“Spam-filters, actually. Once they became selfmodifying, spam-filters and spam-bots got into a war to see which could act more human, and since their failures invoked a human judgement about whether their material were convincingly human, it was like a trillion Turing-tests from which they could learn. From there came the first machineintelligence algorithms, and then my kind.”

I Row-Boat, Cory Doctorow, 2005: https://craphound.com/overclocked/Cory_Doctorow_-_Overclocke...