"The main obstacle to a reconstruction that closely links the western Aryas to the Avestan Airyas is, in my opinion, the one arising from the theories that the Medes and the Persians emigrated from the North rather than from the East, that is to say, for instance, from south-east Russia.... Now, the obstacle that arises from the theory of the Medes and the Persians having emigrated from the North ... on the basis of a highly conjectural interpretation of the archaeological evidence, is now removed by the archaeologists themselves. A body of evidence... orients us in quite a different direction, namely towards that of a migratory movement, probably a slow, progressive one, from East to West, along the great Khorasan Road..... A much more convicing theory than that of the western Iranians having emigrated from North to South across the Caucasus is that of a slow, progressive East-West emigration, a gradual penetration as it were, over the centuries, from the end of the 2nd millenium to the first half of the 1st millenium B.C. ... Having done away with the obstacle provided by the theory of the trans-Caucasian migration..., we can see both these peoples as western branches of those same Airyas that in the Younger Avesta are described as being settled in such a large part of the eastern Iranian world...."