Indeed we do not have a good, computational understanding of what makes brains efficient. It's plausible that growing new pathways could contribute to the effic

Indeed we do not have a good, computational understanding of what makes brains efficient. It's plausible that growing new pathways could contribute to the efficiency of the brain, but is that the only reason the brain is efficient? What about the brain's spiking communication? What about the synaptic and dendritic dynamics? Are any of these "features" useful or just vestigial byproducts of evolution? Without that computational understanding, it's hard to make satisfying arguments one way or the other about what exactly makes the brain efficient. You can cast neuromorphic chip development as a path to realizing that understanding. Recall how convolutional neural networks only realized their heyday once the hardware resources to implement them (i.e. GPUs) was readily available. Once GPUs made running CNNs practical, people found all sorts of new ways to understand and use neural networks. In other works, the computational model and the implementing hardware must be co-developed before something actually useful is possible.