The manuscript of Zheng and colleagues tackles one of the key questions of neuroscience: what makes the human brain unique? Perhaps not surprisingly, 21% of the genes exhibit species-differential gene expression in the visual cortex between the mouse and the human, and a large number of genes were found to label specific cell types uniquely in one species. While this is a very valuable resource, these findings are somewhat challenging to interpret in the context of human “uniqueness”: 1) the compared tissue was the visual cortex, which is presumably less different (or at least “differently” different) between the mouse and the human than the prefrontal cortex and hippocampus, which have both a very different cytoarchitecture and gene expression profile; and 2) the comparison was between mouse and human, and not human and non-human primate.

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