One big problem regarding maps depicting human migrations is the assumed graduality and continuity. Authors depict the movements as slow, gradual, and constant, perhaps imagining people moving only a few kilometers each lifetime, in a gradual expansion that the people of the time likely barely even realised. In such an illustatration (left) it often looks like a blob that grows larger and larger in all directions with Geographic Continuity all the way. This is of course wrong, and not how humans migrated at all.
Investigating settlement archaeology and c14 dating, Its clear that Humans migrated in controlled, conscious bursts, reaching entirely new areas within a single generation. Entire tribes of families set out into consciously chosen basins, valley or plateaus, reaching them within a single lifetime and ignoring the less fertile land on the way. From thereon, they would gradually move out into the less immediatly attractive land, with different tribes breaking off and forming new exclaves as the population grew, repeating the process. These migrations were often massive and happened in the span of a few generations, such as is evident with the Corded Ware migration, which saw its people reach the Baltics, Poland, Denmark, Germany and parts of Russia in just a hundred years, and from thereon, its descendant, the Bell Beakers, reached Brittain, France, Iberia and Italy in a hundred years or even less again in a seperate burst.
(The maps below are illustrative and totally arent based on the Indo European migrations at all)