Affinity of Ancient and Modern Italians

July 5, 2012

Ancient DNA analysis reveals that Ötzi the Iceman clusters with modern Southern Europeans and closest to Italians (the orange "Europe S" dots in the plots below), especially those from the island of Sardinia. Other Italians pull away toward Southeastern and Central Europe consistent with geography and some post-Neolithic gene flow from those areas (e.g. Italics, Greeks, Etruscans, Celts), but despite that and centuries of history, they're still very similar to their prehistoric ancestor.

The first analysis was to determine if the Iceman's autosomal DNA shows an affinity to any specific population or if he remains an outlier among contemporary samples. We intersected...his genome with the population reference sample consisting of more than 1,300 Europeans...125 individuals from seven North African populations ranging from Egypt to Morocco...and 20 Qatari samples from the Arabian Peninsula. When plotting the Iceman's genotype along the first two major axes of variation in Principal Component space (PC1 versus PC2), PC1 is driven by a north-to-south gradient differentiating North Africans from Europeans, and PC2 aligns individuals along north-to-south gradient within Europe (Fig. 3a). The Iceman clusters nearest to southern European samples, suggesting no greater genetic affinity with the North African or Middle Eastern components of variation than present day southern Europeans (Fig. 3a).

When considering only European populations, however, we observe that the Iceman clusters closest with five outlier contemporary samples from south-western Europe. In particular, the Iceman abuts the Italian samples originating from geographically isolated regions such as Sardinia (Fig. 3b). Analysis of a larger set of samples, including Sardinians from HGDP across a smaller subset of SNPs, further supports the clustering of the Iceman with samples from Sardinia based on autosomal SNPs (Fig. 3f). [...] The affinity of the Iceman's genome to modern Sardinian groups may reflect relatively recent common ancestry between the ancient Sardinian and Alpine populations, possibly due to the diffusion of Neolithic peoples.

Keller et al. "New insights into the Tyrolean Iceman's origin and phenotype as inferred by whole-genome sequencing". Nature Communications, 2012.