Indo-European Invasions into Europe

http://www.theguardian.com/science/2014/sep/18/ancient-ancestors-europeans-dna-study

The findings suggest that the arrival of modern humans into Europe more than 40,000 years ago was followed by an influx of farmers some 8,000 years ago, with a third wave of migrants coming from north Eurasia perhaps 5,000 years ago. Others from the same population of north Eurasians took off towards the Americas and gave rise to Native Americans.

Genetically speaking, there seems to be no trace of any genetically significant movement of Indo-European people into Europe either (unless it is the farmers, but linguists think that 8000 years ago is too far back.  The last population-genetically significant influx of people into India was 12,000 years ago or earlier.)  On the other hand, the vocabulary of a language like Greek is estimated to be more than 30% non-Indo-European (e.g., compared to less than 4% of the 10,000 word vocabulary of the Rg Veda), so a elite dominance language replacement theory might work for Greece, where it can't work for the language of the Rg Veda.  The only way it might work is if an Indo-European language was superposed on a previous Indo-European language.