What makes us human? It is the large-sized human cerebral cortex. How to make a large-sized human cerebral cortex? It is the increase in the neurogenic period. How is the length of the neurogenic period regulated? More specifically, it is critical to understand how cortical neurogenesis in the human brain lasts for more than 130 days, whereas the same process takes only about 7 days in mice. The figure shows that BMP7 is expressed by increasing numbers of cortical radial glial cells (stem cells) during mammalian development and evolution. BMP7 promotes neurogenesis, inhibits gliogenesis, and thereby increases the length of neurogenic period. Therefore, it is the BMP7 gene that drives evolutionary expansion of the mammalian cortex.