We covered the whole issue of size and complexity in my following entry:

Friday, December 16, 2016, 20:37 I suggest reading it again. Complexity of the neo-cortex is vital to sapiens brains being so different. 16 million neurons. Western gorilla has 9.1 million. Growth from 350 cc in Lucy like hominins to 1,300 cc is discussed. Each jump is not just size but a more complex cortex.