"The “Machiavellian intelligence” hypothesis (or the “social brain” hypothesis) posits that large brains and distinctive cognitive abilities of humans have evolved via intense social competition in which social competitors developed increasingly sophisticated “Machiavellian” strategies as a means to achieve higher social and reproductive success. "
The most advanced concept known at a given time has always been used as a metaphor to explain certain phenomena, the brain used to be likened to a machine, then a computer, now a quantum computer ("resonance computer") and in similar ways the idea of the social brain could be better understood as a eusocial brain. (Wilson, 2012)
Social phenomena are easier to read than eusocial ones, since the latter are emergent.
What makes the brain eusocial?
Eusociality is the highest level of sociality in the animal kingdom, and is defined by caste-based organization, and more complex mediation than in non-eusocial animals.
The use of specialization, and that minds accumulate memes - connections - over time so resident memes guide attention and act as a filter, means that the brain is not just social (*sekwe, to follow), it is eusocial in the sense that it is being mediated by society as a whole, which has its own intent.