Academic citations provide a simple way to track this evolution.

ECONOMIST: Free exchange

If nature always stuck to simple plans, it would be easier to track the paths of evolution, but nature does not have that luxury.

NEWYORKER: It Ain��t Necessarily So

Speaking for the industry, Stuart Ingis, general counsel for the Digital Advertising Alliance, said the decision to adopt do-not-track is an "evolution" of the industry's approach.

WSJ: Web Companies Agree to Support 'Do Not Track' System