastal city of Ashkelon (ASH_IA1) showed evidence of mobility of populations related to southern Europe around the Bronze Age to Iron Age transition (Feldman et al., 2019).
Estimating the ancestry proportions in present-day Middle Eastern populations with substantial sub-Saharan African admixture (as well as multiple sources of admixture from different parts of the Mediterranean), is difficult. We addressed the problem by developing two statistical techniques and then testing the robustness of our inference on the basis of a comparison between these methods, simulations, and perturbations of the input (see STAR Methods; Methods S1F–S1K). We examined 14 present-day populations that are historically or geographically linked to the Southern Levant and tested the contributions of East Africa, Europe, and the Middle East (combining Southern Levant Bronze Age populations and Zagros-related Chalcolithic ones) to their ancestry. We found that both Arabic-speaking and Jewish populations are compatible with having more than 50% Middle-Eastern-related ancestry. This does not mean that any these present-day groups bear direct ancestry from people who lived in the Middle-to-Late Bronze Age Levant or in Chalcolithic Zagros; rather, it indicates that they have ancestries from populations whose ancient proxy can be related to the Middle East. The Zagros- or Caucasian-related ancestry flow into the region apparently continued after the Bronze Age. We also see an Eastern-African-related ancestry entering the region after the Bronze Age with an approximate south-to-north gradient. In addition, we observe a European-related ancestry with the opposite gradient (north-to-south). Given the difficulties in separating the ancestry components arriving from the Southern Levant and the Zagros, an important direction for future work will be to reconstruct in high resolution the ancestry trajectories of each present-day group, and to understand how people from the Southern Levant Bronze Age mixed with other people in later periods in the context of processes known from the rich archaeological and historical records of the last three millennia.
STAR★Methods