Understanding 6th-century barbarian social organization and migration through paleogenomics

Abstract

Despite centuries of research, much about the barbarian migrations that took place between the fourth and sixth centuries in Europe remains hotly debated. To better understand this key era that marks the dawn of modern European societies, we obtained ancient genomic DNA from 63 samples from two cemeteries (from Hungary and Northern Italy) that have been previously associated with the Longobards, a barbarian people that ruled large parts of Italy for over 200 years after invading from Pannonia in 568 CE. Our dense cemetery-based sampling revealed that each cemetery was primarily organized around one large pedigree, suggesting that biological relationships played an important role in these early medieval societies. Moreover, we identified genetic structure in each cemetery involving at least two groups with different ancestry that were very distinct in terms of their funerary customs. Finally, our data are consistent with the proposed long-distance migration from Pannonia to Northern Italy.

Fig. 1

Archeological and genetic characterization of Szólád and Collegno. a Map of Europe showing the location (blue dots) of the two cemeteries and regional context is included (the Roman province of Pannonia in burgundy and the Longobard Kingdom in beige). b, c Spatial distribution of graves in Szólád and Collegno (first period burials only) with indication of sex (different shapes), genetic ancestry (different colors) and summary of archeology (yellow dots for presence/absence of grave furnishings and green dots for the presence of wooden elements in grave structure). Kindreds (in the biological sense) are indicated by gray shading in b and c. N = FIN + GBR + CEU, S = TSI. The map image in a is modified from the original Blank_map_of_Europe_(with_disputed_regions).svg (https://commons.wikimedia.org/wiki/File:Blank_map_of_Europe_(with_disputed_regions).svg) by maix (https://commons.wikimedia.org/wiki/User:Maix) and is licensed under the Creative Commons Attribution-Share Alike 2.5 Generic license

Fig. 2

Principal component analysis of Szólád and Collegno. a Procrustes PCA of modern Europeans (faded small dots are individuals, larger circle is median of individuals) along with samples from Szólád (filled circles), Collegno (filled triangles) and other Migration Period samples. Szólád and Collegno samples are filled with colors based on estimated ancestry from ADMIXTURE. NWE, modern northwest Europe; NE, modern northern Europe; NEE, modern northeast Europe; CE, modern central Europe; EE, modern eastern Europe; WE, modern western Europe; SE, modern southern Europe; SEE, modern southeast Europe; HUN, modern Hungarian. b Procrustes PCA of modern and Bronze Age Europeans along with samples from Szólád and Collegno and other Migration Period samples. Gray dots are modern Europeans as shown in a. NWb, Bronze Age northwest Europe; Nb, Bronze Age northern Europe; NEb, Bronze Age northeast Europe; Cb, Bronze Age Europe; Eb, Bronze Age Europe; Wb, Bronze Age western Europe; SEb, Bronze Age southeast Europe; ITb, Bronze Age Italy; ITn, Neolithic Italy

Fig. 3

Genetic structure of Szólád and Collegno. Model-based ancestry estimates from ADMIXTURE for Szólád (a) and Collegno (b) using 1000 Genomes Project Eurasian and YRI populations to supervise analysis. Note that high contamination was identified in CL31 and overlaid with a pink hue in b

Fig. 4

Major kindreds in Szólád and Collegno. Kindreds SZ1 (a), CL1 (b), and CL2 (c), with colors corresponding to criteria and labeling in Fig. 2. ADMIXTURE coefficients (vertical bars on side of each individual) estimated using 1000 Genomes European populations only. Dashed lines indicate relationships of unknown degree (including past inbreeding in the parents of CL97). d Displays strontium isotope ratios for Kindreds CL1 and CL2 where available. Estimate of local range at Collegno is shown using black shading, as detailed in Fig. 4. Numbers indicate generations (1 being the oldest, 3 being the youngest)

Fig. 5

Strontium isotope ratios in Szólád and Collegno. Evidence for migrants at Collegno and Szólád, as suggested by ⁸⁷Sr/⁸⁶Sr values of human tooth enamel and environmental reference samples. Isotopic data from Szólád were taken from the ref.. The vertical lines indicate where multiple teeth were sampled from the same individual. The gray band denotes the local bioavailable strontium isotope range. Individuals falling outside of this are considered non-local. A: Collino di Superga (clays and marls); B: Lago Piccolo di Avigliana (glacial deposits); C: Castello di Avigliana (serpentinite, green schist); D: Collegno site (Pleistocene gravels); E: Bakony Mountains; F: vegetation south of Lake Balaton; G: water south of Lake Balaton; H: soil near Szólád (Szólád data from the ref.). Color coding scheme corresponds to ancestry criteria and labeling in Fig. 2, though samples represented in black are those lacking genomic data. To ease readability of the figure, the ⁸⁷Sr/⁸⁶Sr values of each ancestry group are arranged in ascending order