I think that paleontologists have determined the diets of the grazing animals of the periglacial regions based on extrapolations by analogy--what do these types of animals eat today, and what were the conditions then. Certainly, though it would have been a spectacular panorama. The Ukraine is (or would be without man) a vast grassy plain, but after the retreat of the ice caps, Russia became a huge forest as did much of the rest of Europe. During the ice ages, trees simply couldn't survive except in riparian gallery forests which were relatively sheltered. What would become the vast forests of post-ice age Eurasia were then grasslands. Just as the North American great plains supported enormous herds of bison and elk--millions of animals--those grasslands would have supported millions and millions of grazing animals. It's easy to see why humans were attracted to an otherwise very brutal environment.