Coalescent

"Sincerely, no idea. But the lineage as such cnonat be as young as only some 1300 years ago. Even if it has been spread partly by Slavic migrations, it needs to have been common before those in the core Slavic area (Poland?)."That's actually a very good point Maju (never thought about it that way). But assuming that the R-M458 lineage is a 1300 year old Slavic marker, the frequencies supposedly present in Greeks seem a bit incredulous.After looking at the map Polak provided at Polish Genes, I only saw two data points in Greece (one in Attica and one in Crete). The other two Balkan data points appear in south-central Albania and Vardarska (i.e. FYROM).From what I can tell, the only Balkan data point surrounded by a visible color shade frequency of R-M458 is in south-central Albania (there is no data point in Bulgaria even though there is a visible color shade frequency of R-M458).The near absence of a color shade frequency in the Greek data points appears to virtually coincide with the very sparse archaeological evidence involving Slavic settlements in Greece (the Oxford Dictionary of Byzantium makes this point abundantly clear despite medieval literary attestations depicting "Slavic tides"). All in all, whatever degree of Slavic admixture occurred in Greece during the Middle Ages was so limited that it was practically nonexistent (I think that in reality, the upper limit for Slavic admixture in the Greek population is much less than 1/10). Of course, I'd avoid putting too much faith in genetic determinism given that genetics is still a young science and you just never know when another team of geneticists decides to "crack" the "R-M458 code" even further to discover that it may be something more than merely a Slavic genetic marker. Always keep an open mind (for what it's worth).