Genomic diversity and structure of prehistoric alpine individuals from the Tyrolean Iceman's territory

Abstract

The Eastern Italian Alps played a crucial bridging role between Mediterranean and Northern alpine populations since Prehistory. However, few prehistoric individuals from that region have been genomically analysed so far. Among them, the Iceman (Copper Age, 3368-3108 BC) showed a relatively high Anatolian-Neolithic-related ancestry and low Hunter-Gatherers (HGs)-related ancestry. To investigate how the genomic structure of alpine groups varied over time and to contextualize the Iceman, we analysed 47 alpine individuals dated from the Mesolithic (6380-6107 BC) to Middle Bronze Age (1601-1295 BC). The Mesolithic genome reveals genetic admixture between Western and Eastern HGs that occurred from ~13700 - 8300 BC. Most individuals from the Neolithic onwards present a genomic structure resembling that of the Iceman, supporting genetic continuity. Few individuals carry different ancestries, such as the Steppe-related ones appearing ~2400 BC. Finally, the study suggests local and non-local admixture events between HGs and Neolithic farmers from this alpine area.

Fig. 1. Geographical distribution of sampling sites and radiocarbon dates.

A Geographic map of Italy and the Alpine arc (left) was performed by using ESRI’s ArcGIS Pro software, and a zoom-in (right) of the Trentino Alto-Adige region in the EIAlp with the location of the archaeological sites from this study (Iceman and Ora/Auer). The number of sampled individuals from each site is near the symbol, coloured according to chronology. The first three letters of the site, also used in the sample identification number, are given in brackets. B Mean radiocarbon dates and calibrated intervals (cal. 2-sigma, 95%) for each dated individual (more details in Supplementary Data 1 and Supplementary Information Fig. S16).

Fig. 2. Principal components analysis (PCA) and multi-dimensional scaling (MDS) representations.

A PCA of ancient individuals from this study projected onto the variation of present-day individuals from Western Eurasia (refer to Supplementary Data 10). B MDS plot of Eurasian HGs individuals based on 1 − f₃ (Mbuti, pop1, pop2) statistic. Comparative data from ref. . ANE Ancient North Eurasian (refer to Supplementary Data 11).

Fig. 3. Pairwise-qpWave analysis among prehistoric alpine individuals.

The black squares indicate individuals from the same chronology (NE Neolithic, CA Copper Age, CA-EBA Copper Age-Early Bronze Age, EBA Early Bronze Age, MBA Middle Bronze Age).

Fig. 4. qpAdm analysis and admixture models of each prehistoric alpine individual.

Each colour represents one of the seven sources used in the models. Number of individuals = n. Villabruna (n = 1), MAD01 (Madonna Bianca, n = 1), EHGs (Eastern Hunter Gatherers, n = 18), CHG (Caucasus Hunter Gatherers, n = 2), AnatoliaN (Anatolian Neolithic farmers, n = 22), IranN (Iranian Neolithic farmers, n = 4) and Steppe (Yamnaya, n = 10). The standard error for each source proportion is indicated by the error bars. No significant model could be found for one individual (ROM303). Haplogroups of the mitochondrial DNA (mtDNA) in all individuals and Y-Chromosome haplogroups in males are indicated on the right-hand side of the graph.