Genetics of the peloponnesean populations and the theory of extinction of the medieval peloponnesean Greeks

The Peloponnese is one of the cradles of the Classical European civilization and an important contributor to the ancient history of Europe. It has also been the subject of a controversy about the ancestry of its present population. In a theory hotly debated by scholars for over 170 years, the German historian Jacob Philipp Fallmerayer proposed that the medieval Peloponneseans were totally extinguished by Slavic and Avar invaders and replaced by Slavic settlers during the 6th century AD. In this study, 2.5 million single-nucleotide polymorphisms were used to investigate the genetic structure of the present Peloponnesean population in a sample of 241 individuals originating in all districts of the peninsula, and to examine predictions of the theory of replacement of the medieval Peloponneseans by Slavs. We found considerable heterogeneity in the Peloponnesean populations, exemplified by genetically distinct subpopulations and by gene flow gradients within the Peloponnese. By principal component analysis (PCA) and ADMIXTURE analysis we demonstrated that the pattern of the Peloponneseans is clearly distinguishable from the populations of the Slavic homeland and is very similar to that of Sicilians and Italians. Using a novel method of quantitative analysis of ADMIXTURE output we found that the Slavic ancestry of Peloponnesean subpopulations ranges from 0.2% to 14.4%. Subpopulations considered by Fallmerayer to be Slavic tribes or to have Near Eastern origin, have no significant ancestry of either. This study rejects the theory of extinction of medieval Peloponneseans and illustrates how genetics can clarify important aspects of the history of a human population.