The evolutionarily ancient subcortical structures are more modular still. In physics, the task is finding a single insight that explains everything. This has led to a tendency to pile far too much workload onto each new principle as it is discovered. To explain human functionality, the invocation of massively parallel neural networks is necessary but not remotely sufficient. Human intelligence is the result of literally hundreds of millions of years of adaptation on top of the simple fact of neural networks.
Emergence has at least two definitions.
This does not mean, however, that the complex, intricate functionality of the brain arises without design. It does not mean that implementing neurons is sufficient to give rise to the complex, layered feature-extraction of the human visual supersystem. The idea that general intelligence does not require complex adaptation is as out of touch with current evolutionary thought as the idea that the brain is an indistinct lump is out of touch with functional neuroanatomy. General intelligence is not simple. That is progress.