The important thing that we have learned from the recent spate of ancient DNA results is that ANE [Ancient North Eurasian autosomal component] and Y-DNA R did not come from an ice age refuge in Europe. The refuge was in Siberia. Any hunter-gatherer in Europe with an element of ANE had ancestors from Siberia. This included EHG and SHG. Foragers with ANE and Y-DNA R did not arrive in Europe until long after the Ice Age maximum.
I hope this map makes matters clear:
http://s13.postimg.org/lwt6blh2v/Ice_Age_Max_Map.gif
I should have added ANE to Y-DNA R in my key.
(...)
I look at DNA samples in their cultural context.
The regions I outlined in red contain hunter-gatherer sites that survived the LGM. These refuge areas were relatively protected in the Ice Age. The coniferous forest refuge near Lake Baikal included the Mal'ta site (24,000 years ago) with a boy carrying ANE autosomal and Y-DNA R. Early pottery was present in the Lake Baikal region - the type that arrived in the Samara region on the Volga c. 7000 BC.
The refuge around the upper Yenisei river was sheltered by mountains. It include..d the site at Afontova Gora, with a male carrying ANE (17,000 years ago). This site had pressure blade-making technology. This complex technique was most probably handed down within families and so would have spread by migration. Like pottery, it arrived between the Urals and the Caspian in the Mesolithic. It also reached Lapland by a more northerly route about 5836 BC.
The major barrier was the expanded Caspian, which butted up against the Urals, as David Anthony pointed out in The Horse, The Wheel and Language. It was not completely impassible, but it seems that the bands of hunter-gatherers who clustered around the Yenisei and Lake Baikal were more tempted to roam from their refuge after the climate improved.