UPDATE: This is the passage I was thinking of, from Orthodoxy; Chesterton was talking about social contract theory rather than evolution, but the idea that the sacred came first holds in spite of the move from critiquing the one theory to the other.
The eighteenth-century theories of the social contract have beenNow we do not know how this will turn out, and it may take longer than any of us are around to find out. We can readily imagine, though -- with Robert E. Howard as much as with Chesterton, as Howard describes this occurring over and over in his Conan stories -- these apes on the road to a rise to civilization, having found the necessary first step.
exposed to much clumsy criticism in our time; in so far as they meant
that there is at the back of all historic government an idea of
content and co-operation, they were demonstrably right. But they really
were wrong, in so far as they suggested that men had ever aimed at
order or ethics directly by a conscious exchange of interests.
Morality did not begin by one man saying to another, "I will not hit you
if you do not hit me"; there is no trace of such a transaction.
There IS a trace of both men having said, "We must not hit each other
in the holy place." They gained their morality by guarding their religion.
They did not cultivate courage. They fought for the shrine, and found
they had become courageous. They did not cultivate cleanliness.
They purified themselves for the altar, and found that they were clean.

