http://www.sciencemag.org/news/2018/05/trio-genes-supercharged-human-brain-evolution

A technique for growing these brain cortical neurons in a lab dish made it possible to track down more genes involved in brain expansion.

Three nearly identical genes could help explain how 0.5 liters of gray matter in early human ancestors became the 1.4-liter organ that has made our species so successful and distinctive. The newly identified genes could also help explain how brain development sometimes goes wrong, leading to neurological disorders.