The cataclysmic Cretaceous-Paleogene extinction event about 65 million years ago led to the rapid demise of many non-neocortex-bearing species that could not adapt quickly enough to a suddenly altered environment. This marked the turning point for neocortex-capable mammals to take over their ecological niche. In this way, biological evolution found that the hierarchical learning of the neocortex was so valuable that this region of the brain continued to grow in size until it virtually took over the brain of Homo sapiens
