Bootstraping humans

Memes made sure they had an environment to thrive on by accelerating the evolution of humans. Research covered in the Guardian describes how the evolution of the human brain has been very quick in confront of that of other species, and attributes it to the pressures of the social environment.

The new replicator takes control of the medium in which it lives: how quick in terms of geological change was the emergence of a life-sustaining environment, once life appeared?