From Andy Coghlan at New Scientist:
We may owe some of our unique intelligence to a generous supply of a signalling chemical called dopamine in brain regions that help us think and plan. Our brains produce far more dopamine in these regions than the brains of other primates like apes.More.
Naturalist ideology requires something like extra dopamine production to be seen as a cause, not an effect. Of course, what we are really talking about is human consciousness, whose origin no one understands. And whatta feast of just-so science!
See also: Human/primate evolution: Eating fruit led to bigger brains?
Climate change made us smart
Retroviruses play a role in development of human brain?
Tooth size not linked to brain size in early humans
Large human brain size easily explained?
Repurposed mammal bone gene fuels cognition in humans?
Human origins: The war of trivial explanations
and
The Science Fictions series at your fingertips: Human evolution